Preferences of <i>D. simulans</i> males.

<p>Mean courtship indices for <i>D. simulans</i> males when paired with: <i>D. simulans</i> females, oe⁻<i>D. melanogaster</i> females (lacking CHCs), oe⁺<i>D. melanogaster</i> females (expressing CHCs), sham-perfumed oe⁻ females and oe⁻ females perfumed with <i>D. melanogaster</i> female CHCs. Error bars indicate standard errors, and columns labeled with different letters are significantly different from one another (pairwise Wilcoxon tests followed by sequential Bonferroni adjustment, p<0.05). N = 15–30.</p

Natural Variation in the Strength and Direction of Male Mating Preferences for Female Pheromones in <i>Drosophila melanogaster</i>

<div><p>Many animal species communicate using chemical signals. In <i>Drosophila</i>, cuticular hydrocarbons (CHCs) are involved in species and sexual identification, and have long been thought to act as stimulatory pheromones as well. However, a previous study reported that <i>D. melanogaster</i> males were more attracted to females that were lacking CHCs. This surprising result is consistent with several evolutionary hypotheses but is at odds with other work demonstrating that female CHCs are attractive to males. Here, we investigated natural variation in male preferences for female pheromones using transgenic flies that cannot produce CHCs. By perfuming females with CHCs and performing mate choice tests, we found that some male genotypes prefer females with pheromones, some have no apparent preference, and at least one male genotype prefers females without pheromones. This variation provides an excellent opportunity to further investigate the mechanistic causes and evolutionary implications of divergent pheromone preferences in <i>D. melanogaster</i> males.</p></div

Preference variation in <i>D. melanogaster</i> males.

<p>Preference indices for <i>D. melanogaster</i> males from 12 inbred genotypes and one outbred population (allRAL) when allowed to choose between perfumed oe⁻ females and sham-perfumed oe⁻ females (lacking CHCs). The preference index is the relative advantage of oe⁻ females over perfumed females, such that positive values indicate a preference for females lacking CHCs. Asterisks above the columns show preference indices that are significantly different from 0 (binomial tests: * p<0.05; ** p<0.01 and significant after sequential Bonferroni adjustment). N (Canton-S)  = 94, all other n = 26–60.</p

The relationship between average egg number and average preference for each line.

<p>The relationship between average egg number and average preference for each line.</p

The effect of distance on oviposition preference.

<p>A Tukey box plot is shown for each genotype * distance combination; red  =  RAL-555, orange  =  RAL-437, green  =  RAL-208, blue  =  RAL-365.</p

The effect of ethanol on oviposition preference.

<p>A: The effect of ethanol on behavior towards yeast is shown for 13 RAL genotypes at three concentrations of ethanol, where each line is a genotype. B: Plot of mean preference of genotypes in A, at two ethanol concentrations, shows that preferences are highly correlated between ethanol concentrations, with more avoidance of yeast substrate at higher ethanol concentration.</p

The average number of eggs laid for 282 inbred lines.

<p>Minimum sample size per line  = 5 females, mean  = 16.1 females. Variance and sample sizes vary considerably between genotypes (see text), and only means are shown for each genotype, for clarity. On the right, a histogram of the same data is shown.</p

The average proportion of eggs laid on y^- media for 213 inbred lines.

<p>Variance and sample sizes vary considerably between genotypes (see text), and only means are shown for each genotype, for clarity. On the right, a histogram of the same data is shown. Minimum sample size per line  = 5 females, mean  = 11.6 females.</p

Violin plots of preference behavior.

<p>Each element contains a Tukey box plot showing the median (white dot), 75% quartile (thick line) and range excluding outliers (thin line). Surrounding the box plot is a kernel density trace, plotted symmetrically on both sides of the boxplot, which provides a graphical comparison of each distribution (following <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0016436#pone.0016436-Hintze1" target="_blank">[34]</a>). Inbred  =  distribution of inbred RAL genotypes; Outbred  =  the F₈ population started from these inbred lines; y-1 and y-2 =  populations selected for a single generation in the direction of 1.00; y+1 and y+2 =  populations after two generations of selection in the direction of 0.00.</p

The distribution of preferences among females of two RAL genotypes (R555 and R365), their F1 offspring (with R555 as the maternal parent), and their F2 offspring.

<p>Median (line), 75% quartile (box), and range excluding outliers (whiskers), and outliers (circles) are shown.</p