Spatiotemporal variation in patterns of genetic diversity, genetic structure, and life history across Zostera marina meadows in North Carolina, USA

Abstract

Seagrass meadows are some of the most productive marine plant ecosystems in the world, yet their loss continues on a global scale. Zostera marina, an ecologically important foundation species, reproduces both sexually and asexually, yielding different levels of genetic diversity throughout its range, which in turn can influence resistance to, and resilience from, environmental disturbances. Understanding the genetic structure and diversity of these populations, and how they fluctuate over space and time, will aid in the conservation and management of seagrasses in an environment where the effects of climate change are likely to be chronic. Using microsatellite data, we examined spatiotemporal genetic structure and genetic diversity of Z. marina over a 10 yr period at 2 sites in North Carolina (USA), the southern limit of its geographic range in the Western Atlantic. Both meadows were genetically diverse, with very little spatial genetic structure existing within and between sites, and relative temporal stability between decadal time points. Within-site kin structure was more pronounced in the earlier years, and allelic richness increased over time at both sites, suggesting an increase in sexual reproduction, potentially in response to thermal stress. Despite the genetic similarities between sites, life history strategies showed phenotypic plasticity, and several metrics of genetic diversity were associated with meadow health. These findings point to the adaptive potential of Z. marina and provide promising insight into how the species will perform as the effects of climate change continue to amplify over the next century.