Evolution of Specialization in Insect-Umbellifer Associations

The plant family Umbelliferae (Apiaceae) consists of almost 3000 species worldwide (112). Members of the family occupy a wide variety of habitats, including deserts, basaltic bluffs, salt and freshwater marshes, chaparral, forests, waste places, and subalpine tundra. Despite the ecological diversity, however, family members display remarkable morphological conservatism. The integrity of the family as a taxonomic unit has been recognized for centuries, from Theophrastus’ establishment of Narthekodes as one of the natural plant families to Tournefort’s unification of its current elements in 1694 (38). Also characteristic of the family is a relatively distinctive insect fauna. Acknowledged as a plant taxon disproportionately free from insect attack (105), the Umbelliferae nonetheless supports a fauna that is primarily oligophagous--restricted to Umbelliferae and, rarely, a few closely related families. Thus, it is not surprising that interactions between umbelliferous plants and their insect associates have received considerable attention from both ecological and evolutionary perspectives. In this review, the fauna of the Umbelliferae is evaluated in the context of recent discussion of the evolution (and implications) of specialization in insect-plant associations. Emphasis placed on the mediation of insect-host interactions by umbellifer chemistry.