聚果榕传粉榕小蜂传粉与产卵之间的权衡

【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。     

聚果榕传粉榕小蜂传粉与产卵之间的权衡

【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。     

母代雌蜂数、进果时间及非传粉小蜂对传粉榕小蜂后代数量及性比的影响

【目的】对性比的研究有助于我们理解自然界生物的选择压力及其所产生的原因和结果,榕树和榕小蜂之间的互惠共生关系以及生物学和生态学特性使其成为研究性比和局域配偶竞争模型（local mate competition）的理想材料。本研究旨在探明榕小蜂性比调节和进化机制。【方法】对分布于西双版纳地区的鸡嗉子榕Ficus semicordata进行了人工控制性放蜂实验。测定了母代雌蜂数量及其进果时间间隔、非传粉小蜂Sycoscapter trifemmensis数量对传粉榕小蜂Ceratosolen gravelyi后代数量（成蜂数量）和性比的影响,并分析了小蜂后代数量和性比的相关性。【结果】在榕果发育期一致的前提下,随着母代雌蜂数量的增加,每头雌蜂的平均后代数量明显下降(P<0.001),后代性比显著升高(P<0.001),后代数量和性比呈显著负相关(P<0.05);随着雌蜂进果间隔的延长,后代数量亦呈现下降趋势,且性比增大,放2头雌蜂和3头雌蜂的处理呈同样趋势,但差异均不显著(P=0.87; P=0.49),小蜂后代数量与性比无显著相关性(P=0.86)。此外,非传粉小蜂数量与传粉小蜂后代数量呈显著负相关(P<0.001),与传粉小蜂性比呈正相关(P<0.001),小蜂后代数量和性比同样呈现显著负相关(P<0.001)。【结论】本实验模拟了自然界中榕 蜂的相互作用,所得结果有助于我们理解自然状态下榕小蜂性比调节模式和机制,以及榕 蜂互利共生系统的进化机制。     

木瓜榕传粉榕小蜂与一种非传粉榕小蜂核型比较分析

【目的】为了明确木瓜榕传粉榕小蜂Ceratosolen emarginatus Mayr及另外一种寄生于木瓜榕雌果内的非传粉小蜂Platyneura sp.染色体核型特征和差异。【方法】本研究采用小牛血清培养脑神经节的方法对寄生于木瓜榕Ficus auriculata Loureiro的两种小蜂进行了染色体核型比较分析。【结果】木瓜榕传粉小蜂的染色体数目为2n(♀)=10,染色体臂指数NF值为20,整个染色体组包含5对中着丝粒染色体,核型类别属Stebbins-1A型;非传粉小蜂Platyneura sp.的染色体数目为2n=12,染色体臂指数NF值为24,染色体组全部为中着丝粒染色体,核型类别属Stebbins-1A型。【结论】两种小蜂除染色体类型和核型类别相同,在其他染色体特征方面均表现出差异。结合前人和本研究结果,我们推测两种小蜂之间染色体核型可能发生了由传粉者向非传粉者的演化,即发生了染色体数目由少到多的演化。     

榕-传粉榕小蜂间的专一性与协同进化

共生体系的长期维持引发了一系列进化问题, 特别是共生双方的相互适应、协同进化成为进化理论的一大挑战。榕和传粉榕小蜂是目前所知的专性最强的共生体系之一, 两者异常丰富的物种组成以及宿主多样的生活型为以上问题的研究提供了理想的体系。早期认为榕与其传粉小蜂间均为狭义协同进化, 一对一原则在该体系中具有普适性。然而近年来发现越来越多的例外, 特别是宿主转移现象在某些地区、某些榕属类群中的普遍存在, 使榕及其传粉小蜂间严格的物种专一性及协同进化发生在物种水平的观点受到质疑, 最近提出了一个新的协同进化模式来解释榕与其传粉小蜂的对应关系。榕与传粉小蜂间的进化模式说明两者间既有狭义的协同进化, 也有发散协同进化关系, 从而导致它们之间物种专一性不同。目前, 两种协同进化模式在该系统中的相对重要性仍存在很大争议, 不同地区、不同榕属类群中两者的物种专一性程度和产生原因可能有很大差异, 榕与传粉榕小蜂系统的复杂性决定了不能将某些地区和某些类群的结论简单扩展, 有关该体系协同进化主导模式的正确评判有待于对不同地区和不同榕属类群对应传粉小蜂的物种组成、来源方式, 以及共生双方的系统发生关系进行更广泛、更深入的研究。     

