Species Distribution Patterns Research Articles

Untangling key abiotic predictors of terrestrial mammal diversity patterns across ecoregions and species groups in Kenya

Understanding the interactions between abiotic (environmental and anthropogenic) factors and species diversity and distribution patterns is fundamental to improving the ecological representativeness of biodiversity management tools such as protected areas (PAs). However, significant knowledge gaps remain about how species’ ecological and evolutionary opportunities are associated with abiotic factors, especially in biodiversity-rich but economically ill-equipped countries such as Kenya. Here, we explored the interactions of terrestrial mammal diversity patterns and abiotic factors across species groups and ecoregions in Kenya. We coupled data on terrestrial mammal occurrences, phylogeny, functional traits, and environmental predictors in Kenya to derive multiple diversity indices, encompassing species richness and phylogenetic and functional richness, and mean pairwise and nearest taxon distances. We explored the interactions of these indices with several abiotic factors using multivariate regression analyses while adjusting for spatial autocorrelation. The results showed weak correlations between species richness versus the phylogenetic and functional diversity indices. The best-fit models explained variable proportions of diversity indices between species groups and ecoregions and consistently retained annual temperature and precipitation averages and seasonality and human footprint as the strongest predictors. Compared to the species-poor xeric northern and eastern Kenya regions, the predictors had weak associations with diversity variances in the species-rich mesic western and central Kenya regions, similar to focal species groups compared to ordinal classifications and the combined species pool. These findings illustrate that climate and human footprint interplay determine multiple facets of terrestrial mammal diversity patterns in Kenya. Accordingly, curbing human activities degrading long-term climatic regimes is vital to ensuring the ecological integrity of terrestrial mammal communities and should be integrated into biodiversity management frameworks. For a holistic representation of critical conservation areas, biodiversity managements should also prioritize terrestrial mammal phylogenetic and functional attributes besides species richness.

Herbs, Shrubs and Trees in Pt. Ravishankar Shukla University Campus, Raipur, Chhattisgarh

The aim of the investigation was to analyse the floral characteristics and phytodiversity pattern of the vegetation of Pt. Ravi Shankar Shukla University Campus, Raipur, Chhattisgarh, India. The results reflect dominancy of monocots over the dicots in the four studied sites. Primarily there are three types of plant present in the college campus Firstly, planted, secondly natural or wild and medicinal plants. Wild species grows very fast which cause a great threat to the natural indigenous medicinal plants. Therefore, proper management and conservative measures needs to be implemented for conservation of indigenous plant species at Pt. Ravi Shankar Shukla University Campus. Distribution pattern of plant species in university campus is very much regular.

Phytodiversity of trees and shrubs in Vindhyabasni Sacred grove, Girwan, Banda, Uttar Pradesh

Sacred groves are the storehouse of medicinal plants, trees, shrubs, and important useful plants for the locals. The present study was conducted to study the diversity of woody vegetation across the topography (pediment, slope and hilltop.) in Vindhyavasini sacred grove, Girwan Banda Uttar Pradesh. The vegetation data were quantitatively analyzed for community characteristics such as species richness, dominance, diversity and distribution pattern by using the quadrat method. A total of 68 sample plots of 32.5×32.5m² for trees and 136 sub-plots of 5×5m² for shrubs were laid down. A total of 32 plant species (18 trees and 14 shrubs) belonging to 20 families were recorded and identified during the study. The highest species diversity and species richness for both trees (0.93, 14) and shrubs (1.77, 11) were recorded in pediment and species richness of the family Combretaceae was the highest (79.56) followed by Lamiaceae (36.78) and Apocynaceae (29.26). Terminalia pendula (IVI -187.80) and Carissa spinarum (IVI-86.89) were the most dominant tree and shrub species respectively. This sacred grove may work as a vital pool for the preservation of endemic and local plant species.

