The Stenopsychid caddisfly Stenopsyche marmorata Navás (Trichoptera;Stenopsychidae) is a repersentative aquatic insect of Japanese running water environment that is broadly distributed across the Japanese archipelago. It is an abundant and dominant standing crop species. We examined the population genetics of S. marmorata with mitochondrial DNA (mtDNA) analyses of 96 specimens sampled across 30 sites within the Tamagawa basin. The results indicated that S. marmorata existed as four distinct population groups within the Tamagawa basin.
The first population group was identified across almost the entire Tamagawa basin except the river source region. It dominated over otherpopulation groups in terms of the number of individuals. This group is known to be widely distributed across the Japanese archipelago (from Hokkaido to Kyushu) and was referred as “Clade VIII” in a previous study (Tojo, et al., 2017). The second population group, which was referred as “Clade VI” in the previous study,was restricted to the middle region of the basin and comprised a small number of individuals. The third and fourth population groups, previously referred as “Clade IV” and “Clade III”, respectively, were observed at the source of the Tamagawa basin. Previous studies have also observed these two groups in the upstreamregion of Tamagawa.
We selected a ca. 658-bp fragment of the gene mitochondrial cytochrome oxidase subunit I (COI) as the DNA barcode for species and population classification, in combination with taxonomical information derived from specimen photographs. Based on this system of classification, 40 species representing 14 families of caddisflies were collected from the Tamagawa basin,Rhyacophilidae(9species),Hydrobiosidae (1 sp.), Glossosomatidae (3 sp.), Philopotamidae (8 sp.),Psychomyiidae (1 sp.), Xiphocentronidae (2 sp.), Polycentropodidae (1 sp.),Arctopsychidae (1 sp.), Hydropsychidae (6 sp.), Lepidostomatidae (3 sp.), Goeridae(1 sp.), Leptoceridae (2 sp.), Odontoceridae(1 sp.), Sericostomatidae (1 sp.).