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Gradients of environmental variability have been proposed to explain spatial variation in patterns of geographical range size. We explore this relationship in NE Pacific algae and NW Atlantic gastropods by using the characteristics of species’ bathymetric distributions as a proxy for tolerance of environmental variability. NE Pacific and NW Atlantic. Data on species bathymetric and geographical distributions were compiled from the literature. For both algae and gastropods, species that inhabit highly seasonal, shallow depth zones have broader latitudinal ranges, and occupy more biogeographical provinces, than species that live in more temporally stable, deeper zones. Furthermore, species that tolerate spatial variability along the bathymetric axis, i.e. those that occur in multiple depth zones, have broader geographical ranges than species restricted to fewer depth zones. Within-range environmental variability, through both space and time, is predictive of large geographical ranges for marine algae and gastropods. Analysis of species distributions across perpendicular gradients (e.g. depth and latitude) is a powerful approach to discerning the mechanisms that govern biogeographical patterns, and provides easily obtainable broad-brush predictions regarding the biogeographical outcomes of global change. [ABSTRACT FROM AUTHOR]

Aim: Tolerance of species to extreme temperatures largely determines their distribution and vulnerability to climate change. We examined thermal tolerance in tropical and temperate alpine plants, testing the hypotheses that: (a) temperate plants are resistant to more extreme temperatures and have an overall wider thermal tolerance breadth (TTB); (b) TTB in temperate plants is wider than TTB in tropical plants during the entire growing season; (c) resistance to frost and heat varies during the season in temperate plants but not in tropical plants; (d) TTB of a species predicts its latitudinal range. Location: Tropical (Ecuador, Bolivia) and temperate (USA, Austria) mountains. Time period: Four periods of the growing season (2014, 2016–2019). Major taxa: Ninety‐six vascular plant species. Methods: We employed the electrolyte leakage method to estimate the temperature resistance, that is, the temperature at which 50% tissue injury (Lt50) occurs in leaves. We used phylogenetic linear mixed‐effect models in a Bayesian framework to test for differences between the plant groups. Results: Temperate and tropical plants do not differ in their temperature resistance. The four hypotheses are rejected since: (a) temperate plants do not have significantly wider overall TTB compared to tropical plants, (b) TTB of temperate plants is wider than TTB of tropical plants only at the end of the temperate summer, (c) seasonal acclimation is observed in both plant groups, (d) the latitudinal range of the plants is not related to TTB. Main conclusions: The lack of TTB differences between temperate and tropical alpine plants is consistent with trends observed in ectothermic animals, which suggests a general latitudinal pattern in high‐elevation poikilotherm organisms. Limited acclimation capacity to cope with long freezing exposures restricts the occurrence of tropical alpine species to thermally aseasonal environments making them particularly vulnerable to climate change. [ABSTRACT FROM AUTHOR]

Aim: The global vertical depth distribution of seagrass species remains poorly understood. Locally, the abundance and distribution of seagrasses is determined by light penetration, but at global levels each seagrass species has very distinct maximum distributional depth ranges, indicating that plant‐associated traits must also influence their specific depth ranges. Seagrass‐specific attributes, such as plant size or architecture, growth or reproductive strategy and their physiological and/or morphological acclimatization potential, have been suggested to be responsible for this variety of vertical distributions. We investigate here whether these species‐specific traits drive differences in the global maximum vertical distribution of seagrasses. Location: Global. Time period: Publications between 1982 and 2020. Major taxa studied: Seagrasses (order Alismatales). Methods: We tested whether the species‐specific maximum vertical distribution of seagrasses can be predicted by (1) their rhizome diameter (a proxy for plant size); (2) their functional resilience (growth/reproductive strategy); or (3) their acclimatization capacity. For the last aspect, we used a systematic review followed by meta‐analytical approaches to select key seagrass traits that could potentially acclimatize to extreme light ranges across different seagrasses. Results: We found that vertical distribution is best explained by the species‐specific acclimatization capacity of various seagrass traits, including saturation irradiance (physiological trait), leaves per shoot (morphological trait) and above‐ground biomass (structural trait). In contrast, our results indicate no predictive power of seagrass size or growth/reproductive strategy on the vertical distribution of seagrasses. Main conclusions: Across the globe, the ability of seagrass species to thrive at a wide range of depths is strongly linked to the species‐specific acclimatization capacity of key traits at different organizational levels. [ABSTRACT FROM AUTHOR]