Marine and estuarine crustacean diversity and assemblage structure in eastern Brazil three years after the Fundão mining dam failure

The present study investigates the spatial and temporal patterns of species richness and assemblage structure of decapod and stomatopod crustaceans in the area impacted by the Fundão dam collapse (Rio Doce basin, Brazil) in November 2015. From October 2018 to September 2019, monthly bottom-trawl samples were collected in estuarine and marine waters of the Rio Doce (directly impacted area) and three other localities. Forty-one crustacean species were recorded, with the overall community structure dominated by six species. The seabob shrimp Xiphopenaeus kroyeri was the most common species, with the coastal marine area near to the Rio Doce mouth being an important fishery ground. Species composition changed significantly among localities, habitats, and seasons, with marine and estuarine assemblages shaped by freshwater discharge. Distribution patterns of species were significantly influenced by the environmental variables potentially altered by tailings, such as turbidity and pH. Species richness and abundance differed among localities; as expected, they were generally higher on the inner shelf than in estuaries and higher during the dry season than the rainy season. Due to the lack of information before the disaster, the low number of species found in the Rio Doce estuary cannot be solely attributed to the disaster but also its freshwater condition. This is the first broad study of the estuarine and coastal marine decapod and stomatopod crustaceans in the region, and we suggest the need for long-term monitoring considering that the effects of this disaster are not easy to detect and probably need multi-year study to be evidenced.

Global benthic biogeographical regions and macroecological drivers for ophiuroids

Delineating biogeographical regions can provide important insights into the processes shaping large‐scale species distribution patterns. Here we aimed to 1) identify global marine benthic biogeographical regions for ophiuroids extending from shallow waters to the deep sea and 2) quantify the importance of contemporary environmental conditions and geological features in shaping the delineated biogeographical regions. We delineated marine benthic biogeographical regions using a bipartite network analysis applied to a historical dataset of brittle stars. We then examined the faunal exchanges between the regions, and applied random forest models to evaluate the relative role of contemporary environmental conditions and tectonic configuration underlying the proposed biogeographic scheme. We propose ten main large biogeographical regions across the benthos. The biogeographical regions with the highest species richness and endemicity rates were found in the Indo‐Pacific region, Tropical West Atlantic and Southern Ocean, and South America. The key transition regions fall within the subarctic areas of the Pacific and the waters surrounding Southern Australia and New Zealand. Tectonic configuration, surface temperature and salinity were found to be the most important predictors of the ten delineated biogeographical regions. Our biogeographic delineation, including the deep sea, is in partial agreement with those proposed in previous studies. Our results suggest that contemporary environmental conditions (sea water temperature and salinity) strongly influence the modern distribution of ophiuroids, but that plate tectonics left a marked imprint on regional species pools. Future work based on multiple benthic taxa, and with a better understanding of the environmental conditions in the deep sea, are needed to evaluate the robustness of our proposed division.

Smart utilization of betaine lipids in the giant clam Tridacna crocea

The giant clam Tridacna crocea thrives in poorly nourished coral reef water by forming a holobiont with zooxanthellae and utilizing photosynthetic products of the symbiont. However, detailed metabolic crosstalk between clams and symbionts is elusive. Here, we discovered that the nonphosphorous microalgal betaine lipid DGCC (diacylglycerylcarboxy-hydroxymethylcholine) and its deacylated derivative GCC are present in all tissues and organs, including algae-free sperm and eggs, and are metabolized. Colocalization of DGCC and PC (phosphatidylcholine) evidenced by MS imaging suggested that DGCC functions as a PC substitute. The high content of GCC in digestive diverticula (DD) suggests that the algal DGCC was digested in DD for further utilization. Lipidomics analysis showing the organ-specific distribution pattern of DGCC species suggests active utilization of DGCC as membrane lipids in the clam. Thus, the utilization of zooxanthellal DGCC in animal cells is a unique evolutionary outcome in phosphorous-deficient coral reef waters.

