Abstract
Five Japanese species of Neoclinus from Shirahama, Japan were studied based on allelic frequencies at 19 genetic loci. Habitat partitioning and overlap in these five species in the waters of Shirahama was also observed. The five species which cooccur in Shirahama are well isolated genetically, each pair of species with clearly distinctive allele in some loci. A resulting phylogenetic tree among five species of Japanese Neoclinus based upon Nei's genetic distances (D) indicates that the Japanese Neoclinus could be divided into two major groups. One consists of N. lacunicola and N. toshimaensis and another three species of N. bryope complex (i.e. bryope, chihiroe and okazakii). This agrees well with the grouping based on morphology. Three members of N. bryope complex showed an imperfect habitat partitioning. However, the obtained results clearly indicate that gene exchanges have not occurred among these three members. N. bryope mainly inhabits tide pools (TP habitat), N. chihiroe mainly in the upper subtidal of moderately exposed rocky reefs (ME habitat), and N. okazakii mainly in the upper subtidal of very exposed rocky reefs (VE habitat). The two species of another major group showed more rigid habitat partitioning. N. lacunicola mainly inhabits ME habitat where it predominates over N. chihiroe and N. toshimaensis inhabits VE habitat where it predominates over N. okazakii.
