【作者】 陶敏；

【导师】 孟玲；

【作者基本信息】 南京农业大学 ， 农业昆虫与害虫防治， 2010， 硕士

【摘要】 由于寄生蜂适应度的实现几乎完全取决能否找到适宜的寄主,故研究搜寻行为就成为探究寄生蜂生活史进化的重要内容。由于室内观察的便利和野外直接观察的限制,长期以来对寄生蜂搜寻行为的研究往往在室内小环境中进行,但观察结果与野外实际表现常常存在不同程度的差异,故需要设计接近于野外的环境来探究寄生蜂真实的搜寻选择行为。衡量寄生蜂的寄主选择性一般用寄生率大小表示,但由于寄生蜂对寄主的产卵选择表现不仅受试验观察环境的影响,而且受到自身生理状态变化的影响,故探究新的估计寄生蜂选择性的变量,就成为寄生蜂搜寻行为生态学研究面临的重要挑战。对此,本论文实验研究以斑痣悬茧蜂[Meteorus pulchricornis (Wesmael)]孤雌生殖品系及其寄主甜菜夜蛾[Spodoptera exigua (Hubner)]幼虫为对象,在接近于野外开放环境的大罩笼中,观察寄生蜂对不同龄期寄主幼虫的搜寻选择行为；并探索运用寄主识别期作为变量,采用生存分析(失效事件分析)中的风险估计模型,估计寄生蜂的寄主选择性。获得以下结论：1.斑痣悬茧蜂在室内条件下的寄主搜寻行为(1)非选择性试验室内条件下采用非选择性试验,观察了斑痣悬茧蜂对甜菜夜蛾不同龄期幼虫的产卵的识别期,用生存分析模型估计寄主被寄生的风险,并研究了寄生经历对该分析的影响。研究结果表明,与2龄寄主幼虫(参照虫龄)相比,3～5龄寄主幼虫被寄生的累计风险比率显著提高(2.6-4.O倍)；而当寄生蜂具有1次寄生经历后再次寄生,对2～4龄幼虫的识别期显著缩短,3～5龄寄主幼虫被寄生的风险与2龄幼虫没有显著差异。由此推测,无寄生经历的斑痣悬茧蜂对较高龄期甜菜夜蛾幼虫表现出明显偏好。(2)选择性试验室内条件下采用选择性实验,观察了斑痣悬茧蜂对甜菜夜蛾不同龄期幼虫的选择频次,用‘’Manly选择比率”(w)估计寄生蜂的选择性。结果表明,无论首次寄生还是再次寄生,斑痣悬茧蜂倾向于选择高龄寄主幼虫。例如,在首次寄生中,斑痣悬茧蜂不选择1龄幼虫,选择2龄寄主的比例最低(10%),但对4龄和5龄幼虫的寄生比例为70%；在再次寄生,很少选择1龄幼虫(3.0%),但对4龄和5龄幼虫的寄生比例为73.0%。2.斑痣悬茧蜂在野外条件下的寄主搜寻行为(1)对各龄期相同密度寄主幼虫的搜寻在室外大型纱笼(长×宽×高=2.5×2.5×1.8)中,采用固定时刻瞬间观察法,记录斑痣悬茧蜂对不同寄主斑块的搜寻与选择行为；然后回收寄主单头饲养,记录寄生数量。结果表明,寄生率随寄主龄期的增大而增大,寄生蜂针刺斑块上寄主的比率基本是随着龄期的增大而不断增大,寄生蜂针刺1龄寄主和2龄期寄主幼虫的比率分别是13%和16%,而针刺3-5龄寄主幼虫的比例高达70%；从寄生比率来看,1-2龄寄主被寄生的比率较低(比例占18%),3-4龄期寄主被寄生的比率与5龄寄主幼虫的寄生比率高达82%。对寄生蜂在不同寄主斑块上的寄生识别期进行的Cox回归模型拟合表明,与1龄寄主幼虫(参照虫龄)相比,只有3龄幼虫被寄生的累计风险比例高于1龄寄主幼虫,2、4、5龄寄主幼虫被寄生的累计风险比例与1龄幼虫无显著差异。(2)对各龄期不同密度寄主幼虫的搜寻野外条件下甜菜夜蛾幼虫的数量随着龄期的增大而减少,为了进一步探明野外条件下寄生蜂对不同龄期寄主的选择偏好,在野外受控条件下,采用(3×3)拉丁方设置寄主斑块,结果表明,寄生蜂发现斑块上寄主数量的比率始终是随着龄期的增大而不断增大,寄生蜂发现1-2寄主和3-4龄寄主幼虫的比率分别是23%和28%,而发现5龄寄主幼虫的比例高达49%；3-4龄寄主被寄生的比率与5龄寄主幼虫被寄生的比率约是1-2龄寄主的3倍(占41%和35%)对寄生蜂识别不同寄主识别期的Cox回归模型拟合分析表明,各龄期之间被寄生的风险差异不显著,但寄主被选择寄生的比率随寄主龄期的增大而增大。更多还原

