The Effect of Gamete Competition on Levels of Gamete Production in a Marine Invertebrate

以前的工作表明，高人口密度导致更激烈的雄性配子竞争和选择这些配子的生产水平增加。这一假设将通过研究自然种群的殖民海鞘密度和雄性配子生产水平之间的空间和时间的相关性进行测试。另外两个考虑因素，可能会修改的影响，雄配子竞争水平的雄配子生产也将进行探讨。首先，自然选择只能作用于总表型变异的遗传部分。其次，选择同时作用于整个表型，因此选择对雄性配子产生的影响可能受到这一点和其他生活史性状之间的遗传相关性的限制，这些性状也受到强选择的影响。雄性配子生产和分配到其他性状或结构之间的负遗传相关性将产生权衡，增强的雄性配子生产被其他性状的减少所抵消。或者，正的遗传相关性会限制选择对作为一个单一单位的总分配模式进行操作。这两个潜在的限制进化将通过实验室育种实验，将估计狭义遗传力的雄性配子生产水平，并探讨可能的遗传相关性雄性配子生产和其他生活史性状。总的来说，这项研究将有助于我们的知识，在海洋生物的生殖策略的演变，通过研究受精过程中可以施加配子生产模式的选择性压力。

Previous work suggests that high population densities result in more intense male gamete competition and select for increased levels of production of these gametes. This hypothesis will be tested by examining spatial and temporal correlations between density and male gamete production levels in natural populations of a colonial ascidian. Two additional considerations which might modify the effect that male gamete competition has on levels of male gamete production will also be explored. First, natural selection can only act on the genetic portion of total phenotypic variance. Secondly, selection acts simultaneously on the entire phenotype, and so the effect of selection on male gamete production could be constrained by genetic correlations between this and other life history traits that are also subject to strong selection. Negative genetic correlations between male gamete production and allocation to other traits or structures would generate a trade off, with enhanced male gamete production offset by reductions in other traits. Alternatively, positive genetic correlations would constrain selection to operate on total allocation patterns as a single unit. These two potential constraints on evolution will be examined via a laboratory breeding experiment that will estimate the narrow sense heritability of male gamete production levels and explore possible genetic correlations between male gamete production and other life history traits. Overall, this study will contribute to our knowledge of the evolution of reproductive strategies in marine organisms by examining the selective pressures that fertilization processes can exert on gamete production patterns.