Patterns of Sperm Precedence Are Not Affected by Female Mating History in Drosophila Melanogaster

Abstract

In promiscuously mating species, there is strong selection on males to maximize their share of paternity through both defensive and offensive means. This has been most extensively examined using the Drosophila melanogaster model system. In these studies, sperm competition has been examined by mating a virgin female to two consecutive males and then determining the fertilization success of both the first male (defending, P1) and the second male (offending, P2). Recent evidence suggests that male defense may be influenced by female mating history (i.e., virgin versus nonvirgin). Here, by mating females to males with three different genotypes, we show that female mating history does not affect male defensive or offensive abilities in sperm competition. We also show that, although female lifetime fecundity was not correlated with the number of times that she mated, it was reduced by increased exposure to males. These data indicate that measures of P1 and P2 previously reported in D. melanogaster may be robust to the specific mating history of the females used in these studies.

Drosophila melanogaster females change mating behaviour and offspring production based on social context

“…In this context, females mating three times failed to show an effect of increased mating on last male sperm precedence [24]. That high remating frequency in our assay dilutes last male precedence (figure 3) is therefore at odds with previous publications.…”

“…100), so increasing number of mates could increase offspring genetic diversity. However, males possess mechanisms ensuring sperm precedence [21] predicting that female mating will not achieve greater offspring diversity because the last male will sire most offspring [24]. We tested this prediction by examining the percentage of offspring sired by the last male when mating with Canton-S females who had already mated with one, two, three or four males (see experiment 3, §2).…”

“…Drosophila melanogaster is a model for last male sperm precedence, but this phenomenon has mainly been explored in the context of females mating twice and with long intervals between copulations (1 -2 days) [21,24]. In this context, females mating three times failed to show an effect of increased mating on last male sperm precedence [24].…”

Partitioning sexual selection into its mating success and fertilization success components

“…Contrary to this expectation, we show that variation in fertilization success influences male reproductive success to approximately the same degree as variation in mating success. These measures are complicated, however, by last-male sperm precedence in D. melanogaster (20,32): In our laboratory-adapted population, the last male to mate a female sires 79% of her offspring on average (33). Thus, the average "mating order" of a male (i.e., his tendency to be the last male to mate a female) is expected to be a major determinant of his success at postcopulatory sexual selection.…”

Direct observation of female mating frequency using time-lapse photography

“…2,12,14,15 However, one serious drawback of using phenotypic markers or male sterilization methods is that usually only two classes of males are employed, so repeated mating by females with males belonging to the same class cannot be detected. Experiments using multiple markers are rare 16 or not possible (e.g., with the sterile male technique) and they still suffer from the same problem of being unable to distinguish repeated matings with males of the same class. Direct observations of matings in the laboratory are also difficult for extended periods of time.…”