The role of wet‐zone fragmentation in shaping biodiversity patterns in peninsular India: insights from the caecilian amphibianGegeneophis

Abstract

Aim Indian biodiversity is concentrated in the wet zone, which is disjunctly distributed in the north-east and in the peninsular Western and Eastern Ghats. The Eastern Ghats region is smaller and less well explored biologically and the affinities and origins of its biota poorly understood. Our aim was to assess whether divergence between east and west lineages might have been caused by fragmentation of the wet zone during Pleistocene climatic fluctuations, by Late Miocene wet-zone contraction or by more ancient events. We present the first dated phylogenetic test of these alternatives by inferring relationships and dating divergences within a wet-zone-restricted lineage endemic to the Eastern and Western Ghats.Location The Eastern and Western Ghats regions of peninsular India.Methods Molecular genetic data (one nuclear and four mitochondrial genes) were newly generated for the only known Eastern Ghats teresomatan caecilian amphibian (Gegeneophis orientalis) and the only Western Ghats congener (G. pareshi) for which molecular data were not previously available. Phylogenetic relationships were inferred for Indian indotyphlids using maximum likelihood and Bayesian inference methods. Divergence times within the inferred phylogeny were estimated using a Bayesian relaxed clock method, with the Seychelles versus Indian indotyphlid divergence calibrated based on the geological separation of their respective continental land masses. ResultsThe single Eastern Ghats species of Gegeneophis is sister to all other (Western Ghats) Gegeneophis. The basalmost (and east-west) split within Gegeneophis likely occurred > 35 Ma. Main conclusions Divergence between Eastern and Western GhatsGegeneophis is too ancient to have been caused by wet-zone contraction in the Miocene or by Pleistocene climatic fluctuations. Our results are consistent with a relatively ancient origin of wet-zone lineages in the Eastern Ghats and a lack of gene flow between Eastern and Western Ghats Gegeneophis for tens of millions of years.

Environmental influences on acoustic divergence inRhinolophusbats of the Western Ghats-Sri Lanka region

“…R. beddomei prefer evergreen forests (Bates and Harrison, 1997;Wordley et al, 2015), which might explain their positive correlation of RF with humidity. R. lepidus colonized peninsular India about 1.5 Ma (Quaternary period), when aridification effects were strong and rainfall was pulsed (Kale et al, 2003;Gower et al, 2016). Rhinolophids of the R. pusillus sub-group (to which R. lepidus belongs), underwent major range expansions in this period (Dejtaradol, 2009;Jiang et al, 2010b (Csorba et al, 2003;Dejtaradol, 2009).…”

The roles of vicariance and isolation by distance in shaping biotic diversification across an ancient archipelago: evidence from a Seychelles caecilian amphibian

“…Phylogenetic relationships among Seychelles caecilians remain incompletely resolved, including identi cation of the closest extant relative of H. rostratus [38,55]. However, analyses of a previously published dataset [25] using the same methods reported in that study found that, applying nine different calibration strategies, mean estimated ages of splits among sampled extant species of Hypogeophis and Grandisonia are in the range of 16.4 -27.9…”

“…The granitic islands are of continental origin [16], and are mountain-top remnants of the largely submerged Seychelles Microcontinent ["Seychellea" of 17] that once formed part of the supercontinent Gondwanaland. These ancient remnants were isolated by the separation from Africa of a landmass [Indigascar of 18] consisting of Madagascar, Seychelles and India [19][20][21][22][23][24]; with the Seychelles becoming fully separated approximately 65 -62 Ma [24,25]. Much of the Seychelles Microcontinent, comprising the exposed (ca.…”

The roles of vicariance and isolation by distance in shaping biotic diversification across an ancient archipelago: evidence from a Seychelles caecilian amphibian

“…Here, we focus on Hypogeophis rostratus (54) because it is the most widespread endemic amphibian in the Seychelles, occurring on 10 of the granitic islands (53). Although the phylogenetic relationships among Seychelles caecilians remain unresolved (52,55), an available estimate dates the split between H. rostratus and its possible closest extant relative at ca.19 Ma (56). Hypogeophis rostratus resides in a variety of habitats and elevations and is often found in high abundance in human altered habitat such as coconut plantations and gardens (pers.…”