US-IALE 2018

AUTHORS: Hayley R. Tumas*, Brian Shamblin, Nathan P. Nibbelink – University of Georgia; Mark Woodrey, Grand Bay National Estuarine Research Reserve; Richard Chandler, Campbell J. Nairn – University of Georgia

ABSTRACT: Common species important for ecological restoration and ecosystem processes are understudied in landscape genetics, but stand to lose as much genetic diversity as rare species from habitat fragmentation. Genetic diversity, maintained in fragmented populations through gene flow, is critical for successful restoration and conserving adaptive potential in a changing climate. Salt marshes are ecosystems valuable to humans and wildlife that are in widespread decline nationally and globally. Black needlerush (Juncus roemerianus Scheele) is the dominant foundational plant species in northeastern Gulf of Mexico salt marshes, and a target species for restoration in the area. We used 19 microsatellite markers to measure levels of genetic and genotypic diversity and characterize population structure in this important clonal macrophyte. Least cost transect analysis (LCTA) was used within a model selection framework to delineate potential dispersal pathways and identify landscape factors (wetland, ocean, forest cover, developed land) influencing population connectivity. Genetic and genotypic diversity were greater than expected for a species believed to use predominantly clonal reproduction, and samples structured into two admixed clusters across the study area. The proportion of developed land across coastal transects and Euclidean distance had the greatest influence on population connectivity, and coastal transects were identified as important for dispersal. Results have important implications for restoration and management techniques that aim to preserve adaptive potential in J. roemerianus and sustain ecosystem processes throughout the salt marsh. This study expands upon an understudied taxon and ecosystem, and demonstrates methodology that could be applied to other common, understudied species.