Policha, Tobias , Dentinger, Bryn T. M. , Grimaldi, David , Ludden, Ashley , Troya, Adrian , Raguso, Robert Andrew , Roy, Bitty A. .
Substrate use by mycophilous Drosophilidae: Implications for the evolution of fungal mimicry by Dracula orchids.
Dracula orchid flowers attract guilds of mushroom-visiting drosophilid flies due to their visual and olfactory mimicry of the gilled caps of basidiomycete fruiting bodies. Mushroom-visiting flies are often polyphagous as a consequence of utilizing the ephemeral resource of fungal fruiting-bodies. If these flies are indeed generalists, they may be particularly susceptible to exploitation by mimicry. Here we ask the question: to what degree are different species of Dracula orchids mimicking specific mushroom models? Or is this a more generalized mimicry system with the orchids exploiting a generic mushroom-like phenotype? To address this hypothesis, we have compared our mushroom field collections in terms of size, and color to the labella of Dracula orchids, looking for particularly similar candidates. Using GCMS, we analyzed volatiles from many species of mushrooms and several species of Dracula orchids. Finally we let the flies demonstrate preferences or specializations. We compared matrices of flies collected from different mushroom genera against a null hypothesis of no preference. To assess preference in attraction to the different species of Dracula we set up two common gardens in relatively different habitats and regularly made insect collections, analyzing this more controlled data set by G-tests. Our data on the mushrooms that co-occur with Dracula orchids indicate that there is not necessarily a single model, but many potential candidates in terms of size, shape, color, and smell. Our insect collections from most mushroom genera are as heterogeneous as predicted by chance, suggesting generalization in the use of mushrooms that co-occur with Dracula. These data suggest that Dracula orchids appear to represent a generalized mimicry system, in which there is a convergence on the mean phenotype of co-occurring mushrooms with Dracula flowers benefitting from the exploitation of generalized perceptual biases in the visitors. However our insect collections from Dracula species in the common gardens do show some asymmetry. From the flower’s perspective there may be tension between attracting generalist mycophagous insects and maintaining reproductive isolation from other sympatric Dracula species.
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1 - University of Oregon, Institute for Ecology & Evolution, 5289 University of Oregon, Eugene, OR, 97403, USA
2 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey, TW9 3DS, UK
3 - American Museum of Natural History, Division of Invertebrate Zoology, Central Park West at 79th St., New York, NY, 1002426, USA
4 - Escuela Politécnica Nacional, Sección de Entomología del Instituto de Ciencias Biológicas, E11-253 Ladrón de Guevara, Quito, Ecuador
5 - Cornell University, Neurobiology and Behavior, W355 Mudd Hall, 215 Tower Road, Ithaca, NY, 14853, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Salon 6/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 1:45 PM
Candidate for Awards:None