Landscape genetics of amphibians in the Santa Monica Mountains 

Researchers: Gary Bucciarelli; H. Brad Shaffer

Affiliation(s): UCLA; La Kretz Center for California Conservation Science

Summary: More than any other taxon, amphibians are at risk of extinction. Over the last 30 years, numerous global regions have documented amphibian population declines. The current estimate of the amphibian rate of extinction is ~ 200 times greater than the background rate of extinction. Areas with high amounts of biodiversity seem to be especially vulnerable. In the species rich Santa Monica Mountains, native amphibians have experienced local extirpation at many streams. Increased fire frequency, drought, and land modification, concurrently acting with global climate change, have compromised native amphibian breeding habitat throughout the Santa Monica Mountains, while introduced predators have negatively affected native amphibian breeding activity, larval survival, and recruitment. Three native amphibian species (Taricha torosa, Pseudacris regilla and P. cadaverina) currently persist in a subset of streams throughout the Santa Monica Mountains. Both T. torosa and P. cadaverina are stream-breeding specialists, but P. regilla is a generalist that will breed in natural habitat, such as streams and ephemeral pools, as well as artificial aquatic habitat within the urban matrix. It is possible that characteristics of the Santa Monica Mountains, such as elevational variation between streams and arid intervening conditions, a lack of standing water, or anthropogenic modifications and disturbances may preclude overland dispersal for these three amphibian species, thereby leading to subdivision at small-scale distances and potential reduced genetic diversity. However, generalist breeding amphibians, such as P. regilla may show increased genetic connectivity since they appear to move and breed more freely through the matrix. Yet, there is no comprehensive characterization of genetic connectivity or genetic variation of amphibian breeding populations across the Santa Monica Mountains. Given the current, extremely limited genetic information available, land managers in the Santa Monica Mountains have little sense of how our local amphibians use the landscape, and therefore how they should be managed and conserved during drought, increased fire regimes, and climate change. For this collaborative project between UCLA and the NPS, we propose to quantify genetic variation across the Santa Monica Mountains for T. torosa and the two Pseudacris sp. using current, next-generation DNA sequencing approaches and cutting-edge biocomputational analyses for each species to create a management and conservation plan for stream breeding amphibians in the region. This collaborative genomics project will result in an understanding of population demography, structure and genetic differentiation, relatedness, and movement patterns across the landscape for each species, and provide the much needed data required to manage and conserve local amphibians.