Meter-resolution imagery of our world and myriad biodiversity records collected through citizen scientists and automated sensors belie the fact that much of the planet's biodiversity remains undiscovered. Conservative estimates suggest only 13 to 18% of all living species may be known at this point [1][2][3][4] , although this number could be as low as 1.5% 5 . This biodiversity shortfall 6,7 strongly impedes the sustainable management of our planet's resources, as the potential ecological and economic relevance of undiscovered species remains unrecognized 8 . Here we use model-based predictions of terrestrial vertebrate species discovery to estimate future taxonomic and geographic discovery opportunities. Our model identifies distinct taxonomic and geographic unevenness in future discovery potential, with greatest opportunities for amphibians and reptiles and for Neotropical and IndoMalayan forests. Brazil, Indonesia, Madagascar, and Colombia emerge as holding greatest discovery opportunities, with a quarter of future species descriptions expected there. These findings highlight the significance of international support for taxonomic

Aim Snake faunal dissimilarity within tropical forests is not well characterized, nor are the factors underlying these patterns. Our aim was to disentangle the ecological and historical factors driving biogeographical subregions (BSR) for snakes.Location Brazilian Atlantic Forest (BAF). MethodsWe compiled 274 snake inventories to build a species-by-site matrix and used unconstrained ordination and clustering techniques to identify the number of snake BSR. We applied an interpolation method to map axes of compositional variation over the whole extent of the BAF, and then classified the compositional dissimilarity according to the number of snake BSR identified a priori. We used multinomial logistic regression models and deviance partitioning techniques to investigate the influence of contemporary climatic stability, productivity, topographic complexity, and historical climate shifts in explaining the BSR. ResultsWe identified 198 snake species organized into six BSR, three of them located along the BAF coast and the other three predominantly inland BSR. Climatic stability made the largest contribution to explaining the variability in snake BSR, followed by productivity and historical variation in climate. Topography was important only if historical variation in climate was excluded from the analysis.Main conclusions The highest rates of snake endemism within BAF were in the coastal BSR, as compared to the inland BSR that are mostly composed of open habitat specialists. Our findings suggest that the topographic complexity of the BAF acts on snake distributions not as a physical barrier, but rather as a climatic barrier, providing historical climate refuges for species living along altitudinal gradients. Overall, the predominance of climatic stability and historic variation in climate in explaining snake BSR reinforces the importance of thermoregulatory constraints in shaping the distribution of tropical ectotherm species.Dev. expl (%) = percentage of deviance explained, AICc = Akaike's information criterion corrected for small sample sizes, wAICc = AICc weight. Cstab = contemporary climatic stability, Prod = productivity, Topo = topographic complexity, Cclim = contemporary climate (Cstab + Prod), Hclim = historical variation in climate. See Methods for individual predictor abbreviation.

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.