The fine-scale genetic structure and dispersal ability of the mayfly Ecdyonurus yoshidae Takahashi (Ephemeroptera: Heptageniidae) in the Sagami River system, southern Kanto Region, Japan

Abstract

• The Sagami River has its source at Lake Yamanaka near Mount Fuji in Japan. • We studied the genetic structure of Mayfly Ecdyonurus yoshidae . • Two haplogroups occur in the Sagami river. • One haplogroup spread throughout the river system. • Another haplogroup may have migrated from an adjacent catchment. Aquatic organisms frequently exhibit clear genetic structures over their distribution ranges. In a previous study, we showed that the mayfly Ecdyonurus yoshidae Takahashi also showed genetic delimitations in the Japanese archipelago. In this paper, we studied the dispersal and migration of this species using the fine-scale genetic structure and historical demographic dynamics in the Sagami River system using the DNA barcoding region mitochondrial cytochrome c oxidase subunit I gene sequence ( COI ). We detected two major haplogroups constructed from 44 distinct haplotypes in 226 specimens collected from 24 sampling sites. From the highest altitude of 530 m to the lowest of 7 m, the dominant haplotype was widespread throughout the rivers and the six tributaries and even spread to isolated microhabitats upstream. We did not observe genetic differentiation among the six tributaries and 24 sampling sites. Consequently, we estimated that the population occurring in the entire river system is maintained as a meta-population by suitable small-scale habitats. We found that E. yoshidae might be capable of crossing areas with unsuitable habitats, such as gorges and rapid streams. Furthermore, one haplogroup experienced population expansion—which affected the genetic structure across the Sagami River system—and another haplogroup might have migrated from an adjacent catchment.