Genetic analyses of rafted macroalgae reveal regional oceanographic connectivity patterns

Abstract

AbstractAimThis study examines beach‐cast rafts of Durvillaea antarctica (bull kelp) along New Zealand's east coast to determine spatial variation in beach‐cast haplotype assemblages. By using genetic markers, the geographical origins of rafted D. antarctica samples can be determined, allowing for the examination of dispersal pathways, distances rafted, and potential barriers to dispersal.LocationAn approximately 1000 km stretch of New Zealand's eastern coastline.Methods686 samples of beach‐cast D. antarctica rafts were collected and sequenced for cytochrome c oxidase subunit 1 in order to infer geographical origins and dispersal dynamics of rafted specimens. Results were examined using principal components analysis (PCA) in order to determine spatial groupings. Analysis of molecular variance (AMOVA) was used to determine statistical support for the detected spatial groups.ResultsHierarchical AMOVA revealed three major regional genetic assemblages, which probably reflect broad oceanographic features. In particular, the north–south genetic partitioning in rafted kelp assemblages either side of the Cape Campbell region in central New Zealand closely corresponds to an oceanographically mediated disjunction previously observed in a number of larval‐dispersed marine invertebrate taxa.Main conclusionsFindings from this study suggest that passively drifting kelp rafts and planktonic invertebrate larvae may be similarly constrained by oceanographic features, and demonstrate how the phylogenetic structure present in populations of D. antarctica provide a framework with which to map dispersal patterns.