Search

The importance of terrestrial coastal ecosystems for maintaining healthy coral reef ecosystems remains understudied. Sea kraits are amphibious snakes that require healthy coral reefs for foraging, but little is known about their requirements of terrestrial habitats, where they slough their skin, digest prey, and breed. Using concurrent microclimate measurements and behavior surveys, we show that a small, topographically flat atoll in Fiji with coastal forest provides many microhabitats that relate to the behaviors of Yellow Lipped Sea Kraits, Laticauda colubrina. Microclimates were significantly related to canopy cover, leaf litter depth, and distance from the high‐water mark (HWM). Sea kraits were almost exclusively observed in coastal forest within 30 m of the HWM. Sloughing of skins only occurred within crevices of mature or dying trees. Resting L. colubrina were significantly more likely to occur at locations with higher mean diurnal temperatures, lower leaf litter depths, and shorter distances from the HWM. On Leleuvia, behavior of L. colubrina therefore relates to environmental heterogeneity created by old‐growth coastal forests, particularly canopy cover and crevices in mature and dead tree trunks. The importance of healthy coastal habitats, both terrestrial and marine, for L. colubrina suggests it could be a good flagship species for advocating integrated land‐sea management. Furthermore, our study highlights the importance of coastal forests and topographically flat atolls for biodiversity conservation. Effective conservation management of amphibious species that utilize land‐ and seascapes is therefore likely to require a holistic approach that incorporates connectivity among ecosystems and environmental heterogeneity at all relevant scales. [ABSTRACT FROM AUTHOR]

Charles Darwin proposed his 'principle of divergence' to account for changes in traits that could promote speciation and coexistence of diverse forms through occupation of different niches to reduce interspecific competition. We explore interspecific foraging behaviour overlap in Fiji's forest birds, and address two main questions: (1) Is there vertical stratification of foraging behavior? and (2) Is there evidence of interspecific competition driving the differences in foraging behaviour? We explore these questions across three foraging guilds, nectarivores (three species), insectivores (two species), and omnivores (two species), and find vertical portioning of foraging in each group. To investigate the effect of interspecific competition, we compared foraging heights of the Orange-breasted Myzomela (Myzomela jugularis) honeyeater on Viti Levu Island (where it coexists with two other honeyeater species) and Leleuvia Island (no other honeyeater species). On the main island Viti Levu, we found evidence for vertical niche partitioning within each foraging guild. On Leleuvia, with the 'one-species only foraging guild', Orange-breasted Myzomela occupied broader vertical foraging niche than on Viti Levu with two other competitor honeyeater species. This result supports the idea that vertical foraging height can be shaped by interspecific competition. The findings of this study support Darwin's principle of divergence in Fiji's forest birds for every foraging guild measured and adds to our understanding of the significance of interspecific competition and niche divergence for patterns of ecological speciation on islands. [ABSTRACT FROM AUTHOR]

The extraordinary diversity of orchids has captivated scientists for more than a century, yet their complex spatial patterns at large scales remain poorly resolved. On islands, orchid diversity patterns are especially puzzling. While some islands are centres of orchid diversity, orchids are underrepresented on most islands. To disentangle such complex patterns, key functional differences among orchids must be considered – a distinction seldom made in biogeographical analyses. Using a global dataset of 454 islands, we tested prominent hypotheses in island biogeography, while simultaneously making the distinction between epiphytes and two terrestrial life forms (geophytes and non‐geophytes). Orchid diversity was unevenly distributed across islands and life forms. Epiphytic orchid diversity strongly increased with temperature, illustrating the near confinement of epiphytes to the tropics. Geophytes became proportionally more important with increasing seasonality, highlighting their ability to withstand harsh climatic conditions. Epiphytes and non‐geophytes both displayed responses (e.g. negative relationship with seasonality) related to their dependence on consistently favourable conditions, possibly because of the absence of subterranean storage organs. This highlights that the factors explaining orchid diversity differ strongly with, and are related to, life form. We suggest that key functional differences within and across plant families be considered in future studies to better understand drivers of complex diversity patterns. [ABSTRACT FROM AUTHOR]

Landslides, resulting from disturbances in slope equilibrium, pose a significant threat to landscapes, infrastructure, and human life. Triggered by factors such as intense precipitation, seismic activities, or volcanic eruptions, these events can cause extensive damage and endanger nearby communities. A comprehensive understanding of landslide characteristics, including spatio-temporal patterns, dimensions, and morphology, is vital for effective landslide disaster management. Existing remote sensing approaches mostly use either optical or synthetic aperture radar sensors. Integrating information from both these types of sensors promises greater accuracy for identifying and locating landslides. This study proposes a novel approach, the ML-LaDeCORsat (Machine Learning-based coseismic Landslide Detection using Combined Optical and Radar Satellite Imagery), that integrates freely available Sentinel-1, Palsar-2, and Sentinel-2 imagery data in Google Earth Engine (GEE). The approach also integrates relevant spectral indices and suitable bands used in a machine learning-based classification of coseismic landslides. The approach includes a robust and reproducible training and validation strategy and allows one to choose between five classifiers (CART, Random Forest, GTB, SVM, and Naive Bayes). Using landslides from four different earthquake case studies, we demonstrate the superiority of our approach over existing solutions in coseismic landslide identification and localization, providing a GTB-based detection accuracy of 87–92%. ML-LaDeCORsat can be adapted to other landslide events (GEE script is provided). Transfer learning experiments proved that our model can be applied to other coseismic landslide events without the need for additional training data. Our novel approach therefore facilitates quick and reliable identification of coseismic landslides, highlighting its potential to contribute towards more effective disaster management. [ABSTRACT FROM AUTHOR]

