The Importance of Oligosulfides in the Attraction of Fly Pollinators to the Brood-Site Deceptive SpeciesJaborosa rotacea(Solanaceae)

Abstract

Premise of research. Brood-site deceptive flowers use dishonest signals-especially floral odors that mimic oviposition substrates-to attract and deceive saprophilous insects to pollinate them. In this work, we recorded the pollinators of the sapromyiophilous species Jaborosa rotacea (Solanaceae) endemic to southern South America. Then, we characterized the floral volatiles of this species, and finally, we carried out field experiments to decouple the effects of scent and color as attractants for saprophilous flies.Methodology. We made direct observations of pollinators in a natural population of J. rotacea. We characterized floral volatiles by means of gas chromatography-mass spectrometry. Subsequently, we used a mixture of 2 oligosulfides (dimethyl disulfide and dimethyl trisulfide), which our analyses revealed were the main constituents of the floral scent of J. rotacea, as baits to determine the attractiveness of this olfactory signal to flies in a geographical region where J. rotacea is not present. Finally, we used the same foul-scented baits in arrays of artificial flowers resembling those of J. rotacea to assess the dual importance of olfactory and visual cues in fly attraction.Pivotal results. Pollination of J. rotacea occurs when saprophilous flies belonging to the families Calliphoridae, Muscidae, and Sarcophagidae-with similar body dimensions to the anther-stigma distance in these flowers-acquire and deposit pollen in the flowers in a nototribic mode. Our chemical analyses revealed that J. rotacea floral scent is chemically simple and features 2 oligosulfide compounds (dimethyl disulfide and dimethyl trisulfide) commonly found in carrion-mimicking flowers. We found that saprophilous flies belonging to the same families that we recorded as pollinators of J. rotacea in its native South American habitat were attracted to foul-scented baits in temperate North America. The flies' visitation frequencies (recorded as approaches and landings on the artificial flowers) depended significantly on the presence of the foul-scented baits.Conclusions. These results support the hypothesis that oligosulfides are universally effective signals by which deceptive flowers may effect pollen dispersal by attracting flies that use carrion or carnivore feces as brood sites.

Variation in floral characters, particularly floral scent, in sapromyophilous Stemona species

“…Floral odor plays a particularly important role in sapromyophilous mimicry systems, with the dominant volatiles being oligosulfides, p ‐cresol, phenol, isoamyl alcohol, and indole (Urru et al ; Jürgens et al ). These volatile compounds appear to act as attractants to floral visitors, as supported by several behavioral studies (Shuttleworth and Johnson ; Moré et al ; Chen et al , ).…”

Spatial and temporal variation in volatile composition suggests olfactory division of labor within the trap flowers of Aristolochia gigantea

“…4C), which, along with dimethyl trisulfide, is indicative of carrion mimicry in brood-site deceptive flowers worldwide (Jürgens et al, 2013). However, in such cases volatile sulfides are the dominant components of simple scent bouquets Kite and Hetterscheid, 1997;Stensmyr et al, 2002) that attract calliphorid, sarcophagid and muscid flies (Moré et al, 2013;van der Niet et al, 2011;Shuttleworth and Johnson, 2010). The complex pattern of floral volatiles emitted by A. gigantea departs markedly from the simple expectations of carrion mimicry.…”

Floral Volatiles in a Sapromyiophilous Plant and Their Importance in Attracting House Fly Pollinators

“…Assuming that P. laevigata mimics breeding sites of the fly, it seems unexpected that males also responded to indole. However, as suggested by Moré et al (2013), fetid scents may not only attract gravid females, but also males, which might use these signals to seek mating opportunities. Alternatively, adult flies might use oviposition sites as their own food source, which also might explain the similarity in responses of the two sexes.…”