Data from: Seascape drivers of Macrocystis pyrifera population genetic structure in the northeast Pacific

At small spatial and temporal scales, genetic differentiation is largely
controlled by constraints on gene flow, while genetic diversity across a
species' distribution is shaped on longer temporal and spatial
scales. We assess the hypothesis that oceanographic transport and other
seascape features explain different scales of genetic structure of giant
kelp, Macrocystis pyrifera. We followed a hierarchical approach to perform
a microsatellite-based analysis of genetic differentiation in Macrocystis
across its distribution in the northeast Pacific. We used seascape genetic
approaches to identify large-scale biogeographic population clusters and
investigate whether they could be explained by oceanographic transport and
other environmental drivers. We then modelled population genetic
differentiation within clusters as a function of oceanographic transport
and other environmental factors. Five geographic clusters were identified:
Alaska/Canada, central California, continental Santa Barbara, California
Channel Islands and mainland southern California/Baja California
peninsula. The strongest break occurred between central and southern
California, with mainland Santa Barbara sites forming a transition zone
between the two. Breaks between clusters corresponded approximately to
previously identified biogeographic breaks, but were not solely explained
by oceanographic transport. An isolation-by-environment (IBE) pattern was
observed where the northern and southern Channel Islands clustered
together, but not with closer mainland sites, despite the greater distance
between them. The strongest environmental association with this IBE
pattern was observed with light extinction coefficient, which extends
suitable habitat to deeper areas. Within clusters, we found support for
previous results showing that oceanographic connectivity plays an
important role in the population genetic structure of Macrocystis in the
Northern hemisphere.