Pollination by flower chafer beetles in Eulophia ensata and Eulophia welwitschii (Orchidaceae)

Little is known about the pollination biology of the large (c. 230 species) African orchid genus, Eulophia. Here we report the discovery of pollination by flower chafer beetles (Cetoniinae; Scarabaeidae) in two color forms of E. ensata and in E. welwitschii. Both species have congested, capitate inflorescences, traits that are generally associated with pollination by flower chafer beetles in Eulophia and other plant genera. Pollinarium reconfiguration, including pollinarium bending and anther cap retention, in these beetle-pollinated species is slow. Such slow reconfiguration is predicted by Darwin's hypothesis to be a mechanism that limits geitonogamous self-pollination by slow moving beetles. A breeding system experiment conducted on E. welwitschii showed that this species, like most others in the genus, is self-compatible, but is dependent on pollinators for fruit set. As all Eulophia species are non-rewarding, the basis of attraction of beetles to flowers of the study species seems to be the generalized resemblance of their inflorescence in terms of flower arrangement and color to the capitula of sympatric rewarding Asteraceae that are utilized as food or rendezvous sites (or both) by flower chafer beetles.