Refugia are key environments in biogeography and conservation. Because of their unique eco‐evolutionary formation and functioning, they should display distinct functional trait signatures. However, comparative trait‐based studies of plants in refugia and non‐refugia are lacking. Here, we provide a comparison between resource‐rich (putative microrefugia for species preferring mesic habitats under increasing aridity) and resource‐impoverished woodlands (non‐refugia) around two granite outcrops in south‐western Australia. We measured and compared six functional traits (bark thickness, foliar δ13C, foliar C:N, leaf dry matter content, plant height, specific leaf area) in four woody species. We performed multiple‐trait, multiple‐species and single‐trait, within‐species analyses to test whether plants in resource‐rich habitats were functionally distinct and more diverse than those in the surrounding resource‐impoverished woodlands. We found that species in resource‐rich woodlands occupied larger and distinct multiple‐trait functional spaces and showed distinct single‐trait values (for specific leaf area and bark thickness). This suggests that plants in resource‐rich woodlands can deploy unique and more diverse ecological strategies, potentially making these putative microrefugia more resilient to environmental changes. These findings suggest that species in microrefugia may be characterised by unique functional signatures, illustrating the utility of comparative trait‐based approaches to improve understanding of the functioning of refugia. [ABSTRACT FROM AUTHOR]

Tropical cyclones (TCs) are large‐scale disturbances that regularly impact tropical forests. Although long‐term impacts of TCs on forest structure have been proposed, a global test of the relationship between forest structure and TC frequency and intensity is lacking. We test on a pantropical scale whether TCs shape the structure of tropical and subtropical forests in the long term.We compiled forest structural features (stem density, basal area, mean canopy height and maximum tree size) for plants ≥10 cm in diameter at breast height from published forest inventory data (438 plots ≥0.1 ha, pooled into 250 1 × 1‐degree grid cells) located in dry and humid forests. We computed maps of cyclone frequency and energy released by cyclones per unit area (power dissipation index, PDI) using a high‐resolution historical database of TCs trajectories and intensities. We then tested the relationship between PDI and forest structural features using multivariate linear models, controlling for climate (mean annual temperature and water availability) and human disturbance (human foot print).Forests subject to frequent cyclones (at least one TCs per decade) and high PDI exhibited higher stem density and basal area, and lower canopy heights. However, the relationships between PDI and basal area or canopy height were partially masked by lower water availability and higher human foot print in tropical dry forests.Synthesis. Our results provide the first evidence that tropical cyclones have a long‐term impact on the structure of tropical and subtropical forests in a globally consistent way. The strong relationship between power dissipation index and stem density suggests that frequent and intense tropical cyclones reduce canopy cover through defoliation and tree mortality, encouraging higher regeneration and turnover of biomass. The projected increase in intensity and poleward extension of tropical cyclones due to anthropogenic climate change may therefore have important and lasting impacts on the structure and dynamics of forests in the future. We show that tropical cyclones have a long‐term impact on the structure of tropical and subtropical forests in a globally consistent way. Forests subject to frequent and intense cyclones exhibit higher stem density and lower canopy heights. The projected changes in tropical cyclone regime may therefore have important and lasting impacts on the structure of forests in the future. [ABSTRACT FROM AUTHOR]

Background Refugia are island-like habitats that are linked to long-term environmental stability and, as a result, high endemism. Conservation of refugia and endemism hotspots should be based on a deep ecological and evolutionary understanding of their functioning, which remains limited. Although functional traits can provide such insights, a corresponding, coherent framework is lacking. Proposed Framework Plant communities in refugia and endemism hotspots should, due to long-term environmental stability, display unique functional characteristics linked to distinct phylogenetic patterns. Therefore, such communities should be characterized by a functional signature that exhibits: (1) distinct values and combinations of traits, (2) higher functional diversity and (3) a prevalence of similar traits belonging to more distantly related lineages inside, compared to outside, of endemism hotspots and refugia. While the limited functional trait data available from refugia and endemism hotspots do not allow these predictions to be tested rigorously, three potential applications of the functional signature in biogeography and conservation planning are highlighted. Firstly, it allows the functional characteristics of endemism hotspots and refugia to be identified. Secondly, the strength of the functional signature can be compared among these entities, and with the surrounding landscape, to provide an estimate of the capacity of endemism hotspots and refugia to buffer environmental changes. Finally, the pattern of the functional signature can reveal ecological and evolutionary processes driving community assembly and functioning, which can assist in predicting the effect of environmental changes (e.g. climate, land-use) on communities in endemism hotspots and refugia. Conclusion The proposed functional signature concept allows the systematic integration of plant functional traits and phylogeny into the study of endemism hotspots and refugia, but more data on functional traits in these entities are urgently needed. Overcoming this limitation would facilitate rigorous testing of the proposed predictions for the functional signature, advancing the eco-evolutionary understanding of endemism hotspots and refugia. [ABSTRACT FROM AUTHOR]

Abstract: Plants respond to changing environmental conditions, and their ability to adjust intra‐specifically to such shifts represents an ecological and evolutionary advantage. We studied seven plant traits for two common, rhizomatous granite outcrop species (the fern Cheilanthes austrotenuifolia, and the herb Stypandra glauca) with seasonal foliage during the cooler, wetter winter months at seven sites across an aridity gradient in southwestern Australia. We investigated trait patterns at regional and habitat scale, by investigating changes in trait values along the aridity gradient, and by comparing two different habitats types (sun‐exposed and sheltered). We expected plants occurring in more arid sites and highly irradiated, shallow‐soil (sun‐exposed) habitats, to exhibit traits indicative of more conservative resource acquisition, retention and use strategies. At the habitat scale, we found support for our prediction, with plants in more stressful, sun‐exposed habitats showing traits’ values associated with more conservative strategies (especially for water), such as smaller plants, denser leaves, higher foliar δ13C and C/N. However, at the regional scale many traits displayed the opposite pattern, suggesting less conservative resource acquisition in more arid sites. This evidence was particularly pronounced for specific leaf area (SLA), which exhibited a significant, positive relationship with increasing aridity. We suggest that the unexpected regional trends in foliar traits relate to shorter lived, faster growing leaves linked to highly efficient resource acquisition and use strategies during the shorter growing season in the more arid regions. These highly exploitative strategies may enable plants to avoid climate extremes, that is, hot and dry periods in the more arid sites. Our findings of contrasting foliar traits responses at different scales support the importance of multi‐scale approaches to quantify the role of intraspecific trait variability. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To determine the role of regional forcing on plot‐level species diversity and composition, and to quantify the relative importance of biogeographical and climatic factors in explaining woody plant diversity and composition at the local‐, island‐ and archipelago‐scale. Location: Forty‐one tropical islands of the Indo‐Pacific region from Madagascar to Hawai‘i Island. Methods: We analysed the diversity and composition of tropical woody plant communities located across 113 plots, 41 islands and 19 archipelagos. We used generalized linear mixed‐effects models and generalized dissimilarity models to determine the role of regional forcing at the island and archipelago scale and to assess the relative importance of biogeographical (area and isolation of islands or archipelagos, geographical distance between plots) and climatic factors in explaining differences in local diversity and composition (species turnover). Analyses were conducted at different geographical scales (local, island and archipelago) and taxonomic levels (species, genus and family). Results: Variation in local (plot‐level) diversity (as species density, the number of species per 100 woody plants) was primarily explained by island and archipelago identity. Maximum species density was positively correlated with the area of an island (or archipelago) and negatively correlated with the isolation of an archipelago. Local climatic variability was also a significant predictor of species density, but less important than regional forcing. Climate variables explained < 20% of the variation in species turnover across all plots. The importance of geographical distance between plots relative to climate in driving species turnover decreased from the species to family level, and from the regional to island level. Main conclusions: Regional forcing was the key driver of local diversity and composition on islands. Island area and archipelago isolation are likely driving local diversity through their effects on the pool of island species. Geographical distance between plots is the main factor explaining species turnover, while at higher taxonomic levels, climatic factors and niche conservatism are the main drivers. [ABSTRACT FROM AUTHOR]

