Meeting Abstract
Flat porcelain crabs (Petrolisthes cinctipes) occupy discrete cobble beaches and mussel beds dotted along the west coast of North America. Adult populations are connected demographically by an ocean-dispersing larval phase resulting in genetic homogeneity across much of the range. However, smaller scale genetic structure may still be at play in this gregariously settling crab, particularly in cohorts of newly settled larvae. Prior observations indicate sibling crabs may be transported cohesively despite a relatively long planktonic duration. Gravid females exhaustively release their brood during a single tide cycle, patchy clusters of porcelain crab larvae are common in pelagic samples, and settling larvae are regularly found in cohorts of 30 or more individuals in the intertidal during peak recruitment. I tested cohorts of porcelain crab settlers from four beaches for greater than expected genetic relatedness using a suite of hundreds of SNPs obtained through traditional RAD-seq. The five total cohorts showed no increased within-group relatedness and the tests detected no sibling or half sibling pairs. Despite the potential for physical and behavioral larval cohesion in this system, marine larvae likely face a number of challenges that break down the association of related individuals over time. Evaluating these challenges within a framework that considers transport processes across variable temporal and spatial scales may help us to understand better the cases where there is evidence of sibling cohesion (e.g. damselfish and spiny lobster) and those cases where we expect no signal of increased genetic relatedness.