Pervasive impacts of climate change on the woodiness and ecological generalism of dry forest plant assemblages

Abstract Climate emergency is a significant threat to biodiversity in the 21st century, but species will not be equally affected. In summing up the responses of different species at the local scale, we can assess changes in the species quantity and composition of biotic assemblages. We used more than 420K curated occurrence records of 3060 plant species to model current and future patterns of plant species distribution in one of the world's largest tropical dry forests—the Caatinga. While allowing different model extrapolation scenarios, we estimated potential changes in the species richness and composition of dryland plant assemblages in response to projected climate change, and assessed how the ecological generalism and woodiness of plant assemblages can be impacted by the climate crisis. More than 99% of plant assemblages were projected to lose species by 2060, with biotic homogenisation—the decrease in spatial beta diversity—forecasted in 40% of the Caatinga. The replacement of narrow‐range woody species by wide‐range non‐woody ones should impact at least 90% of Caatinga plant assemblages. The exacerbated species loss in the dryland plant assemblages was connected to the heterogenisation and homogenisation of biotic assemblages. Still, the magnitude of climate change impacts on ecological generalism and woodiness patterns of dryland plant assemblages differ according to the direction of the biotic change process. Synthesis. The future increase in aridity will change the patterns of woodiness and ecological generalism of tropical dry forest plant assemblages by decreasing vegetation diversity and complexity. The projected biotic changes in dryland plant assemblages indicate the erosion of ecosystem services linked to biomass productivity and carbon storage. We highlight the importance of long‐term conservation planning for maintaining tropical dry forests.

Potential impact of climate change on spatial distribution of two savannah amphibian species in West Africa

AbstractClimate change affects biodiversity, notably by modifying species habitats. In the West African savannahs, amphibian species are widespread. Despite their importance in ecosystems, little is known about the potential impacts of future climate change on these amphibians, hence the need to study the future distribution patterns of West African savannah amphibian species. We performed species distribution modelling to forecast the current and future distribution of two species Hyperolius nitidulus and Ptychadena bibroni in West Africa. Based on the global climate model MIROC5 and two future climate scenarios (RCP 4.5 and RCP 8.5), we assessed trends in the evolution of suitable habitat areas of these two amphibian species. We found that H. nitidulus is likely to lose significant proportions of their current habitats in the future due to climate change, while P. bibroni is likely to gain new suitable habitats. Our study suggests that some savannah amphibian species that are currently classified as Least Concern by the IUCN would be negatively affected by future climate change as shown by the distribution patterns of H. nitidulus. It is therefore necessary to consider all amphibian species, whether widely distributed or endemic, in future conservation strategies for amphibians in West Africa.

Conserving useful plants for a sustainable future: species coverage, spatial distribution, and conservation status within the Millennium Seed Bank collection

A substantially rich diversity of the world’s recorded useful plants (UPs) is captured within the Millennium Seed Bank collection hosted by the Royal Botanic Gardens, Kew, at Wakehurst, UK with 13,598 species (34%) belonging to 3696 genera and 325 families. This constitutes just over half of the total accessions and one third of the species and covers all 9 continents, 8 realms, 14 biomes, 34 biodiversity hotspots and 175 countries. The most common beneficial use category within the captured diversity is medicinal, then species with environmental, material, and human food value. About 86% of conserved UP species have a ‘Least Concern’ conservation status but 8% are identified as globally threatened. The advantages of mutual, continued, and long-term partnership (e.g., Mexico) are showcased when conserving plants important for local communities and addressing conservation challenges beyond seed banking. However, the geographic coverage suffers from a lack of partnerships with some parts of the world. Also, a low number of accessions contributed from many countries means that insufficient native range is yet to be captured for many species. This is particularly the case for restricted or narrow distribution species from families or genera with a high incidence of recalcitrant or short-lived seeds. Future planning must tailor better to cover the spatial distribution patterns for individual species, thereby improving the number of accessions and geographical coverage for those captured. Moreover, seed biology research should characterise desiccation tolerance and develop complementary, novel conservation methods, such as cryopreservation, to strengthen conservation options for UP species.

