Population structure of the Common Snook: Evidence of genetic isolation in the Gulf of Mexico and connectivity across the western Atlantic

ABSTRACT Objective The Common Snook Centropomus undecimalis is a species widely distributed throughout the western Atlantic, playing a key ecological role in coastal and estuarine ecosystems. Despite its broad distribution from Florida to southeastern Brazil, little is known about the genetic patterns underlying its population connectivity. This study aimed to characterize the genetic structure of this species and to infer patterns of genetic diversity and connectivity across its range. Methods A total of 100 individuals collected from Florida to southeastern Brazil were genotyped at 11 microsatellite loci. Genetic structure was assessed using Bayesian clustering analysis, discriminant analysis of principal components, and analysis of molecular variance. Genetic differentiation among populations was estimated by pairwise FST, and recent gene flow was inferred from migration proportions among the identified genetic profiles. Results Three distinct genetic profiles were identified: one exclusive to the southern Gulf of Mexico (Gulf Profile) and two along the Atlantic coast (Northern and Southern profiles), both contributing to a central mixed zone in northern South America. Analysis of molecular variance revealed greater variation within populations (68.8%). When admixed individuals (