Abstract:The epicuticle of various Drosophila species consists of long-chain cuticular hydrocarbons (CHCs) and their derivatives that play a role in waterproofing and a dynamic means of chemical communication. Here, via gas chromatography and mass spectrometry, we identified and quantified the epicuticular composition of D. recens and D. subquinaria, two closely related species that show a pattern of reproductive character displacement in nature. Twenty-four compounds were identified with the most abundant, 11-cis-Vacc… Show more
“…Branch lengths are proportional to evolutionary time. *Evidence for TAG-expression is based on Curtis et al, 2013. DOI:
http://dx.doi.org/10.7554/eLife.01751.00310.7554/eLife.01751.004Figure 1—figure supplement 1.Representative UV-LDI spectra from distantly related drosophilids in the Drosophila subgenus.Signals corresponding to sex-specific TAGs (in red) are identified based on the exact mass measurements, predicted elemental composition, and number of double bonds. Labeled signals correspond to potassiated molecules [M + K] + .…”
Section: Resultsmentioning
confidence: 99%
“…Previous studies of Sophophora and Drosophila flies identified alkanes, alkenes, and oxygen-modified hydrocarbons as the major lipids used as pheromones (Jallon and David, 1987; Greenspan and Ferveur, 2000). Recently, triacylglycerides (TAGs), which are normally found in the fat bodies and used for energy storage, were observed on the cuticles of flies from the Drosophila repleta and Drosophila quinaria groups (Yew et al, 2011; Curtis et al, 2013). However, almost nothing is known about the structure, chemical diversity, conserved expression, and functional roles of these exogenously secreted TAGs.…”
Pheromones play an important role in the behavior, ecology, and evolution of many organisms. The structure of many insect pheromones typically consists of a hydrocarbon backbone, occasionally modified with various functional oxygen groups. Here we show that sex-specific triacylclyerides (TAGs) are broadly conserved across the subgenus Drosophila in 11 species and represent a novel class of pheromones that has been largely overlooked. In desert-adapted drosophilids, 13 different TAGs are secreted exclusively by males from the ejaculatory bulb, transferred to females during mating, and function synergistically to inhibit courtship from other males. Sex-specific TAGs are comprised of at least one short branched tiglic acid and a long linear fatty acyl component, an unusual structural motif that has not been reported before in other natural products. The diversification of chemical cues used by desert-adapted Drosophila as pheromones may be related to their specialized diet of fermenting cacti.DOI:
http://dx.doi.org/10.7554/eLife.01751.001
“…Branch lengths are proportional to evolutionary time. *Evidence for TAG-expression is based on Curtis et al, 2013. DOI:
http://dx.doi.org/10.7554/eLife.01751.00310.7554/eLife.01751.004Figure 1—figure supplement 1.Representative UV-LDI spectra from distantly related drosophilids in the Drosophila subgenus.Signals corresponding to sex-specific TAGs (in red) are identified based on the exact mass measurements, predicted elemental composition, and number of double bonds. Labeled signals correspond to potassiated molecules [M + K] + .…”
Section: Resultsmentioning
confidence: 99%
“…Previous studies of Sophophora and Drosophila flies identified alkanes, alkenes, and oxygen-modified hydrocarbons as the major lipids used as pheromones (Jallon and David, 1987; Greenspan and Ferveur, 2000). Recently, triacylglycerides (TAGs), which are normally found in the fat bodies and used for energy storage, were observed on the cuticles of flies from the Drosophila repleta and Drosophila quinaria groups (Yew et al, 2011; Curtis et al, 2013). However, almost nothing is known about the structure, chemical diversity, conserved expression, and functional roles of these exogenously secreted TAGs.…”
Pheromones play an important role in the behavior, ecology, and evolution of many organisms. The structure of many insect pheromones typically consists of a hydrocarbon backbone, occasionally modified with various functional oxygen groups. Here we show that sex-specific triacylclyerides (TAGs) are broadly conserved across the subgenus Drosophila in 11 species and represent a novel class of pheromones that has been largely overlooked. In desert-adapted drosophilids, 13 different TAGs are secreted exclusively by males from the ejaculatory bulb, transferred to females during mating, and function synergistically to inhibit courtship from other males. Sex-specific TAGs are comprised of at least one short branched tiglic acid and a long linear fatty acyl component, an unusual structural motif that has not been reported before in other natural products. The diversification of chemical cues used by desert-adapted Drosophila as pheromones may be related to their specialized diet of fermenting cacti.DOI:
