Drivers Of Species Richness Research Articles

Environmental gradients structure gorgonian assemblages on coral reefs in SE Sulawesi, Indonesia

Indonesian coral reefs are the epicenter of marine biodiversity, yet are under rapid anthropogenically induced decline. Therefore, ecological monitoring of high diversity taxa is paramount to facilitate effective management and conservation. This study presents an initial report from a comprehensive survey of shallow-water (0–15 m) gorgonian assemblage composition and structure across sites with varying habitat quality within the Wakatobi Marine National Park (WMNP), SE Sulawesi, Indonesia. Current estimates of over 90 morphospecies from 38 genera and 12 families within the calcaxonian, holaxonian and scleraxonian groups are reported. This extensive survey confirms high local gorgonian abundance, diversity and species richness in the absence of anthropogenic influence and increasing with depth. Notably, morphological variants of the zooxanthellate species Isis hippuris Linnaeus, 1758, and Briareum Blainville, 1830, drive site and habitat assemblage differences across environmental gradients. Azooxanthellate taxa, particularly within the Plexauridae, drive species richness and diversity with depth. Of the 14 predictor variables measured, benthic characteristics, water flow and natural light explained just 30% of gorgonian assemblage structure. Furthermore, zooxanthellate and azooxanthellate taxa partitioned distinct gorgonian communities into two trophic groups—autotrophs and heterotrophs, respectively—with contrasting diversity and abundance patterns within and between study sites. This study strongly supports the WMNP as an area of high regional gorgonian abundance and diversity. Varying ecological patterns across environmental clines can provide the foundation for future research and conservation management strategies in some of the most biodiverse marine ecosystems in the world.

Divergent response to forest structure of two mobile vertebrate groups

Abstract Taxonomic and functional diversity of animals respond to habitat heterogeneity. However, how structural heterogeneity at the stand level of differently managed forests drives species richness across taxa is not clear. Here we analyze how birds and bats, sharing the ability to fly, respond to the structural composition of the vegetation layers in differently managed forests. We combined datasets of birds and bats and compared their response as taxonomic vs. functional richness towards forest structure. Overall our results revealed that bird and bat species richness were positively correlated and species richness of both taxa peaked within the same forest stands. In contrast to our prediction that richness of mobile vertebrates with similar ecological traits (the ability to fly) should respond alike to forest stand characteristics, our results showed almost no congruence. Using Generalized Linear Mixed Effects Modeling (GLMM) with model selection based on AICc and model averaging, we found that taxonomic richness of birds and bats as well as functional richness (based on main diet and foraging mode) responded to forest structure in very different ways. While the taxonomic richness of birds was mainly associated with the structural parameters contrast and forest height, representing tall trees and a relatively closed canopy, richness of bat species increased with vertical and horizontal heterogeneity within forest stands. Our findings indicate that functional richness is more useful to understand responses of bird and bats species richness to land use, forest structure and forest management, rather than focusing solely on taxonomic groups.

Naturalized alien flora of the Indian states: biogeographic patterns, taxonomic structure and drivers of species richness

Despite an existing India-wide inventory of alien plant species, an inventory documenting the occurrence of naturalized alien plant species in each of the Indian states (including union territories) was not available yet. We compiled from the literature a list of naturalized alien vascular plant species with data on their occurrence in 33 Indian states, and related the richness of naturalized species per state to climate, socioeconomic parameters and human influence. In total, we report 471 naturalized species in India, which represents 2.6% of the total flora of this country, and for 449 of them we provide the distribution in the states. The highest and lowest numbers of naturalized species are reported from Tamil Nadu (332) and the island Lakshadweep (17), respectively. The families richest in naturalized species are Compositae (75), Leguminosae (60) and Poaceae (36). The highest numbers of naturalized aliens occurs in states located at lower latitudes in the tropics, and in more northernly located states that even in the dry period still have relatively high amounts of precipitation. Naturalized species richness of a state is furthermore positively related to socioeconomic factors represented by the percentage of the population living in urban areas, and human population density. The state-wise inventory of naturalized alien species improves our knowledge on threats associated with plant invasions in India, and can be used to provide arguments for promoting programs on conservation of native biodiversity in the country as well as in particular states.

