Inconsistency between morphological diversity and genetic structuring: proposal for one species of Undaria in Japan

Abstract Genetic structure analyses have yielded some examples of inconsistencies between genetic and morphological information. Here, eleven nuclear microsatellite markers and mitochondrial haplotypes were used to examine the genetic structure and gene flow among Japanese Undaria pinnatifida populations and the congeneric species U. undarioides and U. peterseniana. Undaria pinnatifida was subdivided into four “Groups” of populations based on Bayesian clustering analysis, Neighbor-net analysis and Principal coordinate analysis (PCoA). Undaria undarioides samples formed a unique Group. In contrast, U. peterseniana samples either grouped with a mixture of U. pinnatifida and U. undarioides clusters or were included within one of the U. pinnatifida clusters. More significantly, Groups of populations shared alleles with geographically adjacent Groups even between different morphospecies. No clear differences between the inter-and intra-specific genetic divergence were observed in either nuclear or mitochondrial markers. As a result, U. undarioides and U. peterseniana were synonymized with U. pinnatifida. Isolation-by-distance suggested the significance of geographical isolation for maintaining the observed divergence.