Refugia can facilitate the persistence of biodiversity under changing environmental conditions, such as anthropogenic climate change, and therefore constitute the best chance of survival for many coral species in the wild. Despite an increasing amount of literature, the concept of coral reef refugia remains poorly defined; so that climate change refugia have been confused with other phenomena, including temporal refuges, pristine habitats and physiological processes such as adaptation and acclimatization. We propose six criteria that determine the capacity of refugia to facilitate species persistence, including long-term buffering, protection from multiple climatic stressors, accessibility, microclimatic heterogeneity, size, and low exposure to non-climate disturbances. Any effective, high-capacity coral reef refugium should be characterized by long-term buffering of environmental conditions (for several decades) and multi-stressor buffering (provision of suitable environmental conditions with respect to climatic change, particularly ocean warming and acidification). Although not always essential, the remaining criteria are important for quantifying the capacity of potential refugia. [ABSTRACT FROM AUTHOR]

Extreme heat events will become more frequent under anthropogenic climate change, especially in Mediterranean ecosystems. Microhabitats can considerably moderate (buffer) the effects of extreme weather events and hence facilitate the persistence of some components of the biodiversity. We investigate the microclimatic moderation provided by two important microhabitats (cavities formed by the leaves of the grass-tree Xanthorrhoea semiplana F.Muell., Xanthorrhoeaceae; and inside the leaf-litter) during the summer of 2015/16 on the Fleurieu Peninsula of South Australia. We placed microsensors inside and outside these microhabitats, as well as above the ground below the forest canopy. Grass-tree and leaf-litter microhabitats significantly buffered against high temperatures and low relative humidity, compared to ground-below-canopy sensors. There was no significant difference between grass-tree and leaf-litter temperatures: in both microhabitats, daily temperature variation was reduced, day temperatures were 1–5°C cooler, night temperatures were 0.5–3°C warmer, and maximum temperatures were up to 14.4°C lower, compared to ground-below-canopy sensors. Grass-tree and leaf-litter microhabitats moderated heat increase at an average rate of 0.24°C temperature per 1°C increase of ambient temperature in the ground-below-canopy microhabitat. The average daily variation in temperature was determined by the type (grass-tree and leaf-litter versus ground-below-canopy) of microhabitat (explaining 67%), the amount of canopy cover and the area of the vegetation fragment (together explaining almost 10% of the variation). Greater canopy cover increased the amount of microclimatic moderation provided, especially in the leaf-litter. Our study highlights the importance of microhabitats in moderating macroclimatic conditions. However, this moderating effect is currently not considered in species distribution modelling under anthropogenic climate change nor in the management of vegetation. This shortcoming will have to be addressed to obtain realistic forecasts of future species distributions and to achieve effective management of biodiversity. [ABSTRACT FROM AUTHOR]

Background and Aims Low-altitude mountains constitute important centres of diversity in landscapes with little topographic variation, such as the Southwest Australian Floristic Region (SWAFR). They also provide unique climatic and edaphic conditions that may allow them to function as refugia. We investigate whether the Porongurups (altitude 655 m) in the SWAFR will provide a refugium for the endemic Ornduffia calthifolia and O. marchantii under forecast climate change. Methods We used species distribution modelling based on WorldClim climatic data, 30-m elevation data and a 2-m-resolution LiDAR-derived digital elevation model (DEM) to predict current and future distributions of the Ornduffia species at local and regional scales based on 605 field-based abundance estimates. Future distributions were forecast using RCP2.6 and RCP4.5 projections. To determine whether local edaphic and biotic factors impact these forecasts, we tested whether soil depth and vegetation height were significant predictors of abundance using generalized additive models (GAMs). Key Results Species distribution modelling revealed the importance of elevation and topographic variables at the local scale for determining distributions of both species, which also preferred shadier locations and higher slopes. However, O. calthifolia occurred at higher (cooler) elevations with rugged, concave topography, while O. marchantii occurred in disturbed sites at lower locations with less rugged, convex topography. Under future climates both species are likely to severely contract under the milder RCP2.6 projection (approx. 2 °C of global warming), but are unlikely to persist if warming is more severe (RCP4.5). GAMs showed that soil depth and vegetation height are important predictors of O. calthifolia and O. marchantii distributions, respectively. Conclusions The Porongurups constitute an important refugium for O. calthifolia and O. marchantii, but limits to this capacity may be reached if global warming exceeds 2 °C. This capacity is moderated at local scales by biotic and edaphic factors. [ABSTRACT FROM AUTHOR]

Tree hollows constitute crucial habitats for fauna and can buffer ambient environmental conditions. The latter property should be especially relevant during extreme weather conditions, which are forecast to increase under anthropogenic climate change. We investigated the buffering capacity of Eucalyptus oleosa F.Muell. ex Miq. subsp. oleosa tree hollows in semi-arid southern Australia for 28 days under a wide range of ambient temperatures. Tree hollows provided more stable microclimates than ambient conditions, maintaining lower temperatures and higher humidity during the day and higher temperatures and lower humidity during the night. Daytime buffering capacity increased slightly with depth and we recorded a maximum buffering of 15.1°C below ambient temperatures. Maximum day time buffering capacity increased at a rate of approximately 0.6°C per 1°C increase in ambient temperature, meaning that maximum buffering capacity was reached during the hottest periods. The high buffering capacity of tree hollows suggests that old trees with deep hollows are important in facilitating the persistence of fauna during extreme weather events. Therefore, protecting old-growth forests and vegetation remnants that are rich in tree hollows is an important strategy for mitigating the impact of climate change on fauna. [ABSTRACT FROM AUTHOR]

