Fragmentation and population declines jeopardize the survival of many species. Excessive reproductive isolation can cause a loss of valuable alleles, decrease genetic variation, induce inbreeding depression, reduce demographic fitness, and lead to reproductive failure. When tree populations are reduced to scattered and clustered individuals, pollen movement is critical to connectivity. This project develops a novel approach that can cover landscape-scale areas and can be integrated into spatially explicit simulation modeling of landscape changes. These new tools are deployed to investigate a threatened tree species, California Valley oak (Quercus lobata). Using allozyme and microsatellite genotypes, the investigators examine three objectives: (1) They will characterize reproductive isolation of individual trees in landscapes with variable conspecific density. (2) They will examine the impact of adult genetic structure and temporal heterogeneity of pollen pools on estimates of pollen movement. (3) They will incorporate estimated parameters into geographic models to simulate the impact of historical and future population decline.
This project represents an excellent case study of the evolutionary dynamics of gene flow and its landscape scale conservation/restoration consequences. It will be applied to a critical California tree species experiencing habitat loss and degradation from residential and agricultural development, a situation in need of information for future management and policy decisions. This research will dovetail issues from evolutionary biology, conservation biology, geography, and public policy of the threatened species.