中国榕小蜂触角感受器形态特征及进化适应性分析

【目的】榕树与传粉榕小蜂体系是协同进化、专性传粉的经典系统,每种榕树上一般还生活有种类丰富、数目众多的非传粉榕小蜂。在选择压力下,榕小蜂为在榕果内生存产生了明显的适应性形态。触角感受器是昆虫通讯系统的单元,其形态是反映生态和进化适应性的最佳特征之一。本文旨在对中国部分传粉和非传粉榕小蜂的触角感受器的形态多样性和进化适应性进行系统研究。【方法】对来源于海南和云南15种榕树上24种榕小蜂54个型的触角感受器形态进行了扫描电镜观察,基于现有的分子系统发育树,对传粉榕小蜂触角感受器的形态特征进行了性状演化分析,并对榕小蜂的形态特征进行了进化适应性分析。【结果】榕小蜂触角感受器普遍存在雌雄二型现象。雌蜂触角感受器种类有毛状、锥状、板状、刺状、钟形、腔锥状和栓锥状等,数目丰富,并且进果产卵的传粉雌蜂和果外产卵的非传粉雌蜂之间、进果产卵的传粉雌蜂和进果产卵的非传粉雌蜂之间在形态上存在差异。传粉雄蜂和不具有雄性多型现象的非传粉雄蜂触角感受器极为退化,具有雄性多型的非传粉雄蜂触角感受器形态在种内不具有显著差异。性状演化分析表明进化路径相当复杂,可能存在多次独立进化过程。触角感受器的形态类型与其进化适应性相关。【结论】榕小蜂触角感受器类型多样,形态变化丰富,并为适应榕果内的生存而产生了进化适应性特点。雌蜂和雄蜂在榕果内受到了完全不同的选择压力,行使不同的生态功能,从而产生了不同的适应性形态。不同的适应性形态可能与雌蜂不同的产卵行为、雄蜂不同的交配策略具有一定联系。该文是首次对中国榕小蜂触角感受器形态进行系统研究的报道,有助于更好地理解榕小蜂的形态特征、进化路线、行为策略和生态关系。     

鸡嗉子榕内传粉小蜂与非传粉小蜂的繁殖稳定共存机制研究

【目的】榕-蜂系统是自然界协同进化和互利共生的典型模型,榕-蜂之间如何实现繁殖分配从而实现稳定共存一直是倍受研究者关注的问题,但对传粉小蜂和非传粉小蜂的繁殖稳定共存研究较少。【方法】本文选取分布在西双版纳地区的雌雄异株榕树鸡嗉子榕Ficus semicordata的雄果,通过对榕果内唯一的传粉小蜂Ceratosolen gravelyi Grandi以及4种非传粉小蜂Philotrypesis dunia Joseph,Apocrypta sp.,Platyneura sp.,Sycoscapter trifemmensis Joseph的产卵时序进行了观察,并对5种小蜂的种群数量进行统计,以及对每种小蜂产卵小花的空间分布、瘿花体积等特征进行了研究。【结果】发现:5种小蜂在产卵时间上存在分离,且传粉小蜂的种群数量远大于其他4种非传粉小蜂的种群数量之和。5种小蜂的瘿花特征也存在差异:瘿花的子房大小不同,且花梗长度即分布空间也有差异,传粉小蜂最接近果腔而非传粉小蜂则更多地利用中层和内层的小花。【结论】结果说明在鸡嗉子榕有限的空间内,5种小蜂通过产卵时间和生长空间的分离,实现了减少竞争以及长期共存的特征,维持了榕-蜂系统的稳定性。     

