GENETIC DIVERSITY AND POPULATION STRUCTURE OF THE SESARMIDAE) ALONG THE NORTH BRAZILIAN COAST

For coastal marine species, gene flow patterns are intricately shaped by environmental factors such as oceanographic currents and river plumes. Despite these natural barriers, pelagic larval duration and salinity tolerance potentially facilitate the movement of individuals, resulting panmixia. This study utilized Cox] mtDNA data to conduct population genetics and structure analysis of the semiterrestrial crab Armases benedicti along the North Brazilian coast. The haplotype network displayed a star-like configuration, indicating recent mutation events and confirming minimal genetic structure. While DAPC analysis identified three distinct genetic clusters, limited genetic differentiation and negligible structuring were evident between Amap & aacute;, the northmost coastal Brazilian state, and Par & aacute; (approx. 400 km from the Amap & aacute; sampling site). Maranh & atilde;o (approx. 600 km from Par & aacute;) exhibited higher Fst values in all pairwise comparisons but remained just one mutational step away from other sites. Despite coastal barriers affecting genetic connectivity, our findings suggest that A. benedicti populations demonstrate low genetic differentiation, hinting the minimal impact of the Amazon plume as a barrier to gene flow, possibly due to the species' adaptability to brackish environments. However, employing more informative genetic markers and conducting complementary ecological studies on larval salinity tolerance remain crucial for a deeper understanding of Armases population dynamics and adaptive strategies.