Sexual recruitment in Zostera marina: A patch to landscape-scale investigation

Seagrasses are a diverse group of clonal marine macrophytes. Their disappearance in recent decades has been an alarming component of estuarine urbanization, effectively transitioning vast portions of global coverage to disturbed or recovering states. Understanding dispersal and recruitment patterns within and among extant populations is now vitally important to predicting both the form and pace of recovery. Working with a perennial ecotype of Zostera marina within a shallow lagoon in Long Island, New York, U.S.A., we combined high resolution, decade-long seagrass mapping with polymorphic microsatellite analysis to examine the interactive effects of pollination and seed dispersal distance on the dynamics of sexual recruitment across a range of spatial scales (centimeters to decameters). We found clone structure to be restricted to less than three meter across a 56,250-m² study site. Pollination distances ranged from 0.57 m to 73.91 m, while seed dispersal varied systematically from 1.85 m to 5.31 m for naked seeds, and randomly throughout the study site (0.17 m to 34.54 m) for seeds deposited by floating reproductive shoots. Pedigree analyses corroborated these findings, with full sibling groups clustering neatly within larger half-sibling kinships at spatial scales of 2-6 m. We successfully demonstrate that over a four-year period sexual reproduction and seedling recruitment played appreciable roles in the colonizing process of Z. marina, configuring the landscape through the deposition of rafted seeds, and contributing to patch expansion via the limited dispersal of naked seeds.