Mating behaviour of Staminodeus vectoris (Coleoptera: Curculionidae), and the value of systematics in behavioural studies

Evolutionary trends in derelomine flower weevils (Coleoptera : Curculionidae): from associations to homology

The host-plant associations and life histories of weevils in the pantropical tribe Derelomini are reviewed in light of new phylogenetic insights. The most immediate derelomine ancestor likely had a ‘special association’ with the inflorescences of palms (Arecaceae) involving pollination and oviposition into dispensable male flowers. Case studies of select genus groups show multiple historical forces driving their diversification. In the South and Central American genus Celetes, abundant host shifts are important, though clearly not enough to account for the existence of all species. Females of the Neotropical genus Staminodeus have remarkable morphogical and behavioural modifications for exploiting the staminodes of cyclanth (Cyclanthaceae) inflorescences. The evolution of males in this genus is mostly explained by sexual selection. Cyclanthura illustrates the potential of the weevils for colonising hosts with widely divergent inflorescence biologies, including arums (Araceae) in the genus Anthurium. Members of the Ganglionus–Systenotelus clade, in turn, are exclusively associated with the cyclanth genus Carludovica. A phylogenetic trend in this group to attack the plants’ seeds has led to a series of counteracting transformations in inflorescence morphology. Overall there were at least three independent secondary host shifts to dicots, including one in the taxonomically complex genus Phyllotrox. The results suggest that in this particular tribe of weevils, focusing on the homology of specific biological traits in individual lineages is more likely to produce new knowledge than a formalistic, large-scale approach.