The Western Ghats (WG) of south India, a global biodiversity hotspot, has experienced complex geological history being part of Gondwana landmass and encountered extensive volcanic activity at the end of Cretaceous epoch. It also has a climatically and topographically heterogeneous landscape. Thus, the WG offer a unique setting to explore the influence of ecological and geological processes on the current diversity and distribution of its biota. To this end, three explicit biogeographical scenarios were hypothesized to evaluate the distribution and diversification of wet evergreen species of the WG – (1) southern WG was a refuge for the wet evergreen species during the Cretaceous volcanism, (2) phylogenetic breaks in the species phylogeny would correspond to geographic breaks (i.e., the Palghat gap) in the WG, and (3) species from each of the biogeographic subdivisions within the WG would form distinct clades. These hypotheses were tested on the centipede genus Digitipes from the WG which is known to be an ancient, endemic, and monophyletic group. The Digitipes molecular phylogeny was subjected to divergence date estimation using Bayesian approach, and ancestral areas were reconstructed using parsimony approach for each node in the phylogeny. Ancestral-area reconstruction suggested 13 independent dispersal events to explain the current distribution of the Digitipes species in the WG. Among these 13 dispersals, two dispersal events were at higher level in the Digitipes phylogeny and were from the southern WG to the central and northern WG independently in the Early Paleocene, after the Cretaceous Volcanism. The remaining 11 dispersal events explained the species’ range expansions of which nine dispersals were from the southern WG to other biogeographic subdivisions in the Eocene-Miocene in the post-volcanic periods where species-level diversifications occurred. Taken together, these results suggest that southern WG might have served as a refuge for Digitipes species during Cretaceous volcanism.
The monotypic genus Dravidogecko, represented by its type-species D. anamallensis, is singular amongst peninsular Indian gekkonid lineages in its endemism to the Western Ghats. Molecular species delimitation approaches reveal at least seven species-level lineages within the genus from its distribution range across the mid–high elevations of the southern Western Ghats of India. These lineages, albeit superficially cryptic, are patently diagnosable from each other by employing a limited but precise set of morphological characters. Six of these lineages that were obscured under the nomen D. anamallensis are herein recognized as distinct species. A reappraisal of the genus Dravidogecko is provided based on external morphology and osteological characters, along with a detailed redescription of the holotype of D. anamallensis. A key to the species based on diagnostic characters is presented. Gene-trees based on mitochondrial and nuclear DNA data recovered marginally disparate topologies and were consequently coalesced into a species-tree for phylogenetic inference. Timetree analysis reveals late Miocene cladogenesis in this group and establishes late Palaeocene divergence from its sister genus, Hemidactylus, making Dravidogecko one of the earliest, extant lizard lineages to have colonized peninsular India.
The Oriental Region has been a focus of biogeographical research for more than two centuries. We examined systematics and biogeography of the centipede genus Rhysida in this region. A robust species hypothesis for the Indian subcontinental and Southeast Asian Rhysida clade uses molecular, morphological and distribution data. Twelve species are recognized in two monophyletic species complexes, eight belonging to the Rhysida immarginata and four to the Rhysida longipes species complex. They include Rhysida aspinosa, Rhysida crassispina, R. immarginata, R. longipes and seven new species, five of which are formally named in this paper: Rhysida ikhalama, Rhysida konda, Rhysida lewisi, Rhysida pazhuthara and Rhysida sada The nine Rhysida species are documented taxonomically and their morphological variation is reviewed. An integrative systematic approach reveals that diversity of Rhysida in the Indian subcontinent has been underestimated. Both species complexes started to diversify in the Early to Late Cretaceous in the Indian subcontinent. The out-of-India hypothesis is supported in both clades, because Southeast Asian species are nested in Indian subcontinental clades. Historical biogeographical analyses suggest two independent post-collision dispersal events, one in the immarginata clade and another where R. longipes expanded its range into Southeast Asia.
The Eocene-Oligocene cooling marks a global shift towards a cooler and drier climate, concurrent with significant turnover in biota globally. In Peninsular India, palynological investigations suggest a shift from wet rainforest vegetation to dry and seasonal species during this period. However, the grassland and open habitats that dominate this region at present expanded relatively recently due to Late Miocene intensification of monsoon seasonality. We test the possible role of these climatic shifts in generating the dry habitat diversity of an endemic radiation of Hemidactylus geckos distributed in both wet and dry habitats, by investigating whether (a) the beginning of the diversification of dry habitat lineages overlap with the Eocene-Oligocene cooling or late Miocene aridification and (b) accompanied by an increase in diversification. Molecular data (two nuclear and two mitochondrial gene fragments) were generated for samples collected across Peninsular India, and along with previously published data, a time-calibrated phylogeny was reconstructed. Ancestral state reconstruction of dry and wet habitat states was carried out on the time-calibrated phylogeny and γ-statistics along with a test for diversity-dependent diversification utilized to examine the trend in lineage accumulation. Results show the ancestral node of this radiation to have a dry habitat state, which began diversifying between 39 and 32 million years ago, concurrent with the Eocene-Oligocene cooling. Furthermore, lineage diversification fit a diversitydependent model of diversification and the γ-statistics revealed an early increase in diversification followed by a slowdown later. The deep divergences of dry habitat lineages concurrent with the Eocene-Oligocene cooling suggest that this could have served as an ecological opportunity facilitating an early increase in lineage diversification of Hemidactylus in this region. These results suggest an ancient origin and long persistence of arid ecosystems in Peninsular India.
2014). Cryptic species and Miocene diversification of Palaearctic naked-toed geckos (Squamata: Gekkonidae) in the Indian dry zone -Zoologica Scripta, 43, 455-471. We sampled Palaearctic naked-toed geckos from across their range in India and used two mitochondrial and two nuclear genes to reconstruct relationships within a global phylogeny. Published sequences of Peninsular Indian Hemidactylus allow us to contrast these two groups in dating analysesproviding insights into the history of the Indian dry zone. Palaearctic naked-toed geckos first moved onto the Indian Plate in the Oligocene, with higher-level diversification probably linked to collision of the Indian and Eurasian plates, and subsequent dispersal into-India and diversification with increasing Miocene aridity. An independent gekkonid radiation with species in the dry zone, Hemidactylus diversified during the same period in Peninsular India. Our results demonstrate that dry zone taxa across India may date back to at least the Miocene, with a potential historical climatic barrier between the Indus and Peninsular Indian Divisions. 'Cyrtopodion' aravallense is revealed to be a complex with seven genetically and environmentally divergent lineages that began diversifying in the late Miocene, congruent with increased aridity in north-western India. This discovery of cryptic diversity in the Indian dry zone represents the first terrestrial vertebrate radiation from north-western central India and highlights how little we understand of the regions' biodiversity, emphasizing the need for systematic geographic sampling and multiline evidence to reveal true patterns of diversity. The ancestor of 'Cyrtopodion' aravallense came into the nascent Indian dry zone in the Miocene and has since diversified, potentially in the absence of any sympatric scansorial rupicolous geckos. Cyrtopodion scabrum represents a unique case of commensalism and shows phylogeographic structure in its presumed native range. The taxonomic implications of our study include a number of undescribed species, recognition of 'Cyrtopodion' as a distinct lineage and the non-monophyly of Altiphylax.
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