Sperm-Female Coevolution: Mechanisms, Models & Theoretical Implications

精子-女性共同进化：机制、模型和理论含义。最近的研究表明，精子和女性生殖道的形状是一致进化的。这种模式可归因于一种被称为女性“精子选择”的过程，当女性与多个男性交配时，女性的生殖行为特征会在父子关系模式中产生偏见，例如偏向受精而选择更长的精子。这里提出的研究将调查(1)女性精子选择的生理机制，(2)具有“辨别”精子变体的能力对女性的可能好处，(3)有助于受精成功的性状变异对男性的成本和好处，以及(4)产生少量大精子对性别差异理论的影响。性别之间的性细胞大小不平等被认为是所有性别差异(例如，身体大小、攻击性、装饰性)的基石。然而，与普遍认为的相反，所有物种的雄性都不会产生很多微小的精子。事实上，精子细胞是最多样化的细胞类型：在几乎所有的动物群体中，它们在大小、形状和结构上进化得如此之快，以至于即使是关系密切的物种通常也可以通过它们的精子来区分。因为拥有正确的特定物种的精子结构是成功繁殖的关键，所以精子分化可能会起到“物种形成引擎”的作用。因此，了解精子进化的原因对于我们理解性别差异的生物学基础和物种形成过程是重要的。

Sperm-female coevolution: mechanisms, models and theoretical implications.Recent work has demonstrated that the shapes of sperm and of the femalereproductive tract evolve in concert. This pattern is attributable to aprocess known as female "sperm choice," with female reproductivetract characteristics producing a bias in patterns of paternity whenfemales mate with multiple males, such as biasing fertilization in favor oflonger sperm. Research proposed here will investigate (1) physiologicalmechanisms of female sperm choice, (2) possible benefits tofemales of having the ability to "discriminate" among sperm variants, (3)costs and benefits to males of variation in traits that contribute tofertilization success, and (4) implications of producing few,large sperm for sex difference theory.Disparity between the sexes in the size of their sex cells is believed tobe the cornerstone of all sex differences (e.g., body size, aggressiveness,ornamentation). However, contrary to popular belief, males of all speciesdo not produce many tiny sperm. In fact, sperm cells are the most diversecell type: in nearly all animal groups, they evolve in size, shape, andstructure so rapidly that even closely related species can usually bediscriminated by their sperm. Because having the correct species-specificsperm structure is pivotal for successful reproduction, sperm divergencemay function as an "engine of speciation." Understanding the causes ofsperm evolution is thus important to our understanding of the biologicalbasis of sex differences and of the process of speciation.