High Genetic Connectivity Inferred from Whole-Genome Resequencing Provides Insight into the Phylogeographic Pattern of Larimichthys polyactis.

Compared with terrestrial biota, marine fishes usually present lower genetic differentiation among different geographical populations because of high-level gene flow and lack of physical barriers. Understanding the genetic structure of marine fishes is essential for dividing management unit and making reasonable protection measures. The small yellow croaker (Larimichthys polyactis) belongs to the family Sciaenidae, which is an economic fish and widely distributed in the Western Pacific. To delineate genetic diversity and phylogeographic pattern, whole-genome resequencing was used to evaluate genetic connectivity, genetic diversity, and spatial pattern of L. polyactis for the first time. We obtained 6,645,711 high-quality single nucleotide polymorphisms (SNPs) markers from 40 L. polyactis individuals. The phylogenetic analysis, STRUCTURE, principal component analysis, and Fst results all indicated that no genetic structure consistent with the distribution pattern was found. This result revealed high genetic connectivity of L. polyactis in different sampling sites. High genetic diversity was also detected, indicating that there was sufficient evolutionary potential to maintain its effective population size. Besides, a similar result of high genetic connectivity and genetic diversity was also detected by mitochondria DNA marker. Our study demonstrated the persistence of high levels of genetic connectivity and a lack of population structure across L. polyactis in different sea areas. This study aimed to analyze the division of population structure and the reason for the decline and not exhaustion of L. polyactis resource on a genetic level.