Aim.  High levels of species richness in mountains are associated with their hypothetical roles as cradles and/or museums of diversity but the generality of these roles remains unknown. To fill this gap, we tested these two hypotheses at a global scale and assessed the direct and indirect effects of abiotic regional features on the variation of montane amphibian richness worldwide. Location. Global Time period: Last 300 million years Major taxa studied. Amphibians Methods. Using an amphibian phylogeny containing 7238 species, along with species distribution and climatic data, we estimated species richness, speciation rates, evolutionary time, terrain roughness, area, and climatic stability for 514 of the world's mountain ranges. Then, we evaluated the direct and indirect effects of these variables on richness patterns across these mountains using structural equation models. Results. We found that most diverse mountain ranges for amphibians are concentrated in the Neotropics, but the fastest speciation rates are not restricted to this region. Instead, we found that evolutionary time, area and climatic stability better explained the global patterns of amphibian diversity in mountains. Species richness is higher in mountain regions with large and climatically stable areas, where early derived lineages originated/established and accumulated through time. Main conclusions. Mountains host and invaluable biodiversity shaped through deep time. Differences in speciation rates do not play a major role in explaining amphibian species richness across mountains. Instead, mountains experiencing milder historical climatic oscillations and having greater available areas for species persistence likely faced lower extinction rates leading to an increased accumulation of amphibian species through time.  This condition highlights the importance of mountains as museums of deep evolutionary legacies and speciose biotas

Continental mountain areas cover less than 15% of global land surface, yet, these regions concentrate over 80% of global terrestrial diversity. One prominent hypothesis to explain this pattern proposes that high mountain diversities could be explained by higher diversification rates in regions of high topographic complexity. While high speciation in mountains has been detected for particular clades and regions, the global extent to which lineages experience faster speciation in mountains remains unknown. Here we address this issue using amphibians as model system (>7,000 species) and found that families showing high diversification rates contain a high proportion of species distributed in mountains. Moreover, we found that lineages inhabiting areas of high topographic complexity speciate faster than lineages occupying areas topographically less complex. When comparing across regions, we identified the same pattern in five biogeographical realms where higher speciation rates are associated with higher levels of complex topography. Low magnitude differences in speciation rates between some low and high complex topographies suggest that high mountain diversity is also affected by low extinction and/or high colonization rates. Nevertheless, our results bolster the importance of mountains as engines of speciation at different geographical scales and highlight their importance for the conservation of global biodiversity.

Isthmian Central America (ICA) is one of the most biodiverse regions in the world, hosting an exceptionally high number of species per unit area. ICA was formed < 25 million years ago and, consequently, its biotic assemblage is relatively young and derived from both colonization and in situ diversification. Despite intensive taxonomic work on the local fauna, the potential forces driving genetic divergences and ultimately speciation in ICA remain poorly studied. Here, we used a landscape genetics approach to test whether isolation by distance, topography, habitat suitability, or environment drive the genetic diversity of the regional frog assemblage. To this end, we combined data on landscape features and mitochondrial DNA sequence variation for nine co-distributed amphibian species with disparate life histories. In five species, we found that at least one of the factors tested explained patterns of genetic divergence. However, rather than finding a general pattern, our results revealed idiosyncratic responses to historical and ecological processes, indicating that intrinsic life-history characteristics may determine the effect of different drivers of isolation on genetic divergence in ICA. Our work also suggests that the convergence of several factors promoting isolation among populations over a heterogeneous landscape might maximize genetic differentiation despite short geographical distances. In conclusion, abiotic factors and geographical features have differentially affected the genetic diversity across the regional frog assemblage. Much more complex models (i.e. considering multiple drivers), beyond simple vicariance of Caribbean and Pacific lineages are needed to better understand the evolutionary history of ICA’s diverse biotas.