Genetic Stability in a Peripheral Isolate of STEPHANOMERIA EXIGUA Ssp. CORONARIA That Fluctuates in Population Size.

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.