Humid tropical alpine environments are crucial ecosystems that sustain biodiversity, biological processes, carbon storage and surface water provision. They are identified as one of the terrestrial ecosystems most vulnerable to global environmental change. Despite their vulnerability, and the importance for regional biodiversity conservation and socio-economic development, they are among the least studied and described ecosystems in the world. This paper reviews the state of knowledge about tropical alpine environments, and provides an integrated assessment of the potential threats of global climate change on the major ecosystem processes. Humid tropical alpine regions occur between the upper forest line and the perennial snow border in the upper regions of the Andes, the Afroalpine belt and Indonesia and Papua New Guinea. Climate change will displace ecosystem boundaries and strongly reduce the total area of tropical alpine regions. Displacement and increased isolation of the remaining patches will induce species extinction and biodiversity loss. Drier and warmer soil conditions will cause a faster organic carbon turnover, decreasing the below-ground organic carbon storage. Since most of the organic carbon is currently stored in the soils, it is unlikely that an increase in above-ground biomass will be able to offset soil carbon loss at an ecosystem level. Therefore a net release of carbon to the atmosphere is expected. Changes in precipitation patterns, increased evapotranspiration and alterations of the soil properties will have a major impact on water supply. Many regions are in danger of a significantly reduced or less reliable stream flow. The magnitude and even the trend of most of these effects depend strongly on local climatic, hydrological and ecological conditions. The extreme spatial gradients in these conditions put the sustainability of ecosystem management at risk. [ABSTRACT FROM AUTHOR]

Aim: An elevated CO2 concentration (eCO2) can increase photosynthesis (Asat) and reduce stomatal conductance (gs); hence, it can benefit tree growth directly by increasing carbon availability and/or indirectly by saving water. However, uncertainties remain regarding the direction and magnitude of these effects, particularly in combination with changes in temperature and water availability. Location: Global. Time period: 1986–2020. Major taxa studied: Trees. Methods: We compiled 3,391 observations from 270 studies and performed a meta‐analysis on: (1) the responses of Asat, gs and intrinsic water‐use efficiency (iWUE) to eCO2, in addition to variations in these responses between species (phylogeny and leaf habit), within species (tree age) and within individuals (canopy position and leaf age); (2) the effects of changes in temperature and/or water availability on these responses; and (3) whether Asat and gs acclimatize to eCO2 in parallel. Results: We found that eCO2 stimulated Asat (β‐factor =.68) and decreased gs (β‐factor = −.36) and that iWUE increased in proportion to eCO2 (β‐factor = 1.01), which conform with the theory of optimal stomatal behaviour. Meanwhile, conifers and older trees showed greater increases in Asat but less decreases in gs than angiosperms and young trees, respectively, with a proportional increase in iWUE being independent of phylogeny and tree age, which support the theory further. Warming had little effect on the responses of Asat and gs to eCO2, whereas drought amplified the Asat response but attenuated the gs response. However, Asat, rather than gs, acclimatized to eCO2, owing to nitrogen reduction, active investment of nitrogen and sink limitation. Main conclusions: Our findings suggest that eCO2 can enhance carbon uptake and reduce water loss at the leaf scale, which may be modified by water stress. This study improves our physiological understanding of tree gas exchange in a changing climate. [ABSTRACT FROM AUTHOR]

Aim: To test if physiological acclimation can buffer species against increasing extreme heat due to climate change. Location: Global. Time period: 1960 to 2015. Major taxa studied: Amphibians, arthropods, brachiopods, cnidarians, echinoderms, fishes, molluscs, reptiles. Methods: We draw together new and existing data quantifying the warm acclimation response in 319 species as the acclimation response ratio (ARR): the increase in upper thermal limit per degree increase in experimental temperature. We develop worst‐case scenario climate projections to calculate the number of years and generations gained by ARR until loss of thermal safety. We further compute a vulnerability score that integrates across variables estimating exposure to climate change and species‐specific tolerance through traits, including physiological plasticity, generation time and latitudinal range extent. Results: ARR is highly variable, but with marked differences across taxa, habitats and latitude. Polar terrestrial arthropods show high ARRs [95% upper confidence limit (UCL95%) = 0.68], as do some polar aquatic invertebrates that were acclimated for extended durations (ARR > 0.4). While this physiological plasticity buys 100s of years until thermal safety is lost, combination with long generation times leads to decreased potential for evolutionary adaptation. Additionally, 27% of marine polar invertebrates have no capacity for acclimation and reptiles and amphibians have minimal ARR (UCL95% = 0.16). Low physiological plasticity, long generations times and restricted latitudinal ranges combine to distinguish reptiles, amphibians and polar invertebrates as being highly vulnerable amongst ectotherms. Main conclusions: In some taxa the combined effects of acclimation capacity and generation time can provide 100s of years and generations before thermal safety is lost. The accuracy of assessments of vulnerability to climate change will be improved by considering multiple aspects of species' biology that, in combination may increase persistence under extreme heat events, and increase the probability for evolutionary rescue. [ABSTRACT FROM AUTHOR]

