Phylogeny and Genetic Variation within Population of Tachypleus gigas (Muller, 1785)

Isolated population of Indian horseshoe crabs, Tachypleus gigas plays an important role in the ecology of several marine organisms, and is being scrutinized for its abundance and morphology by many researchers. However, limited information is available about its genetic variability and evolution. Samples of horseshoe crab were collected from the east coasts of India and analysed for their phylogenetic relationship, genetic variability and structure within population based on the cytochrome oxidase I (COI) gene sequence. Analysis of molecular variance revealed two groups with significant genetic differentiation indices (F_ST = 0.544, p < 0.001), and the number of migrants (Nm) was estimated as 0.11 individuals per generation. Maximum likelihood results revealed two distinct clusters, showing that the evolution of the Indian population was genetically diverse forming a separate clade from other Southeast Asian populations, moderately with a low gene flow. Considering the ecological, economic and evolutionary significance of T. gigas and its declining population, there is a pressing need for conservation measures.