Relicts in the mist: Two new frog families, genera and species highlight the role of Pantepui as a biodiversity museum throughout the Cenozoic

The iconic mountains of the Pantepui biogeographical region host many early-diverging endemic animal and plant lineages, concurring with Conan Doyle's novel about an ancient "Lost World". While this is the case of several frog lineages, others appear to have more recent origins, adding to the controversy around the diversification processes in this region. Due to its remoteness, Pantepui is challenging for biological surveys, and only a glimpse of its biodiversity has been described, which hampers comprehensive evolutionary studies in many groups. During a recent expedition to the Neblina massif on the Brazil-Venezuela border, we sampled two new frog species that could not be assigned to any known genus. Here, we perform phylogenetic analyses of mitogenomic and nuclear loci to infer the evolutionary relationships of the new taxa and support their description. We find that both species represent single lineages deeply nested within Brachycephaloidea, a major Neotropical clade of direct-developing frogs. Both species diverged >45 Ma from their closest relatives: the first is sister to all other Brachycephaloidea except for Ceuthomantis, another Pantepui endemic, and the second is sister to Brachycephalidae, endemic to the Brazilian Atlantic Forest. In addition to these considerable phylogenetic and biogeographic divergences, external morphology and osteological features support the proposition of two new family and genus-level taxa to accommodate these new branches of the amphibian tree of life. These findings add to other recently described ancient vertebrate lineages from the Neblina massif, providing a bewildering reminder that our perception of the Pantepui's biodiversity remains vastly incomplete. It also provides insights into how these mountains acted as "museums" during the diversification of Brachycephaloidea and of Neotropical biotas more broadly, in line with the influential "Plateau theory". Finally, these discoveries point at the yet unknown branches of the tree of life that may go extinct, due to global climate change and zoonotic diseases, before we even learn about their existence, amphibians living at higher elevations being particularly at risk.

Species diversity and biogeography of an ancient frog clade from the Guiana Shield (Anura: Microhylidae: Adelastes, Otophryne, Synapturanus) exhibiting spectacular phenotypic diversification

The outstanding biodiversity of the Guiana Shield has raised many questions about its origins and evolution. Frogs of the genera Adelastes, Otophryne and Synapturanus form an ancient lineage distributed mostly across this region. These genera display strikingly disparate morphologies and life-history traits. Notably, Synapturanus is conspicuously adapted to fossoriality and is the only genus within this group to have dispersed further into Amazonia. Moreover, morphological differences among Synapturanus species suggest different degrees of fossoriality that might be linked to their biogeographical history. Through integrative analysis of genetic, morphometric and acoustic data, we delimited 25 species in this clade, representing a fourfold increase. We found that the entire clade started to diversify ~55 Mya and Synapturanus ~30 Mya. Members of this genus probably dispersed three times out of the Guiana Shield both before and after the Pebas system, a wetland ecosystem occupying most of Western Amazonia during the Miocene. Using a three-dimensional osteological dataset, we characterized a high morphological disparity across the three genera. Within Synapturanus, we further characterized distinct phenotypes that emerged concomitantly with dispersals during the Miocene and possibly represent adaptations to different habitats, such as soils with different physical properties.

Lizards from the Lost World: two new species and evolutionary relationships of the Pantepui highland Riolama (Gymnophthalmidae)

The Pantepui region of northern South America harbours an endemic fauna that differs dramatically from those of the surrounding lowland rainforests and savannas. A component of this unique fauna is Riolama, a poorly known genus of microteiid lizards with four described and two undescribed species restricted to tepui mountains. We here implement an integrative approach to formally describe the two unnamed species and investigate the phylogenetic relationships and timing of diversification in Riolama using a fossil-calibrated molecular approach. Our results suggest that diversification initiated in Riolama during the Oligocene (c. 28 Mya), thereby characterizing the genus as an ancient lineage. This supports the Plateau biogeographic hypothesis to explain the diversification of the Pantepui fauna. Our divergence time estimation analysis also provides an updated temporal framework for the diversification of the highly diverse Gymnophthalmidae clade.

Répteis da Estação Ecológica Serra Geral do Tocantins, Brasil Central

Os Cerrados sul-americanos abrigam alta diversidade de répteis, incluindo elevado número de endemismos. No entanto, o conhecimento desta diversidade é ainda incompleto frente à acelerada transformação das paisagens naturais no Brasil central. Constituem, portanto, uma das regiões prioritárias para estudo e conservação da biodiversidade mundial. Estudos intensivos sobre a fauna de répteis do Cerrado são necessários e urgentes para melhor compreensão dos processos que levaram à sua origem e distribuição e para subsidiar ações de conservação. Por meio de métodos padronizados, amostramos duas regiões ainda inexploradas da Estação Ecológica Serra Geral do Tocantins, situada na região do Jalapão. Registramos 45 espécies de répteis para a EESGT e entorno, o que representa uma riqueza alta e comparável à de outras regiões bem amostradas do Cerrado. Curvas de acumulação e estimadores indicam que a riqueza local de lagartos e anfisbenídeos aproxima-se da riqueza real enquanto a de serpentes é subestimada. A distribuição não-aleatória das espécies na paisagem concorda com evidências anteriores sugerindo utilização diferencial dos hábitats pelos répteis. Reunindo os resultados do presente estudo com os de levantamentos prévios realizados na região, registramos 88 espécies de répteis para o Jalapão sendo oito registros novos que incluem Bachia oxyrhina uma espécie recém descrita da região. As espécies da área apresentam três padrões gerais de distribuição: (1) espécies endêmicas do Cerrado, (2) espécies compartilhadas com domínios da diagonal de formações abertas sul-americanas, e (3) espécies de ampla ocorrência, compartilhadas também com ecossistemas florestais. Prevalecem espécies de ampla distribuição, porém é grande o número de espécies típicas do Cerrado, incluindo cinco possivelmente endêmicas do Jalapão, e há contribuição importante da fauna da Caatinga. A distribuição dos répteis em escala local e regional demonstra a necessidade de considerar a heterogeneidade paisagística para o planejamento de diretrizes visando à conservação em regiões do Cerrado. Por sua grande extensão, posição biogeográfica e complexidade de relevo e tipos de hábitat, a EESGT tem papel fundamental para a preservação e conhecimento da diversidade de répteis do Cerrado.