Sexual Isolation and Cuticular Hydrocarbon Differences between Drosophila santomea and Drosophila yakuba

Abstract

Drosophila santomea and Drosophila yakuba are two sister species inhabiting Saõ Tomé island. Previous studies showed that both species display strong reproductive isolation, although they can produce a few viable hybrids. Our study tried to understand the mechanism of this ethological isolation between two allopatric strains. A strong sexual isolation was confirmed, with a marked asymmetry. Comparisons of latency times to either courtship or copulation suggest that males do not discriminate females, whereas D. yakuba females, but not D. santomea females, accept their homospecifics more quickly. Cuticular hydrocarbon compositions of both species and sexes were also established with gas chromatography (GC) and GC/mass spectrometry analysis. All have (Z)-7-tricosene as their major compound. There are several quantitative differences between species for few minor compounds. The largest difference concerns n-heneicosane, which is more abundant in D. santomea than in D. yakuba flies (up to seven times more between males). A similar quantitative difference was also found in a pair of sympatric strains. Furthermore, D. yakuba males artificially perfumed with n-heneicosane were discriminated negatively by D. yakuba females, suggesting a role for this compound in the sexual isolation between these two species.

A Model-Based Analysis of Chemical and Temporal Patterns of Cuticular Hydrocarbons in Male Drosophila melanogaster

“…If endogenous variation causes all compounds to vary as a simple multiple of the TA, then expressing each compound amount as a proportion of the TA for the sample is an unbiased estimator of relative abundances (RA). The relative abundance measure also corrects for internal variability of the measurement system, and has been used extensively in Drosophila CH literature [16], [20], [21]. Other authors have used a log-contrast method in which the logarithm of the ratio of a compound of interest to another compound is used [22]–[24].…”

“…As CH levels in our flies represent around 6.4% of total body lipids, a 100% turnover rate per day represents an allocation of 6.4% of lipids to CH maintenance. Since about 50% of CH are monoenes which have been shown to be involved in male sexual signaling [1], [16], [38], this implies that the metabolic cost of male sexual signaling may be equivalent to the daily production of 3% of total body lipids – a small but significant cost, especially given the high energy cost of lipid production. A recent study using wild-derived D. melanogaster strains[39] showed that there is significant segregating genetic variation for levels of almost all male CHs, and that some QTLs for CH variation co-locate with QTLs for starvation and longevity.…”

Comparative analysis of epicuticular lipid profiles of sympatric and allopatric field populations of Anopheles gambiae s.s. molecular forms and An. arabiensis from Burkina Faso (West Africa)

“…Knowledge of CHCs is currently much more limited for medically important Diptera. However also in these, experimental bioassays have suggested that CHCs may also act as contact pheromones during mating, as previously demonstrated in Drosophila (Ferveur, 1997;Cobb and Jallon, 1990;Kim et al, 2004;Ferveur, 2005;Mas and Jallon, 2005). CHCs have been hypothesized to mediate sexual attractiveness during courtship in Culex species (Gjullin et al, 1967), co-specific mate recognition in different Stegomyia species (Nijhout and Craig, 1971) and female sexual receptivity in An.…”

The role of courtship song in female mate choice in South American Cactophilic Drosophila

“…subquinaria complex [55] and the D . yakuba species group [56]. However, we cannot rule out the possibility that D .…”