Search

Background: Biomass allocation reflects functional tradeoffs among plant organs and thus represents life history strategies. However, little is known about the patterns and drivers of biomass allocation between reproductive and vegetative organs along large environmental gradients. Here, we examined how environmental gradients affect biomass and the allocation between reproductive and vegetative organs. We also tested whether the allocation patterns conform optimal or allometric partitioning theory. Methods: We collected 22 Artemisia species along a large environmental gradient in China and measured reproductive (infructescences including seeds) and vegetative (leaves, stems and roots) mass for each plant. We then used standardized major axes regressions to quantify the relationships between reproductive and vegetative organs and linear mixed-effect models to examine the effect of environmental gradients (climate and soil) on biomass allocation patterns. Results: We found significant negative correlations between total biomass of Artemisia and the first principal component of climate, an axis that was negatively correlated with temperature and precipitation. Overall, there were significant isometric relationships between reproductive and vegetative mass. In addition, the ratio of reproductive to vegetative mass increased with the second principal component of climate (representing climate variability), but decreased with the second principal component of soil (representing bulk density and available water capacity). These patterns were consistent at the individual and interspecific levels, but were mixed at the intraspecific level. Conclusions: Our findings of the plastic responses of biomass allocation to environmental gradients support the optimal partitioning theory (OPT). The isometric relationships between reproductive and vegetative organs indicate that plant growth and reproduction are intricately linked. Furthermore, the plasticity of biomass ratios of reproductive to vegetative organs to climate variability and soil physical properties suggests that the flexible allocation between growth and reproduction is crucial for successful adaptation to diverse habitats. [ABSTRACT FROM AUTHOR]

Metacommunity theory addresses local interactions and regional processes, offering a powerful framework to comprehend the species composition of a region and the factors that shape its structure along environmental gradients. By incorporating spatial dynamics, the metacommunity analysis explores the relationships that govern the ecological communities at different spatial scales. The objective of this work is to describe the structure of a metacommunity of living benthic foraminifera, to relate it to physical and chemical variables of water and sediment, and to identify the environmental characteristics associated with the assemblages. A total of 534,416 living benthic foraminifera (BF), belonging to 65 species, were sampled in 2016–2020 at 106 stations along a strong salinity gradient across five urban coastal lagoons along the coast of Rio de Janeiro State (Brazil). Elements of metacommunity structure (EMS) analysis identified four distinct assemblages of living BF across the lagoonal systems. These metacommunities fitted a quasi-nested pattern, with the total variation explained by a shared influence of environmental factors (primarily hydrological drivers associated with marine influence, such as salinity, pH, and temperature) and spatial predictors. Organic enrichment descriptors (TOC, TS, CHO, PTN, LIP) played a secondary role in the ordination of the sites. The findings demonstrate the potential of the EMS approach as a valuable tool for establishing a baseline in environmental monitoring plans. [ABSTRACT FROM AUTHOR]

The biogeochemical niche (BN) hypothesis is based on the concentrations of the predominant elements of a given organism to be stoichiometrically matched in order for it to function adequately. However, it is unknown how BN is represented by different plant organs and to what extent environment or evolution affects BN. We measured C, N, P, K, Ca and Mg concentrations in leaves, stems and roots of 1022 individuals of 62 Artemisia species collected across China to quantify BNs of the three organs. The BN of leaves was offset from and smaller in volume than that of stems and roots. BNs of the three organs differed in their sensitivities to environmental gradients, and leaves were less responsive to environmental variation than stems and roots in both BN volumes and positions. Environmental gradients had larger effects on BN positions than on BN volumes of all three organs. The BN volumes and positions of leaves and roots had no phylogenetic signal, while stem BN had a weak signal, that is, repeated species divergences from various Artemisia branches explained most of the BN variation of the three organs. The BN hypothesis cannot be fully tested using the elemental composition of a single organ owing to different physiological mechanisms and diverse responses of BN among organs. At least in Artemisia, leaves are strongly constrained in a limited elemental niche space to support a relatively stable supply of elements for leaf functioning, especially photosynthesis. In contrast, stems and roots develop larger elemental hypervolumes also representing nutrient storage and other functions. The BNs of Artemisia showed different environmental responses between volumes and positions, allowing these species to adjust elemental concentrations while maintaining a stable overall elemental composition under different environmental conditions. Synthesis. In conclusion, BNs of extant Artemisia populations are determined mostly by short‐term phenotypic responses to current environmental conditions and/or genotypic variation, while the recently evolved species diversity results mostly from species‐specific and organ‐specific use of nutrients and little by early divergence in the phylogeny. [ABSTRACT FROM AUTHOR]

[Display omitted] • Abundance and richness were lower in third-order sites than in fourth-order sites in the studied stream. • Environmental variables were spatially structured. • Water conductivity was the main driver of parasite β -diversity. Parasites can provide suitable models for studying β-diversity due to their strict dependence on both the environment and the biology and distribution of their hosts, aiding in the interpretation of any patterns that hosts can display. With the aim of quantifying the relative importance of host features, environmental factors and spatial distances as drivers of fish parasite β-diversity along a unidirectional gradient, the structure of fish parasite assemblages was analysed using generalised dissimilarity models (GDMs). A total of 150 poeciliid fish were examined for larval trematodes, recording host features and physical parameters of each sampling site along the stream. Differences among digenean communities increased when Strahler order changed along the stream, associated with increasing species richness and abundance downstream. Environmental gradient, spatial distance and host features were identified as significant determining factors of species turnover, with conductivity being the most important, followed by spatial distance. In the present study, environmental variables were spatially structured along the stream, their effects as structurers of parasite β-diversity being higher than the pure environmental or the pure distance effect. Such predominance prevents us from establishing at what point on the continuum from niche to neutrality these communities are located. Results from the present research contribute to improving our knowledge of the factors that shape parasite community changes, and underline the importance of considering the pure and shared effects of spatial, environmental and host feature factors in order to determine the real contribution of each one as a determinant of parasite β- diversity. [ABSTRACT FROM AUTHOR]

In this study, we describe plant communities along the mesotopographic gradient in the low‐elevation subcontinental mountains of NE Finland (Utsjoki region). We sampled vascular plants, bryophytes and lichens along 18 mesotopographic ridge‐snowbed transects comprising a total of 180 plots. We used non‐metric multidimensional scaling (NMDS) ordination with envfit to explore the differentiation of plant communities in relation to mesotopography, elevation, rock cover, cover of bare ground, snowbed size and snowmelt time. The classification of communities was performed using DIANA clustering. Plant communities were differentiated along the mesotopographic gradient, snowmelt time, elevation and rock cover. The DIANA analysis distinguished seven clusters corresponding to the following communities: Betula nana–Lichenes heath, Empetrum–Myrtillus–Stereocaulon heath, Empetrum–Pleurozium–Lichenes heath, graminoid‐rich snow‐protected heath, Oreojuncus trifidus–Avenella flexuosa snow‐protected heath, Polytrichastrum sexangulare–liverwort snowbed, and Salix herbacea–Kiaeria starkei snowbed. Because of the strong impact of snowmelt time on plant community structure and distribution of communities, it is likely that climate change‐induced changes in snow conditions are affecting tundra vegetation and especially snowbeds are threatened. Snowbed communities in the Utsjoki region roughly align with previously described vegetation associations of mountain areas in NW Europe. The assignment of the graminoid‐rich snow‐protected heath community remains uncertain. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim Location Taxon Methods Results Main Conclusions An ecological community consists of species of various abundances that reflect their responses to the environmental conditions. A classic macroecological pattern, the species abundance distribution (SAD), has been studied for diverse taxa and communities and integrated into numerous modelling tools. Despite its widespread use, a mathematical model that can capture variations in the empirical SAD and describe its response to environmental changes is still lacking. By integrating the Maximum Entropy Theory of Ecology (METE) with a generalised entropy called Rényi's entropy, we aim to develop a new ecoinformatic model that can predict the variation of empirical SAD along multiple environmental gradients.Panama.Angiosperms.We extend the METE using the Rényi's entropy as an uncertainty measure. We apply this extended METE, called Rényi model, to the tree abundance data from 49 plots in Panama and predict the SAD within each plot. We estimate Rényi's parameter q by fitting the predicted SAD to the empirical SAD in each plot. We further compile climate and soil data from the Panama plots and analyse their relationships with the estimated q using multiple regressions.Rényi model provides adequate description of the empirical SADs and outperforms lognormal or log‐series models in 40 of the 49 tree plots, according to the Akaike information criterion. Variations in Renyi's q estimates (from 1/2 to 1) reflect shifts in the empirical SADs. Multiple regressions reveal that P, Al and NH4, three soil chemicals that are important for tree growth and species distribution, significantly affect Renyi's q across plots.These findings suggest that the Rényi model and Rényi's q can characterise the SAD of communities under environmental changes. They also indicate the potential of using generalised entropies to predict macroecological patterns in stressed ecosystems. [ABSTRACT FROM AUTHOR]