Genomics of extreme ecological specialists: multiple convergent evolution but no genetic divergence between ecotypes of Maculinea alcon butterflies

Biotic interactions are often acknowledged as catalysers of genetic divergence and eventual explanation of processes driving species richness. We address the question, whether extreme ecological specialization is always associated with lineage sorting, by analysing polymorphisms in morphologically similar ecotypes of the myrmecophilous butterfly Maculinea alcon. The ecotypes occur in either hygric or xeric habitats, use different larval host plants and ant species, but no significant distinctive molecular traits have been revealed so far. We apply genome-wide RAD-sequencing to specimens originating from both habitats across Europe in order to get a view of the potential evolutionary processes at work. Our results confirm that genetic variation is mainly structured geographically but not ecologically — specimens from close localities are more related to each other than populations of each ecotype from distant localities. However, we found two loci for which the association with xeric versus hygric habitats is supported by segregating alleles, suggesting convergent evolution of habitat preference. Thus, ecological divergence between the forms probably does not represent an early stage of speciation, but may result from independent recurring adaptations involving few genes. We discuss the implications of these results for conservation and suggest preserving biotic interactions and main genetic clusters.

Preface: Emerging trends in aquatic ecology II

You are now consulting the celebratory volume 750 of Hydrobiologia, the international journal of aquatic sciences. The journal has, since its first volume in March 1948, now exactly 67 years ago, covered a lot of ground and has seen a lot of change in the landscape of scientific publishing in general, and in that of aquatic biodiversity in particular. It has evolved from a fairly locally managed journal, to an international journal with ever increasing impact and ranking. With an ISI 2013 Impact Factor of 2.212, it now ranks 32 out of 103 journals in ‘‘Marine and Freshwater Biology’’. But in the ‘‘Marine Sciences and Fisheries’’ Category of Google Scholar, Hydrobiologia ranks proudly at a 9th place with an H5 index of 39 (the highest being Marine Ecology Progress Series with an H5-index of 49). Of course, such metrics never tell the entire story, and if one wants to judge the quality of a journal, other measures of performance must also be taken into account. Of these, the quality of the authorship, of the readership and of the editorial board are paramount. The present volume is very much a joint effort of the editors of Hydrobiologia and their collaborators and we are proud to present you the result. Each paper in this volume has at least one editor of Hydrobiologia as (co-) author, but for some papers, several editors joined forces. For example, the bibliometric paper by Siqueira et al. (2015) has three editors as authors, while the review on aquatic invasive species (Havel et al., 2015) authors a team of five Hydrobiologia editors. The title of the present special issue, ‘‘Emerging Trends in Aquatic Ecology’’, promises a wide canvas of topics, and although we have certainly not covered all ‘‘Emerging Trends’’, we are convinced that the present volume features a fair number of them. In the opening paper, Siqueira et al. (2015) explore the differences in approach to biodiversity analyses (using species richness as a response variable) between aquatic and terrestrial ecologists. They analyse the results of a systematic literature search and conclude that differences between such aquatic and terrestrial studies are not substantial. However, they do stress that there is a need for more hypothesisdriven research by both groups of ecologists, and for more research on mechanisms driving species richness variability in aquatic systems. The Marine Strategy Framework Directive (MSFD) is central to EU policy on marine (biodiversity) conservation in European Seas. Yet, as with the EU Guest editor: Koen Martens / Emerging Trends in Aquatic Ecology

