聚果榕传粉榕小蜂传粉与产卵之间的权衡

Trade-off between pollination and oviposition of the pollinator Ceratosolen sp. (Hymenoptera: Agaonidae) in monoecious Ficus racemosa

【目的】榕树(Ficus)依赖专性榕小蜂(Agaonidae)传粉,同时为传粉榕小蜂提供繁衍后代的场所,两者形成动植物间经典的协同进化关系。在雌花期果内,榕小蜂需在有限的存活时间内完成传粉和产卵,而传粉榕小蜂如何在传粉与产卵之间进行权衡仍然是悬而未解的问题。本研究旨在明确传粉榕小蜂——一种栉颚榕小蜂Ceratosolen sp.在雌雄同株的聚果榕Ficus racemosa雌花期果内的行为活动及繁殖模式。【方法】借助测微尺测量聚果榕榕果雌花花柱长度与传粉榕小蜂(Ceratosolen sp.)产卵器长度,通过显微视频记录传粉榕小蜂在雌花期果内搜索、传粉及产卵行为;结合单果控制性引蜂试验,测定不同阶段榕小蜂个体大小、孕卵量、携粉量,以及雄花期最终繁殖的榕小蜂后代和榕果种子数量。【结果】聚果榕雌花花柱长度存在树间变异,榕小蜂产卵器长度比绝大多数的雌花花柱长,说明该小蜂可以产卵于大部分的雌花子房里。通常个体大的榕小蜂孕卵量更多,但个体大小与携粉量之间相关性不显著。观察发现,榕小蜂进入雌花期榕果内,前6 h集中产卵,可产下孕卵量的95%,平均搜索用时27 s,产卵用时46 s,此期间传粉行为少见,花粉筐中携带花粉量亦无明显变化;榕小蜂进果后6-24 h,主要执行传粉,其行为主动,连贯高效,单次传粉用时平均为2 s,最终可传完携粉量的80%。控制引蜂试验也证实榕小蜂进入榕果内前6 h主要执行产卵繁殖后代,之后6-24 h主要执行传粉以繁殖榕树种子。【结论】在雌雄同株的聚果榕雌花期榕果内,榕小蜂先产卵、后传粉。本研究首次展示了传粉榕小蜂在聚果榕雌花期榕果内的产卵和传粉行为,并获得与行为相匹配的产卵量和传粉繁殖量,反映了具主动传粉行为的榕小蜂在传粉和产卵之间存在时间和数量上的权衡。

【Aim】Ficus relies on the pollination of obligate wasps(Agaonidae)and provides the breeding place for the pollinator,which forms a classic coevolutionary relationship between plants and animals.In the receptive female figs,the wasp needs to pollinate and lay eggs within the limited survival time,and the balance between pollination and oviposition of wasp remains an open question.This study aims to ascertain the behavior and reproductive pattern of active pollinator Ceratosolen sp.in the receptive female figs of monoecious Ficus racemosa.【Methods】The style length of female flowers of F.racemosa and the ovipositor length of its pollinating fig wasps(Ceratosolen sp.)were measured under the microscope with micrometer,and the searching,oviposition and pollination behaviors of pollinating fig wasps were observed and recorded by video combined with the controlled experiments.After the pollinator was introduced to enter receptive female figs,the body sizes,egg loads,and pollen loads were measured at different stages.Finally,the numbers of fig wasp offspring and seeds in controlled figs were counted in male floral phase.【Results】The style length of female flowers of F.racemosa had variation between trees,but the ovipositor length of fig wasps was longer than the style length of most female flowers,indicating that the fig wasps can lay eggs in the ovaries of most female flowers.In general,larger pollinators had more egg loads,but the correlation between body size and pollen load was not significant.Behavioral observation showed that fig wasps mainly laid eggs in the first 6 h that they entered receptive female figs,laying about 95%of eggs in the ovaries.In receptive female figs,fig wasps averagely spent 27 s to search appropriate female flowers,and the oviposition time was averagely 46 s.During this period,the pollination behavior was rarely observed,and the number of pollen grains in pollen pockets did not vary significantly.After fig wasps entered the figs for 6-24 h,they mainly performed active pollination consistently and efficiently pollinated female flowers.The average time for pollination was 2 s,and at last 80%of the pollen loads were pollinated.The controlled experiment also confirmed that fig wasps mainly oviposited and produced their offspring in the first 6 h after entering fig,and then pollinated female flowers to produce fig seeds in the next 6-24 h.【Conclusion】In the receptive female figs of monoecious F.racemosa,fig wasps firstly lay eggs and then actively pollinate female flowers.The oviposition and pollination behaviors of fig wasps were exhibited for the first time,and the number of eggs laid and seed production matching the behaviors were determined,reflecting that the actively pollinated fig wasps have the trade-off between pollination and oviposition about time and quantity.