Estimates of dark diversity, species that belong to a given species pool but are not present locally, can help to understand how environmental conditions influence species distribution. However, it remains uncertain whether dark diversity can predict the absence of indicator species in preserved environments after environmental changes. We explored the sensitivity of dark diversity (the set of species absent from a particular area), in detecting the absence of Zygoptera (Odonata) indicative of preserved forest environments in altered habitats, and the influence of sample coverage on the detected patterns. We sampled 98 streams in the Amazon region, where the dark diversity of Zygoptera was estimated based on probabilistic species co-occurrence patterns using the Beals index, encompassing 16 species in the Santarém/Belterra region and 23 species in the Paragominas region. The mean total richness of observed Zygoptera species in Paragominas, 42.7 species, and Santarém/Belterra, 25.93 species, was higher than the estimated mean dark diversity for the two study sites, which were 12.32 and 12.20 species, respectively. The dark diversity was not effective in detecting the absence of forest-indicator Zygoptera in human-altered streams and exhibited a positive relationship between Zygoptera dark diversity and species common to different environments concerning environmental integrity only in Paragominas, but not in Santarém. We found that there is a possibility that observed values of dark diversity may occasionally be subject to sampling coverage biases. In this regard, we suggest considering sampling coverage alongside field-collected biological datasets to assess whether it is related to dark diversity. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the impact of genotype-environment interaction (GEI) on the manifestation of traits such as age at first calving (AFC), age at first service (AFS), and calving interval (CI) through the application of the reaction norm model in Holstein cattle raised in Paraná state, Brazil. Utilizing data from the milk testing service of the Paraná Association of Holstein Cattle Breeders (APCBRH), this study analyzed records from 179,492 animals undergoing their first, second, and third lactations from the years 2012 to 2022. These animals were part of 513 herds spread across 72 municipalities in Paraná. The environmental gradient was established by normalizing contemporary group solutions, derived from the animal model, with the 305-day-corrected milk yield serving as the dependent variable. Subsequently, reaction norms were determined utilizing a Random Regression Model. Spearman’s correlation was then applied to compare the estimates of breeding values across different environmental gradients for the studied traits. The highest EG (+ 4) indicates the least challenging environments, where animals experience better environmental conditions. Conversely, lower EG (-4) values represent the most challenging environments, where animals endure worse conditions. The only trait that exhibited a moderate heritability magnitude was AFC (0.23) in the least challenging environmental condition. The other traits were classified as having low heritability magnitudes regardless of the evaluated environmental gradient. While minimal evidence was found for the influence of GEI on CI, a clear GEI effect was observed for AFC and AFS across all environmental gradients examined. A reversal in genotype ranking occurred under extreme environmental conditions. The findings suggest that the best-performing genotype under one environmental gradient may not necessarily excel under another. [ABSTRACT FROM AUTHOR]

Plant hydraulic traits are essential for understanding and predicting plant drought resistance. Investigations into the mechanisms of the xylem anatomical traits of desert shrubs in response to climate can help us to understand plant survival strategies in extreme environments. This study examined the xylem anatomical traits and related functional traits of the branches of seven Calligonum mongolicum populations along a precipitation gradient, to explore their adaptive responses to climatic factors. We found that (1) the vessel diameter (D), vessel diameter contributing to 95% of hydraulic conductivity (D95), hydraulic weighted vessel diameter (Dh), vessel density (VD), percentage of conductive area (CA), thickness-to-span ratio of vessels ((t/b)2), and theoretical hydraulic conductivity (Kth) varied significantly across sites, while the vessel group index (Vg), wood density (WD), and vulnerability index (VI) showed no significant differences. (2) Principal component analysis revealed that efficiency-related traits (Kth, Dh, D95) and safety-related traits (VI, VD, inter-wall thickness of the vessel (t)) were the primary factors driving trait variation. (3) Precipitation during the wettest month (PWM) had the strongest influence, positively correlating with (t/b)2 and negatively with D, D95, Dh, CA, and Kth. (4) Structural equation modeling confirmed PWM as the main driver of Kth, with indirect effects through CA. These findings indicate that C. mongolicum displays high plasticity in xylem traits, enabling adaptation to changing environments, and providing insight into the hydraulic strategies of desert shrubs under climate change. [ABSTRACT FROM AUTHOR]

Abstract Background Biomass allocation reflects functional tradeoffs among plant organs and thus represents life history strategies. However, little is known about the patterns and drivers of biomass allocation between reproductive and vegetative organs along large environmental gradients. Here, we examined how environmental gradients affect biomass and the allocation between reproductive and vegetative organs. We also tested whether the allocation patterns conform optimal or allometric partitioning theory. Methods We collected 22 Artemisia species along a large environmental gradient in China and measured reproductive (infructescences including seeds) and vegetative (leaves, stems and roots) mass for each plant. We then used standardized major axes regressions to quantify the relationships between reproductive and vegetative organs and linear mixed-effect models to examine the effect of environmental gradients (climate and soil) on biomass allocation patterns. Results We found significant negative correlations between total biomass of Artemisia and the first principal component of climate, an axis that was negatively correlated with temperature and precipitation. Overall, there were significant isometric relationships between reproductive and vegetative mass. In addition, the ratio of reproductive to vegetative mass increased with the second principal component of climate (representing climate variability), but decreased with the second principal component of soil (representing bulk density and available water capacity). These patterns were consistent at the individual and interspecific levels, but were mixed at the intraspecific level. Conclusions Our findings of the plastic responses of biomass allocation to environmental gradients support the optimal partitioning theory (OPT). The isometric relationships between reproductive and vegetative organs indicate that plant growth and reproduction are intricately linked. Furthermore, the plasticity of biomass ratios of reproductive to vegetative organs to climate variability and soil physical properties suggests that the flexible allocation between growth and reproduction is crucial for successful adaptation to diverse habitats.

Abstract Background Bacteria, Archaea, and Microeukaryotes comprise taxonomic domains that interact in mediating biogeochemical cycles in coastal waters. Many studies have revealed contrasting biogeographic patterns of community structure and assembly mechanisms in microbial communities from different domains in coastal ecosystems; however, knowledge of specific biogeographic patterns on microbial co-occurrence relationships across complex coastal environmental gradients remains limited. Using a dense sampling scheme at the regional scale, SSU rRNA gene amplicon sequencing, and network analysis, we investigated intra- and inter-domain co-occurrence relationships and network topology-based biogeographic patterns from three microbial domains in coastal waters that show environmental gradients across the inshore-nearshore-offshore continuum in the East China Sea. Results Overall, we found the highest complexity and connectivity in the bacterial network, the highest modularity in the archaeal network, and the lowest complexity, connectivity, and modularity in the microeukaryotic network. Although microbial co-occurrence networks from the three domains showed distinct topological features, they exhibited a consistent biogeographic pattern across the inshore-nearshore-offshore continuum. Specifically, the nearshore zones with intermediate levels of terrestrial impacts reflected by multiple environmental factors (including water temperature, salinity, pH, dissolved oxygen, and nutrient-related parameters) had a higher intensity of microbial co-occurrence for all three domains. In contrast, the intensity of microbial co-occurrence was weaker in both the inshore and the offshore zones at the two ends of the environmental gradients. Archaea occupied a central position in the microbial inter-domain co-occurrence network. In particular, members of the Thaumarchaeota Marine Group I (MGI, now placed within the Family Nitrosopumilaceae of the Phylum Thermoproteota) appeared to be the hubs in the biogeographic shift between inter-domain network modules across environmental gradients. Conclusions Our work offers new insights into microbial biogeography by integrating network features into biogeographic patterns, towards a better understanding of the potential of microbial interactions in shaping biogeographic patterns of coastal marine microbiota.

