Abstract
Genetic diversity of common freshwater shrimp Palaemon paucidens in the Kanto region (Tokyo, Kanagawa and Chiba) of Japan, was investigated using mitochondrial 16S rDNA sequence analysis. All 98 individuals collected at 31 localities were determined to be type A, which included 52 individuals collected at 18 localities in Inner Tokyo Bay Basin. A total of 12 haplotypes were detected, which were phylogenetically classified into 3 groups (designated by A-I, A-II and A-III). Number of individuals comprising each group was 44 for A-I, 38 for A-II and 16 for A-III. A-II was determined to be an indigenous group distributing central to northern Japan. A part of A-I group may be domestic alien probably originated from Lake Biwa. A-III was determined to be invasive group probably originated from commercially imported individuals from Korea and/or China. Although the human-mediated contact between indigenous and alien groups must threat the genetic integrity of indigenous group, nothing is known about hybridization and genetic introgression among these groups.
