Meeting Abstract
Mosquitoes are important vectors of disease, but they are also important pollinators of Platanthera obtusata orchids. These orchids are inconspicuous and blend with the surrounding foliage. Despite being relatively cryptic, these orchids attract a diversity of tiger mosquitoes (Aedes spp.), raising the question of how the orchids attract the mosquitoes. In field experiments we found that mosquitoes are the dominant pollinator of this orchid species. To identify how these orchids attract the mosquitoes, we first examined the orchid scent, which could act as a long-distance cue. Using dynamic sorption methods and GCMS, we found that the orchids emit a scent comprised of common blood-host volatiles as well as other attractants (eg, oviposition). To identify the constituents in the scent that the different Aedes spp. respond to, we used Gas Chromatography linked with Electroantennography (GC-EAG). Results from these experiments showed that the different Aedes species responded to similar constituents in the scent. Behavioral experiments using an olfactometer demonstrated that an artificial mixture of the EAG-active constituents elicited significant attraction compared to the no-odor control. Finally, using two-photon microscopy and bath-applied and genetically encoded calcium indicators we examine how the orchid mixture was processed by the mosquito antennal lobe (AL), primary site of olfactory processing in the brain. AL responses to the olfactory stimuli showed that the orchid mixture was processed in a non-linear manner relative to responses to the individual constituents. Together, these results show that the mosquito olfactory system encodes complex scents differently than individual volatiles, and that scent may play an important role in mediating this unique plant-pollinator system.