Abstract Environmental gradients can influence morpho-physiological and life-history differences in natural populations. It is unclear, however, to what extent such gradients can also modulate phenotypic differences in other organismal characteristics such as the structure and function of host-associated microbial communities. In this work, we addressed this question by assessing intra-specific variation in the diversity, structure and function of environmental-associated (sediment and water) and animal-associated (skin and gut) microbiota along an environmental gradient of pollution in one of the most urbanized coastal areas in the world. Using the tropical sea cucumber Holothuria leucospilota, we tested the interplay between deterministic (e.g., environmental/host filtering) and stochastic (e.g., random microbial dispersal) processes underpinning host-microbiome interactions and microbial assemblages. Overall, our results indicate that microbial communities are complex and vary in structure and function between the environment and the animal hosts. However, these differences are modulated by the level of pollution across the gradient with marked clines in alpha and beta diversity. Yet, such clines and overall differences showed opposite directions when comparing environmental- and animal-associated microbial communities. In the sea cucumbers, intrinsic characteristics (e.g., body compartments, biochemistry composition, immune systems), may underpin the observed intra-individual differences in the associated microbiomes, and their divergence from the environmental source. Such regulation favours specific microbial functional pathways that may play an important role in the survival and physiology of the animal host, particularly in high polluted areas. These findings suggest that the interplay between both, environmental and host filtering underpins microbial community assembly in H. leucospilota along the pollution gradient in Hong Kong.

Environmental gradients can influence morpho-physiological and life-history differences in natural populations. It is unclear, however, to what extent such gradients can also modulate phenotypic differences in other organismal characteristics such as the structure and function of host-associated microbial communities. In this work, we addressed this question by assessing intra-specific variation in the diversity, structure and function of environmental-associated (sediment and water) and animal-associated (skin and gut) microbiota along an environmental gradient of pollution in one of the most urbanized coastal areas in the world. Using the tropical sea cucumber Holothuria leucospilota, we tested the interplay between deterministic (e.g., environmental/host filtering) and stochastic (e.g., random microbial dispersal) processes underpinning host-microbiome interactions and microbial assemblages. Overall, our results indicate that microbial communities are complex and vary in structure and function between the environment and the animal hosts. However, these differences are modulated by the level of pollution across the gradient with marked clines in alpha and beta diversity. Yet, such clines and overall differences showed opposite directions when comparing environmental- and animal-associated microbial communities. In the sea cucumbers, intrinsic characteristics (e.g., body compartments, biochemistry composition, immune systems), may underpin the observed intra-individual differences in the associated microbiomes, and their divergence from the environmental source. Such regulation favours specific microbial functional pathways that may play an important role in the survival and physiology of the animal host, particularly in high polluted areas. These findings suggest that the interplay between both, environmental and host filtering underpins microbial community assembly in H. leucospilota along the pollution gradient in Hong Kong. [ABSTRACT FROM AUTHOR]

Background: Bacteria, Archaea, and Microeukaryotes comprise taxonomic domains that interact in mediating biogeochemical cycles in coastal waters. Many studies have revealed contrasting biogeographic patterns of community structure and assembly mechanisms in microbial communities from different domains in coastal ecosystems; however, knowledge of specific biogeographic patterns on microbial co-occurrence relationships across complex coastal environmental gradients remains limited. Using a dense sampling scheme at the regional scale, SSU rRNA gene amplicon sequencing, and network analysis, we investigated intra- and inter-domain co-occurrence relationships and network topology-based biogeographic patterns from three microbial domains in coastal waters that show environmental gradients across the inshore-nearshore-offshore continuum in the East China Sea. Results: Overall, we found the highest complexity and connectivity in the bacterial network, the highest modularity in the archaeal network, and the lowest complexity, connectivity, and modularity in the microeukaryotic network. Although microbial co-occurrence networks from the three domains showed distinct topological features, they exhibited a consistent biogeographic pattern across the inshore-nearshore-offshore continuum. Specifically, the nearshore zones with intermediate levels of terrestrial impacts reflected by multiple environmental factors (including water temperature, salinity, pH, dissolved oxygen, and nutrient-related parameters) had a higher intensity of microbial co-occurrence for all three domains. In contrast, the intensity of microbial co-occurrence was weaker in both the inshore and the offshore zones at the two ends of the environmental gradients. Archaea occupied a central position in the microbial inter-domain co-occurrence network. In particular, members of the Thaumarchaeota Marine Group I (MGI, now placed within the Family Nitrosopumilaceae of the Phylum Thermoproteota) appeared to be the hubs in the biogeographic shift between inter-domain network modules across environmental gradients. Conclusions: Our work offers new insights into microbial biogeography by integrating network features into biogeographic patterns, towards a better understanding of the potential of microbial interactions in shaping biogeographic patterns of coastal marine microbiota. [ABSTRACT FROM AUTHOR]

There is wide consensus that climate change will seriously impact flowering plants and their pollinators. Shifts in flowering phenology and insect emergence as well as changes in the functional traits involved can cause alterations in plant-pollinator interactions, pollination success and plant reproductive output. Effects of rising temperatures, advanced snowmelt and altered precipitation patterns are expected to be particularly severe in alpine habitats due to the constrained season and upper range margins. Yet, our understanding of the magnitude and consequences of such changes in life history events and functional diversity in high elevation environments is incomplete. This special issue collects novel insights into the effects of climate change on plant-pollinator interactions in individual plant species and on network structure of entire plant and pollinator communities in alpine ecosystems. Using simulated changes of earlier snowmelt, natural gradients of variation in temperature, precipitation and snowmelt, or a long-term monitoring approach, these studies illustrate how plant species, plant communities, and pollinators respond to variation in environmental conditions associated with scenarios of ongoing climate change. The collection of papers presented here clearly demonstrates how spatial or temporal variation in the environmental climatic context affects flower abundances and plant community composition, and the consequences of these changes for pollinator visitation, pollination network structure, pollen transfer dynamics, or seed production. As changes in the availability of flowers, fruits, and seeds are likely to impact on other trophic levels, the time is ripe and pressing for a holistic multitrophic view of the effects of climate change on biotic interactions in alpine ecological communities. [ABSTRACT FROM AUTHOR]

Background: Variations in community-level plant functional traits are widely used to elucidate vegetation adaptation strategies across different environmental gradients. Moreover, studying functional variation among different forest types aids in understanding the mechanisms by which environmental factors and functional strategies shift community structure. Methods: Based on five plant functional traits, including four leaf and one wood trait, for 150 woody species, we analyzed shifts in the community-weighted mean trait values across three forest types in a karst forest landscape: deciduous, mixed, and evergreen forests. We also assessed the relative contributions of stochastic processes, environmental filtering, and niche differentiation to drive community structure using a trait-based null model approach. Results: We found marked changes in functional strategy, from resource acquisition on dry, fertile soil plots in deciduous forests to resource conservation on moist, infertile soil conditions in evergreen forests. The traitbased null model showed strong evidence of environmental filtering and convergent patterns in traits across three forest types, as well as low niche differentiation in most functional traits. Some evidence of overdispersion of LDMC and LT occurred to partially support the recent theory of Scheffer and Van Nes that competition could result in a clumped pattern of species along a niche axis. Discussion: Our findings suggest a change in environmental gradient from deciduous to evergreen forest, together with a shift from acquisitive to conservative traits. Environmental filtering, stochastic processes, niche differentiation, and overdispersion mechanisms together drive community assembly in karst forest landscapes. These findings will contribute to a deeper understanding of the changes in functional traits among karst plants and their adaptive strategies, with important implications for understanding other community assemblies in subtropical forest systems. [ABSTRACT FROM AUTHOR]

Understanding the relationship between intraspecific trait variability (ITV) and its biotic and abiotic drivers is crucial for advancing population and community ecology. Despite its importance, there is a lack of guidance on how to effectively sample ITV and reduce bias in the resulting inferences. In this study, we explored how sample size affects the estimation of population‐level ITV, and how the distribution of sample sizes along an environmental gradient (i.e., sampling design) impacts the probabilities of committing Type I and II errors. We investigated Type I and II error probabilities using four simulated scenarios which varied sampling design and the strength of the ITV‐environment relationships. We also applied simulation scenarios to empirical data on populations of the small mammal, Peromyscus maniculatus across gradients of latitude and temperature at sites in the National Ecological Observatory Network (NEON) in the continental United States. We found that larger sample sizes reduce error rates in the estimation of population‐level ITV for both in silico and Peromyscus maniculatus populations. Furthermore, the influence of sample size on detecting ITV‐environment relationships depends on how sample sizes and population‐level ITV are distributed along environmental gradients. High correlations between sample size and the environment result in greater Type I error, while weak ITV–environmental gradient relationships showed high Type II error probabilities. Therefore, having large sample sizes that are even across populations is the most robust sampling design for studying ITV‐environment relationships. These findings shed light on the complex interplay among sample size, sampling design, ITV, and environmental gradients. [ABSTRACT FROM AUTHOR]

