Among the possible consequences of fragmentation for cactus wren viability is genetic isolation, which could lead to loss of genetic variability and ability to adapt to changing environments. In 2011, USGS scientists Barbara Kus and Amy Vandergast initiated a collaborative study to examine genetic population structure of coastal cactus wrens throughout their southern California range. In this study, researchers describe genetic connectivity in the coastal cactus wren in San Diego County. To gain a broader perspective, they also obtained samples from the Nature Reserve of orange County, where many of the remaining coastal cactus wrens are found in that county. These data provide excellent resolution for describing current population structure in the species, reveal the gene flow regime, and provide insight on current levels of genetic diversity within populations. Understanding these patterns will aid in management of current coastal cactus wrens populations and future efforts in habitat restoration.

From this study, scientists found coastal cactus wrens to be highly isolated from one another in their southern California range(Barr et al. 2015). These results prompted management actions to attempt to restore connectivity among cactus wren populations, including habitat protection and restoration. The goal of Subtask 4.2 is to repeat the 2011 genetics study in the Otay, Sweetwater/San Diego and San Pasqual Valley genetic clusters. Specifically, the objectives are to:

1) Determine whether genetic diversity and effective population size have changed in the intervening 6 years with management to increase cactus scrub and improve connectivity, or in response to drought-associated population declines.
2)Prepare recommendations for managing gene flow and/or population expansion to enhance genetic diversity and effective population size.