Data from: Contemporary evolution of sea urchin gamete-recognition proteins: experimental evidence of density-dependent gamete performance predicts shifts in allele frequencies over time

Species whose reproductive strategies evolved at one density regime might be poorly adapted to other regimes. Field and laboratory experiments on the sea urchin Strongylocentrotus franciscanus examined the influences of the two most common sperm bindin alleles, which differ at two amino acid sites, on fertilization success. In the field experiment, the Arginine/Glycine (RG) genotype performed best at low densities and the Glycine/Arginine (GR) genotype at high densities. In the lab experiment, the RG genotype had a higher affinity with available eggs, whereas the GR genotype was less likely to induce polyspermy. These sea urchins can reach 200 years of age. The RG allele dominates in old sea urchins, whereas younger sea urchins have near equal RG and GR allele frequencies. A latitudinal cline in RG and GR genotypes is consistent with longer survival of sea urchins in the north and with predominance of RG genotypes in older individuals. The oldest sea urchins were likely conceived at low densities, before sea-urchin predators, like sea otters, were overharvested and sea urchin densities exploded off the west coast. Contemporary evolution of gamete-recognition proteins might allow species to adapt to shifts in abundances and reduces the risk of reproductive failure in altered populations.

繁殖策略在某一密度调控模式下演化的物种，往往难以适配其他密度条件。针对红海胆（Strongylocentrotus franciscanus）开展的野外与实验室实验，探究了两种最常见的精子结合蛋白（bindin）等位基因对受精成功率的影响——这两种等位基因仅在两个氨基酸位点存在序列差异。野外实验结果表明，精氨酸/甘氨酸（RG）基因型在低密度种群中表现最优，而甘氨酸/精氨酸（GR）基因型则在高密度种群中适配性更佳。室内实验中，RG基因型与可受精卵子的结合亲和力显著更高，而GR基因型诱发多精受精的概率则更低。这类红海胆的自然寿命可达200年，老年个体中RG等位基因占绝对主导地位，而年轻个体的RG与GR等位基因频率近乎相等。RG与GR基因型的纬度梯度分布格局，与北部海域红海胆存活率更高的观测结果一致，也与老年个体中RG基因型占优的结论相符。现存最古老的红海胆，其亲本繁殖时种群密度尚低——彼时海獭等红海胆的主要捕食者尚未被过度捕捞，北美西海岸海域的红海胆种群密度尚未出现爆发式增长。配子识别蛋白的当代演化过程，或可帮助物种适应种群丰度的动态变化，进而降低受干扰种群发生生殖失败的风险。