Coral calcification is critical for reef growth and highly dependent on environmental conditions. Yet, little is known about how corals calcify under sub-optimal conditions (e.g., turbid waters, high nutrients, sedimentation) or coral growth in understudied regions such as the Colombian Caribbean. We therefore assessed the calcification and linear extension rates of five coral species across an inshore-to-offshore gradient in the Colombian Caribbean. A suite of environmental variables (temperature, light intensity, visibility, pH, nutrients) measured during the rainy season (May – November 2022) demonstrated more sub-optimal conditions inshore compared to offshore. Across all species, calcification rates were 59% and 37% lower inshore compared to the offshore and midshore sites, respectively. Across all sites, massive corals calcified up to 92% more than branching species but were more susceptible to heat stress and sub-optimal inshore conditions. However, branching species had reduced survival due to extreme climatic events (i.e., bleaching, hurricanes). A comparison with published rates for the wider Caribbean revealed that massive species in the Colombian Caribbean grow up to 11 times more than those in the wider Caribbean while branching species generally have similar growth rates, but this finding may have been influenced by fragment size and/or heat stress. Our findings indicate that present-day environmental conditions, coupled with more frequent extreme climatic events, will favor massive over branching species in midshore areas of the Colombian Caribbean. This suggests a possible shift towards faster calcifying massive species in future coral communities, possibly exacerbating the ongoing regional decline in branching species over the last decades. [ABSTRACT FROM AUTHOR]

Background and Aims Latitudinal diversity gradients have been intimately linked to the tropical niche conservatism hypothesis, which posits that there has been a strong filter due to the challenges faced by ancestral tropical lineages to adapt to low temperatures and colonize extra-tropical regions. In liverworts, species richness is higher towards the tropics, but the centres of diversity of the basal lineages are distributed across extra-tropical regions, pointing to the colonization of tropical regions by phylogenetically clustered assemblages of species of temperate origin. Here, we test this hypothesis through analyses of the relationship between macroclimatic variation and phylogenetic diversity in Chinese liverworts. Methods Phylogenetic diversity metrics and their standardized effect sizes for liverworts in each of the 28 regional floras at the province level in China were related to latitude and six climate variables using regression analysis. We conducted variation partitioning analyses to determine the relative importance of each group of climatic variables. Key Results We find that the number of species decreases with latitude, whereas phylogenetic diversity shows the reverse pattern, and that phylogenetic diversity is more strongly correlated with temperature-related variables compared with precipitation-related variables. Conclusions We interpret the opposite patterns observed in phylogenetic diversity and species richness in terms of a more recent origin of tropical diversity coupled with higher extinctions in temperate regions. [ABSTRACT FROM AUTHOR]

Many cooperatively breeding species live in groups with complex structure—large group sizes, low and variable kin structure, and multiple breeding pairs. Since these mixed‐kin groups typically form because of immigration of unrelated individuals of both sexes in addition to limited offspring dispersal, differences in patterns of dispersal can generate variation in group structure, even within the same species or population. Here, we examine how environmentally mediated dispersal patterns influence variation in group structure in the plural breeding superb starling (Lamprotornis superbus), an avian cooperative breeder that inhabits a spatiotemporally variable savanna environment and forms mixed‐kin groups with variable group sizes and more than one breeding pair per group. Using 4068 genome‐wide polymorphic loci and fine‐scale, remotely sensed ecological data from 22 groups sampled across a nearly 200 km2 environmental gradient in central Kenya, we find evidence of not only frequent and long‐distance dispersal in both sexes (low isolation‐by‐distance and weak genetic structure), but also directional dispersal from small groups in lower quality habitat with low normalised difference vegetation index (NDVI) to large groups in higher quality habitat with high NDVI. Additionally, we find stronger genetic structure among groups in lower quality habitat, and higher genetic diversity and lower relatedness of groups in higher quality habitat. Previous work using long‐term data from groups in the same population has shown that groups with lower relatedness are larger and have more breeding pairs. Long‐distance, directional dispersal to maximise individual fitness can thus lead to smaller and simpler kin‐based social groups in lower quality habitat, but larger and more complex mixed‐kin groups in higher quality habitat. Such intraspecific, within‐population variation in group structure, including variation in kin structure of social groups, could have profound implications for the relative importance of the evolutionary mechanisms (i.e. direct vs. indirect fitness benefits) underlying the formation of cooperative societies. [ABSTRACT FROM AUTHOR]

How communities of living organisms assemble has long been a central question in ecology. The impact of habitat filtering and limiting similarity on plant community structures is well known, as both processes are influenced by individual responses to environmental fluctuations. Yet, the precise identifications and quantifications of the potential abiotic and biotic factors that shape community structures at a fine scale remains a challenge. Here, we applied null model approaches to assess the importance of habitat filtering and limiting similarity at two spatial scales. We used 63 natural vegetation plots, each measuring 5 × 5 m, with three nested subplots measuring 1 × 1 m, from the 2021 field survey, to examine the alpha diversity as well as beta diversity of plots and subplots. Linear mixed‐effects models were employed to determine the impact of environmental variables on assembly rules. Our results demonstrate that habitat filtering is the dominant assembly rules at both the plot and subplot levels, although limiting similarity assumes stronger at the subplot level. Plot‐level limiting similarity exhibited a positive association with fine‐scale partitioning, suggesting that trait divergence originated from a combination of limiting similarity and spatial partitioning. Our findings also reveal that the community assembly varies more strongly with the mean annual temperature gradient than the mean annual precipitation. This investigation provides a pertinent illustration of non‐random assembly rules from spatial scale and environmental factors in plant communities in the loess hilly region. It underscores the critical influence of spatial and environmental constraints in understanding the assembly of plant communities. [ABSTRACT FROM AUTHOR]

Silicon (Si) content in plant tissues is considered a functional trait that can provide multiple morpho‐physiological benefits to plant individuals. However, it is still unclear whether and how these individual benefits extend to plant community processes and ecosystem functioning. Here we investigated how plant Si content is associated with plant community properties and the ecosystem structure of herbaceous communities in Israel. We sampled 15 sites across the Mediterranean and desert ecosystems and built models to evaluate how plant silicon content (community‐weighted mean and standard variation) is associated with variables such as species richness, biomass production, plant cover, and functional diversity. Finally, we used model selection techniques to test whether models depicting plant Si content perform better than models using data on soil Si instead. Sites with lower susceptibility to drought had significantly more Si‐accumulating grass species and higher soils Si content. Models with plant Si content instead of soil Si, always performed better, although those considering Si content variation had overall stronger associations with community properties than only mean Si content. For instance, up to 51% of plant Si content variation was explained by climate, biomass production, and species richness, combined. Still, mean plant Si content and plant cover combined explained up to 42% of plant functional diversity. Our results suggest the that plant Si content serves as a proxy for understanding the ecological properties and functioning of arid and Mediterranean ecosystems. Nevertheless, the significance of Si has not been fully explored in other ecosystem types, where its influence may be less pronounced compared with the ecosystems examined in this study. In light of various global change scenarios, enhancing our understanding of Si as a plant functional trait could help bridge existing knowledge gaps and improve ecological modeling, thus enabling more accurate forecasts of changes in plant distributions. [ABSTRACT FROM AUTHOR]

Elucidating changes in the structure and function of plant communities along different elevation ranges will help researchers to analyze the strategies plant communities use in environments and processes influencing niche differentiation. The aims of this paper are to reveal the underlying mechanisms and ecological processes governing the development of subtropical forest ecosystem plant communities. This paper analyzes the forest vegetation of the Wuyi Mountains across the following three elevation ranges: low elevation, mid elevation, and high elevation, spanning from 560 to 2150 m. Twenty and twenty-three dominant tree and shrub layer species, respectively, were identified based on their importance values, and their niches and species associations were further analyzed based on the elevation range. The results showed interspecific associations between tree and shrub species, with the strongest associations observed at mid-elevations. The analysis of niche width and overlap showed that the number of pairs of species with a higher degree of niche overlap decreased with increasing elevation, suggesting that resource use varied at different elevations for both tree and shrub layer species, which may be related to the adaptive capacity of plants at different elevations to the environment and resource use strategies. These findings should contribute to a deeper understanding of the ecological functioning and structural framework of plant communities on Wuyi Mountain. [ABSTRACT FROM AUTHOR]

