Phylogeography of a canopy‐forming kelp, Eisenia bicyclis (Laminariales, Phaeophyceae), based on a genome‐wide sequencing analysis

Abstract

Analyses of phylogeographic patterns and genetic diversity provide fundamental information for the management and conservation of species. However, little is published about these patterns in Japanese kelp species. In this study, we conducted phylogeographic analyses of a canopy‐forming kelp, Eisenia bicyclis, based on genome‐wide SNPs identified by ddRAD‐seq. We obtained 1,299 SNPs for 76 samples from nine localities across the distribution. STRUCTURE, NeighborNet, and discriminant analysis of principal components consistently showed high genetic differentiation among the Eastern Pacific, Central Pacific, and Sea of Japan coastal regions. Relatively strong gene flow was detected only within populations in the Eastern Pacific and in the Sea of Japan. Genetic diversity and genetic uniqueness were high in the Central Pacific and low in the Sea of Japan. These results suggest that there were at least three independent refugia corresponding to the three regions during the Last Glacial Maximum (LGM). Furthermore, relatively larger populations in the Central Pacific and smaller populations in the Sea of Japan have been maintained in the demographic history from before the LGM to the present. These phylogeographic histories were supported by an Approximate Bayesian Computation analysis. From a conservation genetics perspective, the loss of southern populations in the Central Pacific would greatly reduce the total genetic diversity of the species. Southern populations in the Sea of Japan, which have relatively low genetic diversity, may be highly vulnerable to environmental change, such as heat waves and increased feeding. Therefore, careful monitoring and conservation are needed in the two regions.

Gene expression of a canopy‐forming kelp, Eisenia bicyclis (Laminariales, Phaeophyceae), under high temperature stress

“…Phylogeographic study of E. bicyclis based on genome‐wide SNPs data revealed the genetic structure of this species (Chimura et al . 2022). However, molecular mechanisms of thermal acclimation to high temperature stress are poorly understood.…”

“…Recent marine heat waves in the southwestern coast of the Sea of Japan induced a drastic loss of the kelp forest in Yamaguchi Prefecture (Yatsuya et al 2014;Yoshida 2016) survival temperature of this species is 30 C for gametophytes and 29 C for young sporophytes (Baba 2010). Phylogeographic study of E. bicyclis based on genome-wide SNPs data revealed the genetic structure of this species (Chimura et al 2022). However, molecular mechanisms of thermal acclimation to high temperature stress are poorly understood.…”