The contemporary distribution of grasses in Australia: A process of immigration, dispersal and shifting dominance

AbstractAimLittle is known about the distribution of grasses throughout Australia. Using endemism as a basis for understanding biogeographical distributions, we hypothesised that contemporary species richness would be the result of environmental factors and dynamic ecological interactions spanning more than 25 Ma.LocationAustralia.TaxonGrasses.MethodsWe mapped the distribution of all Australian grass species and modelled climatic and landscape correlates according to photosynthetic type (C3 or C4), endemism, age in Australia, phylogenetic lineage and traits linked to dominance, using height as a proxy. Age classes comprised ‘Ancient’ (Gondwanan), and three others related to migration during the Sunda‐Sahul Interchange (SSI): Early, Mid or Recent. In some analyses, ‘Ancient’, ‘Early SSI’ and ‘Mid SSI’ were combined into ‘Pre‐Recent SSI’.ResultsOverall, species richness of C4 grasses increased with warmer mean annual temperatures, while richness of C3 grasses was higher in cooler areas. Recent SSI species had strong associations with summer rains and were dominant in the continent's northeast, with Pre‐Recent SSI species concentrated in the southeast, a pattern largely reflecting photosynthetic type (C4 and C3 respectively). Endemic and shared species distribution patterns support a migration sequence in which most C3 Pooideae and Panicoideae genera arrived in Australia before the Pliocene aridifications, followed by C4 Chloridoideae as aridification increased, with C4 Andropogoneae immigrating most recently across Lake Carpentaria's open habitats in the later Pleistocene. Recent SSI shared species were significantly taller than Pre‐Recent SSI endemic grasses.Main ConclusionsThe few grasses present in Australia before the Pliocene grew in cooler areas. The influx of taller Recent SSI grasses contributed to dramatic environmental changes—including creation of the northern savannas—with repercussions for resident taxa. Contemporary methods of fuel management could be promoting invasion by grass, thereby jeopardising the conditions suited to ancient taxa and threatening the region's evolutionary history.

Landscape heterogeneity drives spatial distribution of palm community in a Neotropical rainforest reserve affected by defaunation

Background: Our study presents the first assessment of the relationships between environmental heterogeneity and the palm community at the landscape scale at the northern boundary of tropical rainforest distribution in America.
 Question: How does landscape-level heterogeneity (edaphic, topographic as well as the density, diversity, and tree biomass) shapes the palm community in a protected reserve affected by defaunation?
 Study site and date: The study was carried out in Los Tuxtlas Tropical Biology Station, Veracruz, Mexico (2020).
 Methods: We delineated landscape units (LUs) based on soil and geomorphology to characterize the biophysical mosaic. We built rank-abundance curves to compare the palm richness and their abundance among LUs. Permutational multivariate analysis of variance (PERMANOVA) and nonmetric multidimensional scaling (NMDS) were applied to detect shifts in the palm community across LUs.
 Results: Integrating abiotic and biotic components by delimiting LUs allowed us to evaluate the multifactorial effect of environmental heterogeneity on the palm community. The density and composition of the palms changed significantly among the LUs, influenced by soil coarse fragments, elevation, slope inclination, and annual precipitation. Tree richness and density had a significant effect on the palm community only when analyzed in combination with the soil-topography variables.
 Conclusions: The results reveal that there is high edaphic and topographic heterogeneity that influences palm species distribution at the landscape scale. The environmental heterogeneity approach allows capturing novel abiotic variation to explain the distribution patterns of palm species and their coexistence in highly diverse tropical communities.

Synchronized multidecadal trends and regime shifts in North Atlantic plankton populations

Abstract Recent changes in oceanic plankton are being reported at unprecedented rates. Most changes are related to environmental factors, and many were identified as driven by climate, either through natural cycles or by anthropogenic effects. However, the separation of both effects is difficult because of the short length of most observational series. Moreover, some changes are related to trends and cycles, while others were perceived as system shifts, often synchronized over large spatial scales. Here, studies on observational series of plankton, with the focus in the North Atlantic, are reviewed. Two main periods of shifts in plankton assemblages were identified: one in the late 1980s and a more recent one at the beginning of the new millennium. While the origin and extent of most shifts varied locally, their synchronization seems to confirm the response of plankton to changes in warming and in large-scale climatic factors. Changes in species abundance and distribution patterns were generally related to hydrographic factors, but also to non-linear effects of warming, the latter particularly affecting species in regions near the limits of their thermal niches. Indeed, most of the changes were attributed to trade-offs between different biological strategies. Taken together, the reviewed case studies indicate a lagged biological response to variations in the local environment driven by large-scale climate forcing. The challenges for interpreting future shifts include considering local changes within a larger geographical area, variations in species life traits, and potential top-down effects of plankton predators.

