DISSERTATION RESEARCH: The Influence of Disease on Seasonal Variation in Amphibian Life History Traits

传染病很少被理解为生命史上的选择性力量。由于疾病的威胁在环境中往往是异质性的，人们可以预料到特征的变异可以将疾病的影响降至最低，但在没有疾病的情况下代价高昂。这一期望可以在南豹蛙和水生真菌样的色米塔蛙的寄主-病原体系统中得到验证。冬季，网纹夜蛾的交配对产卵较大，而秋季则以个体产卵群形式产卵。温暖的水可能会促进两栖虫卵的病原体--腐竹的传播。在较温暖的月份，分离卵块可能会减少腐殖症的传播。这项研究将记录两个繁殖季节青蛙的感染威胁和产卵行为类型。析因实验将测试在两个繁殖季节(秋季和冬季)产卵行为(单独和集体)和疾病(存在和不存在)的重要性。这将是第一次研究病原体与环境之间的相互作用以及这种相互作用对宿主生活史的影响的实证研究。面对全球环境变化和世界范围内的两栖动物灭绝，了解这种相互作用尤为重要。

Infectious diseases are poorly understood as selective forces on life history. Since the threat of disease is often heterogeneous in the environment, one would expect variation in traits that minimize the impact of diseases but are costly in their absence. This expectation can be tested in the host-pathogen system of the southern leopard frog, Rana utricularia and the aquatic, fungus-like chromista, Saprolegnia ferax. In the winter R. utricularia mating pairs lay large communal egg masses, while in the fall they lay their eggs in individual masses. The transmission of Saprolegnia, a pathogen of amphibian eggs, may be facilitated by warmer water. Separating egg masses may reduce Saprolegnia transmission in warmer months. This study will record the threat of infection and the type of egg-laying behavior of the frogs during both breeding seasons. A factorial experiment will test the importance of egg-laying behavior (single vs. communal) and disease (presence vs. absence) during both breeding seasons (fall vs. winter). This will be the first empirical study to examine the interaction between a pathogen and the environment and the effect of this interaction on a host.s life history. Understanding this interaction is particularly important in the face of global environmental change and worldwide amphibian extinctions.