Macroecological conclusions based on IUCN expert maps: A call for caution

AbstractAimInternational Union for Conservation of Nature (IUCN) expert maps are increasingly used in macroecological research. However, they have not been produced for this purpose. Macroecological insights based exclusively on this type of data could therefore be misleading. Here we compare, for a large taxonomic group (bats) and an entire biogeographical realm (Africa), the species‐specific discrepancies between IUCN maps and species distribution models (SDMs) that approximate the complete geographical range of species. We then examine the implications for a typical macroecological analysis that explores environmental correlates of species richness.LocationContinental Africa.Time periodAround 2000.TaxaBats (Chiroptera).MethodsWe measure disagreement between IUCN expert maps and SDMs at both the species (geographical ranges) and the aggregated level (range size–frequency distributions and species richness). We further quantify the difference in absolute and relative weight assigned to three variables hypothesized to drive species richness: primary productivity, climatic seasonality and environmental heterogeneity.ResultsLocation, shape and size of individual species’ ranges, derived richness patterns and range size–frequency distributions differ substantially. SDMs predict larger and more complex geographical ranges, and species’ range sizes vary less. The spatial congruence of richness hotspots among both datasets is only 42%. These discrepancies are large enough to alter the absolute explanatory power of environmental correlates, whereas the redundancy in the variation explained increases markedly when richness is inferred using SDM‐based estimates of complete species ranges.Main conclusionsIUCN expert maps differ considerably and systematically from SDMs built to estimate complete species ranges, primarily because of their intentional greater sensitivity to geographical sampling bias. This property is desirable in a conservation context but unwanted in most macroecological analyses. We therefore caution against the use of IUCN expert maps in macroecology and recommend at least gauging the robustness of results using additional range estimates designed to approximate the complete geographical range of species.

Species richness of multiple functional groups peaks in alpine tundra in subarctic Alaska

AbstractClimate warming has initiated changes to vegetation across subarctic North America with potential to dramatically alter the distribution of biodiversity of vascular plants, mosses, and macrolichens. However, landscape‐scale studies of the patterns and drivers of species richness in this region are scarce, raising the possibility that dramatic changes to biodiversity could occur undetected over a wide area with serious consequences for ecosystem integrity and conservation. We used a hierarchical, systematic design to compile a uniquely large and comprehensive diversity dataset for our study area in subarctic North America. We utilized a unified sampling frame at the landscape scale to record diversity of vascular plants, mosses, and macrolichens as the three primary components of vegetation species richness. We applied Bayesian hierarchical modeling techniques to identify site attributes associated with richness of the three functional groups. We also examined whether richness of groups was positively or negatively inter‐correlated across multiple spatial scales. Our goal was to quantify the fundamental relationships of species richness with site attributes across this landscape to better understand the possible responses of species richness to habitat changes forecast to occur in the subarctic as a result of a warming climate and other stressors. Moss, vascular plant, and terricolous macrolichen species richness were strongly inter‐correlated, due to an underlying marked positive association of each with increasing elevation into the alpine zone across multiple spatial scales. Our results further reveal varying influences of factors such as soil pH, disturbance, and plant canopy cover on diversity in these physiologically different functional groups. Taken together, the patterns revealed by our work provide a new framework to consider how predicted habitat changes wrought by warming climates in interior Alaska may affect fundamental diversity patterns of primary producers in the future, with important implications for ecosystem function and conservation.

Species‐specific environmental preferences associated with a hump‐shaped diversity/temperature relationship across tropical marine fish assemblages

AbstractAimTo identify key environmental factors associated with local fish species richness across a large tropical marine region.LocationWider Caribbean region.MethodsSpecies richness estimates were based on a sightings database covering the wider Caribbean region. Environmental variables considered were distance to key habitats, habitat area, temperature, depth, salinity, nutrient concentration, as well as natural and anthropogenic disturbance. We test the significance of associations between these factors and species richness, establish the shape of these relationships and use spatial cross‐validation to test the generality of these results. Species‐specific environmental associations within these relationships were then tested.ResultsFive environmental variables showed significant associations with species richness, but only two, temperature and depth, proved robust to spatial cross‐validation. Temperature was the best performing environmental predictor, showing a unimodal relationship with species richness and optimum temperatures consistent across analytical choices and data sets. Relationships between species richness and other environmental factors were also typically unimodal. Variation in species‐specific temperature associations was significant within species richness gradients; with a higher number of species associated with optimal temperatures.Main conclusionsTemperature represents the dominant environmental predictor of fish species richness identified by our study, showing a hump‐shaped curve, peaking at around 27.4°C. This meant that the warmest sites within our study were not necessarily the most species rich. Variation in species thermal niches may play a key role in driving species richness gradients, with significant general positive trend for fish species to occur in locations exhibiting optimum sea surface temperatures.

