Population structure and genetic connectivity of the freshwater shrimp Potimirim brasiliana Villalobos, 1959 inhabiting a continental island

Abstract

ABSTRACT Insular regions present peculiar characteristics, including small populations resulting from prolonged evolutionary isolation. Such conditions make these areas sensitive to anthropogenic changes. By consequence, these areas are interesting for studying genetic and adaptative processes. This study had two main goals: to evaluate the demographic structure (distribution, frequency of individuals in size classes, and sex ratio) and to assess the genetic diversity of a freshwater shrimp population of Potimirim brasiliana on the continental São Sebastião Island. Subsequently, population structure (size, abundance, and sex ratio) and genetic analyses (network haplotype and genetic distance of the mitochondrial marker cytochrome oxidase subunit 1 – COI) were analysed to compare the spatial distribution and connectivity of individuals along separated areas exposed to different conditions of dispersal. Three different areas were defined along the island (sheltered area – SA, exposed area – EA, and south extremity – SE). We found males and females in all areas except SE. The percentage of males was greater in the EA, that of non-ovigerous females was greater in the SE and that of ovigerous females was greater in the SA. Females were larger than males in all areas. No genetic structural difference was found between the studied areas and no genetic differences were detected in relation to the inland population. The strategy developed by P. brasiliana in the areas of the São Sebastião Island involves a differential occupation among the demographic groups in and maintaining connectivity between different and separated areas of the island by larval dispersal.