Plants adjust to abiotic conditions by changing their anatomical, morphological, and physiological traits. Traits can vary independently or in an integrated manner, known as trait variation and covariation respectively. It has been hypothesized that a trade-off would emerge along a gradient of abiotic constraints in which trait variation would be favored under resource-rich conditions while covariation under resource-limited ones. Although many studies have provided empirical support for this trade-off, a consensus has not yet emerged, due to a lack of support in some cases. This study investigated variation and covariation in three leaf and four wood traits of 74 woody species from a rainforest, a semideciduous forest, and a Restinga heath vegetation in the Atlantic Forest, which are subjected to different water-related constraints. We asked: Is there a variation-covariation trade-off within and across vegetation types? How does incorporating intraspecific variability change the magnitude and pattern of trait covariation? We found a variation-covariation trade-off and a positive relationship both within and across vegetation types. Wood variation was higher and covariation was lower in the rainforest, likely due to the greater water availability. Conversely, wood trait covariation was higher and variation was lower in the Restinga and seasonal semideciduous forest. Differences between vegetation types are likely related to the species' strategies to prevent hydraulic failure, particularly for Restinga species that adjust their wood density and xylem vessel density in a coordinated manner. Accounting for intraspecific trait variability increased covariation across all vegetation types, particularly in the Restinga. This highlights the loss of functional information when analyses are based solely on species' mean trait values. Our results also contribute to this discussion by providing evidence that the trade-off or a positive relationship between trait variation and covariation may be context-dependent. [ABSTRACT FROM AUTHOR]

Selection pressures differ along environmental gradients, and traits tightly linked to fitness (e.g., the visual system) are expected to track such variation. Along gradients, adaptation to local conditions might be due to heritable and nonheritable environmentally induced variation. Disentangling these sources of phenotypic variation requires studying closely related populations in nature and in the laboratory. The Nicaraguan lakes represent an environmental gradient in photic conditions from clear crater lakes to very turbid great lakes. From two old, turbid great lakes, Midas cichlid fish (Amphilophus cf. citrinellus) independently colonized seven isolated crater lakes of varying light conditions, resulting in a small adaptive radiation. We estimated variation in visual sensitivities along this photic gradient by measuring cone opsin gene expression among lake populations. Visual sensitivities observed in all seven derived crater lake populations shifted predictably in direction and magnitude, repeatedly mirroring changes in photic conditions. Comparing wild-caught and laboratory-reared fish revealed that 48% of this phenotypic variation is genetically determined and evolved rapidly. Decreasing intrapopulation variation as environments become spectrally narrower suggests that different selective landscapes operate along the gradient. We conclude that the power to predict phenotypic evolution along gradients depends on both the magnitude of environmental change and the selective landscape shape. [ABSTRACT FROM AUTHOR]

Sexual dimorphism can evolve in response to sex-specific selection pressures that vary across habitats. We studied sexual differences in subterranean amphipods Niphargus living in shallow subterranean habitats (close to the surface), cave streams (intermediate), and cave lakes (deepest and most isolated). These three habitats differ because at greater depths there is lower food availability, reduced predation, and weaker seasonality. Additionally, species near the surface have a near-even adult sex ratio (ASR), whereas species from cave lakes have a female-biased ASR. We hypothesized (a) a decrease in sexual dimorphism from shallow subterranean habitats to cave lake species because of weaker sexual selection derived from changes in the ASR and (b) an increase in female body size in cave lakes because of stronger fecundity selection on account of oligotrophy, reduced predation, and weaker seasonality. We measured body size and two sexually dimorphic abdominal appendages for all 31 species and several behaviours related to male competition (activity, risk-taking, exploration) for 12 species. Species with an equal ASR that live close to the surface exhibited sexual dimorphism in all three morphological traits, but not in behaviour. The body size of females increased from the surface to cave lakes, but no such trend was observed in males. In cave lake species, males and females differed neither morphologically nor behaviourally. Our results are consistent with the possibility that sexual and fecundity selection covary across the three habitats, which indirectly and directly, respectively, shape the degree of sexual dimorphism in Niphargus species. [ABSTRACT FROM AUTHOR]

Abstract Understanding the relationship between intraspecific trait variability (ITV) and its biotic and abiotic drivers is crucial for advancing population and community ecology. Despite its importance, there is a lack of guidance on how to effectively sample ITV and reduce bias in the resulting inferences. In this study, we explored how sample size affects the estimation of population‐level ITV, and how the distribution of sample sizes along an environmental gradient (i.e., sampling design) impacts the probabilities of committing Type I and II errors. We investigated Type I and II error probabilities using four simulated scenarios which varied sampling design and the strength of the ITV‐environment relationships. We also applied simulation scenarios to empirical data on populations of the small mammal, Peromyscus maniculatus across gradients of latitude and temperature at sites in the National Ecological Observatory Network (NEON) in the continental United States. We found that larger sample sizes reduce error rates in the estimation of population‐level ITV for both in silico and Peromyscus maniculatus populations. Furthermore, the influence of sample size on detecting ITV‐environment relationships depends on how sample sizes and population‐level ITV are distributed along environmental gradients. High correlations between sample size and the environment result in greater Type I error, while weak ITV–environmental gradient relationships showed high Type II error probabilities. Therefore, having large sample sizes that are even across populations is the most robust sampling design for studying ITV‐environment relationships. These findings shed light on the complex interplay among sample size, sampling design, ITV, and environmental gradients.

Plants growing outside their native range may be confronted by new regimes of herbivory, but how this affects plant chemical defence profiles has rarely been studied.Using Plantago lanceolata as a model species, we investigated whether introduced populations show significant differences from native populations in several growth and chemical defence traits. Plantago lanceolata (ribwort plantain) is an herbaceous plant species native to Europe and Western Asia that has been introduced to numerous countries worldwide.We sampled seeds from nine native and 10 introduced populations that covered a broad geographic and environmental range and performed a greenhouse experiment, in which we infested half of the plants in each population with caterpillars of the generalist herbivore Spodoptera littoralis. We then measured size‐related and resource‐allocation traits as well as the levels of constitutive and induced chemical defence compounds in roots and shoots of P. lanceolata.When we considered the environmental characteristics of the site of origin, our results revealed that populations from introduced ranges were characterized by an increase in chemical defence compounds without compromising plant biomass. The concentrations of iridoid glycosides and verbascoside, the major anti‐herbivore defence compounds of P. lanceolata, were higher in introduced populations than in native populations. In addition, introduced populations exhibited greater rates of herbivore‐induced volatile organic compound emission and diversity, and similar chemical diversity based on untargeted analyses of leaf methanol extracts.In conclusion, the geographic origin of the populations had a significant influence on morphological and chemical plant traits, suggesting that P. lanceolata populations are not only adapted to different environments in their native range, but also in their introduced range. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The separation of sexes in dioecious plants enables males and females to adopt different strategies to balance reproduction and growth, but can also lead to female susceptibility due to their high reproductive burden. Understanding if a dioecious species is susceptible or adaptable in the face of worsening abiotic conditions would be useful for revegetating habitats under climate change. Our study compared four populations of the Australian native shrub, Pimelea microcephala subsp. microcephala (n = 885) across an annual rainfall gradient of ∼250–400 mm to understand the impact of decreasing rainfall on size classes, growth metrics, sex ratio, the proportion of juveniles and spatial distributions. We found that irrespective of site rainfall, male and female plants achieved similar sizes. The populations exhibited four size classes, defined by height, diameter and sex, but not site rainfall (unpaired group method with arithmetic mean cluster analysis, p <.05). Spatially, populations reflected the clumped distribution of overlying canopy cover, and did not demonstrate niche partitioning between sexes. The lack of population variation with rainfall indicates that the species may be suitable for arid zone revegetation in arid regions with declining rainfall. Conservation management of the species should include maintaining canopy tree cover to encourage seed dispersal. [ABSTRACT FROM AUTHOR]

Rapid evolution in colonising populations can alter our ability to predict future range expansions. Recent theory suggests that the dynamics of replicate range expansions are less variable, and hence more predictable, with increased selection at the expanding range front. Here, we test whether selection from environmental gradients across space produces more consistent range expansion speeds, using the experimental evolution of replicate duckweed populations colonising landscapes with and without a temperature gradient. We found that the range expansion across a temperature gradient was slower on average, with range‐front populations displaying higher population densities, and genetic signatures and trait changes consistent with directional selection. Despite this, we found that with a spatial gradient range expansion speed became more variable and less consistent among replicates over time. Our results therefore challenge current theory, highlighting that chance can still shape the genetic response to selection to influence our ability to predict range expansion speeds. [ABSTRACT FROM AUTHOR]