Patterns and drivers of plant biodiversity in Chinese university campuses

Urban biodiversity is strongly correlated with human well-being and is quickly becoming a new research field. Most previous studies in this field focus on patterns of species richness but few consider species and trait compositions and how these are shaped by anthropogenic and environmental drivers. Such information, however, is critical for effective planning and management of urban species. We compiled published species lists from 71 Chinese university campuses. We also collected environmental data for each campus, including anthropogenic (campus age and area) and environmental variables (climate and topography), to explore the distribution patterns and the drivers of species richness, composition and traits. We found that university campuses in China maintain substantial plant diversity, including at least 1565 woody and 1614 herbaceous species. The distribution pattern of campus species richness was mostly driven by anthropogenic variables, being positively correlated with campus age and size. In contrast, campus species composition and leaf traits were mostly driven by climate variables. This was especially true for woody plants of which campus species composition and traits were more constrained by mean annual temperature than herb species. Our study provides a basic but diverse database for the selection of campus plants, which can benefit the management of urban ecosystems. Our results reveal that landscape design can influence urban species richness, species composition is still restricted by the natural environment. Hence, many endangered species can be protected in these human-friendly urban ecosystems if they have suitable traits adapted to local climatic conditions.

Pattern or process? Evaluating the peninsula effect as a determinant of species richness in coastal dune forests.

The peninsula effect predicts that the number of species should decline from the base of a peninsula to the tip. However, evidence for the peninsula effect is ambiguous, as different analytical methods, study taxa, and variations in local habitat or regional climatic conditions influence conclusions on its presence. We address this uncertainty by using two analytical methods to investigate the peninsula effect in three taxa that occupy different trophic levels: trees, millipedes, and birds. We surveyed 81 tree quadrants, 102 millipede transects, and 152 bird points within 150 km of coastal dune forest that resemble a habitat peninsula along the northeast coast of South Africa. We then used spatial (trend surface analyses) and non-spatial regressions (generalized linear mixed models) to test for the presence of the peninsula effect in each of the three taxa. We also used linear mixed models to test if climate (temperature and precipitation) and/or local habitat conditions (water availability associated with topography and landscape structural variables) could explain gradients in species richness. Non-spatial models suggest that the peninsula effect was present in all three taxa. However, spatial models indicated that only bird species richness declined from the peninsula base to the peninsula tip. Millipede species richness increased near the centre of the peninsula, while tree species richness increased near the tip. Local habitat conditions explained species richness patterns of birds and trees, but not of millipedes, regardless of model type. Our study highlights the idiosyncrasies associated with the peninsula effect—conclusions on the presence of the peninsula effect depend on the analytical methods used and the taxon studied. The peninsula effect might therefore be better suited to describe a species richness pattern where the number of species decline from a broader habitat base to a narrow tip, rather than a process that drives species richness.

Nitrogen deposition and climate change have increased vascular plant species richness and altered the composition of grazed subalpine grasslands

Summary Atmospheric nitrogen (N) deposition and climate warming are two major components of global change that drive species richness and composition in plant communities. However, their combined effects have been insufficiently investigated across large spatial and temporal scales particularly in high‐elevation, nutrient‐limited ecosystems. We examine whether and how N deposition and climate warming have altered the plant richness and the composition of subalpine semi‐natural, extensively grazed grasslands of the Pyrenees, using two complementary approaches: (i) analysis of 553 relevés to explore vegetation changes across large ecological gradients including temperature and N deposition (spatial approach) and (ii) a re‐sampling of a subset of 40 sites among the 553 sites to assess temporal changes over the past decades (temporal approach). Both approaches showed that the vascular plant species richness increased when temperature and cumulative N deposition increase, shifting the species composition towards more thermophilic and eutrophic communities. Synthesis. We hypothesize that the release from abiotic constraints (milder temperature and higher nitrogen availability) due to global changes and long‐standing extensive grazing counteracting the negative effects of nitrogen deposition have been responsible for the diversity and compositional changes of plant communities over the last decades in the Pyrenees. Thus, in contrast with other grasslands, high‐elevation grazed grasslands may increase in species diversity with nitrogen deposition under climate warming.