Aim Predicted distributions of invasive species are often not congruent between their realized native and introduced ranges, but the reasons for this are rarely investigated empirically. We tested for niche shift in an invasive species using a simple framework combining environmental niche models ( ENMs) and niche-limiting thermal tolerance traits. Location Australia and South Africa. Methods The red-legged earth mite, Halotydeus destructor, native to South Africa, is a major agricultural pest in Australia and has expanded its range to areas not predictable from its native range in the last 40 years. Revisiting recently constructed ENMs for H. destructor, we select populations in both native and invasive ranges that appear to occupy different niches. We characterize thermal tolerance traits and test for acclimation patterns of cold tolerance of these H. destructor populations to test for niche shifts. Results Australian populations had an increased upper thermal threshold for movement and were able to recover from cold stress more rapidly than South African populations. Australian populations also differed in trait means from the likely source population in South Africa. Acclimation patterns were conserved across ranges for most populations, with 10 ° C acclimation lowering the onset of and recovery from cold tolerance and 15 ° C raising them when compared with field-acclimated populations. Main conclusions These results support the prediction, based on ENMs, that H. destructor may have undergone a niche shift by adapting to environmental conditions in Australia. The increase in thermal resistance has implications for how this invasive species will respond to future climate change. [ABSTRACT FROM AUTHOR]

Aim Climate change may cause loss of genetic diversity. Here we explore how a multidisciplinary approach can be used to infer effects of past climate change on species distribution and genetic diversity and also to predict loss of diversity due to future climate change. We use the arctic-alpine plant Salix herbacea L. as a model. Location Europe, Greenland and eastern North America. Methods We analysed 399 samples from 41 populations for amplified fragment length polymorphism (AFLP) to identify current patterns of genetic structure and diversity and likely historical dispersal routes. Macrofossil records were compiled to infer past distribution, and species distribution models were used to predict the Last Glacial Maximum (LGM) and future distribution of climatically suitable areas. Results We found strong genetic differentiation between the populations from Europe/East Greenland and those from Canada/West Greenland, indicating a split probably predating the LGM. Much less differentiation was observed among the four genetic groups identified in Europe, and diversity was high in the Scandinavian as well as in southern alpine populations. Continuous distribution in Central Europe during the last glaciation was inferred based on the fossil records and distribution modelling. A 46–57% reduction in suitable areas was predicted in 2080 compared to present. However, mainly southern alpine populations may go extinct, causing a loss of about 5% of the genetic diversity in the species. Main conclusions From a continuous range in Central Europe during the last glaciation, northward colonization probably occurred as a broad front maintaining diversity as the climate warmed. This explains why potential extinction of southern populations by 2080 will cause a comparatively low loss of the genetic diversity in S. herbacea. For other species with different glacial histories, however, the expected climate-change induced regional extinction may cause a more severe loss of genetic diversity. We conclude that our multidisciplinary approach may be a useful tool for assessing impact of climate change on loss of genetic diversity. [ABSTRACT FROM AUTHOR]

Aim To test whether satellite-derived NDVI values obtained during the growing season as delimited by the onset of phenological phases can be used to map bioclimatically a large region such as Fennoscandia. Location Fennoscandia north of about 58° N and neighbouring parts of NW Russia. Methods Phenology data on birch from 15 research stations and the half-monthly GIMMS-NDVI data set with 8 × 8 km2 resolution from the period 1982–2002 were used to characterize the growing season. To link surface phenology with NDVI data, new algorithms on a pixel-by-pixel basis that show high correlation with phenophases on birch were developed. Then, time-integrated values (TI NDVI) during the phenologically defined growing season were computed to produce a bioclimatological map of Fennoscandia, which was tested and correlated with growing degree days (GDD) obtained from 20 meteorological stations. The map was also compared vs. traditional bioclimatic maps, and analysed for error factors distorting NDVI values. Results The correlation between GDD and TI NDVI data during the phenologically defined growing season was very high. Therefore, the TI NDVI map could be presented as a bioclimatic map reflecting GDD. However, several major areas have interfering factors distorting NDVI values, such as the pixel heterogeneity caused by the altitudinal mosaic in western Norway, the mosaic of lakes in southeastern Finland, and the agriculture-dominated areas in southern Fennoscandia. Main conclusions TI NDVI data from the phenologically defined growing season during 1982–2002 in Fennoscandia can be processed as a bioclimatic map reflecting GDD, except for the areas distorting NDVI values by their strong ground-cover heterogeneity. [ABSTRACT FROM AUTHOR]