Insight into the evolutionary history ofIndoplanorbis exustus(Bulinidae: Gastropoda) at the scale of population and species

Abstract

The history of a lineage is intertwined with the history of the landscape it inhabits. Here we showcase how the geo-tectonic and climatic evolution of South Asia and surrounding landmasses have shaped the biogeographical history of Indoplanorbis exustus, a tropical Asian, freshwater snail. We amplified partial COI gene fragments from all over India and combined this with a larger dataset from South and Southeast Asia to carry out phylogenetic reconstruction, species delimitation analysis and population genetic analyses. Two nuclear genes were also amplified from a few individuals per putative species to carry out divergence dating and ancestral area reconstruction analyses. The results suggest that I. exustus dispersed out of Africa into India during the Eocene. Furthermore, molecular data suggest I. exustus is a species complex consisting of multiple putative species. Primary diversification took place in the Northern Indian plains or in Northeast India. The speciation events appear to be primarily allopatric caused by a series of aridification events starting from the late Miocene to early Pleistocene. None of the species appears to have any underlying genetic structure suggestive of high vagility. All the species underwent population fluctuations during the Pleistocene, probably driven by the Quaternary climatic fluctuations.

Phylogeny of freshwater mollusc genus Brotia H. Adams, 1866 (Gastropoda: Pachychilidae) from north-east India

“…However, India also received many biotic elements from South-East Asia c. 55 Ma and again during the mid-Miocene (17-14 Ma; Klaus et al 2016 and references therein). Recent studies highlighted the biogeography of some Indian freshwater gastropods and provided insights into the origin in India and underlying dispersal patterns (Köhler and Glaubrecht 2007;Köhler and Dames 2009;Saha et al 2022;Sil et al 2019Sil et al , 2020Sil et al , 2022Sil et al , 2023. These studies have revealed the 'out-of-Asia' and 'into-India' scenarios for the freshwater pachychilid genus Paracrostoma, a close relative of Brotia (Köhler and Glaubrecht 2007).…”