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

Abstract

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.

Speciation and secondary contact in a fossorial island endemic, the São Tomé caecilian

“…Besides imposing transient physical barriers to gene flow, volcanic eruptions may also favour divergence through local adaptation when populations become isolated in distinct environments. This hypothesis is consistent with associations of the two caecilian lineages within distinct precipitation regimes and habitats across the island (Figure 4), which may reflect local adaptation to specific soil microhabitats (Torres‐Sánchez et al, 2019) as demonstrated in other fossorial vertebrates (Fouquet et al, 2021; Martín et al, 2013). Associations between habitat type and lineage divergence were also reported in reed frogs (Bell & Irian, 2019) and fruit flies (Coyne et al, 2002; Matute & Coyne, 2010) on São Tomé, suggesting that this pattern may be widespread across a variety of organisms on the island, although the specific mechanisms of local adaptation are likely to differ between fossorial versus surface‐dwelling taxa.…”

Comparative osteology of the fossorial frogs of the genus Synapturanus (Anura, Microhylidae) with the description of three new species from the Eastern Guiana Shield

“…However, genetic, morphological and acoustic variation across this range suggests that some of these populations may not belong to S. mirandaribeiroi. The similarity between the skull and humerus of the paratype (MNHN-RA-1974.0397) and that of specimens from southwestern French Guiana, Suriname and the Manaus region, an area encompassing the type locality of S. mirandaribeiroi, strongly suggests conspecificity (Fouquet et al, 2021). Moreover, genetic data indicate that these specimens form a lineage related to populations located in the southern part of the Amazon River basin (Synapturanus sp.…”

“…Within the Neotropics, microhylids represent 18% of the total number of described species (Frost, 2021) and belong to two major groups: Gastrophryninae Fitzinger, 1843, the most species rich subfamily with 81 species (Frost, 2021) distributed from southern North America to Argentina; and a species poor clade formed by the monotypic Adelastinae Peloso, Frost, Richards, Rodrigues, Donnel dergo endotrophic development (Nelson & Lescure, 1975;Pyburn, 1975;1977;Menin et al, 2007). Although no direct observations have been reported, the overall morphology, and notably the shape of the snout and humerus, suggest a head-first, forward-burrowing, behavior (Keeffe & Blackburn, 2020;Fouquet et al, 2021). Overall, Synapturanus are poorly known, and the scarcity of basic data on their life-history and rarity in zoological collections is easily explained by their secretive lifestyle.…”

“…Using a combination of genetic, acoustic and morphological data, Fouquet et al, 2021 demonstrated that the diversity in Otophryninae is largely underestimated. For Synapturanus, for example, the study suggests that at least another 15 species could be formally recognized.…”

Cantos de las ranas y los sapos de Colombia: estado actual del conocimiento y perspectivas de investigación en ecoacústica

“…en el departamento de Vaupés, región Amazonía. Por el contrario, los últimos cantos de anuncio descritos al momento de finalizar nuestra revisión fueron para las especies Pristimantis alius, P. ingles y Synapturanus salseri [68,69]. El canto de anuncio ha sido descrito más de una vez para el 53.4% de las especies (n = 164 spp.…”