Brazilian moist forests and savannas are some of the most species-rich biomes in the Neotropics. In the transition zones between these regions, ecotones often accumulate even higher taxonomic diversity. However, whether these ecotonal communities consist of overlapping species widespread from the neighbouring biomes or a specific set of locally adapted species still needs to be clarified. Regional differences in species richness may be influenced by factors such as species' environmental tolerances, life forms, or species' range sizes. To investigate the species richness found in ecotones, we used the 'milk-weed' family (Apocynaceae), which comprises both widespread and narrowly distributed trees, lianas, and shrubs, as a model to evaluate if (i) their observed richness in ecotones is promoted by widespread species or by locally adapted species; (ii) trees, lianas, and shrubs show different richness patterns in savannas, ecotones, and forests; and (iii) species found in ecotones have broader environmental tolerances than other species in the family. We used a taxonomically curated georeferenced dataset to compare the range sizes of 643 species of Apocynaceae from 73 genera listed for Brazil, comprising 298 species with a liana life form and 345 trees, herbs, or shrubs. We recorded 335 predominantly forest species, 56 savanna species, and 152 ecotone species, for which we quantified species richness, areas of occurrence, precipitation, and temperature ranges and tested for differences in range sizes and environmental tolerances between habits and ecoregions. Our results indicate that (i) Apocynaceae species occurring in ecotones have wider geographical ranges than species not occurring in ecotones; (ii) lianas showed higher area-weighted richness in ecotones than other life forms; and (iii) species found in ecotones had broader environmental tolerances than species restricted to moist forests or savannas. These results indicate that the species richness found in ecotones between savannas and moist forests in Brazil is not necessarily a consequence of higher endemism and local adaptation but may also be a result of overlapping ranges of widespread species typically associated with neighbouring biomes. Together, our findings add to our understanding of ecotones and biomes as continuous, gradual biogeographical transitions instead of sharply defined ecological units. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Silicon (Si) content in plant tissues is considered a functional trait that can provide multiple morpho‐physiological benefits to plant individuals. However, it is still unclear whether and how these individual benefits extend to plant community processes and ecosystem functioning. Here we investigated how plant Si content is associated with plant community properties and the ecosystem structure of herbaceous communities in Israel. We sampled 15 sites across the Mediterranean and desert ecosystems and built models to evaluate how plant silicon content (community‐weighted mean and standard variation) is associated with variables such as species richness, biomass production, plant cover, and functional diversity. Finally, we used model selection techniques to test whether models depicting plant Si content perform better than models using data on soil Si instead. Sites with lower susceptibility to drought had significantly more Si‐accumulating grass species and higher soils Si content. Models with plant Si content instead of soil Si, always performed better, although those considering Si content variation had overall stronger associations with community properties than only mean Si content. For instance, up to 51% of plant Si content variation was explained by climate, biomass production, and species richness, combined. Still, mean plant Si content and plant cover combined explained up to 42% of plant functional diversity. Our results suggest the that plant Si content serves as a proxy for understanding the ecological properties and functioning of arid and Mediterranean ecosystems. Nevertheless, the significance of Si has not been fully explored in other ecosystem types, where its influence may be less pronounced compared with the ecosystems examined in this study. In light of various global change scenarios, enhancing our understanding of Si as a plant functional trait could help bridge existing knowledge gaps and improve ecological modeling, thus enabling more accurate forecasts of changes in plant distributions.

Abstract How communities of living organisms assemble has long been a central question in ecology. The impact of habitat filtering and limiting similarity on plant community structures is well known, as both processes are influenced by individual responses to environmental fluctuations. Yet, the precise identifications and quantifications of the potential abiotic and biotic factors that shape community structures at a fine scale remains a challenge. Here, we applied null model approaches to assess the importance of habitat filtering and limiting similarity at two spatial scales. We used 63 natural vegetation plots, each measuring 5 × 5 m, with three nested subplots measuring 1 × 1 m, from the 2021 field survey, to examine the alpha diversity as well as beta diversity of plots and subplots. Linear mixed‐effects models were employed to determine the impact of environmental variables on assembly rules. Our results demonstrate that habitat filtering is the dominant assembly rules at both the plot and subplot levels, although limiting similarity assumes stronger at the subplot level. Plot‐level limiting similarity exhibited a positive association with fine‐scale partitioning, suggesting that trait divergence originated from a combination of limiting similarity and spatial partitioning. Our findings also reveal that the community assembly varies more strongly with the mean annual temperature gradient than the mean annual precipitation. This investigation provides a pertinent illustration of non‐random assembly rules from spatial scale and environmental factors in plant communities in the loess hilly region. It underscores the critical influence of spatial and environmental constraints in understanding the assembly of plant communities.

Abstract Background Understanding community assembly mechanisms across taxa and space is fundamental for microbial ecology. However, the variability and determinants of assembly processes over taxa and space remain unclear. Here, we investigated taxonomic dependency and spatial heterogeneity in bacterial assembly mechanisms across coastal waters in the East China Sea using neutral and null models with customized visualization strategies. Results Overall, bacterial assembly mechanisms varied across broad taxonomic groups (phyla and proteobacterial classes) and space at the regional scale. A determinism–stochasticity balanced mechanism governed total bacterial assembly, while taxonomic dependency existed in assembly mechanisms and ecological processes. Among community ecological features, niche breadth and negative-to-positive cohesion ratio were strongly associated with the determinism-to-stochasticity ratio of bacterial groups. Bacterial assembly mechanisms commonly exhibited spatial heterogeneity, the extent and determinants of which varied across taxonomic groups. Spatial assembly of total bacteria was directly driven by many environmental factors and potential interactions between taxa, but not directly by geographic factors. Overall, the bacterial groups with higher spatial heterogeneity in assembly mechanisms were more related to environmental and/or geographic factors (except Bacteroidetes), while those with lower heterogeneity were more related to ecological features. Conclusions Our results confirm the pervasiveness of taxonomic dependency and spatial heterogeneity in bacterial assembly, providing a finer understanding about regulation across complex coastal waters.

This study was carried out to examine modelling the effects of environmental gradients on bloom-forming Cyclotella species. Plankton samples were collected with a 20 µm mesh plankton net. The physicochemical characteristics were determined in situ, and the nutrients were analyzed in the laboratory using the APHA 2012. The highest mean cell density of 355.43±49.55 Cells L-1 was recorded in station 4, and the lowest of 63.33±17.02 Cells L-1 in station 2 for C. antiqua. In contrast, 360.81±70.05 Cells L-1 was recorded in station 3, with the lowest of 204.67±61.67 Cells L-1 in station 2 for C. meneghiniana spp. respectively. Principal component analysis revealed that TDS, DO, PO4, NO3 and NO2. In contrast, a positive relationship, while pH and salinity had a negative relationship with C. antiqua. Nitrite, TDS, and DO show a positive relationship, while salinity, phosphate, temperature, and pH negatively correlated with C. meneghiniana across stations. TDS, DO, and NO2 were the most used forecast predictors for Cyclotella spp., which were positively correlated. The observed data were compared with the simulated result. Cyclotella antiqua and meneghiniana increased with a rise in TDS and NO2 as the forecast predictors to ascertain its effect on the predicted species. The increasing human-induced anthropogenic pressure is primarily influencing the eutrophication of water. With an increase in nutrients (TDS and NO2), that species may form a bloom. There is a need for best management practices to address nutrient discharge in the central Bonny estuary.

Plant hydraulic traits are essential for understanding and predicting plant drought resistance. Investigations into the mechanisms of the xylem anatomical traits of desert shrubs in response to climate can help us to understand plant survival strategies in extreme environments. This study examined the xylem anatomical traits and related functional traits of the branches of seven Calligonum mongolicum populations along a precipitation gradient, to explore their adaptive responses to climatic factors. We found that (1) the vessel diameter (D), vessel diameter contributing to 95% of hydraulic conductivity (D95), hydraulic weighted vessel diameter (Dh), vessel density (VD), percentage of conductive area (CA), thickness-to-span ratio of vessels ((t/b)2), and theoretical hydraulic conductivity (Kth) varied significantly across sites, while the vessel group index (Vg), wood density (WD), and vulnerability index (VI) showed no significant differences. (2) Principal component analysis revealed that efficiency-related traits (Kth, Dh, D95) and safety-related traits (VI, VD, inter-wall thickness of the vessel (t)) were the primary factors driving trait variation. (3) Precipitation during the wettest month (PWM) had the strongest influence, positively correlating with (t/b)2 and negatively with D, D95, Dh, CA, and Kth. (4) Structural equation modeling confirmed PWM as the main driver of Kth, with indirect effects through CA. These findings indicate that C. mongolicum displays high plasticity in xylem traits, enabling adaptation to changing environments, and providing insight into the hydraulic strategies of desert shrubs under climate change.

