Seagrass movement: oceanographic modelling and genetic data reveal connectivity patterns of Posidonia oceanica along the Western coast of Sicily

Movement is fundamental to the ecology and evolutionary dynamics of species and populations. In marine environment seed dispersal plays a key role in shaping the distribution and genetic complexity of seagrass meadows and affect their resilience capacity under disturbance. Understanding seed movement pathways is thus critical to support effective conservation and restoration actions. We collected beach cast fruits of the Mediterranean seagrass Posidonia oceanica from nine localities along the Western coast of Sicily, along with adult shoots from eight putative donor meadows. We determined levels of genetic diversity of both established meadows and seed cohorts, and their genetic differentiation. Genetic assignment tests were used to infer the most likely meadow of origin of seeds and were complemented with Lagrangian simulations to assess all possible connections among seed sources and collection sites based on ocean surface currents. A significant genetic differentiation was found between beached seed s and adjacent meadows, indicating mixing of dispersing seeds across the study area, and long distance dispersal events. Oceanographic simulations highlighted that the potential connectivity between sites was conditioned by marine circulation features. Key source meadows were identified based on their ability to provide sexual propagules. Such information can guide management actions and advance conservation of marine biodiversity.