Genetic structure of Ilyoplax delsmani (Crustacea: Decapoda: Brachyura: Dotillidae) on the western Indonesian waters

Abstract

Estuarine crab disperses passively to different areas during their larval stage through sea currents. Ilyoplax delsmani, one of the estuarine crabs, is widely distributed in the Indo-Malaysia Archipelago. The present study aims to discern the genetic structure of Ilyoplax delsmani in the western part of Indonesia. Specimens were collected from three sites, i.e. one site in Kalimantan and two sites in Java Island. We analyzed the genetic structure of I. delsmani with COI gene using MEGA-X, DNASP v6.12.03, Arlequin v3.5.2.2., and Network v10.2. The constructed phylogenetic tree with MEGA-X with maximum likelihood (ML) using Kimura 2 parameter based on the COI gene revealed two distinct clades, i.e., Kalimantan_5133-Java_5135 as Clade 1 and Java_5136 as Clade 2. The genetic distance within the clade range from 0.2% to 2.2%, meanwhile the distance between the clades is approximately 19.3%–20.7%. Moreover, the haplotype network and FST values calculated between pairs of localities generate a congruent result with the phylogenetic tree. Through calculation using MEGA-X, we estimate that the divergence time between both clades is approximately 42.49 mya, aligning with the middle Eocene period. Hence, we deduce that both clades represent distinct species.