Kin Recognition in Polyphenic Species

摘要本研究将使用两栖动物作为模型系统来了解某些动物如何以及为什么识别它们的亲属。亚利桑那虎蝾螈的幼虫很不寻常，因为它们在自然界中有两种不同的类型：一种是“典型”的形态，一种是“食人”的形态。只有当幼虫在高密度拥挤时才会产生食人形态，这种形态主要以其他虎蝾螈为食。当与亲缘关系不同的较小的幼虫住在一起时，食人族优先食用亲缘关系较低的个体，无论是在实验室还是在野外。这种区别在那些特别可能产生食人变体的科的幼虫中最为明显。这项研究将测试两个非排他的进化假设，关于食人族为什么能认出他们的亲戚。首先，通过不吃近亲，食人族可以间接地增加自己的基因代表性或“包容性”适应性，因为他们有共同的血统。另外，食人族可能会避免吃近亲，以减少他们死于疾病的几率。在自然界中，一种致命的细菌可以感染这些动物，而同类相食是获得这种疾病的一种特别有效的方式。此外，这种传染性病原体可能在近亲之间高度传播，可能是因为亲属具有相似的免疫系统。这项研究将使用实地观察以及实地和实验室实验来检验每个假设所做出的具体预测。虎蝾螈是分离亲缘歧视的直接和间接适应度结果的理想模型系统。因此，这项研究有望帮助解决为什么某些动物识别亲属，这对目前有关利他主义进化的理论很重要。这项研究还将增进对亲属关系在疾病传播中的作用的了解。

Pfennig, David 9512110 Abstract This research will use amphibians as a model system to understand how and why certain animals identify their relatives. Larval Arizona tiger salamanders are unusual in that they occur in nature as two distinct types: a 'typical' morph and a 'cannibal' morph. The cannibal morph is produced only when larvae are crowded at high densities, and this morph feeds primarily on other tiger salamanders. When housed with smaller larvae that differ in relatedness, cannibals preferentially consume less related individuals, both in the laboratory and in the field. This discrimination is most pronounced among larvae from families that are especially likely to produce cannibal morphs. This research will test two non-exclusive evolutionary hypotheses on why cannibals recognize their relatives. First, by not eating a relative, with whom the cannibal shares some genes due to common descent, cannibals can indirectly increase their own genetic representation or "inclusive" fitness in the population. Alternatively, cannibals may avoid eating kin to lessen their chances of dying from disease. In nature, a deadly bacterium can infect these animals, and cannibalism is an especially efficient way of acquiring the disease. Moreover, this infectious agent may be highly transmissible among close relatives, perhaps because kin have similar immune systems. This research will use field observations and field and laboratory experiments to test specific predictions made by each hypothesis. Tiger salamanders are an ideal model system for separating the direct and indirect inclusive fitness consequences of kin discrimination. This study thus promises to help resolve why certain animals recognize kin, which is important to current theories concerning the evolution of altruism. The research will also increase understanding of the role of kinship in disease transmission.