Wang RuiWu, Wen XiaoLan, Chen Chun, Shi Lei, Compton Stephen G
State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650223, China,
Sci China Life Sci. 2015 May;58(5):492-500. doi: 10.1007/s11427-015-4848-x. Epub 2015 Apr 11.
It is generally believed that physical heterogeneity in common resource or evolutionary restraint can sufficiently prevent direct conflict between host and symbionts in mutualism systems. Our data on fig/fig wasp reciprocal mutualism (Ficus racemosa), however, show that structural barriers of female flowers or genetic constraints of pollinators previously hypothesized exist, but cannot sufficiently maintain the mutualism stability. The results show that a positive relationship between seed and wasp production could be maintained in warm season, which might be because of density dependence restraint among foundresses and their low oviposition and pollination efficiency, keeping common resource (female flowers) utilization unsaturated. Whilst, a negative correlation between wasp offspring and viable seed production was also observed in cold season, which might be that the increased oviposition and pollination efficiency maximized the common resource utilization. The fitness trade-off between fig and pollinator wasps is greatly affected by environmental or ecological variations. The local stability might result from temporal low exploitation efficiency of pollinators together with interference competition among pollinators. We suggest that host repression through the active regulation of bract closure, which can create interference competition among the foundresses and prevent extra more foundresses sequential entry in fruit cavities, would help the figs avoiding the cost of over-exploitation. This essentially takes the same role as sanctioning of cheating or competitive behaviors.
人们普遍认为，公共资源中的物理异质性或进化限制能够充分防止互利共生系统中宿主与共生体之间的直接冲突。然而，我们关于榕树/榕小蜂互惠共生关系（聚果榕）的数据表明，先前假设的雌花结构障碍或传粉者的遗传限制确实存在，但不足以维持共生关系的稳定性。结果表明，在温暖季节，种子产量与榕小蜂数量之间可以维持正相关关系，这可能是由于雌蜂之间的密度依赖限制以及它们较低的产卵和授粉效率，使得公共资源（雌花）的利用不饱和。同时，在寒冷季节也观察到榕小蜂后代数量与可存活种子产量之间呈负相关，这可能是因为产卵和授粉效率的提高使公共资源的利用达到了最大化。榕树与传粉榕小蜂之间的适合度权衡受到环境或生态变化的极大影响。局部稳定性可能源于传粉者暂时的低利用效率以及传粉者之间的干扰竞争。我们认为，通过苞片闭合的主动调节来实现宿主抑制，这可以在雌蜂之间产生干扰竞争，并防止更多额外的雌蜂依次进入果实腔室，这将有助于榕树避免过度利用的代价。这本质上与对欺骗或竞争行为的制裁起到相同的作用。
