Sex ratio variation in gastrointestinal nematodes of Svalbard reindeer; density dependence and implications for estimates of species composition
Sex ratio variation in gastrointestinal nematodes of Svalbard reindeer; density dependence and implications for estimates of species composition
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DOI：
10.1017/s0031182004006298
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发表时间：
2004-12
期刊：
影响因子：
2.4
通讯作者：
A. Stien;M. Dallimer;R. Irvine;O. Halvorsen;R. Langvatn;S. Albon;J. Dallas
中科院分区：
文献类型：
--
作者：
A. Stien;M. Dallimer;R. Irvine;O. Halvorsen;R. Langvatn;S. Albon;J. Dallas
估计物种的强度和丰度为胃肠道线虫群落的生态学、进化和流行病学研究提供了必要的数据。当只有雄性具有易于评分的物种特有形态特征时，这些估计通常来自于成年雄性的物种组成。这种估计假设群落中所有物种具有相同的成虫性别比。我们利用聚合酶链反应法鉴定了斯瓦尔巴群岛驯鹿基础群落中的三圆线虫格鲁氏Ostertagia gruehneri和Marshallagia marshalli两种成年雌性，从而评估了这一假设。雄虫的比例略高于雄虫的比例。成虫性别比例的季节性变化和密度依赖性仅在古氏夜蛾中发现。讨论了这种性别比变化的可能的人口统计学机制，并提出了产生密度依赖性别比的随机模型。性别比例的变化在一些以男性为基础的感染强度估计中造成了重大偏差，而在丰度估计中，只有在冬末的样本中才明显存在重大和一致的偏差。我们的研究结果表明，估计性别比例在低丰度线虫物种的个体宿主水平研究中特别重要。
Estimates of the intensity and abundance of species provide essential data for ecological, evolutionary and epidemiological studies of gastrointestinal nematode communities. These estimates are typically derived from the species composition of adult males when only males have readily scorable species-specific morphological traits. Such estimation assumes that all species in the community have the same adult sex ratio. We evaluated this assumption for the trichostrongyle nematodes Ostertagia gruehneri and Marshallagia marshalli in infracommunities in Svalbard reindeer by identifying to species adult females using a polymerase chain reaction assay. The proportion of males was found to be slightly higher in O. gruehneri than in M. marshalli. Evidence for seasonal variation and density dependence in the adult sex ratio was only found for O. gruehneri. Possible demographic mechanisms for such sex ratio variation are discussed, and stochastic models that generate density-dependent sex ratios proposed. Sex ratio variation caused substantial bias in some male-based estimates of intensity of infection, while substantial and consistent bias in estimates of abundances was only evident in late winter samples. Our results suggest that estimating sex ratios can be particularly important in individual host level studies of nematode species of low abundance.