「普通種」の中の絶滅危惧種あるいは集団：「スジエビ」の例

抄録

One of the important roles of conservation genetics in planning conservation strategies for threatened or endangered species is to assess aspects of genetic diversity throughout the distribution range of the target species using appropriate genetic markers. Based on the results of such surveys, ESUs (Evolutionarily Significant Units) and MUs (Management Units) to which actual conservation efforts should be focused will be established. On the other hand, even for “common species” that are distributed over a wide geographic range and frequently seen in the field, a genetic survey over the entire distribution range may reveal the existence of cryptic species and populations of threatened status within each cryptic species. The common freshwater shrimp Palaemon paucidens (sensu lato) which is distributed in almost all areas of the Japanese archipelago, has revealed the existence of two cryptic species called A and B types, respectively. This paper first reviewed the history of the discovery of these two types, beginning with allozyme analysis, and the comparative studies between the types. Then, the geographical distribution of the lineages within each type and the results of the investigation of the occurrence of reproductive isolation between lineages revealed by more recent DNA analyses were introduced, as well as the status and ecological and genetic characteristics of the third type (C type) newly discovered on Amami-Oshima Island. Finally, we discussed the importance of research on genetic diversity of “common” species, which are often underestimated for conservation issues.