Zhang Zhi-Qiang, Sanderson John P, Nyrop Jan P
Department of Entomology, Cornell University, Comstock Hall, 14853, Ithaca, NY, USA.
Department of Entomology, New York State Agricultural Experiment Station, Cornell University, 14456, Geneva, NY, USA.
Oecologia. 1992 May;90(2):185-196. doi: 10.1007/BF00317175.
Responses of the predaceous mites Phytoseiulus persimilis, Typhlodromus (=Metaseiulus) occidentalis, and Amblyseius andersoni to spatial variation in egg density of the phytophagous mite, Tetranychus urticae, were studied in the laboratory.The oligophagous predator P. persimilis showed initially a direct density dependent foraging time allocation and variation in foraging time increased with prey density. With changes in prey density due to predation, predator foraging rates (per hour) decreased with time and density dependent foraging gradually became density independence, because P. persimilis continued to respond to initial prey density, instead of the changing prey density and distribution. The consequent spatial pattern of predation by P. persimilis was density independent, although slopes of predation rate-prey density regressions increased with time.Compared with P. persimilis, the narrowly polyphagous predator T. occidentalis responded relatively slowly to the the presence or absence of prey eggs but not to prey density: the mean and variation of foraging time spent in patches with prey did not differ with prey density, but was significantly greater in patches with prey eggs than in patches without eggs. Prey density and distribution changed only slightly due to predation and overall foraging rates remained more or less constant. The consequent spatial pattern of predation by T. occidentalis was inversely density dependent. As with P. persimilis, slopes of predation rate-prey density regressions increased with time (i.e. the inverse density dependence in T. occidentalis became weaker through time).The broadly polyphagous predator A. andersoni showed density independent foraging time allocation with variation independent of prey density. With changes in prey density over time due to prey depletion, overall foraging rates decreased. The consequent spatial pattern of predation by A. andersoni also changed through time; it initially was inversely density dependent, but soon became density independent.Overall, P. persimilis and T. occidentalis spent more time in prey patches than A. andersoni, suggesting that A. andersoni tended to spend more time moving outside patches. The overall predation rates and searching efficiency were higher in P. persimilis than in A. andersoni and T. occidentalis. Predator reproduction was highest in P. persimilis, lower in T. occidentalis and the lowest A. andersoni.The differences in response to prey distribution among the three predaceous species probably reflect the evolution of these species in environments with different patterns of prey distribution. The degree of polyphagy is a major determinant of the aggregative response, but other attributes such as handling time are also important in other aspects of phytoseiid foraging behavior (e.g. searching efficiency or predation rate).
在实验室中研究了捕食性螨类智利小植绥螨、西方盲走螨（=加州新小绥螨）和安德森钝绥螨对植食性螨类二斑叶螨卵密度空间变化的反应。寡食性捕食者智利小植绥螨最初表现出直接的密度依赖性觅食时间分配，且觅食时间的变化随猎物密度增加。由于捕食导致猎物密度变化，捕食者的觅食率（每小时）随时间下降，且密度依赖性觅食逐渐变为密度独立性，因为智利小植绥螨继续对初始猎物密度做出反应，而非变化中的猎物密度和分布。因此，智利小植绥螨的捕食空间格局是密度独立的，尽管捕食率 - 猎物密度回归的斜率随时间增加。
与智利小植绥螨相比，狭食性捕食者西方盲走螨对猎物卵的有无反应相对较慢，但对猎物密度无反应：在有猎物的斑块中花费的觅食时间的平均值和变化与猎物密度无关，但在有猎物卵的斑块中显著长于无卵斑块。由于捕食，猎物密度和分布变化很小，总体觅食率大致保持不变。因此，西方盲走螨的捕食空间格局是负密度依赖性的。与智利小植绥螨一样，捕食率 - 猎物密度回归的斜率随时间增加（即西方盲走螨的负密度依赖性随时间变弱）。
广食性捕食者安德森钝绥螨表现出与猎物密度无关的觅食时间分配，且变化与猎物密度无关。随着时间推移由于猎物消耗导致猎物密度变化，总体觅食率下降。因此，安德森钝绥螨的捕食空间格局也随时间变化；它最初是负密度依赖性的，但很快变为密度独立的。
总体而言，智利小植绥螨和西方盲走螨在猎物斑块中花费的时间比安德森钝绥螨多，这表明安德森钝绥螨倾向于在斑块外花费更多时间移动。智利小植绥螨的总体捕食率和搜索效率高于安德森钝绥螨和西方盲走螨。捕食者的繁殖在智利小植绥螨中最高，在西方盲走螨中较低，在安德森钝绥螨中最低。
这三种捕食性物种对猎物分布反应的差异可能反映了这些物种在具有不同猎物分布模式的环境中的进化。多食性程度是聚集反应的主要决定因素，但其他属性如处理时间在植绥螨觅食行为的其他方面（如搜索效率或捕食率）也很重要。
