小果油茶上油茶象的产卵策略

Oviposition strategy of the camellia weevil, Curculio chinensis( Coleoptera: Curculionidae),on oil tea( Camellia meiocarpa)

【目的】油茶象Curculio chinensis Chevrolat是我国特有木本油料树种——油茶Camellia spp.的专性蛀果害虫,常导致其大量落果。本文旨在揭示该虫发生危害与寄主果实大小的关系,并探讨其产卵行为策略。【方法】于油茶象产卵高峰期在小果油茶Camellia meiocarpa林随机采摘960个果实,清查油茶象刺孔数和窝卵数,并对果重、果长和果径进行了测量,用单因素方差分析比较产卵果、取食果和非受害果大小差异性,用线性回归分析果实特征对油茶象取食及产卵活动的影响。同时对油茶象雌虫进行了果实大小选择性试验,用配对样本t检验分析选择果与非选择果的大小差异性。【结果】在果重、果长、果径和果实体积方面,产卵果>取食果>非受害果(P<0.01),刺孔数、窝卵数和寄生率与果实大小呈极显著线性正相关(P<0.01),说明油茶象雌虫优先选择大果实取食和产卵。当两供试果实差异显著时,油茶象雌虫对大果实表现出明显的偏好选择性,危害12 h后,重受害果长度和直径都显著大于轻受害果(P<0.01)。油茶象雌虫每次只产1粒卵,卵单产是油茶象本身的属性,与果实特征无关。【结论】油茶象优先选择大果实取食,支持最优觅食理论。油茶象优先选择大果实产卵。窝卵数越小,油茶象种内竞争越弱,幼体正常发育并成功脱果的概率越高,适合度增加。卵单产是油茶象应对寄主果实食物资源限制作用的一种"风险分散"行为适应策略。

【Aim】The camellia weevil,Curculio chinensis Chevrolat,is an important pest attacking fruits of the oil tea Camellia,an endemic genus to China,and causes tremendous fruit drop of its host plants.To reveal the oviposition strategy of C. chinensis,we explored the relationships between oviposition activity of C. chinensis and the traits of its host fruit. 【Methods 】During the most active oviposition season,960 fruits of C. meiocarpa were collected randomly from an oil tea（ Camellia meiocarpa） farm.The number of punctures and clutch size of C. chinensis,as well as the weight,length and diameter of each fruit were measured,and the difference of fruit size among oviposition-punctured fruits,feedingpunctured fruits and non-damaged fruits was analyzed through one-way ANOVA（ LSD）,and the effect of fruit traits on feeding and oviposition activity was analyzed through linear regression model. A choice test of the pest on fruits size was carried out,and the difference of fruit size between selected and nonselected fruits was analyzed by paired-samples t test. 【Results 】 Oviposition-punctured fruits of C.meiocarpa were significantly larger than feeding-punctured fruits,while the latters were significantly larger than non-damaged fruits in terms of weight,length,diameter,and volume（ P 0. 01）. The number of punctures,clutch size and weevil parasitism rate were positively correlated with fruit size（ P 0. 01）,suggesting that parental weevils prefer larger fruits to feed and oviposite. The female adults of C.chinensis showed obvious preference to larger fruits when the difference of fruit size between the two fruits tested was significant,and heavily damaged fruits were significantly larger than lightly damaged fruits in terms of length and diameter after infection by female adults of C. chinensis for 12 h. Independent of host fruit traits,C. chinensis laid one egg in each puncture hole. 【Conclusion】C. chinensis adults prefer larger fruits to feed,which supports the optimal foraging theory. C. chinensis adults also prefer larger fruits to oviposite. The small clutch size would reduce intraspecific competition C. chinensis between offsprings and increase the probability of larval development,and thus they would be more likely to successfully exit from host fruits. We infer that the single egg laying behavior in C. chinensis is a riskspreading strategy,an adaptation toward limited food resource.