title: Habitat fragmentation in coastal southern California disrupts genetic connectivity in the cactus wren (Campylorhynchus brunneicapillus).
abstract: 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.
authors.affiliation: U.S. Geological Survey, Western Ecological Research Center, San Diego Field Station, 4165 Spruance Road, Suite 200, San Diego, CA, 29101, USA.
authors.forename: Kelly R
authors.initials: KR
authors.lastname: Barr
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Kus
authors.forename: Kristine L
authors.initials: KL
authors.lastname: Preston
authors.forename: Scarlett
authors.initials: S
authors.lastname: Howell
authors.forename: Emily
authors.initials: E
authors.lastname: Perkins
authors.forename: Amy G
authors.initials: AG
authors.lastname: Vandergast
mesh_terms: D000483:Alleles; D000818:Animals; D001499:Bayes Theorem; D002140:California; D016000:Cluster Analysis; D003247:Conservation of Natural Resources; D017753:Ecosystem; D014644:Genetic Variation; D005828:Genetics, Population; D018895:Microsatellite Repeats; D008962:Models, Theoretical; D020308:Songbirds / Q000235:genetics*; D014507:Urbanization
keywords: coastal sage scrub; conservation; habitat loss; landscape genetics; songbird; wildfire