Molecular systematics of some Indo-Pacific asterinids (Echinodermata, Asteroidea): does taxonomy reflect phylogeny?

Asterinid sea-stars represent a cosmopolitan element of the world s shallow marine invertebrate communities. Asterinids are typically pentagonal or stellate in form, with flat ventral surfaces adapted for clinging to hard substrates (Clark and Downey, 1992). Clark (1993) listed 18 genera and 117 species of the Asterinidae worldwide. Rowe and Gates (1995) listed eight genera and 37 species of asterinids from the Australian region, including 10 Asterina and 10 Patiriella species. Subsequently, a total of seven new asterinid species have been described from Australia and the Pacific (O Loughlin, 2002; O Loughlin et al., 2002, 2003). O Loughlin (2002) established the new genus Meridiastra for the temperate Australian Asterina atyphoida and three of the new species: M. nigranota, M. fissura (both southern Australia), and M. rapa (Rapa Island). Several Australasian species currently placed in Patiriella (e.g., P. oliveri, P. regularis, P. gunnii, and P. exigua) were previously allocated to Asterina. Systematists adopted Patiriella for many Southern Hemisphere species following Clark s (1938, 1946) studies of the Australian fauna. However, Clark and Downey (1992) remained non-committal on the status of Patiriella: ‘‘reassessment of whether or not this rank should be that of a genus or a subgenus seems better left to one of the several Australasian specialists to determine.’’ Taxonomic instability extends to genera such as Patiria which Clark (1983) synonymised with Asterina.