Data from: Habitat fragmentation in coastal southern California disrupts genetic connectivity in the Cactus Wren (Campylorhynchus brunneicapillus)

Achieving long-term persistence of species in urbanized landscapes
requires characterizing population genetic structure to understand and
manage the effects of anthropogenic disturbance on connectivity.
Urbanization over the past century in coastal southern California has
caused both precipitous loss of coastal sage scrub habitat and declines in
populations of the cactus wren (Campylorhynchus brunneicapillus). Using 22
microsatellite loci, we found that remnant cactus wren aggregations in
coastal southern California comprised 20 populations based on strict exact
tests for population differentiation, and 12 genetic clusters with
hierarchical Bayesian clustering analyses. Genetic structure patterns
largely mirrored underlying habitat availability, with cluster and
population boundaries coinciding with fragmentation caused primarily by
urbanization. Using a habitat model we developed, we detected stronger
associations between habitat-based distances and genetic distances than
Euclidean geographic distance. Within populations, we detected a positive
association between available local habitat and allelic richness and a
negative association with relatedness. Isolation-by-distance patterns
varied over the study area, which we attribute to temporal differences in
anthropogenic landscape development. We also found that genetic bottleneck
signals were associated with wildfire frequency. These results indicate
that habitat fragmentation and alterations have reduced genetic
connectivity and diversity of cactus wren populations in coastal southern
California. Management efforts focused on improving connectivity among
remaining populations may help to ensure population persistence.