de Queiroz Alan, Rodriguez-Robles Javier A
Am Nat. 2006 May;167(5):684-94. doi: 10.1086/503118. Epub 2006 Apr 5.
Evolutionary changes in animal diets must often begin through the inclusion of a novel food type as a minor component of the diet. An aspect of this initial change that has rarely been studied is the relationship between the existing diet and the use of specific novel foods. We used comparative analyses to test the hypothesis that, in snakes, feeding on squamate (lizard and snake) eggs or bird eggs--items that represent evolutionarily derived and, in most cases, minor components of the diet--is associated with feeding on squamates or birds, respectively. Phylogenetic concentrated-changes tests indicate a significant tendency for predation on eggs to arise in snake lineages characterized by feeding on the corresponding animals. These results also generally hold for analyses including only snake species that are likely to encounter eggs and are large enough to ingest them. The inferred histories of specialized egg eaters also support the hypothesis. Because snakes often use chemical cues to recognize prey, the observed phylogenetic patterns might be explained by chemical similarities between eggs and adult animals. Our results suggest broad effects of predispositions on snake diets and thus illustrate how historical contingencies can shape the ecology of organisms.
动物饮食的进化变化通常必须从将一种新的食物类型作为饮食的次要成分纳入开始。这种初始变化中一个很少被研究的方面是现有饮食与特定新食物的使用之间的关系。我们使用比较分析来检验这样一个假设，即在蛇类中，以有鳞目动物（蜥蜴和蛇）的卵或鸟类的卵为食——这些食物代表了进化而来的、在大多数情况下是饮食中的次要成分——分别与以有鳞目动物或鸟类为食有关。系统发育集中变化测试表明，在以相应动物为食的蛇类谱系中，捕食卵有显著的倾向。这些结果对于仅包括可能遇到卵且体型足够大能够吞食卵的蛇类物种的分析也普遍成立。专门食卵者的推断历史也支持这一假设。由于蛇类经常利用化学线索来识别猎物，观察到的系统发育模式可能可以用卵与成年动物之间的化学相似性来解释。我们的结果表明了倾向对蛇类饮食的广泛影响，从而说明了历史偶然性如何塑造生物体的生态。
