Abstract
Spatial environmental heterogeneity may favorably sustain genetic diversity of wild populations through adaptive divergence. We empirically examined the relationship between habitat structure and genetic diversity of stream mayfly Ephemera strigata populations at riverine reach scale. The habitat structure was delineated by a high precision GPS among 11 riverine sites in the Natori River, Miyagi Japan and genetic diversity was quantified at nine loci presumably under selection identified through a genome wide scan of 319 AFLP loci. Out of the nine adaptive loci, two had a strong association with the index of habitat structure, indicating a significant variation of allele frequency and genetic diversity along a gradient of the percentage of the total area of lentic habitats (i.e., backwater and isolated pool, range = 0.0 - 11.2 %). Particular environmental features reserved in these lentic habitats such as low current and high amount of deposited organic matters may enhance local adaptation of specific genotypes, leading to higher adaptive genetic variation within reaches. Our result highly suggests the importance of conservation of lentic habitats in river to sustaining genetic diversity of aquatic organisms.
