日本・東南アジア産Neonesidae属(甲殻亜門,貝形虫綱,ポドコピーダ目)8種の系統関係と生物地理

抄録

Phylogenetic relationships of eight species of Neonesidea from Japan and southeastern Asia were estimated for the first time. Carapaces of the eight species were categorized into a bean-shaped group and a teardrop-shaped group by the general shape in lateral view. These two groups respectively correspond to the Neonesidea pateriformis group and the N. schuizi group defined by Maddocks (1969) based on the carapace shape and muscle scars for the African and European Neonesidea species. Each of the Neonesidea pateriformis group (4 species) and N. schuizi group (4 species) from Asia generally had their own characteristic features in the pore distribution pattern and the male copulatory organ, and the grouping was considered to reflect phylogeny. However, N. oligodentata, included in the N. pateriformis group by the carapace shape, had a different type of copulatory organ and pore distribution pattern from other species of the group, and was therefore estimated to be phylogenetically distant from the others. Neonesidea oligodentata is exclusively distributed around Japan, up to cool-temperate Hokkaido as the northern limit which is the northernmost world record for the distribution of intertidal Neonesidea species. This would lead us to a scenario where an ancestor of N. oligodentata speciated from the N. paterformis group at or to the south of Japan, and has adapted to the cool environ ment around the Japanese Islands.