Ancognatha vulgaris (Melolonthidae, Cyclocephalini): a specialized pollen-feeding scarab associated with wax palms (Ceroxylon spp., Arecaceae) in Andean cloud forests of Colombia

摘要

With 22 species, Ancognatha is the fourth most species-rich genus of Neotropical cyclocephaline scarabs (Melolonthidae, Cyclocephalini), an important group of anthophilous insects associated with palms (Arecaceae). Unlike other members of the tribe, which predominantly inhabit low-altitude ecosystems, Ancognatha spp. are most common in montane areas, at elevations of 1500 to over 4000 m a.s.l. In the cloud forests of the Andes of Colombia, we investigated the association between Ancognatha vulgaris and seven species of wax palms (Ceroxylon spp.) from 2009 to 2013. Male and female A. vulgaris can be characterized as specialized florivores recovered in abundances of up to 40 individuals at both male and female inflorescences of all studied species of wax palms, which they also used for shelter and as aggregation sites for mating. The night-active beetles preferably fed on the pollen released in high quantities by staminate flowers of male inflorescences, but were also observed gnawing on the pistillate flowers of female inflorescences. We hypothesize that wax palm inflorescences are a key resource for the maintenance of populations of A. vulgaris under the extreme environmental conditions of Andean montane ecosystems, an assumption supported by their overlapping biogeographical distributions.