Floristic composition, life history traits and phytogeographic distribution of forest vegetation in the Western Himalaya

IntroductionScientific documentation of the qualitative forest vegetation parameters of a biogeographical area provides baseline information to guide conservation strategies and design policies for biodiversity management regulations.MethodsWe present one of the most comprehensive qualitative vegetation analyses to evaluate the entire structure and function of an ecosystem in the remote northern part of the Kashmir Himalaya, India. Several multivariate ecological community analyses were conducted after determining the presence of plant species in the various habitats using a random sampling technique.ResultsIn total, 155 plant species belonging to 120 genera and 49 families occurred in the area. Asteraceae was the largest family (12% of plant species) followed by Rosaceae (11%). The patterns of species distribution across families were uneven, with 50% of the species belonging to only 7 families, and 23 families being monotypic. In terms of functional groups, the herbaceous growth form dominated. Therophytes were the dominant life form, indicating that the vegetation was disturbed. According to the phytogeographical research, 65% of the species documented in the study area were native, 15% were invasive, 14% naturalized, and 5% being casual. The majority (30%) of exotic species were reported along roadsides. Of all the species found, 39% grew in their natural habitats, such as forests, and 11% were scattered along roadsides. Plant species were grouped in five different clusters based on their floristic similarity. According to the estimated diversity indices, natural forest has the greatest values for Shannon’s and Simpson’s index. We found that the study area serves as the natural habitat for several significant, endangered medicinal plants, including Arnebia benthamii, Bergenia ciliata, Delphinium roylei, Gentiana kurroo, Phytolacca acinosa, Saussurea costus, and Trillium govanianum. Therefore, we recommend that human intervention in natural regeneration efforts be prioritized in these habitats to increase the population of these species.ConclusionExamining species features from the perspective of functional groups contributes to our understanding of the ecological aspects of the flora. It may also be useful in developing management plans to ensure long-term management of forest landscapes in this remote Himalayan region.

Limnological factors that affect waterbird assemblages in semi-arid reservoirs of Tigray National Regional State, northern Ethiopia

Published accounts of the conservation of biodiversity indicate that understanding patterns of species distribution and richness is crucial. However, what drives patterns of species composition in a landscape remains debatable. I examined the relationship between limnological characteristics of reservoirs, morpho-edaphic variables, biological variables, and patterns of bird species richness and distribution. Six limnological, three morpho-edaphic variables, and biological variables were recorded for 35 reservoirs and analyzed by multivariate statistical techniques. To investigate the most important explanatory factors influencing avian species richness and their distribution, redundancy analysis (RDA) was used. A total of 85 bird species from 54 genera, with a mean species richness 14.23 ± 6.72 (mean ± standard deviation) per reservoir, were recorded. The RDA analysis identified two significant RDA axes, and 34.4% of the variation in species richness is explained by environmental variation (R2adj = 0.34375; P < 0.001). Bird species richness was positively correlated with the surface area of reservoirs. I showed here that reservoir size and environmental heterogeneity were the important features that affect bird species richness, thus providing an important insight into the ecological relationship between waterbird species richness and the limnological characteristics of reservoirs. The strong positive correlation between species richness and both size and environmental variables underscores the importance of these reservoir features in the management of wildlife conservation. Large, environmentally heterogeneous reservoirs can support more species than small, environmentally homogeneous reservoirs because large, environmentally heterogeneous limnetic ecosystems can provide different resources for nesting, foraging, and roosting habitats for a diversified bird species. The result here also plays a role towards strengthening our knowledge of aquatic bird ecology and the natural history of African-Eurasian Migratory waterbirds.

