Lineage delimitation and description of nine new species of bush frogs (Anura: Raorchestes, Rhacophoridae) from the Western Ghats Escarpment

Abstract

Bush frogs of the genus Raorchestes are distributed mainly in the Western Ghats Escarpment of Peninsular India. The inventory of species in this genus is incomplete and there is ambiguity in the systematic status of species recognized by morphological criteria. To address the dual problem of taxon sampling and systematic uncertainty in bush frogs, we used a large-scale spatial sampling design, explicitly incorporating the geographic and ecological heterogeneity of the Western Ghats. We then used a hierarchical multi-criteria approach by combining mitochondrial phylogeny, genetic distance, geographic range, morphology and advertisement call to delimit bush frog lineages. Our analyses revealed the existence of a large number of new lineages with varying levels of genetic divergence. Here, we provide diagnoses and descriptions for nine lineages that exhibit divergence across multiple axes. The discovery of new lineages that exhibit high divergence across wide ranges of elevation and across the major massifs highlights the large gaps in historical sampling. These discoveries underscore the significance of addressing inadequate knowledge of species distribution, namely the "Wallacean shortfall", in addressing the problem of taxon sampling and unknown diversity in tropical hotspots. A biogeographically informed sampling and analytical approach was critical in detecting and delineating lineages in a consistent manner across the genus. Through increased taxon sampling, we were also able to discern a number of well-supported sub-clades that were either unresolved or absent in earlier phylogenetic reconstructions and identify a number of shallow divergent lineages which require further examination for assessment of their taxonomic status.

Glaciations, gradients, and geography: multiple drivers of diversification of bush frogs in the Western Ghats Escarpment

“…The southern and central regions of the Western Ghats are characterized by the presence of tall mountains, termed as 'massifs' here, with intervening plateaus and valleys that separate them (figure 4b). Our sampling covered 13 of the 14 massifs and also spanned the entire elevational gradient from sea level to approximately 2650 m in the southern and central Western Ghats (see the electronic supplementary material; see also [31]). …”

“…Another clade composed of four lineages (clade H, figure 4) showed in situ diversification with all the lineages currently restricted to the Agasthyamalai massif (figure 4b). In the case of sympatric sister lineages from the Nilgiri massif, morphological separation between the sister lineages in L1a indicates potential habitat differences between the two [31]. The sister lineages from the Anaimalai massif, Raorchestes beddomii and Raorchestes theurkaufi, also show differences, with the former occurring in open canopy habitats including forest edges and the latter restricted to forests.…”

“…Recently, we uncovered a large number of new lineages of bush frogs (Genus Raorchestes, Family: Rhacophoridae) from this Escarpment [31]. These bush frogs are endemic to the Escarpment and their high diversity makes them good models to test multiple hypotheses of diversification.…”

Opportunities and challenges in using remote sensing for identifying grassland restoration sites and invasive tree species management in a global biodiversity hotspot

“…The shola grassland also supports an endangered ungulate (Nilgiri tahr, Nilgiritragus hylocrius; (Alempath, 2008)) and a threatened bird (Nilgiri Pipit, Anthus nilghiriensis; (Lele et al;Robin et al, 2014)). Additionally, there are at least 20 frog species that are restricted to these grasslands (Abraham et al, 2015;Biju et al, 2010;Princy et al, 2017;Vijayakumar et al, 2014). Although locally common, all these species are specialists that are restricted to the narrow ecological range of the montane grasslands of the Shola Sky Islands.…”

Climatic and geographic barriers drive distributional patterns of bird phenotypes within peninsular India

“…Addressing regional biogeographic patterns requires either large phylogenetic datasets at small spatial scales (Agarwal et al 2014, Vijayakumar et al 2014 or community-level distribution assessments (Tamma and Ramakrishnan 2015). The birds of the Indian sub-continent have poor phylogenetic data (Reddy 2014).…”