Mimicking Livor Mortis: a Well-Known but Unsubstantiated Color Profile in Sapromyiophily

Abstract

By emitting strong scents resembling rotting organic materials suitable for oviposition and/or foraging of flies, sapromyiophilous flowers mimic the substrates that attract flies as pollinators. It has been suggested that the wide range of volatile organic compounds emitted by this deceptive pollination system reflects the trophic preferences of flies to different types of substrate, including herbivore and carnivore feces, carrion, and fruiting bodies of fungi. Previous studies suggest that floral scents play a particularly important role in sapromyiophily. However, few studies on the relative importance of floral color or synergy between visual and olfactory cues in sapromyiophily have been substantiated. In this study, we analyzed fetid floral odor, floral pigment composition, and reflectance of an Amorphophallus konjac C. Koch inflorescence, and we conducted bioassays with different visual and/or olfactory cues to explore an unsubstantiated color profile in sapromyiophily: mimicking livor mortis. Our analysis showed A. konjac can emit oligosulphide-dominated volatile blends similar to those emitted by carrion. Necrophagous flies cannot discriminate between the color of an inflorescence, livor mortis, and floral pigments. We concluded that mimicking livor mortis may represent a common tactic of pollinator attraction in "carrion flower" systems within angiosperms.

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

“…Color changes in a carcass, including dull‐red livor mortis and greenish discoloration, are caused by various physical and chemical processes in blood (Nashelksy and McFelley ; Goff ). We recently demonstrated that mimicking livor mortis is a substantiated color profile in sapromyophily (Chen et al ). Therefore, we hypothesize that Stemona flowers mimic different decay phases to attract a wider range of saprophagous insects.…”

“…Stemona is a new taxon exhibiting sapromyophily Sapromyophily has evolved several times in unrelated angiosperm families (Vereecken and McNeil 2010;J€ urgens et al 2013;Chen et al 2015aChen et al , 2015b. The flowers/inflorescences of these plants mimic carrion, dung, or the fruiting bodies of fungi by emitting putrid smells.…”

“…To attract saprophilous flies that pollinate their flowers or inflorescences, sapromyophilous plants mimic the fetid odor signals that the flies use to locate their oviposition sites and/or food resources on animal dung or carrion (Stensmyr et al ; Jürgens et al , ; Vereecken and McNeil ). Fetid volatiles emitted by the flowers/inflorescences of sapromyophilous plants include oligosulfides (dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS)); 1‐pyrroline, which has a semen‐like odor associated with carrion; aliphatic acids, which are generally associated with rotting fruits; pyrazines, which are associated with urine or late‐stage carcasses; and p ‐cresol and indole, which are associated with dung (Kite et al ; Johnson and Jürgens ; van der Niet et al ; Jürgens et al ; Chen et al , ). The function of these fetid compounds as pollinator attractants has been demonstrated in physiological experiments and field or laboratory bioassays (Stensmyr et al ; Shuttleworth and Johnson ; van der Niet et al ; Chen et al , ).…”

“…Fetid volatiles emitted by the flowers/inflorescences of sapromyophilous plants include oligosulfides (dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS)); 1‐pyrroline, which has a semen‐like odor associated with carrion; aliphatic acids, which are generally associated with rotting fruits; pyrazines, which are associated with urine or late‐stage carcasses; and p ‐cresol and indole, which are associated with dung (Kite et al ; Johnson and Jürgens ; van der Niet et al ; Jürgens et al ; Chen et al , ). The function of these fetid compounds as pollinator attractants has been demonstrated in physiological experiments and field or laboratory bioassays (Stensmyr et al ; Shuttleworth and Johnson ; van der Niet et al ; Chen et al , ). To date, detailed studies of the floral profiles of sapromyophilous plants have focused on Araceae, Apocynaceae, Orchidaceae, and Rafflesiaceae, only a subset of the more than 20 angiosperm families that include sapromyophilous taxa (Jürgens et al ).…”

“…Some saprophilous flies can perceive different colors, suggesting that flower color is important for attracting these pollinators (Fukushi 1989;Aak and Knudsen 2011;Jers akov a et al 2012;Chen et al 2015a). For example, visual cues are important when a female blowfly selects a final landing site for oviposition and/or food (Wall and Fisher 2001;Gomes et al 2007).…”