Aim We examine variation in woody plant species richness and endemism within tropical dry forest on oceanic islands and determine what climatic and biogeographic metrics best explain native species richness and endemism across archipelagos, islands and plots. Location Oceanic islands in the Pacific. Methods Stand-level sampling (0.1 ha) at 35 different dry forest sites across 16 islands, and five archipelagos (New Caledonia, Fiji, Marquesas, Marianas and Hawaii). Descriptors of native species richness and endemism were calculated at the plot, island and archipelago level. Biogeographic and climate metrics at the archipelago, island and plot level were drawn from the literature and computer databases. The effects of biogeographic and climate metrics were investigated using linear mixed-effects models. Results Dry forests of New Caledonia and Fiji had the highest native species richness, while New Caledonia and Hawaii had the highest endemism. Native species richness and endemism within tropical dry forests on oceanic islands are primarily influenced by biogeographic metrics, especially isolation of the archipelago, and not climatic metrics. Most variance in native species richness and endemism (60% and 64%) is at the archipelago level compared with the island (8%, 16%) and plot (32%, 15%) level. At the island level, species richness in tropical dry forest is affected by precipitation, while island area significantly affects endemism. The area of forest fragments is an important predictor of native species richness and endemism in plots. Main conclusions Although dry forests in the Pacific have been exceptionally deforested and degraded, high native species richness and endemism remains in a number of forest fragments. Biogeographic metrics explain most of the variance in native species richness and endemism across scales, while climatic metrics are important at the island level. First-order assessments of native richness and endemism at the archipelago, island and stand-level are possible for forest types on oceanic archipelagos. [ABSTRACT FROM AUTHOR]

The independent island nations of the South Pacific have a rich and threatened terrestrial biota. Despite considerable investment of resources into conservation over the last three decades, biodiversity is dwindling and protected area systems remain inadequate. This lack of success is caused by important differences in cultural, economic, landownership, and social factors in developing Pacific Island countries, compared to developed nations that often fund conservation programs and plans. Despite the obvious need for capacity building and information exchange among stakeholders, little collaboration and development has eventuated. A coordinated and integrated approach, focusing conservation resources on national priorities, is essential to achieve efficient conservation. This will need to include active involvement of landowners, a good sociocultural understanding of target communities, improved collaboration between the various stakeholders, provision of sustainable alternative economic activities, and a commitment to long funding cycles for projects. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim Identifying and protecting refugia is a priority for conservation under projected anthropogenic climate change, because of their demonstrated ability to facilitate the survival of biota under adverse conditions. Refugia are habitats that components of biodiversity retreat to, persist in and can potentially expand from under changing environmental conditions. However, the study and discussion of refugia has often been ad hoc and descriptive in nature. We therefore: (1) provide a habitat-based concept of refugia, and (2) evaluate methods for the identification of refugia. Location Global. Methods We present a simple conceptual framework for refugia and examine the factors that describe them. We then demonstrate how different disciplines are contributing to our understanding of refugia, and the tools that they provide for identifying and quantifying refugia. Results Current understanding of refugia is largely based on Quaternary phylogeographic studies on organisms in North America and Europe during significant temperature fluctuations. This has resulted in gaps in our understanding of refugia, particularly when attempting to apply current theory to forecast anthropogenic climate change. Refugia are environmental habitats with space and time dimensions that operate on evolutionary time-scales and have facilitated the survival of biota under changing environmental conditions for millennia. Therefore, they offer the best chances for survival under climate change for many taxa, making their identification important for conservation under anthropogenic climate change. Several methods from various disciplines provide viable options for achieving this goal. Main conclusions The framework developed for refugia allows the identification and description of refugia in any environment. Various methods provide important contributions but each is limited in scope; urging a more integrated approach to identify, define and conserve refugia. Such an approach will facilitate better understanding of refugia and their capacity to act as safe havens under projected anthropogenic climate change. [ABSTRACT FROM AUTHOR]

We compare the floristic composition of tropical dry forests at the stand level using Gentry's transect method (0.1 ha) in some of the largest and highest-quality remaining fragments in the Pacific (Hawai'i, 15 sites; Fiji, 9; the Marianas, 3; the Marquesas, 6; New Caledonia, 7) and compare results with neotropical dry forests. A total of 299 species or morphospecies =2.5 cm diameter at breast height were identified from all 40 sites in the Pacific. Rubiaceae (28 spp.), Euphorbiaceae (25 spp.), Fabaceae (23 spp.), Sapindaceae (18 spp.), and Myrtaceae (17 spp.) were the most speciose families in Pacific dry forest; however, no family dominated across regions in the Pacific. The most common species by frequency and density in each region were native with the exception of Hawai'i, which contains a high number of nonnative species. Observed and estimated (Chao 2) levels of native species richness show that New Caledonia and Fiji contain the highest species richness followed by Hawai'i, the Marianas, and the Marquesas. There is very little overlap at the native species level among regions, with Hawaiian dry forests the most dissimilar at the native species, genus, and family level and New Caledonia and Fiji the most similar. Unlike mainland neotropical dry forest, dry forests in the Pacific contain very few deciduous species and a low proportion of wind-dispersed species. There is a high proportion of dioecious species in Hawai'i, which is similar to the neotropics; however, other Pacific regions have fewer dioecious species. [ABSTRACT FROM AUTHOR]