Drivers of bird diversity in an understudied African centre of endemism: The Angolan Central Escarpment Forest

SummaryNatural habitats are being rapidly lost due to human activities. It is therefore vital to understand how these activities influence biodiversity so that suitable guidelines can be established for conservation. This is particularly important in understudied, high biodiversity, areas such as the Angolan Escarpment. Here we examine which habitat characteristics drive bird diversity and endemic species presence at Kumbira Forest, a key site in the Central Escarpment Forest. Bird diversity was sampled by 10 min bird point counts, whereas habitat characteristics were measured by a combination of ground-based vegetation surveys and remotely sensed data modelling of Landsat images. GLM, multi-model inference and model averaging were used to determine the most important variables driving species richness and the presence of endemics. The remote sensing variables performed poorly in predicting presence of Red-crested Turaco Tauraco erythrolophus and Gabela Bushshrike Laniarius amboimensis but they contributed significantly to explain species richness and Gabela Akalat Sheppardia gabela presence, both of which were associated with greater canopy cover. Liana density and elevation were also important explanatory variables in certain cases. Conservation actions at Kumbira should focus on increasing canopy cover and maintaining forest integrity (as measured by liana density), as these actions are likely to have the most positive outcomes for the avifauna.

Biogeographical region and environmental conditions drive functional traits of estuarine fish assemblages worldwide

AbstractAssessing trait–environment relationships is crucial for predicting effects of natural and human‐induced environmental change on biota. We compiled a global database of fish assemblages in estuaries, functional traits of fishes and ecosystem features of estuaries. And we quantified the relative importance of ecosystem features as drivers of patterns of fish functional traits among estuaries worldwide (i.e. drivers of the proportions of fish traits). In addition to biogeographical context, two main environmental gradients regulate traits patterns: firstly temperature, and secondly estuary size and hydrological connectivity of the estuary with the marine ecosystem. Overall, estuaries in colder regions, with larger areas and with higher hydrological connectivity with the marine ecosystem, have higher proportions of marine fish (versus freshwater), macrocarnivores and planktivores (versus omnivores, herbivores and detritivores) and larger fish, with greater maximum depth of distribution and longer lifespan. The observed trait patterns and trait–environment relationships are likely generated by multiple causal processes linked to physiological constraints due to temperature and salinity, size‐dependent biotic interactions, as well as habitat availability and connectivity. Biogeographical context and environmental conditions drive species richness and composition, and present results show that they also drive assemblage traits. The observed trait patterns and trait–environment relationships suggest that assemblage composition is determined by the functional role of species within ecosystems. Conservation strategies should be coordinated globally and ensure protection of an array of estuaries that differ in ecosystem features, even if some of those estuaries do not support high species richness.

The geographical diversification of Furnariides: the role of forest versus open habitats in driving species richness gradients

AbstractAimExplaining species richness gradients in space and time requires understanding the evolutionary processes that ultimately alter the number of species. Here we examine species richness differences between primary habitats (forest versus open) for Furnariides birds, a Neotropical endemic bird clade, to test three major historical hypotheses – diversification rate, out of the tropics and tropical niche conservatism – and assess the role of evolutionary processes in driving the Furnariides species richness gradient.LocationNeotropics.MethodsWe used phylogenetic and spatial data to tests the historical hypotheses. First, we used GeoSSE and Bayesian Analysis of Macroevolutionary Mixture models to evaluate differential diversification and dispersal rates between habitats. Second, we quantify the root distance of each species and examined the phylogenetic structure of the richness gradient and the correlation between total species richness and the richness of early‐diverged and recently originated species.ResultsFurnariides species richness is higher in forest than in open habitats. However, we found higher speciation, extinction, and dispersal rates in open when compared to forest habitats, resulting in a higher diversification rate in open habitats and higher dispersal rate out of open habitats than into them. The phylogenetic structure of the richness gradient showed strong spatial pattern, with early diverged species richness peaking in forest habitats and driving the overall Furnariides gradient.Main conclusionsThe Furnariides species richness gradient results from the joint effect of differential rates of macroevolutionary processes. Our findings highlight dispersal and extinction as dominant forces driving richness differences between habitats, through the addition and extirpation of species from open to forest habitats. Differences in species richness between habitats support niche conservatism of forest habitat preferences of Furnariides species. We suggest that open habitats are effective evolutionary arenas and a key to the maintenance of bird diversity in forest habitats over evolutionary time.

