Moore Janice, Gotelli Nicholas J
Department of Biology, Colorado State University, Fort Collins, Colorado, 80523.
Department of Biology, University of Vermont, Burlington, Vermont, 05405.
Evolution. 1996 Apr;50(2):807-819. doi: 10.1111/j.1558-5646.1996.tb03890.x.
Adaptation is the usual context for interpreting parasite-host interactions. For example, altered host behavior is often interpreted as a parasite adaptation, because in some cases it enhances parasite transmission. Resistance to parasites also has obvious adaptive value for hosts. However, it is difficult to evaluate the adaptive significance of host-parasite interactions without considering the historical context in which these traits have evolved and if they can be predicted by host (or parasite) phylogeny. We examined the influence of host phylogeny on patterns of altered behavior and resistance to parasitism in a cockroach-acanthocephalan system. A consensus cladogram for cockroach subfamilies was produced from the morphological data of McKittrick. We used this cladogram to predict patterns of altered host behavior in seven cockroach host species. Each species was experimentally infected with a single species of acanthocephalan, Moniliformis moniliformis, a parasite that is transmitted when cockroaches are eaten by rodent final hosts. Activity patterns, substrate choices, and responses to light were measured for control and infected animals. These data were recoded into a behavioral matrix of discrete characters. We determined the most parsimonious distribution of the behavioral characters on the tree obtained from McKittrick's data. We then measured the concordance between the behavioral data and the cockroach cladogram with the consistency index (CI). We compared the observed CI to the expected value based on a randomization of observed character states. For three different models of evolutionary character change, there was no evidence of strong concordance (significantly large CI) between altered host behavior and host relationships. Parsimony analysis of the interior nodes of the phylogenetic reconstruction suggested that unaltered behavior was the ancestral state for most host behaviors. We also compared host phylogeny to a data set on the susceptibility of 29 cockroach species to infection with M. moniliformis. At the species level, there was a significant concordance between susceptibility and host phylogeny. This pattern was consistent with the finding that susceptibility of species varied significantly among different subfamilies. However, at the subfamily level, susceptibility was not strongly concordant with phylogeny. We predict that, given enough time, resistance should be lost in subfamilies that are currently resistant to parasitism. In spite of the potential importance of phylogeny in the evolution of behavior and susceptibility, we found little evidence for phylogenetic effects in this system. We conclude that changes in the behavioral responses of hosts to parasites and, to a lesser extent, changes in susceptibility are more frequent than cockroach speciation events in different cockroach lineages. This finding strengthens the assertion that at least some of the altered behaviors are adaptive for host and/or parasite.
适应是解释寄生虫与宿主相互作用的常见背景。例如，宿主行为的改变通常被解释为一种寄生虫适应，因为在某些情况下它会增强寄生虫的传播。对寄生虫的抗性对宿主也具有明显的适应性价值。然而，如果不考虑这些特征进化的历史背景以及它们是否可以通过宿主（或寄生虫）系统发育来预测，就很难评估宿主 - 寄生虫相互作用的适应性意义。我们研究了宿主系统发育对蟑螂 - 棘头虫系统中行为改变模式和抗寄生模式的影响。根据麦基特里克的形态学数据生成了蟑螂亚科的一致分支图。我们使用这个分支图来预测七种蟑螂宿主物种中宿主行为改变的模式。每个物种都用一种单一的棘头虫物种——念珠棘头虫进行实验性感染，这种寄生虫在蟑螂被啮齿动物终末宿主食用时传播。对对照动物和感染动物测量了活动模式、底物选择和对光的反应。这些数据被重新编码为一个离散特征的行为矩阵。我们确定了从麦基特里克的数据中获得的树上行为特征的最简约分布。然后我们用一致性指数（CI）测量行为数据与蟑螂分支图之间的一致性。我们将观察到的CI与基于观察到的特征状态随机化的预期值进行比较。对于三种不同的进化特征变化模型，没有证据表明宿主行为改变与宿主关系之间存在强烈的一致性（显著大的CI）。系统发育重建内部节点的简约分析表明，未改变的行为是大多数宿主行为的祖先状态。我们还将宿主系统发育与一组关于29种蟑螂物种对念珠棘头虫感染易感性的数据进行了比较。在物种水平上，易感性与宿主系统发育之间存在显著的一致性。这种模式与不同亚科之间物种易感性差异显著的发现一致。然而，在亚科水平上，易感性与系统发育并不高度一致。我们预测，假以时日，目前对寄生具有抗性的亚科中的抗性将会丧失。尽管系统发育在行为和易感性进化中具有潜在重要性，但我们在这个系统中几乎没有发现系统发育效应的证据。我们得出结论，宿主对寄生虫行为反应的变化，以及在较小程度上易感性的变化，在不同蟑螂谱系中比蟑螂物种形成事件更频繁。这一发现强化了这样一种观点，即至少一些改变的行为对宿主和/或寄生虫是适应性的。
