Rothman Lorne D, Darling D Christopher
Department of Zoology, University of Toronto, M5S 1A1, Toronto, Ontario, Canada.
Department of Entomology, Royal Ontario Museum, 100 Queen's Park, M5S 2C6, Toronto, Ontario, Canada.
Oecologia. 1990 May;83(1):1-6. doi: 10.1007/BF00324625.
A parasitoid assemblage consisting of four hymenopteran species caused larval and pupal mortality of the host Gnorimoschema gallaeosolidaginis. In the absence of discrete host patches, the relationship between densities of hosts and parasitized hosts was examined on scales of 0.25, 1, 4, 16 and 25 m within a 400 m plot and between ten 16 m plots within a 1·3 km area. Within the 400 m plot, positive density dependence was observed on scales of 1, 4 and 16 m. Rates of parasitism were found to be density independent across the ten 16 m plots. The nature of parasitoid and host spatial patterns were examined at the 400 m plot by using Goodall's (1974) paired-quadrat variance function, and by fitting the observed distribution of galls and parasitized galls to the Poisson and negative binomial on three scales. Postive density dependence at the 400 m plot occurred in the context of a host density gradient and may indicate aggregation of search time by parasitoids. However, significant responses on scales of 4 and 16 m may only reflect the sum of parasitoid responses on lower scales because of this gradient. Predominance of significant responses on a 1 m scale may be related to the high degree of variation in host density, and limits to active searching range of parasitoids.
由四种膜翅目物种组成的寄生蜂组合导致了寄主Solidago gallaeosolidaginis幼虫和蛹的死亡。在没有离散寄主斑块的情况下，在400米样地内0.25、1、4、16和25米的尺度上，以及在1.3千米区域内的十个16米样地之间，研究了寄主密度与被寄生寄主密度之间的关系。在400米样地内，在1、4和16米的尺度上观察到了正密度依赖性。在十个16米样地中，寄生率与密度无关。通过使用古道尔（1974）的配对样方方差函数，并在三个尺度上将观察到的虫瘿和被寄生虫瘿的分布拟合到泊松分布和负二项分布，在400米样地研究了寄生蜂和寄主的空间格局性质。400米样地中的正密度依赖性发生在寄主密度梯度的背景下，可能表明寄生蜂搜索时间的聚集。然而，由于这种梯度，4米和16米尺度上的显著反应可能仅反映了较低尺度上寄生蜂反应的总和。1米尺度上显著反应的优势可能与寄主密度的高度变化以及寄生蜂主动搜索范围的限制有关。