The value of urban and peri-urban conservation efforts within a global biodiversity hotspot

Background: Systematic conservation planning (SCP) is a key tool in conservation prioritisation. It has recently been applied within the eThekwini Municipal Area (EMA), South Africa, a rapidly developing metro located within a biodiversity hotspot. Most vegetation types within this region are threatened, yet have received limited scientific attention. Objectives: To assess forb biodiversity of coastal and near-coastal grasslands and contextualise potential drivers of species variation to the EMA context. Method: We quantified forb species richness, frequency and species composition, determined the variation of these amongst plots and sites, and assessed which variables were responsible for this variation. Results: Site forb species richness ranged from 33 to 84 species per site, with the most frequent species differing across the seven sites. Beta diversity was higher across than within sites. Distance to the closest traditional medicine market and site perimeter-to-area ratio were the greatest drivers of species richness, whilst altitude, aspect, mean temperature and rainfall seasonality were the main contributors to species composition patterns. Conclusion: SCP can use key environmental and climatic categories to improve selection of grasslands to maximise both species richness and variation in species composition. A more fine-scale systematic conservation plan will, in turn, provide a more robust basis for development decisions. The outcomes illustrate the importance of urban and peri-urban conservation efforts, including fine-scale conservation planning, in contributing to regional, national conservation targets.

Experimental evidence does not support the Habitat Amount Hypothesis

For a half century, habitat configuration – the arrangement of habitat patches within a landscape – has been central to theories of landscape ecology, population dynamics, and community assembly, in addition to conservation strategies. A recent hypothesis advanced by Fahrig (2013) would, if supported, greatly diminish the relevance of habitat configuration as a predictor of diversity. The Habitat Amount Hypothesis posits that the sample area effect overrides patch size and patch isolation effects of habitat fragmentation on species richness. It predicts that the amount of habitat in a local landscape, regardless of configuration, is the main landscape‐level determinant of species richness. If habitat amount is indeed the major, landscape‐level driver of species richness, the slopes of the species–area relationship (SAR) for otherwise similar fragmented and unfragmented landscapes should be indistinguishable. We tested the Habitat Amount Hypothesis with data from two replicated and controlled habitat fragmentation experiments that disentangle the effects of habitat amount and configuration. One experiment provided time‐series data on plant species richness and the other on micro‐arthropod species richness. We found that, relative to less fragmented habitats, the SARs for fragmented habitats have significantly higher slopes and that the magnitude of the difference in slopes increased over time. Relatively more species were lost in smaller areas when fragments were more isolated. In both experiments, the proportion of species lost due to increased habitat fragmentation was nearly identical to the proportion lost due to reduced habitat amount. Our results provide a direct and experimentally derived refutation of the Habitat Amount Hypothesis, supporting the long‐held view that in addition to area, patch isolation and configuration are important determinants of species richness. Differences in species richness between fragmented and non‐fragmented habitats increase over time, demonstrating that long‐term studies are needed to understand the effects of fragmentation, above and beyond the amount of habitat lost.

Drivers of species richness and compositional change in Scottish coastal vegetation

AbstractQuestionWhat are the main drivers of vegetation change within coastal dune and machair habitats and are these amenable to action to protect biodiversity at a local and national scale?LocationCoastal areas of Scotland.MethodsA national‐scale, quadrat‐based re‐visitation survey was used to assess where changes were occurring in terms of species richness and composition. Regression trees and linear mixed modelling were used to identify the main drivers of change between 1976 and 2010.ResultsThere were losses of habitat to erosion (4.7% of previously visited quadrats) and development (2.3%). Species richness changes were largely positive where sand dune and machair habitats remain part of an agricultural management system in the Inner and southern part of the Outer Hebrides. Richness losses were driven by acidic deposition and reduced grazing. Compositional changes were less related to agricultural changes, climate change and pollutant deposition than species richness changes.ConclusionsReintroduction of grazing to coastal areas appears to be a policy that would have positive effects on biodiversity, as would continued efforts to reduce atmospheric deposition and coastal planning that allowed for realignment as sediment supply decreases and sea level rise continues.

