Abstract
We analyzed epicuticular hydrocarbon variation in geographically isolated populations of D. mojavensis cultured on different rearing substrates and a sibling species, D. arizonae, with ultraviolet laser desorption/ionization mass spectrometry (UV-LDI MS). Different body parts, i.e. legs, proboscis, and abdomens, of both species showed qualitatively similar hydrocarbon profiles consisting mainly of long-chain monoenes, dienes, trienes, and tetraenes. However, D. arizonae had higher amounts of most hydrocarbons than D. mojavensis and females of both species exhibited greater hydrocarbon amounts than males. Hydrocarbon profiles of D. mojavensis populations were significantly influenced by sex and rearing substrates, and differed between body parts. Lab food–reared flies had lower amounts of most hydrocarbons than flies reared on fermenting cactus substrates. We discovered 48 male- and species-specific hydrocarbons ranging in size from C22 to C50 in the male anogenital region of both species, most not described before. These included several oxygen-containing hydrocarbons in addition to high intensity signals corresponding to putative triacylglycerides, amounts of which were influenced by larval rearing substrates. Some of these compounds were transferred to female cuticles in high amounts during copulation. This is the first study showing that triacylglycerides may be a separate class of courtship-related signaling molecules in drosophilids. This study also extends the kind and number of epicuticular hydrocarbons in these species and emphasizes the role of larval ecology in influencing amounts of these compounds, many of which mediate courtship success within and between species.
Highlights
Exchange of chemical, auditory, and visual cues during courtship in many species is required for successful courtship and mating
We focus on Baja California and mainland Sonora populations of D. mojavensis, and a sympatric Sonoran population of D. arizonae
We show that cactus-reared flies using UV-LDI-o-TOF MS analysis revealed quantitatively similar cues in animals are epicuticular hydrocarbons (CHCs) profiles as shown by previous gas chromatography-mass spectrometry (GC-MS) analyses, but uncovered previously undetected oxygenated CHC components, as well a large number of different CHCs and putative triacylglycerides localized in the anogenital region of males
Summary
Auditory, and visual cues during courtship in many species is required for successful courtship and mating. Species and population-specific signaling is often required by both sexes prior to fertilization in multiply mating species where mate choice decisions may result in increased fitness for offspring due to sexual selection. In different species or more diverged populations, these signals can relay information about species status and influence sexual isolation [1,2]. Perhaps the beststudied chemical cues in animals are epicuticular hydrocarbons (CHCs) in Drosophila that serve as contact pheromones during physical contact phases of courtship. Hydrocarbon ‘‘perfuming’’ or rub-off experiments have demonstrated the pheromonal role of CHCs as either species or population specific compounds that influence mating success in different Drosophila species [7,8,9,10]. Some compounds transferred during copulation, primarily from males to females, are deposited on the female anogenital cuticle that can inhibit remating by other males [14,15,16,17]
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