芦苇收割对宫苍仁蚧密度及其五种寄生蜂共寄生关系的影响

【目的】本文旨在揭示芦苇Phragmites australis(Cav.)Trin.ex Steudel收割对宫苍仁蚧Nipponaclerda biwakoensis Kuwana密度及其5种寄生蜂寄生率和共寄生关系的影响及作用机制。【方法】在上海九段沙湿地上沙的芦苇未收割区和收割区分别设置16个和20个样方,于2011年7月和9月进行重复采样,对未收割区和收割区的蚧虫密度、寄生蜂寄生率、共寄生关系和雌性比率分别进行比较分析。【结果】芦苇收割能够显著降低蚧虫密度(P<0.001);从7月到9月,寄生蜂总寄生率呈增高趋势,但7月芦苇未收割区和收割区间寄生蜂总寄生率差异不显著(P>0.05),而9月芦苇收割区寄生蜂总寄生率则显著高于未收割区(P<0.001);而寄生蜂总寄生率与蚧虫密度相关性并不显著。不同寄生蜂对芦苇收割的响应不同,且存在时间差异性。7月,Aprotocetus sp.的寄生率最高,且在收割区的寄生率显著高于未收割区(P<0.05),而其他寄生蜂寄生率均较低。9月,Aprotocetus sp.的寄生率呈下降趋势,而其余寄生蜂寄生率则呈升高趋势;而且除Encyrtidae sp.外,其他寄生蜂寄生率在未收割区和收割区间存在显著差异(P<0.001)。此外,芦苇收割还显著增加Boucekiella depressa与Astymachus japonicus的共寄生率(P<0.001),并显著减少B.depressa与Aprotocetus sp.的共寄生率(P<0.001)。除Aprotocetus sp.(P<0.05)外,芦苇收割对寄生蜂的雌性比率无显著影响。【结论】不同寄生蜂对芦苇收割的响应,不仅依赖于蚧虫密度,而且还与寄生蜂的扩散能力和竞争能力等生物学特性有关。因此,芦苇收割能通过多种途径影响寄生天敌和宫苍仁蚧的高营养级互作关系,需引起足够的重视。

Effects of cutting Phragmites australis on the density of the scale insect Nipponaclerda biwakoensis Kuwana and multiparasitism relationships of its five parasitoids

Objectives] The aim of this paper is to investigate the effects of reed cutting on the density of the scale insect Nipponaclerda biwakoensis and the parasitism rates and multiparasitism relationships between the five parasitoids that parasitize it. Methods] Sixteen experimental plots in an uncut Phragmites australis （Cav.） Trin. ex Steudel community and twenty plots in a cut P australis community on Shangsha Island in the Jiuduansha wetland nature reserve, Shanghai, were repeatedly sampled in July and September of 2011. Differences in the scale insect density, parasitism rates, multiparasitism relationships and female ratios of the five parasitoids between the cut （C） and uncut （UC） plots were statistically compared. Resultsl Reed cutting significantly decreased scale insect density （P〈0.001）; the total parasitism rate of the five parasitoids significantly increased from July to September. The total parasitism rate was not significantly different between C and UC plots in July （P〉0.05）, but was significantly higher in C than in UC plots in September （P〈0.001）. The total parasitism rate of the five parasitoids was not significantly related to scale insect density. Responses of the five parasitoids to reed cutting were different and varied with sampling season. In July, the parasitism rate of Aprotocetus sp. was higher than that of all other parasitoids, and was significantly higher in C than in UC plots （P〈0.05） when the parasitism rates of other parasitoids were low. In September, the parasitism rate of Aprotocetus sp. decreased, while the parasitism rates of other parasitoids increased. Except for the Encyrtidae sp., the parasitism rates of other parasitoids were significantly different between UC and C plots （P〈0.001）. Reed cutting significantly increased the multiparasitism rate of Boucekiella depressa and Astymachus japonicus （P〈0.001）, and decreased the multiparasitism rate of B. depressa and Aprotocetus sp. （P〈0.001）. Except for Aprotocetus sp. （P〈0.05）, reed cutting had no significant effects on the female ratios of other parasitoids. Conclusion] Responses of five parasitoids to reed cutting not only depend on scale insect density but also to their own biological characteristics such dispersal and competitive ability. Therefore, reed cutting can affect interactions between parasitoids and N. biwakoensis through many different mechanisms.