Genetic divergence and signatures of historical isolation of the traditionally harvested Amolops marmoratus from the Darjeeling Hill Region in the Himalaya Biodiversity Hotspot

Abstract

The Darjeeling Hill Region (DHR) has numerous freshwater bodies, such as hill streams, springs, and temporary water pools. It receives abundant rainfall and has extensive forest cover, which together play vital roles in sustaining frog diversity. Amolops marmoratus is among the notable hillstream frogs, known for its wide geographic distribution and status as a local delicacy. Thus, A. marmoratus is an important subject for studying genetic divergence and population structure along with anthropogenic pressure. This research investigates the standard morphological characteristics and genetic relationships of A. marmoratus globally using 16S rRNA and COI gene sequences. Our results revealed low estimates of nucleotide and gene diversity in A. marmoratus from the DHR, whereas comparatively higher values were observed in Southeast Asia, China, and Myanmar. Higher FST values were noted between the DHR populations and those from other Asian regions, whereas lower FST values were found among populations from Myanmar and Southeast Asia. However, these comparisons warrant caution given unequal sample sizes and the potential for cryptic lineage diversity within this taxonomically complex group. Phylogenetic analysis indicated distinct clades corresponding to different regions, with comparatively shorter branches and limited founders in the DHR group. The significantly negative Fu’s Fs value, along with a unimodal mismatch distribution, indicated a deviation from demographic equilibrium reflecting a historical post-founder demographic expansion. These findings indicate strong regional differentiation for A. marmoratus. The inherently reduced genetic diversity of A. marmoratus in the DHR is consistent with historical demographic processes and geographic isolation. Furthermore, local frog-eating practices may act as a severe contemporary stressor on this already genetically depauperate population. We recommend framing conservation guidelines and increasing awareness among locals to promote a balanced ecosystem and ensure the long-term survival of A. marmoratus in the DHR.