School of Biological Sciences, Monash University, Clayton, 3800, Victoria, Australia.
Evolution. 2010 May;64(5):1257-66. doi: 10.1111/j.1558-5646.2009.00912.x. Epub 2009 Nov 26.
Explanations for the evolution of polyandry often center on the idea that females garner genetic benefits for their offspring by mating multiply. Furthermore, postcopulatory processes are thought to be fundamental to enabling polyandrous females to screen for genetic quality. Much attention has focused on the potential for polyandrous females to accrue such benefits via a sexy- or good-sperm mechanism, whereby additive variation exists among males in sperm competitiveness. Likewise, attention has focused on an alternative model, in which offspring quality (in this context, the sperm competitiveness of sons) hinges on an interaction between parental haplotypes (genetic compatibility). Sperm competitiveness that is contingent on parental compatibility will exhibit nonadditive genetic variation. We tested these models in the Australian cricket, Teleogryllus oceanicus, using a design that allowed us to partition additive, nonadditive genetic, and parental variance for sperm competitiveness. We found an absence of additive and nonadditive genetic variance in this species, challenging the direct relevance of either model to the evolution of sperm competitiveness in particular, and polyandry in general. Instead, we found maternal effects that were possibly sex-linked or cytoplasmically linked. We also found effects of focal male age on sperm competitiveness, with small increments in age conferring more competitive sperm.
多配偶制进化的解释通常集中在这样一个观点上，即雌性通过多次交配为其后代获得遗传益处。此外，交配后过程被认为是使多配偶雌性能够筛选遗传质量的基础。人们非常关注多配偶雌性是否可以通过性感或优质精子机制获得这些好处，因为雄性在精子竞争力方面存在附加变异。同样，人们也关注另一种模式，即后代的质量（在这种情况下是儿子的精子竞争力）取决于亲本单倍型（遗传相容性）之间的相互作用。取决于亲本相容性的精子竞争力将表现出非加性遗传变异。我们在澳大利亚蟋蟀（Teleogryllus oceanicus）中测试了这些模型，使用了一种设计，使我们能够将精子竞争力的加性、非加性遗传和亲本方差分开。我们发现该物种不存在加性和非加性遗传方差，这对这两个模型在特定情况下，特别是在精子竞争力的进化和多配偶制的进化中的直接相关性提出了挑战。相反，我们发现了可能与性别相关或细胞质相关的母体效应。我们还发现了焦点雄性年龄对精子竞争力的影响，年龄的微小增加赋予了更有竞争力的精子。
