Policha, Tobias , Grimaldi, David , Dentinger, Bryn , Manobanda, Rocío , Ludden, Ashley , Troya, Adrian , Roy, Bitty .
Do Dracula orchids exploit guilds of fungus visiting flies? New perspectives on a brood-site mimicry.
Dracula orchid flowers are hypothesized to be mushroom mimics because their labella look and smell like mushrooms. To test the mimicry hypothesis we used collections and observations to examine the guilds of insect visitors to Dracula species as well as to co-occurring mushrooms in the cloud forests of Ecuador. We document significant overlap in visitors - mostly from the genera Zygothrica and Hirtodrosophila (Drosophilidae). Many fly species that visit Dracula are also found on mushrooms (55% (27 shared spp./49 total spp.)), and the guilds visiting Dracula spp. are positively associated with the guilds visiting mushrooms (-0.3088 Standard Mantel Statistic; p=0.0080). Furthermore, the presence of pollinia carried by some caught flies enable us to document individuals visiting both mushrooms and Dracula flowers. Our results suggest a bi-modal attraction strategy by the flowers with over half of the visitors belonging to fungal associated taxa, while the remainder appear to be ±specialists, either visiting exclusively one Dracula species or visiting more than one Dracula species, but not mushrooms. To test the hypothesis that this is a brood site mimicry system we conducted field studies where we observed a variety of behaviors common to both host groups, including courtship behaviors such as semaphoring (wing movements), proboscis extension (feeding behavior – we know yeasts occur on these surfaces), obtaining shelter, defending territory, and mating. There were no significant differences in the amount of time insects spent doing these activities on mushrooms vs. Dracula flowers. Given this suite of shared behavior we hypothesized that flies may also oviposit in both substrates. To determine which substrate led to the highest fitness for the flies we reared flies (>1200 individuals) from mushrooms (n=45 individuals; 21 spp.), Dracula spp. (n=35 individuals; 4 spp.) and other flowers (control) (n=11 individuals; 7 spp.). The differences were dramatic; hundreds of flies from mushrooms, very few flies hatched out of Dracula flowers, and there was no overlap in species identity of the hatchlings from these two substrates. The brood-site mimicry hypothesis is supported by our data. Flies that otherwise breed in mushrooms are spending time on Dracula flowers, where they can move pollinia, but do not successfully breed. These flies are still getting rewards from their visitation -- mating site, shelter, etc. so the deception is not a total loss of fitness. This puts the mimicry relationship somewhere on the continuum between Batesian (deception) and Müllerian (convergence).
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1 - University of Oregon, Institute for Ecology & Evolution, 5289 University of Oregon, Eugene, OR, 97403, USA
2 - American Museum of Natural History, Division of Invertebrate Zoology, Central Park West at 79th St. , New York, NY, 1002426, USA
3 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey, TW9 3DS, UK
4 - Universidad de Los Andes, Instituto de Ciencias Ambientales y Ecológicas, Núcleo La Hechicera, Mérida, 5101, Venezuela
5 - Escuela Politécnica Nacional, Sección de Entomología del Instituto de Ciencias Biológicas, Ladrón de Guevara E11-253, Quito, Ecuador
Presentation Type: Oral Paper:Papers for Topics
Location: Firs South/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 8:30 AM
Candidate for Awards:None