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Riley, S.P.D.; Pollinger, J.; Serieys, L.; Sikich, J.A.; Dalbeck, L.; Wayne, R.K.; Ernest, H.B.
Population genetics of a small, isolated population of mountain lions: barriers, inbreeding, and genetic rescue
2014  Conference Proceeding

Mountain lions persist naturally at low densities and can be particularly sensitive to the effects of habitat loss and fragmentation, including genetic effects such as inbreeding and the loss of genetic diversity. The Santa Monica Mountains, northwest of Los Angeles area, are completely isolated from other large natural areas by urban development and large freeways, specifically the 101 Freeway to the north. Locations of GOS radio-collared mountain lions indicate that these freeways are a significant barrier to mountain lion movement. To evaluate the effects of these barriers in more detail, we genotyped 26 lions captured as part of a long-term National Park Service study, as well as 16 other lions in the area at 54 microsatellite loci. Mountain lions in the Santa Monica Mountains had significantly lower genetic diversity than those north of freeway as measured by expected heterozygosity and numbers of alleles. More broadly, this small population also exhibited the lowest levels of genetic diversity that have been reported both in California and throughout the west. Based on pedigree construction and gene-drop analysis, individual male mountain lions can have very high reproductive success and dominate the gene pool of this population. Because of our detailed knowledge of this small population, we were able to document that individual events significantly affected its population genetics. Specifically, a young male (P12) immigrated into the population form north of the 101 Freeway, he possessed 20 alleles that were not previously present in the Santa Monica Mountains population, 19 of which he passed on to his offspring, increasing the population-level diversity. However, we also documented multiple instances of close-inbreeding, specifically between fathers and daughters, something that has rarely been reported in this species and which had measurably negative effects on genetic diversity. Currently, connectivity between the Santa Monica Mountains and other natural areas to the North is very limited; maintaining and enhancing connectivity will be critical for the long-term demographic and genetic health of mountain lion populations in this and other fragmented landscapes.

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