1. Testing the comparative strength and influence of age and area of islands, proximity of source propagules and disturbances on community assembly, species diversity and vegetation structure has proved difficult at large scales. The little-studied rain forests in the Tropical South Pacific (TSP) provide a unique study area to investigate determinants of community dynamics, with islands varying in age, isolation, area and cyclone frequency. We tested the effects of biogeographical factors and cyclone frequency on the species composition, species diversity and forest structure of old-growth rain forest using 1-ha inventory plots on 12 islands between New Guinea and the Solomon Islands. 2. As predicted by the General Dynamic Model of Oceanic Island Biogeography, the biogeographical variables of archipelago age and island area are the most important factors affecting species richness and diversity, with older and larger islands having higher richness and diversity. There is no significant effect of cyclone frequency on species diversity. 3. The theory that diversity drives endemism is not supported in this system as endemism is not correlated with species diversity. Instead, age and isolation of an island best explain patterns of endemism, with the latter suggesting dispersal limitations between archipelagos. 4. Proximity to source area influences species composition of lowland tropical rain forests in the TSP, which is also supported by a strong correlation between geographic distance and floristic similarity. Vector-fitting onto non-metric multidimensional scaling suggests that archipelago age and cyclone frequency may, in addition to proximity to source area, influence species composition. This implies that a species’ tolerance to cyclones affects its abundance at different cyclone frequencies. 5. Synthesis. Both biogeographical variables (island area and isolation) and cyclone frequency appear to affect community assembly in lowland rain forests in the TSP. While species are hence not ecologically equivalent, interspecific ecological differences do not seem to affect the overall patterns of species diversity, which are mostly determined by biogeographical variables, as predicted by the neutral theory. [ABSTRACT FROM AUTHOR]

Aim The biogeographical patterns and drivers of diversity on oceanic islands in the tropical South Pacific (TSP) are synthesized. We use published studies to determine present patterns of diversity on TSP islands, the likely sources of the biota on these islands and how the islands were colonized. We also investigate the effect of extinctions. Location We focus on oceanic islands in the TSP. Methods We review available literature and published molecular studies. Results Examples of typical island features (e.g. gigantism, flightlessness, gender dimorphism) are common, as are adaptive radiations. Diversity decreases with increasing isolation from mainland sources and with decreasing size and age of archipelagos, corresponding well with island biogeographical expectations. Molecular studies support New Guinea/Malesia, New Caledonia and Australia as major source areas for the Pacific biota. Numerous studies support dispersal-based scenarios, either over several 100 km (long-distance dispersal) or over shorter distances by island-hopping (stepping stones) and transport by human means (hitch-hiking). Only one vicariance explanation, the eastward drift of continental fragments (shuttles) that may have contributed biota to Fiji from New Caledonia, is supported by some geological evidence, although there is no evidence for the transport of taxa on shuttle fragments. Another vicariance explanation, the existence of a major continental landmass in the Pacific within the last 100 Myr (Atlantis theory), receives little support and appears unlikely. Extinction of lineages in source areas and persistence in the TSP has probably occurred many times and has resulted in misinterpretation of biogeographical data. Main conclusions Malesia has long been considered the major source region for the biota of oceanic islands in the TSP because of shared taxa and high species diversity. However, recent molecular studies have produced compelling support for New Caledonia and Australia as alternative important source areas. They also show dispersal events, and not vicariance, to have been the major contributors to the current biota of the TSP. Past extinction events can obscure interpretations of diversity patterns. [ABSTRACT FROM AUTHOR]

Tropical dry forests are a unique and threatened ecosystem in the Pacific and globally. In Fiji, the endangered Fijian crested iguana (Brachylophus vitiensis) is endemic to tropical dry forests. Yadua Taba Island contains one of the best remaining stands of tropical dry forest in the Pacific along with the largest (and only secure) population of B. vitiensis in Fiji and has been proposed as a translocation source for iguana conservation. In this study we determined the major vegetation types on Yadua Taba and identified forest habitat preferences of B. vitiensis to (1) characterize the island's habitats for tropical dry forest regeneration monitoring and (2) understand which forest types are preferred by iguanas for future translocation projects. Vegetation data were collected using reconnaissance, entitation, line transects, and aerial photos. Iguana abundance data were collected by nocturnal surveys of permanent transects. Six major vegetation types were identified of which tropical dry forest was the largest (46% of the island), followed by a combination of rocky cliff-shrubland/grassland vegetation (26%). Our conservative estimate of B. vitiensis population size on Yadua Taba is 12,000 iguanas, the majority of which occur in tropical dry forest. Superabundance of the dry forest understory tree Vavaea amicorum, the favorite fruit species of iguanas, may help account for the high density of iguanas observed. These results highlight the ecological link between tropical dry forest and B. vitiensis and emphasize the importance of rehabilitation or conservation of tropical dry forest habitat in potential iguana translocation sites as part of the management plan for B. vitiensis throughout the Fiji Islands. [ABSTRACT FROM AUTHOR]

Aim Cycads constitute an ancient plant group that is generally believed to disperse poorly. However, one group of cycads (subsection Rumphiae) is thought to have dispersed relatively recently from a Malesian source area westwards to East Africa and eastwards into the Pacific, using a floatation-facilitating layer in their seeds. We use morphological and allozyme characters to investigate the relationships among the species within this group and to deduce whether the wide distribution was achieved by recent dispersal (as evidenced by high genetic similarity) or more distant vicariance events (high genetic differentiation). Location We examined specimens collected throughout the range of subsection Rumphiae, from East Africa through Southeast Asia to Tonga in the South-west Pacific. Methods We investigated relationships within subsection Rumphiae of the genus Cycas by analysing 18 variable (11 informative) morphological characters and 22 allozyme loci for seven of the 10 species currently assigned to this taxon. Results Distinctive morphological characters are few and fail to resolve relationships within the group. Allozyme data show that species within this subsection are closely related and suggest that there are two groups within the subsection, one comprising Cycas thouarsii (East Africa) and C. edentata (the Philippines), and the other the remaining species (from Malesia and the Pacific). The Australian species C. silvestris is sister to subsection Rumphiae in the morphological analysis but is closely allied to C. rumphii (nested within the subsection) in the allozyme analysis, suggesting that Rumphiae may be paraphyletic and that characters thought to be taxonomically important may need to be re-evaluated. Main conclusions Cycads within subsection Rumphiae are closely related, and the wide distribution of this group was probably achieved through relatively recent oceanic dispersal events. Separate events probably account for the dispersal of these cycads into the Pacific and to Africa. The origin and distribution of C. silvestris (Australia) could be explained by a dispersal event from New Guinea or may have resulted from a former land connection between Australia and New Guinea. [ABSTRACT FROM AUTHOR]

