Department of Zoology, Stockholm University, 106 91 Stockholm, Sweden.
Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
Cells. 2021 Sep 9;10(9):2369. doi: 10.3390/cells10092369.
Sperm competition is a widespread phenomenon that shapes male reproductive success. Ejaculates present many potential targets for postcopulatory selection (e.g., sperm morphology, count, and velocity), which are often highly correlated and potentially subject to complex multivariate selection. Although multivariate selection on ejaculate traits has been observed in laboratory experiments, it is unclear whether selection is similarly complex in wild populations, where individuals mate frequently over longer periods of time. We measured univariate and multivariate selection on sperm morphology, sperm count, and sperm velocity in a wild population of brown anole lizards (). We conducted a mark-recapture study with genetic parentage assignment to estimate individual reproductive success. We found significant negative directional selection and negative quadratic selection on sperm count, but we did not detect directional or quadratic selection on any other sperm traits, nor did we detect correlational selection on any trait combinations. Our results may reflect pressure on males to produce many small ejaculates and mate frequently over a six-month reproductive season. This study is the first to measure multivariate selection on sperm traits in a wild population and provides an interesting contrast to experimental studies of external fertilizers, which have found complex multivariate selection on sperm phenotypes.
精子竞争是一种广泛存在的现象，它塑造了雄性的生殖成功。精液中有许多潜在的适合度目标（例如精子形态、数量和速度），这些目标往往高度相关，并且可能受到复杂的多元选择的影响。尽管在实验室实验中已经观察到对精液特征的多元选择，但在个体经常长时间交配的野外种群中，选择是否同样复杂尚不清楚。我们在一个棕色鬣蜥（Anolis sagrei）的野生种群中测量了精子形态、精子数量和精子速度的单变量和多变量选择。我们进行了一项标记-重捕研究，并进行了遗传亲子关系分配，以估计个体的生殖成功。我们发现精子数量存在显著的负向定向选择和负二次选择，但我们没有检测到任何其他精子特征的定向或二次选择，也没有检测到任何特征组合的相关性选择。我们的结果可能反映了雄性在六个月的繁殖季节中产生大量小精液并频繁交配的压力。这项研究是首次在野生种群中测量精子特征的多元选择，与外部受精的实验研究形成了有趣的对比，外部受精的实验研究发现了对精子表型的复杂多元选择。
