Anthropogenic factors and sea level rise are destroying coastal habitats and fragmenting populations of salt marsh species with unknown impacts on the genetic diversity, and consequently resiliency, of marsh ecosystems. Salt marshes provide important habitat to many species, and ecosystem services including storm protection, flood attenuation, and carbon sequestration. The persistence of salt marshes in the Gulf of Mexico is dependent on the dominant foundation species and ecosystem engineer, black needlerush (Juncus roemerianus). To conserve ecosystem function and population persistence in the salt marsh, management of J. roemerianus must address the preservation of genetic diversity in natural and restored sites. High genetic diversity in clonal macrophytes has been linked to greater resistance to disturbance and increased restoration success. We are conducting a population genetic analysis on J. roemerianus across a significant portion of the species’ range from eastern Mississippi to northern South Carolina. Using 19 microsatellite markers we calculated metrics to assess the current level of genetic diversity and delineated population structure using the program STRUCTURE. A landscape genetic analysis was performed across the irregularly flooded marshes in the northern Gulf of Mexico to study the effect of anthropogenic and natural landscape factors on genetic patterns in the species.
Results/Conclusions
Populations from the Gulf of Mexico had greater genetic diversity than expected from a highly clonal species with an average observed heterozygosity of 0.58. Clonal replicates comprised approximately half of all collected samples. Across the Gulf of Mexico, samples were structured into two populations signifying large-scale population structure. Landscape genetic analyses indicate a correlation between developed land and genetic distance in J. roemerianus. Our results have direct implications for current J. roemerianus restoration and management practices. The continued use of clonally propagated stock in restoration projects will create restored sites that do not reflect the genetic diversity in natural marsh systems. Population connectivity and preservation of genetic diversity may be affected by coastal development.