Species composition and life history traits of trees in native forests in the dry zone of Fiji were investigated. Areas receiving less than 2500 mm yr-1 of rain and covered with native forest were identified using maps, aerial photographs, estimated climate (WorldClim), and field reconaissance. Ten forest remnants were identified and species lists and data on natural history and disturbance were compiled. Cluster analysis and DECORANA identified two principal forest types, moist forest (MF) and tropical dry forest (TDF), each defined by unique climate, species composition, and tree life history characteristics. TDF (reported for the first time from Fiji) has a pronounced dry season (5 consecutive months with <100 mm rainfall each) and several deciduous canopy species. MF lacks a pronounced dry season and has few deciduous species. The amount and variability of rainfall seem to influence the type of forest in a particular location and disturbance is negatively correlated with precipitation. TDF are probably Fiji's most endangered ecosystems. [ABSTRACT FROM AUTHOR]

The flora and vegetation of an area in north-eastern Vanua Levu that is part of Fiji's last major system of mesic forest were studied and revealed a mosaic of vegetation types, including mesic sclerophyll forest, transition forest, stunted Dacrydium nidulum forest, mangrove forest, montane forest, brackish and freshwater wetlands, and disturbed landscapes. This is much more diverse than indicated by the previous "dry forest" label. The flora comprises more than 268 native species, several of which are rare or narrowly distributed. Relatively large and undisturbed stretches of vegetation and the presence of rare and novel species and vegetation types suggest that the landowners should be given every possible assistance in protecting this unique landscape. [ABSTRACT FROM AUTHOR]

Nasoata Island is a predominantly mangrove island located near the outflow and delta of the Rewa River, Fiji's largest and longest river. The river originates on the eastern slopes of Mt. Tomaniivi in the Central Highlands of Viti Levu. The island has been selected as an integral coastal site for Fiji's PABITRA Gateway Transect. Information is provided on: (1) the reasons it was selected as a PABITRA site; (2) geographical, geological, climatic, and edaphic setting; (3) the vegetation; and (4) brief notes on the fauna, with particular focus on the avifauna. Because of its rich flora and fauna, Nasoata Island is an excellent "prototype" coastal and mangrove site for enhancing our understanding of the complexities of island biodiversity, both within Fiji and in relation to other small offshore islands within the broader PABITRA network. [ABSTRACT FROM AUTHOR]

Savura is one of the seven focal sites of the Pacific-Asia Biodiversity Transect (PABITRA) Gateway Transect in Fiji. The site is composed of tropical lowland rain forest located in southeastern Viti Levu and consists of two adjacent watershed reserves, the Savura Forest Reserve and the Vago Forest Reserve. A total of 560 indigenous species (52% endemic) of vascular plants is recorded for this focal site. Savura has been chosen for the establishment of a large permanent plot of 12 ha following the methods proposed by the Centre of Tropical Forest Science (CTFS). This involves the recording of name, diameter at breast height (DBH), and precise location of every tree with 1 cm or more DBH. A total of 5,494 individuals with a total basal area of 2,752 m² was recorded in the first 6,000 m² of this CTFS/PABITRA permanent plot. The Myristicaceae (species of the genus Myristica) was the dominant family in numbers of individuals (14.4%) and basal area (35.6%). Tree ferns (Cyatheaceae [8.2% of individuals, 14.6% basal area]) and the Clusiaceae (8.6% of individuals, 12.8% basal area) are other major components. After this initial census, subsequent censuses will be carried out every 5 yr and should give insights on spatial dynamics, recruitment and mortality, and long-term changes in populations of tree species. [ABSTRACT FROM AUTHOR]

Botanical studies along mountain-to-sea transects are a key component of the Pacific-Asia Biodiversity Transect (PABITRA) project. For the Fiji PABITRA Wet-Zone Transect, it is suggested that four basic categories of biodiversity data (species inventory, plant community description, ecological data on the species and community level, and long-term monitoring) be collected within the seven biodiversity study sites (Mt. Tomaniivi/Wabu, Monasavu, Sovi Basin, Waisoi, Waibau, Savura, and Nasoata/Valolo Islands) covering an elevational gradient from sea level to 1,300 m. Currently, Sovi and Waibau are without data, except for vegetation descriptions based on aerial photographs. However, data from baseline surveys is now available for Sovi. Most of the data available on Mt. Tomaniivi/Wabu and Savura are extrapolated from collections and studies in adjacent areas, but in both areas data collection has recently begun. Only Waisoi and Nasoata/Valolo have species checklists and descriptions of the various plant communities, with ecological studies having been conducted only in the former. Because basic data (species lists, plant communities) are lacking in many areas, obtaining such data is a primary objective of PABITRA in Fiji. Other issues that should be considered are inclusion of other sites in the network of focal sites and a standardized way of data entry and basic data analysis. [ABSTRACT FROM AUTHOR]

Microsites are created by abiotic and biotic features of the landscape and may provide essential habitats for the persistence of biota. Forest canopies and understorey plants may moderate wind and solar radiation to create microclimatic conditions that differ considerably from regional climates. Skirt‐forming plants, where senescent leaves create hut‐like cavities around the stem, create microsites that are sheltered from ambient conditions and extreme weather events, constituting potential refuges for wildlife. We investigate day and night temperatures and humidity for four locations (grass tree cavities, soil, 20 cm above‐ground, 1 m above‐ground) in a South Australian forest with relatively open canopy of stringybark eucalypts (Eucalyptus baxteri, E. obliqua) and an understorey of skirt‐forming grass trees (Xanthorrhoea semiplana) at 5, 10, 20, and 40 m from the forest edge. We also measured the percentage of canopy and understorey covers. Generally, temperature and humidity differed significantly between more sheltered (grass tree cavities, soil) and open‐air microsites, with the former being cooler during the day and warmer and more humid during the night. Furthermore, our results suggest that canopy cover tends to decrease, and understorey cover tends to increase, the temperature of microsites. Distance to the edge was not significantly related to temperature for any microsite, suggesting that the edge effect did not extend beyond 10 m from the edge. Overall, grass trees influenced microclimatic conditions by forming a dense understorey and providing cavities that are relatively insulated. The capacity of grass tree cavities to buffer external conditions increased linearly with ambient temperatures, by 0.46°C per degree increase in maximum and 0.25°C per degree decrease in minimum temperatures, potentially offsetting climate warming and enabling persistence of fauna within their thermal limits. These climate moderation properties will make grass trees increasingly important refuges as extreme weather events become more common under anthropogenic climate change. [ABSTRACT FROM AUTHOR]