基于28S, COI和Cytb基因序列的薜荔和爱玉子传粉小蜂分子遗传关系研究

薜荔和爱玉子均属于桑科榕属植物,二者为同一物种的原变种与变种的关系,早期研究认为这两种榕树与同一种传粉榕小蜂(Wiebesia pumilae (Hill))建立了稳定的互利共生关系,但近期在形态学、生态学、传粉生物学等方面对二者的研究结果表明,薜荔传粉小蜂和爱玉子传粉小蜂之间可能发生了遗传分化。实验用核糖体28SrDNAD1-D3区、线粒体Cytb及COI基因部分序列,对采自福建3个不同样地的薜荔传粉小蜂和3个不同品系的栽培爱玉子的传粉小蜂进行分析,结果表明:(1)薜荔传粉小蜂和爱玉子传粉小蜂的核糖体28S序列的碱基组成中A,T,G,C 4种含量较平均,C+G的平均含量(56%)稍高于A+T的含量(44%)。线粒体Cytb序列中A+T的含量(76.1%)明显高于C+G的含量(23.9%),COI序列中A+T的含量(71.9%)也明显高于G+C的含量(28.1%),这是膜翅目昆虫线粒体基因的普遍特征。在薜荔和爱玉子传粉小蜂的线粒体Cytb及COI基因中,密码子第三位点A+T的含量最高。(2)比较薜荔和爱玉子传粉小蜂的3种分子标记的变异范围显示,28S进化速度较Cytb及COI序列慢,比较保守,更适合科、亚科等较高分类单元的研究。薜荔传粉小蜂与爱玉子传粉小蜂之间的亲缘关系较近,采用Cytb与COI序列进行分析更为精确。(3)用Cytb及COI序列对薜荔传粉小蜂与爱玉子传粉小蜂之间的遗传距离进行分析显示,薜荔传粉榕小蜂个体间Cytb序列平均遗传距离为0.0054,爱玉子传粉小蜂个体间的Cytb遗传距离为0.0164;薜荔传粉小蜂与爱玉子传粉小蜂群体之间的Cytb序列平均遗传距离为0.1385;COI序列的薜荔传粉榕小蜂个体间遗传距离为0.0048,爱玉子传粉小蜂各样本间平均遗传距离为0.0102;薜荔传粉小蜂与爱玉子传粉小蜂群体间COI序列平均遗传距离为0.1896,两群体间的遗传距离(差异大于10%以上)明显大于群体内各样本之间的遗传距离,表明薜荔传粉小蜂与爱玉子传粉小蜂之间已经发生了很大的遗传分化,其变异水平达到了种间分化水平,即薜荔传粉小蜂与爱玉子传粉小蜂为两个不同的种。     

鸡嗉果榕榕小蜂产卵时序与种群数量分析

榕树与传粉榕小蜂的互惠共生体系被多种非传粉榕小蜂利用。在同一个榕果中,具有较高种群密度的传粉榕小蜂和多种非传粉榕小蜂生存在一起并相互作用。通过野外观察和采样分析的方法,对鸡嗉果榕内5种榕小蜂（传粉榕小蜂Ceratosolen gravelyi;非传粉榕小蜂Apocrypta sp., Philotrypesis dunia, Platyneura cunia和Sycoscaptertr ifemmensis）的产卵行为进行了研究。结果证明,鸡嗉果榕内生活的各种榕小蜂通过比较严格的产卵时序在榕果内产卵以占领不同的生态位,这反映了这些榕小蜂各自的生物学特性。自然种群数量分析表明,单个非传粉榕小蜂物种的种群数量几乎不与传粉榕小蜂种群数量呈负相关,而所有非传粉榕小蜂物种的种群个体总量与传粉榕小蜂的种群个体数呈正相关,这可能是多个物种共存于单个榕果内的进化适应。     

传粉榕小蜂与非传粉小蜂间寄主识别行为的趋同进化

在高度专性传粉的榕树-榕小蜂互惠共生系统中普遍存在着一些非传粉小蜂,它们中的一些种类进入果腔后也能为榕树传粉,且在形态和物候上已与传粉榕小蜂发生了趋同进化。但其寄主识别行为是否也与传粉榕小蜂发生了趋同进化还不得而知。我们在西双版纳选择了钝叶榕(Ficuscurtipes)及其3种进果繁殖小蜂开展了相关的行为实验。3种小蜂中,1种是钝叶榕的专性传粉榕小蜂(Eupristina sp.),另外2种是寄居性非传粉小蜂(杨氏金小蜂Diaziellayangi和Lipothymus sp.),这2种非传粉小蜂进入果腔后也像传粉榕小蜂那样为钝叶榕传粉。我们以钝叶榕不同发育时期的榕果及这3种小蜂为材料,采用Y型嗅觉仪观察了这3种小蜂对各发育时期榕果和信息化学物质6-甲基-5-庚烯-2-醇、6-甲基-5-庚烯-2-酮及这2种化合物的混合物的选择行为。结果表明,当提供雌花期榕果与其他发育时期榕果和空气对照供这3种小蜂选择时,它们均显著地偏向于选择雌花期榕果;当提供雄花期榕果与其他发育时期榕果和空气对照供这3种小蜂选择时,它们均显著地偏向于选择其他发育时期榕果和空气对照,即都会避开雄花期榕果;此外,这3种小蜂均对钝叶榕雌花期果释放的一种主要化合物6-甲基-5-庚烯-2-醇的同一剂量(1μL)表现出显著的偏好。这一结果为传粉榕小蜂与非传粉小蜂间的寄主识别行为趋同进化的假说提供了证据。     