Abstract Introduction Harnessing positive plant–soil feedbacks via crop rotations is a promising strategy for sustainable agriculture. These feedbacks are often context‐dependent, and how soil heterogeneity explains this variation is unknown. Plants influence soil properties, including microbes, by exuding specialized metabolites. Benzoxazinoids, specialized metabolites released by cereals such as wheat and maize, can alter rhizosphere microbiota and performance of plants subsequently growing in the exposed soils and are thus an excellent model to study agriculturally relevant plant–soil feedbacks. Materials and Methods To understand local variation in soil properties on benzoxazinoid‐mediated plant–soil feedbacks, we conditioned plots with wild‐type maize and benzoxazinoid‐deficient bx1 mutants in a grid pattern across a field, and we then grew winter wheat in the following season. We determined accumulation of benzoxazinoids, root‐associated microbial communities, abiotic soil properties and wheat performance in each plot and then assessed their associations. Results We detected a marked gradient in soil chemistry and microbiota across the field. This gradient resulted in significant differences in benzoxazinoid accumulation, which were explained by differential benzoxazinoid degradation rather than exudation. Benzoxazinoid exudation modulated microbial diversity in root and rhizospheres during maize growth, but not during subsequent wheat growth, while the chemical fingerprint of benzoxazinoids persisted. Averaged across the field, we did not detect feedbacks on wheat performance and defence, apart from a transient decrease in biomass during vegetative growth. Closer analysis, however, revealed significant feedbacks along the chemical and microbial gradient of the field, with effects gradually changing from negative to positive along the gradient. Conclusion Overall, this study revealed that plant–soil feedbacks differ in strength and direction within a field and that this variation can be explained by standing chemical and microbial gradients. Understanding within‐field soil heterogeneity is crucial for the future exploitation of plant–soil feedbacks in sustainable precision agriculture.

Climate change has been increasing the frequency and severity of drought periods. There is a need to understand how this water scarcity affects aquatic communities. The main aim of this work was to compare the macroinvertebrate communities and their bioindicator value (ecological status sensu the Water Framework Directive) in three Regions [northeast (N), central (C) and south (S)] of Portugal along a water availability and climate gradient, in two consecutive years that reflect hydrologically distinct scenarios (2018 versus 2019). The period prior to sampling (summer and autumn 2017) was extremely dry and hot, whereas climatic fluctuations in 2018–2019 (when the sampling occurred) were closer to the norm. A total of 28 sampling sites were surveyed in streams of Regions where water scarcity is differentially constitutive. The results showed a consistent environmental and ecological gradient in both years, despite the background differences. A coinciding mineralization, temperature, riparian cover and water availability gradient clearly separated Regions C (wettest) and S (driest), with Region N occupying an intermediate position. Region C had overall higher ecological quality (prevalence of sensitive organisms) in both years. Despite our a priori expectations that 2018 would represent a much more stressful condition, with larger differences across Regions (because of their constitutive background), the data suggest that macroinvertebrate communities may be resilient or adapted, to some degree, to hydrological fluctuations. Signs of more favourable conditions in 2019 were also observed (general improvement in ecological status). Studies across hydrological and climatic gradients (in time and space) are particularly important where water availability is becoming more challenging. [ABSTRACT FROM AUTHOR]

Understanding the drivers of variability in plant diversity from local to landscape spatial scales is a challenge in ecological systems. Environmental gradients exist at several spatial scales and can be nested hierarchically, influencing patterns of plant diversity in complex ways. As plant community dynamics influence ecosystem function, understanding the drivers of plant community variability across space is paramount for predicting potential shifts in ecosystem function from global change. Determining the scales at which stress gradients influence vegetation composition is crucial to inform management and restoration of tidal marshes for specific functions. Here, we analyzed vegetation community composition in 51 tidal marshes from the San Francisco Bay Estuary, California, USA. We used model-based compositional analysis and rank abundance curves to quantify environmental (elevation/tidal frame position, distance to channel, and channel salinity) and species trait (species form, wetland indicator status, and native status) influences on plant community variability at the marsh site and estuary scales. While environmental impacts on plant diversity varied by species and their relationships to each other, overall impacts increased in strength from marsh to estuary scales. Relative species abundance was important in structuring these tidal marsh communities even with the limited species pools dominated by a few species. Rank abundance curves revealed different community structures by region with higher species evenness at plots higher in the tidal frame and adjacent to freshwater channels. By identifying interactions (species-species, species-environment, and environment-trait) at multiple scales (local, landscape), we begin to understand how variability measurements could be interpreted for conservation and land management decisions. [ABSTRACT FROM AUTHOR]

Anthropogenic impacts are typically detrimental to tropical coral reefs, but the effect of increasing environmental stress and variability on the size structure of coral communities remains poorly understood. This limits our ability to effectively conserve coral reef ecosystems because size specific dynamics are rarely incorporated. Our aim is to quantify variation in the size structure of coral populations across 20 sites along a tropical‐to‐subtropical environmental gradient on the east coast of Australia (~ 23 to 30°S), to determine how size structure changes with a gradient of sea surface temperature, turbidity, productivity and light levels. We use two approaches: 1) linear regression with summary statistics (such as median size) as response variables, a method frequently favoured by ecologists and 2) compositional functional regression, a novel method using entire size–frequency distributions as response variables. We then predict coral population size structure with increasing environmental stress and variability. Together, we find fewer but larger coral colonies in marginal reefs, where conditions are typically more variable and stressful, than in tropical reefs. Our model predicts that coral populations may become gradually dominated by larger colonies (> 148 cm2) with increasing environmental stress. Fewer but bigger corals suggest low survival of smaller corals, slow growth, and/or poor recruitment. This finding is concerning for the future of coral reefs, as it implies that current marginal populations, or future reefs in increasingly stressful environmental conditions may have low recovery potential. We highlight the importance of continuously monitoring changes to population structure over biogeographic scales. [ABSTRACT FROM AUTHOR]

Mean fire interval (MFI) is the average time between successive fires, influenced by environmental factors such as latitude, elevation, and vegetation type. This study evaluated the relationship between MFI and latitude in conifer forests of western North America. First, we obtained pre-fire-disruption MFI data from dendrochronology-based fire history studies in western Canada, the United States, and Mexico montane ranges. Then, we used generalized additive models (GAMs) to evaluate the relationship between MFI and latitude, considering elevation and conifer forest type as covariables. In addition, we mapped the spatial mean fire intervals (SMFIs) through inverse distance weighting (IDW). MFI increased significantly at higher latitudes, influenced by elevation and conifer forest type (R2 = 0.7). Furthermore, we found longer MFI in high elevations of the Madrean Archipelago, the Rocky Mountains, and the Alaska Range. Fire frequency also decreased in the boreal, Douglas-fir, and subalpine forests, with MFI longer than 20 yr. Moreover, the shortest SMFIs were found in the Mexican sierras and the Madrean Archipelago, with fire intervals between 4.1 and 5.6 yr. Our results showed a latitudinal gradient of MFI in conifer forests of western North America, which provides valuable information for fire management and the restoration of natural fire regimes. [ABSTRACT FROM AUTHOR]

Background. Cleaning symbiotic interactions are an important component of coral reef biodiversity and the study of the characteristics of these interacting species networks allows to assess the health of communities. The coral reefs of Jardines de la Reina National Park (JRNP) are subject to a protection gradient and there is a lack of knowledge about the effect of different levels of protection on the cleaning mutualistic networks in the area. The present study aims to characterize the mutualistic cleaning networks in the reefs of JRNP and to assess the potential effect of the protection gradient on their characteristics. Methods. We visited 26 reef sites distributed along the National Park and performed 96 band transects (50 m × 4 m). Low, medium and highly protected regions were compared according to the number of cleaning stations and the abundance and number of species of clients and cleaners associated with them. Additionally, we built interaction networks for the three regions and the entire archipelago based on a total of 150 minutes' video records of active cleaning stations. Weassessed ecological networks characteristics (specialization, nestedness) using network topological metrics. Results. We found a high diversity and complex cleaning interaction network with 6 cleaner species and 39 client species, among them, the threatened grouper Epinephelus striatus was one of the most common clients. Noclear effect of the protection level on the density, abundance or diversity of cleaners and clients was detected during this study. However, we found that the network structure varied among regions, with the highly protected region being more specialized and less nested than the other regions. Our research reveals some patterns that suggest the effect of fishing pressure on cleaning symbiosis, as fishing may reduce the abundance and composition of client species, especially those that are targeted by fishers. However, fishing pressure may not be the main factor influencing cleaning symbiosis inside of the National Park, as other factors, such as habitat quality or environmental conditions may have stronger effects on the demand for cleaning services and the interactions between cleaners and clients. Our research provides insights into the factors that influence cleaning symbiosis and its implications for coral reef conservation and management. [ABSTRACT FROM AUTHOR]

