Contrasting Genetic Diversity and Connectivity at the Eastern Range Edge of the Mediterranean Seagrass ( Posidonia oceanica )

Abstract

Populations at a species' distribution edges often present reduced gene flow, increased impact of genetic drift, and impoverished genetic variation, globally compromising their ability to adapt to environmental changes. This study assessed the genetic diversity, structure, and connectivity of the Mediterranean endemic seagrass Posidonia oceanica at its easternmost distribution limit, from diverse thermal regimes around Cyprus, contextualised within a set of 16 Turkish populations in the Levantine and Aegean Seas (eastern Mediterranean). The genetic assessments were based on sets of 13 to 16 microsatellite loci, depending on the analysis. Our findings revealed lower genotypic and allelic richness in the Cypriot populations, which also presented lower connectivity and higher differentiation among them in comparison to the Turkish ones. Additionally, the genetic and genotypic diversity and the connectivity of Cypriot populations were highly variable, with populations presenting high diversity and connectivity, while others exhibited extremely low diversity and high isolation. The discrepancies among the Cypriot populations were potentially due to differences in the sexual reproductive output related to the different thermal regimes around the island and the presence of barriers to gene flow along the island's southern coastline. This study advances our understanding of the genetic connectivity and genetic diversity of range‐edge P. oceanica populations in the Eastern Mediterranean. This knowledge can guide the management of conservation and ecosystem restoration initiatives for this habitat‐forming seagrass species.

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