Chemical mediation and niche partitioning in non-pollinating fig-wasp communities

1. The parasitic chalcidoid wasps associated with the species-specific and obligatory pollination mutualisms between Ficus spp. and their agaonid wasp pollinators provide a good model to study the functional organization of communities. 2. However, communities of non-pollinating fig wasps (NPFWs) remain little characterized, and their functioning and evolutionary dynamics are still poorly understood. 3. We studied the communities of NPFWs associated with the monoecious F. racemosa and the dioecious F. hispida. Associated with these two fig species are a total of seven wasp species belonging to three genera. These species present contrasts in life history traits and in timing of oviposition. The species studied are thus broadly representative of the communities of NPFWs associated specifically with fig-pollinator mutualisms. 4. In our study systems, there is temporal segregation of oviposition time among members of NPFW communities. 5. We tested the role of volatile chemicals in the attraction of NPFWs associated with these two fig species, and tried to determine if chemical mediation can explain the organization of the communities. 6. We conducted odour choice tests using a Y-tube olfactometer. All the NPFWs studied were shown to use volatile chemicals produced by the fig to locate their host. Furthermore, the signals used by each species depended on the phenological stage of the fig they exploit. 7. Results demonstrated that the pattern of oviposition results from the utilization of volatile signals produced by figs that vary in their composition at different stages of fig development. Thus, chemical mediation allows resource partitioning in the NPFW communities associated with fig-pollinator mutualisms, and suggests hypotheses to explain coexistence in other parasite communities.     

The occurrence of fig wasps in the fruits of female gynodioecious fig trees

Fig trees are pollinated by wasp mutualists, whose larvae consume some of the plant's ovaries. Many fig species (350+) are gynodioecious, whereby pollinators generally develop in the figs of ‘male’ trees and seeds generally in the ‘females.’ Pollinators usually cannot reproduce in ‘female’ figs at all because their ovipositors cannot penetrate the long flower styles to gall the ovaries. Many non-pollinating fig wasp (NPFW) species also only reproduce in figs. These wasps can be either phytophagous gallers or parasites of other wasps. The lack of pollinators in female figs may thus constrain or benefit different NPFWs through host absence or relaxed competition. To determine the rates of wasp occurrence and abundance we surveyed 11 dioecious fig species on Hainan Island, China, and performed subsequent experiments with Ficus tinctoria subsp. gibbosa to identify the trophic relationships between NPFWs that enable development in female syconia. We found NPFWs naturally occurring in the females of Ficus auriculata, Ficus hainanensis and F. tinctoria subsp. gibbosa. Because pollinators occurred only in male syconia, when NPFWs also occurred in female syconia, overall there were more wasps in male than in female figs. Species occurrence concurred with experimental data, which showed that at least one phytophagous galler NPFW is essential to enable multiple wasp species to coexist within a female fig. Individuals of galler NPFW species present in both male and female figs of the same fig species were more abundant in females than in males, consistent with relaxed competition due to the absence of pollinator. However, these wasps replaced pollinators on a fewer than one-to-one basis, inferring that other unknown mechanisms prevent the widespread exploitation by wasps of female figs. Because some NPFW species may use the holes chewed by pollinator males to escape from their natal fig, we suggest that dispersal factors could be involved.     

