Nectar usage in a southern Arizona hawkmoth community

1. Hawkmoths (Sphingidae) are important plant associates at two lifehistory stages: larvae are herbivorous, whereas adults are nectar feeders and often pollinators. The diversity and identities of plants used for nectar is poorly known, however. 2. This study takes a community-level approach to hawkmoth nectar plant usage in a semi-arid grassland habitat in southern Arizona, U.S.A. 3. Pollen carried on the proboscis was identified from over 700 individuals of 14 hawkmoth species attracted to lights over a 2-year period. 4. Two plant species dominated pollen loads, suggesting that hawkmoths use these species extensively as nectar sources: Datura wrightii (Solanaceae), a classic hawkmothpollinated plant, and Agave palmeri (Agavaceae), which is known to be used extensively by bats. Field surveys indicate that both species are relatively rare in the flowering community. Little or no pollen was present on the moths from the most common plant species in flower during the study. 5. The dominance of Agave in pollen loads suggests that this typically bat-pollinated species may be subsidising pollinator populations of the hawkmoth-pollinated flora. 6. Three groups of hawkmoths within this community are identified based on larval diets (reported in the literature) and adult diets (documented here): those that, at a given site, heavily exploit the same plant species at both life-history stages (Manduca sexta and M. quinquemaculata); those that have broad local associations at both life-history stages (Hyles lineata); and those that exhibit narrow but non-overlapping local associations at the two life-history stages (all other hawkmoths at this site).