Comparison of Symbiodiniaceae diversities in different members of a species complex (Cnidaria: Anthozoa: Zoantharia)-implications for ecological adaptations to different microhabitats.

In this study we compared genotypes of zoantharian host-associating algal symbionts among species, which are among the dominant benthic reef organisms in the Ryukyu Archipelago, Japan, and evaluated Symbiodiniaceae diversities of closely related congeneric species. We targeted a species complex of the zoantharian genus (, sp. yoron, ) living among different microhabitats in a narrow reef area of Tokunoshima Island. For phylogenetic analyses, we used two DNA marker regions; nuclear internal transcribed spacer (ITS) and plastid mini-circle non-coding region (psbA), both of which have previously been used to determine Symbiodiniaceae genotypes of zoantharian species. Our results showed that all species hosted symbionts of the genus , with genotypic compositions of this genus showing some variations among the three different species. Additionally, we found that the genotypic composition was statistically different among species, and among specimens in different microhabitats. Our results suggest that ecological divergence among these three species may be related to differing Symbiodiniaceae diversities that may in turn contribute to eco-physiological adaptation into different microhabitats on coral reefs.