Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
Evolution. 2012 Jun;66(6):1709-21. doi: 10.1111/j.1558-5646.2012.01606.x. Epub 2012 Apr 1.
Life-history variables including egg size affect the evolutionary response to sexual selection in broadcast-spawning sea urchins and other marine animals. Such responses include high or low rates of codon evolution at gamete recognition loci that encode sperm- and egg-surface peptides. Strong positive selection on such loci affects intraspecific mating success and interspecific reproductive divergence (and may play a role in speciation). Here, we analyze adaptive codon evolution in the sperm acrosomal protein bindin from a brooding sea urchin (Heliocidaris bajulus, with large eggs and nonfeeding or lecithotrophic larval development) and compare our results to previously published data for two closely related congeners. Purifying selection and low relative rates of bindin nonsynonymous substitution in H. bajulus were significantly different from selectively neutral bindin evolution in H. erythrogramma despite similar large egg size in those two species, but were similar to the background rate of nonsynonymous bindin substitution for other closely related sea urchins (including H. tuberculata, all with small egg size and feeding planktonic larval development). Bindin evolution is not driven by egg size variation among Heliocidaris species, but may be more consistent with an alternative mechanism based on the effects of high or low spatial density of conspecific mates.
生活史变量，包括卵大小，影响有性选择的进化反应在广播产卵海胆和其他海洋动物。这种反应包括在配子识别基因座的密码子进化率高或低，这些基因座编码精子和卵表面肽。这些基因座的强烈正选择影响种内交配成功率和种间生殖分歧（并可能在物种形成中发挥作用）。在这里，我们分析了从胎生海胆（Heliocidaris bajulus，卵大，无营养或非营养性幼虫发育）的精子顶体蛋白结合蛋白中的适应性密码子进化，并将我们的结果与以前发表的两个密切相关的同属种的数据进行了比较。尽管这两个物种的卵大小相似，但 H. bajulus 中的纯化选择和低相对结合蛋白非同义取代率与 H. erythrogramma 中选择性中性的结合蛋白进化显著不同，但与其他密切相关的海胆（包括 H. tuberculata，卵小，摄食浮游幼虫发育）的背景非同义结合蛋白取代率相似。结合蛋白的进化不是由 Heliocidaris 物种之间的卵大小变化驱动的，而是可能更符合基于同种配偶空间密度高低的替代机制。
