Dr Robert Miller, Paige Miller1, Stephen Whitaker1, 2, Jayson Smith3, Richard Ambrose4, Peter Raimondi5
1Marine Science Institute, University of California Santa Barbara , , , 2National Park Service, Channel Islands National Park, , , 3Biological Sciences, California State Polytechnical University Pomona, , , 4Department of Environmental Health Sciences, University of California Los Angeles, , , 5Department of Biology, University of California Santa Cruz, ,
Rockweeds are a group of conspicuous brown seaweeds (Phaeophyceae) in the Order Fucales (Fucoids) and are dominant components of temperate intertidal and shallow subtidal rocky habitats. Ecologically, rockweeds are often considered to be foundation species, essential in ecosystem functioning and facilitating high biodiversity. In California, USA, the rockweed Silvetia compressa has declined over the past three decades, and at many sites its extirpation has not been followed by recovery, motivating consideration of population restoration. We examine the population genetics of this species across 27 sites spanning ~600 km of coastline from central to southern California, including the Channel Islands. Using NextRAD genotyping by sequencing, we sampled the genome of 760 individuals and identified >300,000 single nucleotide polymorphisms (SNPs) across the genome. Corresponding with its low dispersal capacity, we find strong population structure across the regions, with site-to-site differences nested within larger-scale patterns of relatedness. The role of natural selection and dispersal distance on the patterns revealed is evaluated and the implications for restoration of this important foundation species are discussed. Because of the low dispersal capacity of rockweeds and the potentially strong selective forces acting on this species, the genetic composition of source populations should be considered in future restoration efforts.
