榕小蜂的产卵模式及其对子代性比的影响

于2007年4月-2007年7月在中国科学院西双版纳热带植物园,通过干预控制榕小蜂产卵的方法研究了聚果榕的传粉榕小蜂Ceratosolen fusciceps和非传粉小蜂Platyneura mayri及垂叶榕的非传粉小蜂Acophila sp.1和Wakerella benjamini等的产卵顺序.对传粉榕小蜂,在完成放蜂后不同间隔时间向榕果内注入乙醚杀死小蜂:对非传粉榕小蜂,在放蜂后不同间隔时间将其从纱网袋内全部放出,从而控制了各种榕小蜂的产卵时间.到榕果成熟后,收集了榕果内的小蜂,并分析比较各种榕小蜂在不同产卵时间下的子代性比.结果表明:Ceratosolen fusciceps、P.mayri和Acophila sp.1在产卵的最初时间内倾向于产下更多的雄性后代,而随后的时间内则产下更多的雌性伴随少量的雄性后代,这样的产卵顺序导致子代性比随着母代产卵时间的延长而下降,榕小蜂后代雌性比例显著高于雄性.同时,子代榕小蜂数晕随母代产卵时间的延长而增加,这在一定程度上解释了单头繁殖雌蜂的子代性比随子代数量的增加而减少的现象.而Wakerella benjamini在产卵顺序上是随机的,在其开始产卵后的不同时间段内子代性比都接近于50%.这一结果表明榕小蜂的产卵顺序与母代产卵时间的长短对子代性比有极为重要的影响.

聚果榕两种非传粉小蜂产卵与果实脱落的关系

下载PDF阅读器在聚果榕与其传粉榕小蜂Ceratosolen fusciceps组成的互利共生系统中,与传粉榕小蜂共存的还有榕树的寄生性小蜂Platyneura testacea和Platyneura mayri.这些寄生性小蜂由于不能给榕树带来任何收益而只是利用榕树的种子或与传粉小蜂竞争植物的雌花资源,因而可能导致榕树与榕小蜂之间合作系统的崩溃.植物果实的脱落机制普遍被认为是维持系统稳定的关键因素之一.然而,定量实验和野外观测发现P. mayri产卵并不会引起果实脱落,只有P. testacea产卵会使果实大量脱落.通过对3株样树进行比较发现:当产卵时的P. testacea数量越多时,它产生的瘿花数就越多,榕果发生脱落的比例越高.P. testacea的过度产卵是导致榕果选择性脱落的主要原因.结果表明:脱落机制并不能完全阻止非传粉小蜂的寄生,榕树只能选择性地脱落掉先于传粉小蜂产卵的榕果.这也同时表明维持榕树与榕小蜂互利共存的机制不仅仅只有榕果的脱落机制,可能还存在其它未被发现的机制.

榕小蜂食性分化与榕树-榕小蜂系统稳定性

在榕树与其传粉小蜂组成的互利阿共生系统中,理解传粉小蜂与各种非传粉小蜂如何共存是解决这一系统稳定性维持机制问题的关键之一.生态位分化被普遍认为是传粉小蜂与各种非传粉小蜂共存的最主要动力.而作为生态位分化中最基础的食性分化在这一系统中如何具体实现尚小清楚.2006年12月至2007年6月.我们以聚果榕(Ficus racemosa)为材料,通过对果内6种榕小蜂进行独立放蜂及两两组合定最放蜂,并对传粉小蜂分别进行不携带花粉和不能产卵的技术处理,研究了寄生在聚果榕果内的5种非传粉小蜂的食性及相互关系,分析了在不同季节下寄生蜂与寄主间的相关系数.研究结果表明:在5种非传粉小蜂中,Platyneura testacea和P mayri是造瘿者,能独立刺激子房发育成瘿花,并使果实发育成熟;而 Apocrypta sp、A.westwoodi和P.agraensis只能寄生于某些已发育的虫瘿,为拟寄生者,它们各自分别与P.testacea,P.mayri和传粉小蜂Ceratosolen fusciceps存在着一对一的寄生关系.拟寄生者与寄主间的相关性在不同季节下会显示出不同的结果,这表明过去文献中用物种间的相关系数推理而确定的食性关系可能是不可靠的.对自然采集榕果内的小蜂群落分析表明,传粉小蜂处于优势地位,这说明在自然情况下非传粉小蜂的种群维持在一个较低水平,对榕树-传粉小蜂系统稳定性影响较小,故能与之长期共存.

Diffusive coevolution and mutualism maintenance mechanisms in a fig-fig wasp system

In reciprocal mutualism systems, the exploitation events by exploiters might disrupt the reciprocal mutualism, wherein one exploiter species might even exclude other coexisting exploiter species over an evolutionary time frame. What remains unclear is how such a community is maintained. Niche partitioning, or spatial heterogeneity among the mutualists and exploiters, is generally believed to enable stability within a mutualistic system. However, our examination of a reciprocal mutualism between a fig species (Ficus racemosa) and its pollinator wasp (Ceratosolen fusciceps) shows that spatial niche partitioning does not sufficiently prevent exploiters from overexploiting the common resource (i.e., the female flowers), because of the considerable niche overlap between the mutualists and exploiters. In response to an exploiter, our experiment shows that the fig can (1) abort syconia-containing flowers that have been galled by the exploiter, Apocryptophagus testacea, which oviposits before the pollinators do; and (2) retain syconia-containing flowers galled by Apocryptophagus mayri, which oviposit later than pollinators. However, as a result of (2), there is decreased development of adult non-pollinators or pollinator species in syconia that have not been sufficiently pollinated, but not aborted. Such discriminative abortion of figs or reduction in offspring development of exploiters while rewarding cooperative individuals with higher offspring development by the fig will increase the fitness of cooperative pollinating wasps, but decrease the fitness of exploiters. The fig fig wasp interactions are diffusively coevolved, a case in which fig wasps diversify their genotype, phenotype, or behavior as a result of competition between wasps, while figs diverge their strategies to facilitate the evolution of cooperative fig waps or lessen the detrimental behavior by associated fig wasps. In habitats or syconia that suffer overexploitation, discriminative abortion of figs or reduction in the offspring development of exploiters in syconia that are not or not sufficiently pollinated will decrease exploiter fitness and perhaps even drive the population of exploiters to local extinction, enabling the evolution and maintenance of cooperative pollinators through the movement between habitats or syconia (i.e., the metapopulations).

西双版纳热带雨林聚果榕小蜂的传粉生态学

对聚果榕小蜂 (Ceratosolensp )传粉生态学进行了首次研究。结果表明 ,聚果榕小蜂的雄蜂比雌蜂早羽化数小时 ;雌蜂羽化不能自行打开瘿花和果肉出蜂口 ,两个出蜂口均需雄蜂开凿。而聚果榕的成熟花粉 ,不能自行地从开裂处散发出来 ,必须经榕小蜂的繁殖性雌蜂采集才能散到表面。羽化后的雌蜂在开裂的雄花中不停地用触角柄节、口器上颚和足推动和采集花粉。雌蜂飞出熟榕果寻找嫩隐头花果 ,一般在外飞翔 5～ 80min。雌蜂进入嫩聚果榕的隐头花果内后 ,立即把粘附在足、头、触角和身上的花粉不停地推动到长柱头雌花中 ,授粉行为长达 4～ 9h。然后 ,才把卵产在短柱头雌花中