| Abstract: | British Umbelliferae form a natural cohesive taxon, having patterns of habitat distribution, reproductive biology and life-history that distinguish them from other British dicotyledons. They are usually found in open sites, and are local or rare in distribution. Almost half of British species have the andromonoecious sex habit. Perfect flowers are usually protandrous. The floral composition of umbels, and the pattern of opening of the inflorescence combine to produce a protogynous effect. These have been interpreted as mechanisms which decrease competition for resources between male and female functions in the plant, such that separate maternal and paternal fitness can become optimal. Seeds often require a chilling treatment, alternating temperatures, or a period of after-ripening before they are capable of germination. Schizocarps are of low weight. This seems to relate to the relative openness of habitat wherein unbellifers are found. Patterns of dry matter distribution reflect the life-history strategies of various umbellifer species. Agromyzid leaf miners parasitize the more widespread species, and those which are found in a greater number of different habitats. |
