The breath of a flower

Abstract

In this article I comment on our findings that floral carbon dioxide (CO2) can be used by Manduca sexta hawkmoths in a scale- and context-dependent fashion. We firstly found, in wind tunnel assays, that diffusing floral CO2 is used as long-distance cue (e.g., meters). Moths track CO2 plumes up-wind in the same manner they track floral odors. Nevertheless, CO2 did not appear to function as a local stimulus for flower probing, evidencing a scale-dependent role in nectar foraging. These results were further enriched by a second finding. In dual choice assays, where moths were offered two scented artificial flowers of which only one emitted above-ambient CO2-levels, female Manduca sexta chose to feed on the CO2 emitting flower only when host-plant volatiles were added to the background. We discuss this apparent measurement of oviposition obligations during foraging in the context of the life histories of both insect and plant species. These findings seem to pinpoint the usually artificial nature of compartmentalizing herbivory and pollination as different, isolated aspects of insect-plant interactions. Insects do not seem to have a defined response to a certain stimulus; instead, motor programs appear to be in response to composite arrangements of external stimuli and inner states. If animal-plant interactions have evolved under these premises, I believe it may prove beneficial to include a non-linear, integrative view of plant multi-signaling and life history aspects into the study of pollination biology.