Genetic differentiation in populations of lane snapper (Luyanus synagris - Lutjanidae) from Western Atlantic as revealed by multilocus analysis

Population genetic structure, genetic diversity and molecular demography of lane snapper Lutjanus synagris were assessed using mitochondrial DNA (control region, cytochrome b and NADH Dehydrogenase, subunit 4) and two nuclear introns (intron 2 of the S7 ribosomal protein gene -S7-2, and intron 6 of the L3 ribosomal protein gene RPL3). Here, we collected specimens from Brazilian and Colombian coasts. In addition, we downloaded available sequences from prior studies conducted in Caribbean and US waters. Population genetic structure analysis did not detect any genetic substructure signal along the Brazilian coast. However, comparisons between Brazilian and Colombian samples provided a significant and high level of genetic subdivision, probably due to the freshwater outflow of the Amazon. Our data also showed a higher genetic diversity index (both mtDNA and nuDNA) in the Colombian populations compared to Brazil. It is should be probably associated with the environmental changes and historical population size differences between these regions. Also, was detected an asymmetric gene flow from Brazil to Colombia, which can explain the high genetic diversity found in the last region, besides being probably, an older and stable population. Bayesian skyline plots clearly indicated that Brazilian population has experienced a historical demographic expansion, which probably began after Last Glacial Maximum.(LGM). On the other hand, our analysis did not detect any demographic change signal for the Colombian population in this period. Our analysis based on a combined dataset indicates that the Atlantic L. synagris populations are interconnected in different levels through this region. While some comparisons have showed no significant difference over hundreds or thousands of kilometers, there were strong population differentiation signals between other localities considering a similar geographical distance.