Eocene–Oligocene cooling and the diversification of Hemidactylus geckos in Peninsular India

Abstract

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.

Granite boulders act as deep‐time climate refugia: A Miocene divergent clade of rupicolous Cnemaspis Strauch, 1887 (Squamata: Gekkonidae) from the Mysore Plateau, India, with descriptions of three new species

“…Each of the three dry zone clades overlaps in distribution with members of the Cyrtodactylus ( Geckoella ) collegalensis complex (Agarwal, 2016; Mirza, Pal, & Sanap, 2010), the south India clade of Hemiphyllodactylus (Agarwal, Khandekar, et al, 2019), and members of the Hemidactylus prashadi clade (Agarwal, Giri, et al, 2019). Cnemaspis is apparently absent from the northern Eastern Ghats, though the gekkonid genera Geckoella , Hemidactylus, and Hemiphyllodactylus, which are all younger entrants in peninsular India dating back to the Eocene–Oligocene, are distributed in the northern Eastern Ghats (Agarwal & Karanth, 2015; Agarwal, Khandekar, et al, 2019; Lajmi & Karanth, 2020). It remains unclear whether the absence of Cnemaspis in the northern Eastern Ghats is a sampling artifact or is linked to an inherent physiological, ecological, or other biogeographic constraint.…”

Repeated evolution of terrestrial lineages in a continental lizard radiation

“…The terrestrial ecomorphs have smaller body size and toepad size, as compared to the scansorial ecomorph. A study by Lajmi and Karanth (2019) found an early increase in lineage accumulation beginning ~36 Mya in this group. Furthermore, ancestral state reconstruction revealed that the ancestor of this radiation was a dry-biome lineage.…”

“…Currently, 39 species of Hemidactylus are described from the Indian radiation, of which 27 species have been included in this study. Additionally, five new putative species delimited as per Lajmi and Karanth (2019) have been added to the study. Details of the species and their habitat information are given in Table S2…”

“…In the Indian Hemidactylus radiation, the patterns of lineage and morphological diversification is not coupled as predicted. The lineage diversification revealed an early increase in lineage accumulation concurrent with the Eocene-Oligocene cooling (Lajmi & Karanth, 2019).…”

“…The Indian radiation of Hemidactylus geckos began diversifying 36 Mya (95% HPD: 32.3-39.4), concurrent with the Eocene-Oligocene cooling. A recent study by Lajmi and Karanth (2019) revealed an early increase in lineage diversification in this radiation followed by a slowdown. Species within the Indian Hemidactylus radiation can be broadly grouped into scansorial species, that is species that inhabit vertical surfaces, and terrestrial or grounddwelling species.…”