The clustering of spatially associated species unravels patterns in tropical tree species distributions

AbstractComplex distribution data can be summarized by grouping species with similar or overlapping distributions to unravel spatial patterns and separate trends (e.g., of habitat loss) among spatially unique groups. However, such classifications are often heuristic, lacking the transparency, objectivity, and data‐driven rigor of quantitative methods, which limits their interpretability and utility. Here, we develop and illustrate the clustering of spatially associated species, a methodological framework aimed at statistically classifying species using explicit measures of interspecific spatial association. We investigate several association indices and clustering algorithms and show how these methodological choices drive substantial variations in clustering outcomes and performance. To facilitate robust decision‐making, we provide guidance on choosing methods appropriate to one's study objective(s). As a case study, we apply our framework to modeled tree distributions in Borneo and subsequently evaluate the impact of land‐cover change on separate species groupings. Based on the modeled distribution of 390 tree species prior to anthropogenic land‐cover changes, we identified 11 distinct clusters that unraveled ecologically meaningful patterns in Bornean tree distributions. These clusters then enabled us to quantify trends of habitat loss tied to each of those specific clusters, allowing us to discern particularly vulnerable species clusters and their distributions. This study demonstrates the advantages of adopting quantitatively derived clusters of spatially associated species and elucidates the potential of resultant clusters as a spatially explicit framework for investigating distribution‐related questions in ecology, biogeography, and conservation. By adopting our methodological framework and publicly available codes, practitioners can leverage the ever‐growing abundance of distribution data to better understand complex spatial patterns among species distributions and the disparate effects of global changes on biodiversity.

Herb stratum diversity and community structure in Gurez valley of Kashmir Himalaya: application of multivariate techniques in community analyses

ABSTRACT In temperate forests, herbs comprise up to 90% of species richness yet received less attention, and their community structure, diversity patterns, and driving mechanisms still remain understudied. We provide a phytosociological overview of herb stratum to develop a vegetation model to characterize and designate vegetation groups and interpret their diversity and species distribution patterns. Multivariate analyses – classification (TWINSPAN) and ordination (indicator species analysis [ISA], non-metric multidimensional scaling [NMDS], and Canonical Correspondence Analysis [CCA]) were applied to data set collected from 32 plots across Gurez valley, Kashmir Himalaya to recognize the understory plant communities, determine the environmental predictors and highlight their significance. Altogether, 131 herbs from 38 families were recorded. TWINSPAN classified understory vegetation into three communities: Tanacetum multicule – Pedicularis pectinata – Aconitum heterophyllum (TPA), Taraxacum officinale – Trifolium repens – Plantago major (TTP), and Impatiens brachycentra – Tussilago farfara – Galium boreale (ITG). Diversity indices and species richness vary significantly, following the trend TTP>TPA>ITG. CCA revealed that disturbances, canopy, altitude, and moisture were the strongest parameters determining species differentiation. The study outlines a methodological workflow based on analytical methods and vegetation-plot data that describe vegetation groups and might be helpful in further in-depth vegetation classification syntheses and decision-making in conservation, global change issues, and management.

Patterns of Forest Species Association in a Broadleaf Forest in Romania

Ecological patterns of species distribution can reveal essential information on the spatial and functional relationship between species or species and their environment. Various approaches can be used to assess species associations, and our study aimed to compare three methods at different scales: the co-occurrence indices for binary presence–absence data, principal component analysis (PCA) on species abundance and point process analysis. Our goal was to gain a deeper understanding of the species’ co-occurrence patterns and notice if the three methods capture roughly the same spatial distribution trends. Our observational study of the analysed sapling community displayed several positive relationships between species (e.g., the association between ash and linden). However, many relationships were inconsistent across different scales. Furthermore, attraction between species was more prevalent than repulsion. Overall, there is a positive association trend, with more relationships being significantly positive across all scales. This trend is consistent with other recent studies of tree–species interaction. Nonetheless, the results suggest that the scale significantly influences spatial patterns of associations. Positive associations tend to be more prevalent on larger scales, while negative associations are more commonly found on smaller scales, regardless of the analysis method used. While the PCA results are less consistent, the point process analysis allowed us to detect more refined patterns of species associations based on the distance of their interaction. In addition, the binary presence–absence analysis provided solid results, with a coarser spatial perspective but with significantly less sampling effort.