Plant diversity on high elevation islands – drivers of species richness and endemism

High elevation islands elicit fascination because of their large array of endemic species and strong environmental gradients. First, I define a high elevation island according to geographic and environmental characteristics. Then, within this high elevation island framework, I address local disturbance effects on plant distribution, drivers of diversity and endemism on the island scale, and global patterns of treeline elevation and climate change. Locally, introduced herbivores have strong negative effects on the summit scrub of my model island La Palma (Canary Islands), while roads have unexpected positive effects on endemics. On the island scale, topography and climate drive diversity and endemism. Hotspots of endemicity are found in summit regions – a general pattern on high elevation islands. The global pattern of treeline elevation behaves quite differently on islands than on the mainland. A thorough literature review and climate projections suggest that climate change will profoundly affect oceanic island floras.

Agriculture rivals biomes in predicting global species richness

Species–area relationships (SARs) provide an avenue to model patterns of species richness and have recently been shown to vary substantially across regions of different climate, vegetation, and land cover. Given that a large proportion of the globe has been converted to agriculture, and considering the large variety in agricultural management practices, a key question is whether global SARs vary across gradients of agricultural intensity.We developed SARs for mammals that account for geographic variation in biomes, land cover and a range of land‐use intensity indicators representing inputs (e.g. fertilizer, irrigation), outputs (e.g. yields) and system‐level measures of intensity (e.g. human appropriation of net primary productivity – HANPP). We systematically compared the resulting SARs in terms of their predictive ability.Our global SAR with a universal slope was significantly improved by the inclusion of any one of the three variable types: biomes, land cover, and land‐use intensity. The latter, in the form of human appropriation of net primary productivity (HANPP), performed as well as biomes and land‐cover in predicting species richness. Other land‐use intensity indicators had a lower predictive ability.Our main finding that land‐use intensity performs as well as biomes and land cover in predicting species richness emphasizes that human factors are on a par with environmental factors in predicting global patterns of biodiversity. While our broad‐scale study cannot establish causality, human activity is known to drive species richness at a local scale, and our findings suggest that this may hold true at a global scale. The ability of land‐use intensity to explain variation in SARs at a global scale had not previously been assessed. Our study suggests that the inclusion of land‐use intensity in SAR models allows us to better predict and understand species richness patterns.

Disentangling the Role of Climate, Topography and Vegetation in Species Richness Gradients.

Environmental gradients (EG) related to climate, topography and vegetation are among the most important drivers of broad scale patterns of species richness. However, these different EG do not necessarily drive species richness in similar ways, potentially presenting synergistic associations when driving species richness. Understanding the synergism among EG allows us to address key questions arising from the effects of global climate and land use changes on biodiversity. Herein, we use variation partitioning (also know as commonality analysis) to disentangle unique and shared contributions of different EG in explaining species richness of Neotropical vertebrates. We use three broad sets of predictors to represent the environmental variability in (i) climate (annual mean temperature, temperature annual range, annual precipitation and precipitation range), (ii) topography (mean elevation, range and coefficient of variation of elevation), and (iii) vegetation (land cover diversity, standard deviation and range of forest canopy height). The shared contribution between two types of EG is used to quantify synergistic processes operating among EG, offering new perspectives on the causal relationships driving species richness. To account for spatially structured processes, we use Spatial EigenVector Mapping models. We perform analyses across groups with distinct dispersal abilities (amphibians, non-volant mammals, bats and birds) and discuss the influence of vagility on the partitioning results. Our findings indicate that broad scale patterns of vertebrate richness are mainly affected by the synergism between climate and vegetation, followed by the unique contribution of climate. Climatic factors were relatively more important in explaining species richness of good dispersers. Most of the variation in vegetation that explains vertebrate richness is climatically structured, supporting the productivity hypothesis. Further, the weak synergism between topography and vegetation urges caution when using topographic complexity as a surrogate of habitat (vegetation) heterogeneity.