广义负二项分布对钉螺分布的拟合

Fitting Generalized Negative Binomial Distribution to the Data of Oncomelania hupensis

目的介绍并应用广义负二项分布研究湖北钉螺的分布规律,为定量化研究提供理论依据。方法随机抽取安徽省池州市贵池区秋浦河沿岸的4块滩地作为研究现场,2005年调查4块滩地的钉螺数据,2006年从中再随机抽取2块滩地进行调查。通过全局最大似然法分别拟合广义负二项分布和负二项分布,比较同一季节不同滩地和不同季节同一滩地的分布拟合结果。结果不同季节、不同滩地的钉螺密度是不同的,但其分布形状均是相似的正偏态分布,广义负二项分布能成功地拟合所有的钉螺数据。不同季节同一滩地间的广义负二项分布参数的变化不一致,同一季节不同滩地广义负二项分布的参数估计结果即使在钉螺密度相近的情况下也不相近,钉螺生存环境的微小差异可以通过广义负二项分布的参数灵敏反映。结论广义负二项分布比负二项分布能更好地反映钉螺分布的复杂性,其将在钉螺的定量化研究领域以及家庭聚集性疾病、寄生虫病和定量生态学的研究中具有重要意义。

Objective To study the distribution of Oncomelania hupensis with generalized negative binomial distribution （GNBD）, and provide the theoretical support for quantitative study. Methods 4 bottom-lands were randomly selected along the Qiupu River in Guichi District, Anhui Province, as the study area to survey the snails in 2005, and 2 bottomlands from the 4 selected bottomlands were randomly chosen to survey the snails in 2006. Global maximum likelihood estimation was used to fit GNBD and negative binomial distribution （NBD）. Results from different bottomlands in the same season and the same bottomlands in different seasons were compared with each other. Results Snail density in different seasons and different bottomlands were different, but they had the similar positive skewness distribution. Generalized negative binomial distribution was successfully fitted to all the snail data. The parameters of GNBD from the same bottomlands in different seasons changed differently, and parameters of GNBD from different bottomlands in the same season were not similar even if their snail density were close. Tiny differences in different habitats of snails could be sensitively reflected by the parameter distinctness of GNBD. Conclusion GNBD could well reflect the complexity of snail distribution than NBD, which will have a great significance for the quantitative study of snails.