GENETIC STABILITY IN A PERIPHERAL ISOLATE OF STEPHANOMERIA EXIGUA ssp. CORONARIA THAT FLUCTUATES IN POPULATION SIZE

L. D. Gottlieb ¹

¹ Department of Genetics, University of California, Davis 95616

Allelic frequencies did not change at five polymorphic loci in seedlings grown from seeds collected in four consecutive years in a geographically peripheral population of the annual plant Stephanomeria exigua ssp. coronaria (Compositae), even though the population number fluctuated during this period by 50:1. Genetic stability is attributed to buffering effects provided by seed storage in the ground. Evidence described elsewhere suggests that this population was the recent progenitor of a new diploid species. The present result indicates that fluctuations in number of individuals in the parental population were probably not involved in the origin of the new species.