Understanding biogeography of rockfishes (genus Sebastes) in northern Japan using environmental DNA

Background/Question/Methods

Since marine environments offer few barriers to dispersal and genetic connectivity, mechanisms underlying diversification and maintenance of biodiversity for marine fishes have long been questioned. Rockfishes (genus Sebastes) are known for an extreme species diversity with over 110 species in the North Pacific including Japanese coasts. In some previous studies, rockfish distributions and cryptic speciation along the coastline or depth gradients have been investigated in the Northeast Pacific. Around Japan, however, their biogeographic features and spatial diversities are poorly understood. In this study, we explored their biogeography along the coasts of northern Japan using an environmental DNA (eDNA) metabarcoding approach. Recently, a DNA metabarcoding primer set (MiSebastes) for identifying eDNA from rockfish species were developed. We modified the MiSebastes primers to use for rockfish assemblages inhabiting around Japan and applied it to eDNA samples collected from northern Japanese coasts.

Results/Conclusions

A total of 14 rockfish species were detected from 36 sites located around rocky shores or artificial structures (e.g., tetrapod, sea walls) across Hokkaido and the northern part of the mainland of Japan. The rockfish assemblages were moderately different along with a latitudinal gradient. Based on a non-metric multidimensional scaling (nMDS) analysis, we found that the occurrences of several species were significantly associated with the regional dissimilarities of the assemblages. Moreover, closely related species exhibited similar distribution patterns, suggesting niche conservatisms due to their recent speciation. Further examinations for their biogeographic and phylogenetic relationships and detailed environmental information will be needed to understand the mechanisms of diversification and coexistences for the rockfishes.