Systematics, biogeography and echolocation of selected Vespertilionids (Chiroptera: vespertilionidae) in Western Ghats, India

Abstract

Resolving bat taxonomy is crucial to understand their remarkable diversity, evolutionary relationships, ecosystem services, managing zoonotic diseases and develop effective conservation strategies. The Western Ghats (WG) biodiversity hotspot, home to nearly 60 bat species, is considered as one of the India’s significant bat hotspots. However, this region harbors considerable cryptic species, particularly within the family Vespertilionidae (vesper bats or evening bats or vespertilionids). The present study was undertaken with the objective of elucidating the taxonomic ambiguity of selected vespertilionids in the WG by using an integrative taxonomic approach, ie, a combination of morphometric, genetic and acoustic data. For the proposed study, bats were sampled from three distinct forested landscapes of southern WG including the Idukki, Thrissur, and Wayanad districts of Kerala. Two individuals belong to the genus Tylonycteris (Bamboo bats) and one individual of Murina (Tube-nosed bat) were collected either using harp traps or mist nets. Eighteen morphological measurements, 16 cranio-dental measurements and nine acoustic parameters were measured and examined for the present study. Statistical analysis identified key distinguishing characters among the sister species of Tylonycteris and Murina. Additionally, DNA was extracted from the voucher specimens using QIAGEN DNeasy Blood and Tissue Kit. The PCR amplification was performed for the mitochondrial gene Cytochrome c oxidase subunit 1 (CO1). Phylogenetic reconstruction of the DNA sequences and calculation of the genetic divergence were conducted using the IQTREE ver. 7.490 and MEGA 7, respectively. The findings of the morphological and cranio- dental analysis revealed that the Tylonycteris genus is primarily distinguished based on prominent skull characteristics including greatest length of skull (GTL), condylo-canine length (CCL), length of upper canine to third upper molar (C-M3), and upper canine width (C1-C1). While the genus Murina have subtle morphological differences among species with forearm length (FA) as a key differentiating character. However, a detailed knowledge on the acoustic variations were lacking in order to understand the 88 overall acoustic diversity of both the genera. Phylogenetic analysis corroborated these findings, identifying significant genetic divergences between the species. The phylogenetic reconstruction confirmed that the Tylonycteris sp and Murina sp. from the WG has an affinity with the Southeast Asian (SEA) counterparts, suggesting a shared biogeographical origin. The observed genetic divergences for Tylonycteris sp. ranged from 6.6 % to 7.6% with T. fulvida and T. pachypus from SEA, while the Murina sp. exhibited a genetic distance of 3.7%, 5.5%, and 5.6% with M. walstoni sequences from South Asia (Nepal), and SEA (Vietnam and Laos), suggesting two potential new species. The present study highlights the importance of using an integrative taxonomic approach in successful species delimitation of bats. Further, this integrative approach represents a crucial step towards resolving the taxonomy of bats.