Dissertation Research: Reproduction and Resource Allocation

把时间和精力分配给生殖对两性都有影响。在这项研究中，精子分配模式的原因和后果将在男性进行调查。从历史上看，这一领域的大多数研究都集中在卵子的生产上，因为卵子的生产成本比精子高。然而，尽管精子比卵子小，雄性的每次射精可能含有大量的精子。最近的研究表明，在许多物种中，用于配子生产的生殖资源对雄性和雌性都是有限的。对雄性精子投入模式至关重要的是雌性与多个雄性交配的程度。这种多次交配在不同雄性的精子之间建立了激烈的竞争，以使同一个卵子受精。这种精子竞争的一个后果是产生大量的射精。W. E. Harris开发的一个动态程序模型为蝾螈（Ambystoma texanum）的精子分配提供了预测。这个物种非常适合进行这样的研究，因为在任何繁殖聚集中，每只雄性可能会储存60多个精子包，每个精子包含有数千个精子，而每只雌性在产卵前可能会将20多个精子包导入生殖道。动态规划模型的预测将通过受控的实验室实验进行检验。精子分配的变化是大多数物种生殖模式的一个关键但尚未得到充分研究的方面。以前，大多数物种的雄性都被认为射精量大，因为大多数精子都有缺陷。最近的理论表明，如果雌性有多个交配对象，精子分配可能是雄性为了最大限度地提高繁殖后代的机会而进行的几种适应之一。这项研究的目的是测试这一理论体系的几个预测。

Allocation of time and energy to reproduction influences both sexes. In this research, the causes and consequences of patterns of sperm allocation in males will be investigated. Historically, most research in this field has concentrated on egg production because an egg is more costly to produce than a sperm is. However, although sperm are smaller than eggs, each ejaculate of a male may contain enormous numbers of sperm. Recent research has revealed that reproductive resources for gamete production can be limited for males as well as for females in many species. Critical to patterns of sperm investment by males is the degree to which females mate with multiple males. Such multiple mating sets up intense competition among sperm of different males to fertilize the same egg. One consequence of such sperm competition is the production of large ejaculates. A dynamic program model developed by W. E. Harris has provided predictions for sperm allocation in the salamander, Ambystoma texanum. This species is highly suitable for such a study because within any breeding aggregation, each male may deposit 60+ sperm packets each containing many thousand sperm, and each female may induct 20+ sperm packets into her reproductive tract before she lays any eggs. Predictions from the dynamic program model will be tested using controlled laboratory experiments. Variation in sperm allocation is a key but understudied aspect of the reproductive pattern of most species. Previously, males of most species were thought to produce large ejaculates because most sperm were defective. More recent theory suggests that sperm allocation may be one of several adaptations of males to maximize their chances of siring offspring if females have multiple mating partners. The goal of this study is to test several predictions of this body of theory.