LEVELS OF GENETIC-VARIATION CAPTURED BY 4 DESCENDANT POPULATIONS OF PINYON PINE (PINUS-EDULIS ENGELM)

An isolated cluster of populations of pinyon pine, Pinus edulis Engelm ., was used to study the evolutionary dynamics of the founding of new populations. A large population at Owl Creek Canyon, Colorado, is 150 to 200 km to the north from the main distribution of pinyon pine. The population at Owl Creek was established approximately 450 years ago fo llowing long-distance dispersal and it is apparently the source of fou r tiny descendant populations that have been established in close prox imity (5.2-11.2 km) within the last century. Genetic variation was est imated with an electrophoretic survey of proteins. Eight of ten protei ns were polymorphic in the analysed populations. The recently establis hed populations showed a reduction in the levels of heterozygosity and a decrease in the mean number of alleles per locus, particularly the two smaller (n < 20) and also more distant sites from Owl Creek (Windy Site and Hewlett Gulch). Measures of genetic diversity among populati ons were consistent with the hypothesis that the four young population s have their source in Owl Creek. In addition, the detected inbreeding might be attributable to the caching of related seeds by birds foragi ng at the source population. The implications of these results for the management of widespread species, such as pinyon pine, are discussed.