Understanding how species diversity is related to sampling area and spatial scale is central to ecology and biogeography. Small islands and small sampling units support fewer species than larger ones. However, the factors influencing species richness may not be consistent across scales. Richness at local scales is primarily affected by small‐scale environmental factors, stochasticity and the richness at the island scale. Richness at whole‐island scale, however, is usually strongly related to island area, isolation and habitat diversity. Despite these contrasting drivers at local and island scales, island species–area relationships (SARs) are often constructed based on richness sampled at the local scale. Whether local scale samples adequately predict richness at the island scale and how local scale samples influence the island SAR remains poorly understood. We investigated the effects of different sampling scales on the SAR of trees on 60 small islands in the Raja Ampat archipelago (Indonesia) using standardised transects and a hierarchically nested sampling design. We compared species richness at different grain sizes ranging from single (sub)transects to whole islands and tested whether the shape of the SAR changed with sampling scale. We then determined the importance of island area, isolation, shape and habitat quality at each scale on species richness. We found strong support for scale dependency of the SAR. The SAR changed from exponential shape at local sampling scales to sigmoidal shape at the island scale indicating variation of species richness independent of area for small islands and hence the presence of a small‐island effect. Island area was the most important variable explaining species richness at all scales, but habitat quality was also important at local scales. We conclude that the SAR and drivers of species richness are influenced by sampling scale, and that the sampling design for assessing the island SARs therefore requires careful consideration. [ABSTRACT FROM AUTHOR]

Complex processes related to biotic and abiotic forces can impose limitations to assembly and composition of plant communities. Quantifying the effects of these constraints on plant functional traits across environmental gradients, and among communities, remains challenging. We define ecological constraint ( C i) as the combined, limiting effect of biotic interactions and environmental filtering on trait expression (i.e., the mean value and range of functional traits). Here, we propose a set of novel parameters to quantify this constraint by extending the trait-gradient analysis (TGA) methodology. The key parameter is ecological constraint, which is dimensionless and can be measured at various scales, for example, on population and community levels. It facilitates comparing the effects of ecological constraints on trait expressions across environmental gradients, as well as within and among communities. We illustrate the implementation of the proposed parameters using the bark thickness of 14 woody species along an aridity gradient on granite outcrops in southwestern Australia. We found a positive correlation between increasing environmental stress and strength of ecological constraint on bark thickness expression. Also, plants from more stressful habitats (shrublands on shallow soils and in sun-exposed locations) displayed higher ecological constraint for bark thickness than plants in more benign habitats (woodlands on deep soils and in sheltered locations). The relative ease of calculation and dimensionless nature of C i allow it to be readily implemented at various scales and make it widely applicable. It therefore has the potential to advance the mechanistic understanding of the ecological processes shaping trait expression. Some future applications of the new parameters could be investigating the patterns of ecological constraints (1) among communities from different regions, (2) on different traits across similar environmental gradients, and (3) for the same trait across different gradient types. [ABSTRACT FROM AUTHOR]

There is a debate concerning the definition and extent of tropical dry forest biome and vegetation type at a global spatial scale. We identify the potential extent of the tropical dry forest biome based on bioclimatic definitions and climatic data sets to improve global estimates of distribution, cover, and change. We compared four bioclimatic definitions of the tropical dry forest biome–Murphy and Lugo, Food and Agriculture Organization (FAO), DryFlor, aridity index–using two climatic data sets: WorldClim and Climatologies at High-resolution for the Earth's Land Surface Areas (CHELSA). We then compared each of the eight unique combinations of bioclimatic definitions and climatic data sets using 540 field plots identified as tropical dry forest from a literature search and evaluated the accuracy of World Wildlife Fund tropical and subtropical dry broadleaf forest ecoregions. We used the definition and climate data that most closely matched field data to calculate forest cover in 2000 and change from 2001 to 2020. Globally, there was low agreement (< 58%) between bioclimatic definitions and WWF ecoregions and only 40% of field plots fell within these ecoregions. FAO using CHELSA had the highest agreement with field plots (81%) and was not correlated with the biome extent. Using the FAO definition with CHELSA climatic data set, we estimate 4,931,414 km2 of closed canopy (≥ 40% forest cover) tropical dry forest in 2000 and 4,369,695 km2 in 2020 with a gross loss of 561,719 km2 (11.4%) from 2001 to 2020. Tropical dry forest biome extent varies significantly based on bioclimatic definition used, with nearly half of all tropical dry forest vegetation missed when using ecoregion boundaries alone, especially in Africa. Using site-specific field validation, we find that the FAO definition using CHELSA provides an accurate, standard, and repeatable way to assess tropical dry forest cover and change at a global scale. [ABSTRACT FROM AUTHOR]

Aim: We mapped global patterns of tree phylogenetic endemism (PE) to identify hotspots and test hypotheses about possible drivers. Specifically, we tested hypotheses related to current climate, geographical characteristics and historical conditions and assessed their relative importance in shaping PE patterns. Location: Global. Time period: We used the present distribution of trees, and predictors covering conditions from the mid‐Miocene to present. Major taxa studied: All seed‐bearing trees. Methods: We compiled distributions for 58,542 tree species across 463 regions worldwide, matched these to a recent phylogeny of seed plants and calculated PE for each region. We used a suite of predictor variables describing current climate (e.g., mean annual temperature), geographical characteristics (e.g., isolation) and historical conditions (e.g., tree cover at the Last Glacial Maximum) in a spatial regression model to explain variation in PE. Results: Tree PE was highest on islands, and was higher closer to the equator. All three groups of predictor variables contributed substantially to the PE pattern. Isolation and topographic heterogeneity promoted high PE, as did high current tree cover. Among mainland regions, temperature seasonality was strongly negatively related to PE, while mean annual temperature was positively related to PE on islands. Some relationships differed among the major floristic regions. For example, tree cover at the Last Glacial Maximum was a positive predictor of PE in the Palaeotropics, while tree cover at the Miocene was a negative predictor of PE in the Neotropics. Main conclusions: Globally, PE can be explained by a combination of geographical, historical and current factors. Some geographical variables appear to be key predictors of PE. However, the impact of historic and current climate variables differs considerably among the major floristic regions, reflecting their unique histories. Hence, the current distribution of trees is the result of globally relevant geographical drivers and regional climatic histories. [ABSTRACT FROM AUTHOR]

