Einum Sigurd, Fleming Ian A
Norwegian Institute for Nature Research, Tungasletta 2, N-7485 Trondheim, Norway.
Am Nat. 2002 Dec;160(6):756-65. doi: 10.1086/343876.
Various models that assume correlations between maternal phenotype and offspring environment predict adaptive variation in egg size within populations. Here we conduct a comparative test of these models using published data on fish egg size. Intrapopulation variation in egg size was most pronounced in fish with demersal eggs and larvae (median coefficient of variation [CV] at family level = 6.5%), where offspring environment is likely influenced by maternal phenotype, and least so in fish with pelagic eggs (CV = 3.6%), which experience a relatively stochastic spatial distribution during incubation. This difference was significant at various taxonomic levels, was robust to variation in mean egg size and habitat (i.e., freshwater or marine), and was mirrored in independent paired contrasts. Fish with demersal eggs and pelagic larvae were not significantly different from those with pelagic eggs (CV = 3.8%), indicating that selection favoring within-population variation in egg size occurs mainly posthatching and that any such selection occurring prehatching may be less intense. These results suggest that patterns of within-population variation in egg size among fish taxa reflect adaptive processes and that maternal effects on the egg size-fitness function may explain apparent discrepancies from the single-optima Smith-Fretwell model.
各种假设母体表型与后代环境之间存在相关性的模型预测了种群内卵大小的适应性变化。在此，我们利用已发表的鱼类卵大小数据对这些模型进行了比较检验。卵大小的种群内变异在具有沉性卵和仔鱼的鱼类中最为明显（家庭水平的变异系数[CV]中位数 = 6.5%），其后代环境可能受母体表型影响，而在具有浮性卵的鱼类中最小（CV = 3.6%），这类鱼在孵化期间经历相对随机的空间分布。这种差异在不同分类水平上均显著，不受平均卵大小和栖息地（即淡水或海洋）变化的影响，且在独立的配对对比中也有体现。具有沉性卵和浮游仔鱼的鱼类与具有浮性卵的鱼类没有显著差异（CV = 3.8%），这表明有利于种群内卵大小变异的选择主要发生在孵化后，并且任何在孵化前发生的此类选择可能强度较小。这些结果表明，鱼类分类群中卵大小的种群内变异模式反映了适应性过程，并且母体对卵大小 - 适合度函数的影响可能解释了与单最优史密斯 - 弗雷特韦尔模型明显不符的情况。