http://dx.doi.org/10.7554/eLife.01751.001
“…In rock-pool beetles (Ochthebius urbanelliae), reinforcement creates isolation between allopatric and sympatric populations, so sympatric populations mate with one another but will not mate with allopatric populations (Porretta and Urbanelli 2012). In Drosophila subquinaria, sympatric females reject allopatric males on the basis of epicuticular compounds (Jaenike et al 2006;Curtis et al 2013;Giglio and Dyer 2013;Dyer et al 2014), while in Drosophila serrata, allopatric females reject sympatric males (Higgie and Blows 2008). Our results are most similar to those for walking stick insects (Nosil et al 2003), in which sympatric females preferred native males over males from foreign pop- ulations regardless of whether the foreign males were from sympatric or allopatric populations.…”
Reinforcement occurs when behavioral isolation is strengthened between species due to selection against hybridization in sympatry. Mate preferences and their target traits may change in sympatry as a consequence of reinforcement. This can potentially generate further behavioral isolation within species if sympatric populations evolve extreme preferences or traits that cause them to reject individuals from foreign populations as mates or be rejected as mates. This process is known as cascade reinforcement. We measured behavioral isolation between sympatric and allopatric populations of Lucania killifish to determine whether isolation evolves due to reinforcement between species and whether reinforcement affects preferences within species, consistent with the cascade reinforcement hypothesis. We measured mate preferences in both sexes between species (Lucania parva vs. Lucania goodei) and within species (among populations of L. parva). Between species, both male and female preferences for conspecifics were highest in sympatric populations. Within species, L. parva females from sympatric populations preferred their own native males over foreign males. Allopatric L. parva females and all L. parva males showed no preferences within species. Within species, behavioral isolation showed no association with ecological variables, such as salinity. Thus, reinforcement is a primary factor generating behavioral isolation in Lucania killifish, creating strong preferences in both sexes among species and leading to cascade reinforcement of female mate preference within species.
“…Such changes may allow males to select for or against females based on their previous exposure to desiccation stress, and/or allow females to signal enhanced desiccation tolerance. In addition, in males the importance of CHCs as sexual displays that affect attractiveness to females has been well established in multiple Drosophila species (e.g., Chenoweth and Blows, 2005;Van Homrigh et al, 2007;Curtis et al, 2013;Chung et al, 2014;Dyer et al, 2014). Sexual selection on CHCs may therefore be antagonistic to desiccation hardening responses, as well as longer-term adaptation to desiccation stress (e.g., Kwan and Rundle, 2010), potentially explaining the reduced response in males in both of these contexts.…”
The success of insects in terrestrial environments is due in large part to their ability to resist desiccation stress. Since the majority of water is lost across the cuticle, a relatively water-impermeable cuticle is a major component of insect desiccation resistance. Cuticular permeability is affected by the properties and mixing effects of component hydrocarbons, and changes in cuticular hydrocarbons can affect desiccation tolerance. A pre-exposure to a mild desiccation stress increases duration of desiccation survival in adult female Drosophila melanogaster, via a decrease in cuticular permeability. To test whether this acute response to desiccation stress is due to a change in cuticular hydrocarbons, we treated male and female D. melanogaster to a rapid desiccation hardening (RDH) treatment and used gas chromatography to examine the effects on cuticular hydrocarbon composition. RDH led to reduced proportions of unsaturated and methylated hydrocarbons compared to controls in females, but although RDH modified the cuticular hydrocarbon profile in males, there was no coordinated pattern. These data suggest that the phenomenon of RDH leading to reduced cuticular water loss occurs via an acute change in cuticular hydrocarbons that enhances desiccation tolerance in female, but not male, D. melanogaster.
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