Species assemblages of insular Caribbean Sticta (lichenized Ascomycota: Peltigerales) over ecological and evolutionary time scales

Phylogenetic approaches to macroevolution have provided unique insight into evolutionary relationships, ancestral ranges, and diversification patterns for many taxa. Similar frameworks have also been developed to assess how environmental and/or spatial variables shape species diversity and distribution patterns at different spatial/temporal scales, but studies implementing these are still scarce for many groups, including lichens. Here, we combine phylogeny-based ancestral range reconstruction and diversification analysis with community phylogenetics to reconstruct evolutionary origins and assess patterns of taxonomic and phylogenetic relatedness between island communities of the lichenized fungal genus Sticta in the Caribbean. Sampling was carried out in the Greater Antilles (Cuba, Jamaica, Dominican Republic, and Puerto Rico) and Lesser Antilles (Dominica, Guadeloupe, and Martinique). Data for six molecular loci were obtained for 64 candidate Caribbean species and used to perform both macroevolutionary phylogenetics, which also included worldwide taxa, and phylobetadiversity analyses, which emphasized island-level communities. Our work uncovered high levels of island endemism (∼59%) in Caribbean Sticta. We estimate initial colonization of the region occurred about 19 Mya from a South American ancestor. Reverse migration events by Caribbean lineages to South America were also inferred. We found no evidence for increased diversification rates associated with range expansion into the Caribbean. Taxonomic and phylogenetic turnover between island-level communities was most strongly correlated with environmental variation rather than with geographic distance. We observed less dissimilarity among communities from the Dominican Republic and Jamaica than between these islands and the Lesser Antilles/Puerto Rico. High levels of hidden diversity and endemism in Caribbean Sticta reaffirm that islands are crucial for the maintenance of global biodiversity of lichenized fungi. Altogether, our findings suggest that strong evolutionary links exist between Caribbean and South American biotas but at regional scales, species assemblages exhibit complex taxonomic and phylogenetic relationships that are determined by local environments and shared evolutionary histories.

Factors limiting the spread of middle- and low-altitude fishes to the Qinghai-Tibet plateau

The distribution pattern of species is determined by the environment and their adaptability to the environment. Qinghai-Tibet Plateau has become a natural laboratory for studying adaptive evolution due to its extreme environmental characteristics such as low temperature, low oxygen, high salinity and high ultraviolet radiation (UVR). Fish are sensitive to the environmental stress, so they are ideal materials for studying high-altitude adaptation of animals. Previous studies have mainly focused on the adaptability of plateau species, but the reasons why plain species cannot spread to the plateau have been ignored. In this study, stress experiments and histological experiments were used to compare the tolerance of six Barbini fishes (family: Cyprinidae) distributed at different altitudes and regions to low temperature, low oxygen, salinity and UVR. Results showed that the tolerance of fishes to high-altitude environmental stress factors was closely related to the environmental stress of their main habitats. The high-altitude fish Gymnocypris eckloni had strong tolerance to all stress factors, while the other five fishes from middle and low altitudes could not adapt to single or multiple stress factors, with significant interspecific differences. Among these factors, middle- and low-altitude fishes showed common low tolerance to UVR, suggesting that high UVR, the factor lacking at low altitude areas, plays an important role. Moreover, during the uplift of the Qinghai-Tibet Plateau, Schizothorax fish disappeared from the middle of the plateau. We speculate that this was caused by its intolerance to the increasingly extreme plateau environment, especially salinity.

Spatial scale affects the importance of deterministic and stochastic factors in the structuring of tadpole assemblages in Brazilian Cerrado

Many factors influence the structure of natural assemblages. Species interaction and environmental factors may generate deterministic patterns, whereas dispersal and ecological drift may generate stochastic patterns. We used pond systems to understand how deterministic and stochastic factors interact and influence tadpole assemblages at different spatial scales. We used variation partitioning and a co-occurrence analysis to evaluate how local environment heterogeneity, species interaction, and spatial variables affected species composition at local and regional scales in Brazilian savanna. Both deterministic and stochastic processes were important to explain tadpole distribution at regional scale, but with a greater contribution of stochastic factors. At local scales, environmental and niche traits were more important to explain tadpole distribution into the habitats. We demonstrate that in Brazilian Cerrado, species composition can be explained by the "MacArthur paradox", in which niche processes are important at local scales, whereas dispersal constraints and population processes lead to stochastic patterns in species distribution at large spatial scales.