Much of the remarkable beta diversity of the Amazon biome is associated with the variety of vegetation types and other broad environmental gradients. We investigated ant assemblages in white-sand vegetation, one of the most distinctive vegetation types in the Amazon. Using pitfall traps in trees and on the ground, we comprehensively surveyed the ant assemblages along a natural gradient of vegetation structure, quantified with ground-LiDAR measurements. We collected individuals of 212 ant species/morphospecies distributed across 53 genera and nine subfamilies. Alpha diversity was not correlated with vegetation complexity, but beta diversity varied widely along the vegetation gradient. Species replacement was the predominant beta-diversity component, with smaller contributions from richness differences and nestedness. Terrestrial species composition was affected by vegetation structure, but arboreal species were more uniformly distributed along the vegetation-complexity gradient. Many habitat-generalist species (sampled in terrestrial and arboreal stratum) were sampled in less-complex parts of the gradient, suggesting that vertical stratification is diluted in more open vegetation. Our data indicate that the high species replacement in a small area increases the conservation value of this vegetation type by allowing much greater overall diversity than would be predicted by local alpha diversity. Implications for insect conservation: Our study demonstrates a remarkable ant-species replacement along a gradient of white-sand vegetation and highlights the importance of conserving this fragile environment, which is threatened by fire, deforestation, and mining. [ABSTRACT FROM AUTHOR]

Questions: Trait–environment relationships hold great promise for elucidating the mechanisms that drive community assembly. We asked to what extent does functional trait coordination underlie the differentiation of acquisitive–conservative strategies along environmental gradients? Also, to what extent does soil water availability determine trait combinations and subsequently shape microhabitat preferences for species with distinct ecological strategies? Location: Yunnan Province, southwest China. Methods: Pearson correlation and trait network analyses were used to quantify trait associations. A combined RLQ–fourth‐corner analysis and a spatial autoregressive error model were employed to examine trait–environment relationships and explain species distribution along environmental gradients. Results: Leaf and stem traits were tightly coordinated along the first RLQ axis. Herein, traits representing construction cost exhibited trade‐offs against traits representing resource acquisition rate, underlying an acquisitive–conservative strategy differentiation along the environmental gradients. Significant overall and bivariate trait–environment relationships were found. In addition, the topographic wetness index contributed substantially to the environmental variation, and significantly influenced most traits alone. These results supported the hypothesis that soil water availability was the key environmental factor in selecting trait combinations and driving the differentiation of acquisitive and conservative strategies for coexisting species compared with other environmental factors. Finally, deciduous and a proportion of the evergreen species were acquisitive, whereas the remaining evergreen species were conservative, preferring wetter and drier microhabitats, respectively. Conclusions: Our findings indicate that soil water availability plays a central role in shaping both the trait combinations and microhabitat preferences of species with different ecological strategies rather than different leaf habits. These findings also highlight the fundamental significance of functional traits in facilitating the differentiation between acquisitive and conservative strategies along environmental gradients. [ABSTRACT FROM AUTHOR]

Question: Predicting the functional response of vegetation to environmental variations remains highly challenging. A first reason is that trait–environment relationships result from joint intraspecific and interspecific responses. A second reason is that most plant communities host sets of species that are expected to display different environmental responses according to their ecophysiological strategies. Location: Mediterranean rangeland, Larzac Plateau, France ("La Fage" INRAE experimental station: 43°55′ N, 3°05′ E). Methods: In a Mediterranean rangeland, we tested whether changes in trait values in response to management intensification (increased resource availability and grazing intensity) differ between annuals and perennials that coexist locally. To capture the multiple facets of plant phenotypes, we studied nine traits related to carbon acquisition and conservation, plant size, water‐use efficiency, phenology and reproduction. Results: For most traits, we evidenced a significant interaction between environment and life history. In particular, changes in trait values were higher in perennials for leaf traits related to tissue density and growth. These differences were explained by: (a) a lower species turnover in annuals, and (b) the presence of species with more distinct trait values across environments in perennials. For most traits, these changes were not accompanied by differential intraspecific variations between annuals and perennials, which invalidates previous theoretical predictions. In addition, the contribution of intraspecific trait variation to among‐communities trait variance was higher for annuals than perennials for most traits. Conclusion: Altogether, our findings highlight that changes in trait values with the environment can depend on functional groups (here, life history), which can further critically impact the assessment of the functional response of communities. They challenge the mean field approaches to communities in which trait aggregation is most often blindly applied, without considering potential different trajectories in response to environmental changes at various nested organizational levels. [ABSTRACT FROM AUTHOR]

One of J.P. Grime's greatest achievements was demonstrating the importance of the relationship between the environment and plant functional traits for understanding community assembly processes and the effects of biodiversity on ecosystem functioning. A popular approach assessing trait–environment relationships is the community weighted means (CWMs) method, which evaluates changes in communities' average trait values along gradients, with Grime being among its first practitioners.Today the CWM method is well‐established but some scholars have criticized it for inflated Type I errors. That is, in some scenarios of compositional turnover along a gradient, CWM tests can provide significant results even for randomly generated traits. Null models have been proposed to correct for such effects by randomizing trait values across species (CWM‐sp). We review different approaches relating traits to the environment within the framework of the accepted dichotomy between species‐level (observations are species) versus community‐level (observations are community parameters) analyses. Between these families of analyses and their combinations, a great variety of methods exist that test different trait–environment relationships, each with different null hypotheses and ecological questions.In classic CWM tests, the null hypothesis focuses on characteristics of trait distributions at the community level along gradients. The Type I error rate should not be a priori considered inflated when this test is used to identify changes in community trait structure affecting the functioning of communities. Trait changes observed with CWM tests may be accurate, but the interpretation that a specific trait drives turnover may be fallacious. Approaches like CWM‐sp may be more appropriate for testing other ecological hypotheses, such as whether trait–environment relationships are widespread across species. In effect, this moves the ecological focus towards species‐level analyses, that is on the adaptive value of traits and their relation to species niches.Synthesis. There is no single trait–environment relationship. Species‐level and community‐level analyses, including variants within them, test different relationships with different null hypotheses, such that the potential for inflated error rates can be misleading. Using a spectrum of methods provides a comprehensive picture of the diversity of trait–environment relationships. [ABSTRACT FROM AUTHOR]

Climate change causes considerable shifts in the geographic distribution of species worldwide. Most data on range movements, however, derive from relatively short periods, within which it is difficult to distinguish directional shifts from random fluctuations. For detecting a shift, it is indispensable to delineate the range precisely. We propose a new method for the delineation based on percolation theory. We suggest marking the boundary between the connected and fragmented occurrence of the species (the hull). We demonstrate the advantages of this connectivity‐based method on simulated examples in which a metapopulation is advancing vs retreating along an environmental gradient with different velocities. The simulations show that the hull is a fractal and has the same dimension (7/4) even when the front is advancing or retreating relatively fast, compared to the generation time. It is particularly robust in the retreating (trailing) edge. Accordingly, we propose marking the range edge at the mean position of the hull, the 'connectivity limit' of the species. Theoretical considerations suggest that the position of the connectivity limit is statistically more reliable than those limits that are delineated according to the outermost occurrences, and the connectivity‐based method is broadly applicable to real‐life data. [ABSTRACT FROM AUTHOR]

Environmental heterogeneity can influence the formation of different vegetation types, even at small spatial scales. However, little is known about the factors that drive communities at local scales and species' mechanisms to adapt to different environments. Here, we investigated the influence of local environmental conditions and spatiality on the floristic variation of woody vegetation and ecological strategies of shrub‐tree species in the Brazilian savanna. We sampled adjacent sites in three substrate types—deep soil at high altitude (in Red Oxisol, with vegetation locally called Typical Cerrado—TCRO), deep soil, sandy and at low elevation (Typical Cerrado in Entisol Quartzipsamment—TCEQ), and shallow soil with rocky outcrops at high elevation (in Entisol Lithic, with vegetation known locally as Rupestrian Cerrado—RCEL). At each environment, we inventoried the vegetation, analyzed the physical–chemical soil properties, and recorded the elevation and geographic coordinates. For the most representative species of each site and the most common one among the environments, we evaluated the functional attributes (leaf nutrient concentration, specific leaf area, and maximum population heights). We showed that substrate type and elevation explain most of the floristic variation at the local scale and that the low nutritional demand constitutes the main strategy used by the species in RCEL, while in TCEQ and TCRO, species are more efficient in resource acquisition. Our results revealed that local ecological factors and processes drive species distribution. Therefore, variations in vegetation, even at the local scale must be considered to conserve biodiversity effectively. [ABSTRACT FROM AUTHOR]