Department of Biology, Life Sciences Complex, 107 College Place, Syracuse University, Syracuse, New York, 13244.
Evolution. 2013 Oct;67(10):3052-60. doi: 10.1111/evo.12132. Epub 2013 May 22.
The outcome of sperm competition is influenced by the relative quantity and quality of sperm among competing ejaculates. Whereas it is well established that individual ejaculate traits evolve rapidly under postcopulatory sexual selection, little is known about other factors that might influence the evolution of ejaculates. For example, the metabolic rate is likely to affect the sperm production rate and the cellular activity or metabolism of sperm, and it has recently been suggested to constrain the evolution of sperm length in large but not small mammals. I thus examined in eutherian mammals how ejaculate quality traits vary with one another and with testis mass, body size, and metabolism. I found all ejaculate traits to covary positively with one another and to increase with relative testis mass. When controlling for testis mass, small-bodied species showed superior sperm quality (but not sperm number). Furthermore, sperm motility and viability were positively associated with the mass-corrected metabolic rate, but the percentage of morphologically normal and acrosome-intact sperm were not. These results indicate that body size and the energy budget may also influence the evolution of ejaculate quality, although these influences appear to vary among traits.
精子竞争的结果受到竞争精液中精子相对数量和质量的影响。虽然已经证实个体精液特征在交配后性选择下迅速进化，但对于可能影响精液进化的其他因素知之甚少。例如，代谢率可能会影响精子的产生速度以及精子的细胞活动或代谢，并且最近有人提出代谢率可能会限制大型但不是小型哺乳动物的精子长度进化。因此，我在真兽类哺乳动物中研究了精液质量特征如何相互变化以及与睾丸质量、体型和代谢之间的关系。我发现所有精液特征都相互正相关，并随着相对睾丸质量的增加而增加。当控制睾丸质量时，体型较小的物种表现出更好的精子质量（但不是精子数量）。此外，精子活力和活力与质量校正代谢率呈正相关，但形态正常和顶体完整精子的比例则没有。这些结果表明，体型和能量预算也可能影响精液质量的进化，尽管这些影响在不同特征之间似乎有所不同。
