Population Genetic Structure of Southern Flounder Inferred from Multilocus DNA Profiles

Abstract

Determination of stock structure is an important component of fisheries management; incorporation of molecular genetic data is an effective method for assessing differentiation among putative populations. We examined genetic variation in Southern Flounder Paralichthys lethostigma within and between the U.S. South Atlantic and Gulf of Mexico basins to improve our understanding of the scale of population structure in this wide‐ranging species. Analysis of amplified fragment length polymorphism (AFLP) fingerprints and analysis of mitochondrial DNA (mtDNA) control region sequences found clear divergence between ocean basins. Based on mtDNA sequences, no genetic differentiation was detected within the U.S. South Atlantic at spatial scales that were broad (among states: North Carolina, South Carolina, Georgia, and Florida) or fine (among estuarine regions within North Carolina). Increased genetic resolution was observed with AFLP fingerprint data, and we found significant subdivision between nearly all Southern Flounder geographic populations, suggesting the presence of finer‐scale genetic population structure within the U.S. South Atlantic. However, AFLP genetic cluster analysis also revealed evidence for a high degree of mixing within the Atlantic basin; patterns of variation, which included genetic similarity between South Carolina and Gulf of Mexico samples, were not aligned closely with geography. We examined the partitioning of genetic variation among groups by using analyses of molecular variance and found no evidence that North Carolina Southern Flounder, which are managed on the state level as a unit stock, are differentiated from the remainder of U.S. South Atlantic Southern Flounder. Our findings indicate only weak structure and the potential for basinwide mixing among Atlantic Southern Flounder, suggesting that cooperation among U.S. South Atlantic states will be essential for the effective assessment of stock dynamics and future management plans.

Disentangling complex genomic signals to understand population structure of an exploited, estuarine‐dependent flatfish

“…Previous studies of stock structure based on allozymes (Blandon et al., 2001 ), mitochondrial DNA (Anderson et al., 2012 ), microsatellites (Wang et al., 2015 ), and otolith morphometrics (Midway et al., 2014 ) have identified differences between southern flounder in the Atlantic and Gulf but failed to demonstrate differences within each region. By contrast, regional and estuarine‐specific differences in life‐history traits such as growth rates and age/size‐at‐maturity have been documented, suggesting the potential for genetic differences at sufficiently small spatial‐scales that microsatellites and mtDNA cannot resolve (Corey et al., 2017 ; Fischer & Thompson, 2004 ).…”

Population structure of mud flounder Paralichthys orbignyanus from the south‐western Atlantic Ocean

“…In general, divergence at the mitochondrial level is moderate or high and nuclear divergence is low. The geographical barriers that explain genetic divergence in these species, in line with P. orbignyanus , are mainly temperature, salinity and the geographical structure near a gulf (Anderson Joel & Karel, 2012; Masashi & Hara, 2001; Rocky Ward et al ., 2001; Shigenobu et al ., 2013; Wang et al ., 2015; Xu et al ., 2012).…”