A NEW BEACH-HOPPER, PLATORCHESTIA PARAPACIFICA N.SP. (AMPHIPODA: TALITRIDAE), FROM SOUTH KOREA, WITH MOLECULAR PHYLOGENY OF THE GENUS PLATORCHESTIA

• Published in: Journal of crustacean biology 2013-11, Vol.33 (6), p.828-842
• Main Authors: Kim, Min-Seop, Jung, Jae-Ho, Min, Gi-Sik
• Format: Article
• Language: English
• Subjects: Systematics, Biogeography and Phylogeny
• ISSN: 0278-0372; 1937-240X

To date, the genus Platorchestia Bousfield, 1982 (Crustacea, Amphipoda) includes 17 species, all of which are adapted to terrestrial and supra-littoral habitats. According to a recent study, some species exist as cryptic species complexes. Here, we describe a new beachhopper, Platorchestia parapacifica, collected from beaches in South Korea. This new species can be easily distinguished from other congeners by the morphology of its antennae 1 and 2, gnathopods, coxal plate 6, pereiopod 7, and telson. We detail the morphological characteristics of P. parapacifica, and compare it with related species. In addition, we demonstrate the phylogenetic relationships of the genus Platorchestia based on the mitochondrial cytochrome oxidase subunit 1. The results of our molecular analyses indicate that the P. platensis-complex is monophyletic and deeply divergent from the P. japonica-complex. Estimation of the genus divergence times using molecular clock analysis suggests that these species shared a most recent common ancestor during the Miocene period (7.9-10.5 million years ago). Notably, common ancestry of the P. japonica complex diverged into two species during the Zanclean and Messinian periods (3.7-6.6 million years ago), while the ancestral talitrid of the P. platensis complex diverged into three species during the Messinian and Tortonian period (6-8 million years ago). Our results reconfirm the usefulness of molecular techniques for biodiversity studies of talitrids, including phylogenetic relationships, species boundaries, and divergence times.