Determining patterns of plant diversity on granite inselbergs is an important task for conservation biogeography due to mounting threats. However, beyond the tropics there are relatively few quantitative studies of floristic diversity, or consideration of these patterns and their environmental, biogeographic, and historical correlates for conservation. We sought to contribute broader understanding of global patterns of species diversity on granite inselbergs and inform biodiversity conservation in the globally significant Southwest Australian Floristic Region (SWAFR). We surveyed floristics from 16 inselbergs (478 plots) across the climate gradient of the SWAFR stratified into three major habitats on each outcrop. We recorded 1,060 species from 92 families. At the plot level, local soil and topographic variables affecting aridity were correlated with species richness in herbaceous (HO) and woody vegetation (WO) of soil‐filled depressions, but not in woody vegetation on deeper soils at the base of outcrops (WOB). At the outcrop level, bioclimatic variables affecting aridity were correlated with species richness in two habitats (WO and WOB) but, contrary to predictions from island biogeography, were not correlated with inselberg area and isolation in any of the three habitats. Species turnover in each of the three habitats was also influenced by aridity, being correlated with bioclimatic variables and with interplot geographic distance, and for HO and WO habitats with local site variables. At the outcrop level, species replacement was the dominant component of species turnover in each of the three habitats, consistent with expectations for long‐term stable landscapes. Our results therefore highlight high species diversity and turnover associated with granite outcrop flora. Hence, effective conservation strategies will need to focus on protecting multiple inselbergs across the entire climate gradient of the region. [ABSTRACT FROM AUTHOR]

Background and aims Dolines are small- to large-sized bowl-shaped depressions of karst surfaces. They may constitute important microrefugia, as thermal inversion often maintains cooler conditions within them. This study aimed to identify the effects of large- (macroclimate) and small-scale (slope aspect and vegetation type) environmental factors on cool-adapted plants in karst dolines of East-Central Europe. We also evaluated the potential of these dolines to be microrefugia that mitigate the effects of climate change on cool-adapted plants in both forest and grassland ecosystems. Methods We compared surveys of plant species composition that were made between 2007 and 2015 in 21 dolines distributed across four mountain ranges (sites) in Hungary and Romania. We examined the effects of environmental factors on the distribution and number of cool-adapted plants on three scales: (1) regional (all sites); (2) within sites and; (3) within dolines. Generalized linear models and non-parametric tests were used for the analyses. Key Results Macroclimate, vegetation type and aspect were all significant predictors of the diversity of cool-adapted plants. More cool-adapted plants were recorded in the coolest site, with only few found in the warmest site. At the warmest site, the distribution of cool-adapted plants was restricted to the deepest parts of dolines. Within sites of intermediate temperature and humidity, the effect of vegetation type and aspect on the diversity of cool-adapted plants was often significant, with more taxa being found in grasslands (versus forests) and on north-facing slopes (versus south-facing slopes). Conclusions There is large variation in the number and spatial distribution of cool-adapted plants in karst dolines, which is related to large- and small-scale environmental factors. Both macro- and microrefugia are therefore likely to play important roles in facilitating the persistence of cool-adapted plants under global warming. [ABSTRACT FROM AUTHOR]

Identifying refugia is a critical component of effective conservation of biodiversity under anthropogenic climate change. However, despite a surge in conceptual and practical interest, identifying refugia remains a significant challenge across diverse continental landscapes. We provide an overview of the key properties of refugia that promote species' persistence under climate change, including their capacity to (i) buffer species from climate change; (ii) sustain long-term population viability and evolutionary processes; (iii) minimize the potential for deleterious species interactions, provided that the refugia are (iv) available and accessible to species under threat. Further, we classify refugia in terms of the environmental and biotic stressors that they provide protection from (i.e. thermal, hydric, cyclonic, pyric and biotic refugia), but ideally refugia should provide protection from a multitude of stressors. Our systematic characterization of refugia facilitates the identification of refugia in the Australian landscape. Challenges remain, however, specifically with respect to how to assess the quality of refugia at the level of individual species and whole species assemblages. It is essential that these challenges are overcome before refugia can live up to their acclaim as useful targets for conservation and management in the context of climate change. [ABSTRACT FROM AUTHOR]

Identification of refugia is an increasingly important adaptation strategy in conservation planning under rapid anthropogenic climate change. Granite outcrops (GOs) provide extraordinary diversity, including a wide range of taxa, vegetation types and habitats in the Southwest Australian Floristic Region (SWAFR). However, poor characterization of GOs limits the capacity of conservation planning for refugia under climate change. A novel means for the rapid identification of potential refugia is presented, based on the assessment of local-scale environment and vegetation structure in a wider region. This approach was tested on GOs across the SWAFR. Airborne discrete return Light Detection And Ranging (LiDAR) data and Red Green and Blue (RGB) imagery were acquired. Vertical vegetation profiles were used to derive 54 structural classes. Structural vegetation types were described in three areas for supervised classification of a further 13 GOs across the region. Habitat descriptions based on 494 vegetation plots on and around these GOs were used to quantify relationships between environmental variables, ground cover and canopy height. The vegetation surrounding GOs is strongly related to structural vegetation types (Kappa = 0.8) and to its spatial context. Water gaining sites around GOs are characterized by taller and denser vegetation in all areas. The strong relationship between rainfall, soil-depth, and vegetation structure (R2 of 0.8–0.9) allowed comparisons of vegetation structure between current and future climate. Significant shifts in vegetation structural types were predicted and mapped for future climates. Water gaining areas below granite outcrops were identified as important putative refugia. A reduction in rainfall may be offset by the occurrence of deeper soil elsewhere on the outcrop. However, climate change interactions with fire and water table declines may render our conclusions conservative. The LiDAR-based mapping approach presented enables the integration of site-based biotic assessment with structural vegetation types for the rapid delineation and prioritization of key refugia. [ABSTRACT FROM AUTHOR]