Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.
PLoS One. 2012;7(4):e34667. doi: 10.1371/journal.pone.0034667. Epub 2012 Apr 5.
Disease can be an important driver of host population dynamics and epizootics can cause severe host population declines. Batrachochytrium dendrobatidis (Bd), the pathogen causing amphibian chytridiomycosis, may occur epizootically or enzootically and can harm amphibian populations in many ways. While effects of Bd epizootics are well documented, the effects of enzootic Bd have rarely been described. We used a state-space model that accounts for observation error to test whether population trends of a species highly susceptible to Bd, the midwife toad Alytes obstetricans, are negatively affected by the enzootic presence of the pathogen. Unexpectedly, Bd had no negative effect on population growth rates from 2002-2008. This suggests that negative effects of disease on individuals do not necessarily translate into negative effects at the population level. Populations of amphibian species that are susceptible to the emerging disease chytridiomycosis can persist despite the enzootic presence of the pathogen under current environmental conditions.
疾病可能是宿主种群动态的重要驱动因素，动物传染病会导致宿主种群数量严重下降。蛙壶菌（Batrachochytrium dendrobatidis，Bd）是导致两栖动物壶菌病的病原体，可能以爆发性或地方性方式存在，并以多种方式危害两栖动物种群。虽然蛙壶菌爆发性传染病的影响已有大量记载，但地方性蛙壶菌的影响却很少被描述。我们使用一种状态空间模型来检验是否存在地方性蛙壶菌会对极易感染蛙壶菌的物种——蟾蜍 Alytes obstetricans 的种群趋势产生负面影响，该模型考虑了观测误差。出人意料的是，从 2002 年到 2008 年，蛙壶菌并没有对种群增长率产生负面影响。这表明疾病对个体的负面影响不一定会转化为种群水平的负面影响。在当前的环境条件下，即使有地方性蛙壶菌的存在，易感染新兴疾病壶菌病的两栖物种的种群也能持续存在。
