DNA-based species delimitation separates highly divergent populations within morphologically coherent clades of poorly dispersing beetles

We compared species-level entities recovered using distance, tree-based, and DNA-character based methods with morphologically defined species in poorly dispersing lyponiine net-winged beetles. The phylogenetic relationships were investigated using the cytochrome c oxidase 1-2 mtDNA fragment. We identified 31 species using a morphology-based concept and additional candidate species were delimited by the general mixed Yule-coalescent method and barcoding threshold within the morphologically coherent lineages owing to high genetic divergence (up to 10.97% within morphologically defined species, highest density 2.5-6.5%). Genetic divergence was positively correlated with geographical distance: lower in continental China where no apparent dispersal barriers are present (r(2)=0.172, P0.001, average increase of genetic distance of 0.32% per 100km) and much higher in Japan (r(2)=0.490, P0.001, 1.81% per 100km). We hypothesize that low dispersal propensity contributed to the high level of intraspecific, geographically structured divergence. DNA-based methods suggested a high number of morphologically undistinguishable species. The observed patterns agree with the model of neutral evolution. The poor dispersers produce gradually divergent populations across the range of the morphologically coherent lineages. We pose the question of what size of range and level of genetic difference justify formal acceptance of a species without morphological divergence from both the taxonomical and conservation management view points.(c) 2015 The Linnean Society of London