Abstract
SUMMARY: Using marker genes the breeding system (mating type gene) and the structure (hairy stalk gene) of a zinc–lead mine population of Armeria maritima, an insect‐pollinated plant, was studied in situ. Strict allogamy occurs in the population in nature although this population shows self‐fertility in experimental garden plots. The population is divided into sub‐populations differing in the frequency of hairy stalked individuals. Gene flow between these sub‐populations is very low (if any) so that the differences, which are likely to have originated by chance, remain constant through generations.