【Abstract】 As the fittness of parasitoids depend on hosts they could find and oviposit, research of foraging behavior has been in focus for study of life history parasitoids. Owing to convenience to study parasitoid behaviours in the lab but difficulty in the field, most of foraging behaviors of parasitoids are studied in the lab. However, what are observed in the lab may not reflections of that performed in the field. Host prefenece of parasitoids are usually measured by parasitism rate, but parasitization of parasitoids can be influenced by both environmental factors and physiological states of parasitoits. Therefore, variables other than parasitism rate are needed for the evaluation of host preference in parasitoids, which are the chanllenges facing behavioral ecologists. The thesis study was conducted to observe foraging behaviors of Meteorus pulchricornis (Wesmael) in a large walk-in cage in the outdoor as compared to those in small cages in the lab. In addition to the traditional variable (parasitism rate) for measuring host selection, the host recognition time was used to measure selection of parasitoids by fitting to Cox proportional hazard model. The main results obtained are summarized as followed below.1. Foraging behaviors of Meteorus pulchricornis in the laboratory(1) Non-choice experimentsTo assess the parasitization hazard of different instar larvae of Spodoptera exigua by Meteorus pulchricornis, the host recognition time of first and subsequent launches were recorded under non-choice condition, and fitted by Cox proportional hazard model of survival analysis. The results showed that L1 host was not susceptible to parasitism, but L3 to L5 hosts were more prone to be attacked than L2 ones by 2.6-4.0 fold. However, survival curves, measuring the fraction of host larvae unparasitized, were compared for the first and subsequent attacks, which indicated that the host recognition time for the first attack on L2-L4 was much less than for the subsequent attack. The study suggests that higher instar larvae are more likely to be attacked by naive parasitoids. (2) Choice experimentsIn order to study the host-instar selection of Meteorus pulchricornis, a choice-experiment was conducted in the lab, and host selection frequencis were observed and estimated by Manly’s selection ratio. Under the multiple-choice condition, the parasitoids preferred higher instar larvae at both first and subsequent attacks as measured by oviposition, where the relative selection ratio in terms of Manly standardized selection ratio was 70% for L4 plus L5 hosts and only 10% for L2 host in the first attack, and 73% for L4 plus L5 hosts and 3.0% for L1 host in the successive attack.2. Foraging behavior of Meteorus pulchricornis in the open-field(1) Foraging behavior for host instars with same densityIn order to study the difference of parasitoids behaviors between the lab and field, half-field experiment was conducted in a cage (2.5×2.5×1.8) with random patches. Foraging behaviors of parasitoids to different host instars were observed instantaneously, and the parasitism rates were caculated. The results showed that parasitism rate was higher in the old patches than in the young ones, the selection ratio of host patches was correlative with the host instar positively. The sting ratio of L1 and L2 were 13% and 16%, but it was up to 70% from L3 to L5, the parasitism ratio was lower on L1-L2 host patches(18%), but it was higher on L3-L5 host patches(82%). Cox proportional hazard model fitted by the host recognition time showed that L3 were more prone to be attacked than L1. However, there were no significant differences among L1, L2, L4 and L5.(2) Foraging behavior of parasitoid to host instars with different densityIn the open-field, the number of hosts often decreased with host instars. To research into the host preference of parasitoids in the field and the influence of host density, the semi-field experiment with different levels of host density was conducted. The results showed that parasitism rate was positively correlated with host instars. The detection rate of L1-2-host patches and L3-4-host patches were 23% and 28% respectively, but was up to 49% for L5-host patch. The parasitism rate was higher in old-host patches than the younger by three-fold. Cox-proportional hazard model fitted by the host recognition time showed that there was no difference among L1-5 host larvae, but the older hosts were preferred to the younger.更多还原