Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106-9620, USA.
Proc Natl Acad Sci U S A. 2012 Feb 7;109(6):2049-53. doi: 10.1073/pnas.1110841109. Epub 2012 Jan 23.
Postcopulatory sexual selection due to sperm competition and/or cryptic female choice has been documented in a diversity of taxonomic groups and is considered a pivotal component of sexual selection. Despite this apparent importance, the relative contribution of postcopulatory fertilization success to overall sexual selection has not yet been measured in any species. Here, we used a laboratory-adapted population of the promiscuous fruit fly Drosophila melanogaster to partition the variance in male reproductive success into mating success (a major component of precopulatory sexual selection) and fertilization success (a major component of postcopulatory sexual selection). We found that fertilization success contributed nearly as strongly as mating success to a male's net performance in sexual selection, but that most of this postcopulatory component was attributable to variation in male mating order (the tendency to be the last male to mate a female). After adjusting for mating order, only ≈2% of the residual variation in male reproductive success was attributable to differential fertilization success. We found no correlation between male mating success and fertilization success in this system. Unlike natural populations of Drosophila, our laboratory population is adapted to a semelparous lifecycle, so our findings will be most applicable to other promiscuous species with strong sperm precedence and one short breeding period per year or lifetime. In these species, fertilization success may have as much influence on male reproductive success as mating success, but the timing of mating (mating order) may be the predominant factor contributing to variation in fertilization success.
由于精子竞争和/或隐性雌性选择而导致的交配后性选择已在多种分类群中得到证实，被认为是性选择的关键组成部分。尽管这一现象显然很重要，但在任何物种中，都尚未测量过交配后受精成功对整体性选择的相对贡献。在这里，我们使用经过实验室驯化的多配偶果蝇（Drosophila melanogaster）种群，将雄性生殖成功的方差分解为交配成功（前交配性选择的主要组成部分）和受精成功（后交配性选择的主要组成部分）。我们发现，受精成功对雄性在性选择中的净表现几乎与交配成功一样重要，但该后交配成分的大部分归因于雄性交配顺序的变化（倾向于成为最后与雌性交配的雄性）。在调整了交配顺序后，雄性生殖成功的剩余变异中只有 ≈2%可归因于不同的受精成功。在该系统中，我们没有发现雄性交配成功与受精成功之间存在相关性。与自然种群的果蝇不同，我们的实验室种群适应了单次繁殖的生命周期，因此我们的发现将最适用于其他具有强烈精子优势和每年或终生只有一个短暂繁殖期的多配偶物种。在这些物种中，受精成功可能对雄性生殖成功的影响与交配成功一样大，但交配时间（交配顺序）可能是导致受精成功变异的主要因素。
