Molecular phylogeny of the Indochinese freshwater mussel genus Scabies Haas, 1911 (Bivalvia: Unionidae)

Abstract

© 2019 by Chulalongkorn University. Molecular phylogeny of the Indochinese freshwater mussel genus Scabies Haas, 1911 was studied. The examined taxa included all seven recognized species of the genus Scabies (S. phaselus, S. anceps, S. scobinatus, S. crispata, S. mandarinus, S. nucleus and S. songkramensis) and two closely related Indochinese species currently assigned to the genus Radiatula Simpson, 1900 (R. humilis and R. pilata). Maximum likelihood (ML) and Bayesian Inference (BI) phylogenetic trees based on the concatenated sequences of two mitochondrial genes (cytochrome oxidase c subunit 1 and 16S ribosomal RNA) and one nuclear gene (28S ribosomal RNA) fragments (1,586 bp) revealed a polyphyletic relationship in both genera compared to the outgroups of other genera from the tribe Indochinellini. Scabies songkramensis was clustered separately from the congeners, whereas R. humilis and R. pilata were grouped within the Scabies clade with high support (88% bootstrap support for ML and a Bayesian posterior probability of 1 for BI), and separated from other members of Radiatula from western Indochina (Myanmar and India). Based on these phylogenetic results, in combination with morphological and biogeographic data, these two Indochinese Radiatula species were transferred to Scabies, as S. humilis (Lea, 1856) comb. nov. and S. pilata (Lea, 1866) comb. nov. The genus Radiatula s.s. should be implied only to taxa endemic to the western Indochinese region, while the genus Scabies are distributed in the Chao Phraya and Mekong River basins and other rivers that drain into the Gulf of Thailand.