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.

Small fish, large river: Surprisingly minimal genetic structure in a dispersal‐limited, habitat specialist fish

“…Habitat specialists, especially those that are also dispersal-limited, often display signatures of high genetic structure (Pilger et al, 2017;Waters & Burridge, 2016). In such species, factors such as poor habitat matrix conditions, geographic distance, and habitat fragmentation have relatively strong impacts on gene flow (Barr et al, 2015;Savage et al, 2010), often leading to isolation or reduced connectivity, even at small spatial scales (Polato et al, 2017;Storfer, Mech, Reudink, & Lew, 2014). We examined the impacts of distance, intervening pool habitats, and a disjunction in our focal taxon's range on gene flow and genetic diversity.…”

Spatiotemporal analysis of gene flow in Chesapeake Bay Diamondback Terrapins (Malaclemys terrapin)

“…; Barr et al . ). The extent to which habitat fragmentation decreases population connectivity, however, is dependent upon the interaction between landscape features and organismal dispersal behaviour (Gu et al .…”

Turtle soup, Prohibition, and the population genetic structure of Diamondback Terrapins (Malaclemys terrapin)

“…An alternative outcome of translocation is that it may harm populations by causing outbreeding depression, harm locally adapted populations by moving them away from an adaptive peak [54, 55], or introduce diseases [56]. Nonetheless, given the extent of the current biodiversity crisis [57–60], including increasing population fragmentation [61–64] conservation-oriented translocation has become increasingly pivotal to maintaining population viability [65]. …”