Several lines of evidence implicate sexual isolation in both initiating and completing the speciation process. While its existence is straightforward to demonstrate, understanding the evolution of sexual isolation requires identifying the underlying phenotypes responsible so that we can determine how these have diverged. Here we study geographic variation in female mate preferences for male sexual displays in the fly Drosophila subquinaria. Female D. subquinaria that are sympatric with its sister species D. recens discriminate strongly against both D. recens and allopatric conspecific males, whereas females from allopatric populations do not. Furthermore, female mate preferences target at least in part a suite of cuticular hydrocarbons (CHCs) in males and geographic variation in CHCs mirrors the pattern of mate discrimination. In this study we quantify female mate preferences for male CHCs from populations that span the geographic range of D. subquinaria. We find that the direction of linear sexual selection varies significantly between populations that are sympatric vs. allopatric with D. recens in a pattern of reproductive character displacement. Differences in preference partially align with existing differences in CHCs and patterns of sexual isolation, although discrepancies remain that suggest the involvement of additional traits and/and more complex, nonlinear preference functions.
Usage Notes:
D. serrata mating trial CHC data
This file contains the gas chromatography data for the epicuticular hydrocarbons (i.e. CHCs) of Drosophila subquinaria ‘mixed stock’ males that were used in binomial choice mating trials with females from each of eight geographic populations. Each row is the data for one male. The columns indicate the day of the mating trial (Day), the replicate vial number (Vial), whether the male was chosen (i.e. mated) or not by the female during the trial (Chosen) and denoted as 1 vs. 0 respectively, the population of the female used in the trial (Pop), and whether this population is sympatric or allopatric to Drosophila recens (Type), with inland allopatric and coastal allopatric regions further denoted. Line denotes the isofemale line from which the female derived. See Table 1 of the paper for a description of the population abbreviations. GC data has had outliers removed but is untransformed and therefore represents the raw, integrated values. Peaks are numbered as described in Curtis et al. 2013. Epicuticular compounds of Drosophila subquinaria and D. recens: Identification, quantification, and their role in female mate choice. Journal of Chemical Ecology: 39: 579–590.
Preference_dryad.csv