How to be a fig wasp down under: The diversity and structure of an Australian fig wasp community

Endophytic insects and their parasitoids provide valuable models for community ecology. The wasp communities in inflorescences of fig trees have great potential for comparative studies, but we must first describe individual communities. Here, we add to the few detailed studies of such communities by describing the one associated with Ficus rubiginosa in Australia. First, we describe community composition, using two different sampling procedures. Overall, we identified 14 species of non-pollinating fig wasp (NPFW) that fall into two size classes. Small wasps, including pollinators, gallers and their parasitoids, were more abundant than large wasps (both galler and parasitoid species). We show that in figs where wasps emerge naturally, the presence of large wasps may partly explain the low emergence of small wasps. During fig development, large gallers oviposit first, before and around the time of pollination, while parasitoids lay eggs after pollination. We further show that parasitoids in the subfamily Sycoryctinae, which comprise the majority of all individual NPFWs, segregate temporally by laying eggs at different stages of fig development. We discuss our results in terms of species co-existence and community structure and compare our findings to those from fig wasp communities on other continents.     

Spatial distribution patterns of three fig wasps on Ficus semicordata: How non-pollinators affect pollinator’s sex ratio

Sex ratio theory is one of the most productive fields in research on evolutionary biology. Pollinating fig wasps, due to their particular natural life history, are considered to be a valuable model for the study of sex ratio evolution. A great deal of research concerning the factors that affect pollinator fig wasp (Agaonidae) progeny sex ratio has been done, and at present three main factors (haplodiploidy, local mate competition and inbreeding) are found to be important at the population level. However, there still exists variation between empirical data and model predictions. Another factor to which little thought has been given before is the effect of non-pollinating fig wasps (NPFWs) which parasitize in the larvae gall of pollinator thus kill pollinators and exploit the fig/fig pollinator mutualistic systems. In this study, we focus on why and how non-pollinating fig wasps distort pollinator fig wasp’s original sex ratio. Through controlling the number of ovipositing foundresses inside a fig, combined with the observation of ovipositing behavior and sequence, we studied three species of wasp in the figs of a dioecious fig Ficus semicordata including the pollinator Ceratosolen gravely and NPFWs Platyneura cunia, Sycoscapter trifemmensis in tropical area of Xishuangbanna from September to December 2009. First, we observed the timing of oviposition of all fig wasps utilizing F. semicordata and found differences when compared to previous studies. Such as P. cunia is the fourth rather then the secondary fig wasps to oviposit on the syconia approximately 10 days after the pollinator. S. trifemmensis oviposits much earlier than previously thought, 14–32 days after the pollinators. We examined the spatial location of male and female progeny of the pollinator. We found foundresses of pollinator prefer to use innermost ovules first. Only at high offspring numbers were the outer ovules used. More male pollinator offspring were developed near the fig cavity, while female pollinator offspring were more evenly distributed among ovule layers. As pollinator offspring numbers increased, this phenomenon became more pronounced. This pattern of segregation of male larvae gall in inner ovules and female larvae gall in outer ovules suggests that female offspring might be more vulnerable to attack by parasitic wasps that oviposit from outside the syconium. Experiments later demonstrated that NPFWs are restricted by their ovipositor length and they prefer to or can only lay their eggs into ovules near the fig wall. Then we examined the spatial location of NPFWs and compared this with the spatial location of male/female progeny of pollinator. NPFWs had a high probability of parasitizing female pollinator larvae. Thus, NPFWs have a substantial effect on the sex ratio of the pollinator, as parasitism risk decreases towards the center of the syconium, where inner ovules provide enemy-free space for most of male pollinator offspring. Partial correlation analyse shows that sex ratio of pollinator progeny has a positive relationship with the number of NPFWs. We suggest that the resulting gradient in offspring viability between male and female contributes to selection on pollinators’ for a less femalebiased sex ratio. When the affect of NPFWs was excluded, the pollinator sex ratio was not in good agreement with local mate competition theory, although it was still female-biased. In addition, the average number of offspring per foundress decreased with increasing foundress number, but pollinator sex ratio was positively related to brood size. Thus, pollinator females do not appear to adjust their sex ratio to foundress density directly, but use brood size and foundress density simultaneously as cues to assess potential LMC.     

榕小蜂温度耐受性及其对种间共存关系的影响

全球已知有约800种榕属(Ficus)植物, 主要分布在热带, 部分种类延伸至亚热带地区。温度是限制榕‒蜂共生系统分布北界的主要因素, 也显著影响榕树及其榕小蜂的繁殖成功, 其中榕小蜂对温度的响应更加敏感。榕小蜂只有在一定的温度范围内才能保持正常的生理机能, 其对温度耐受能力直接影响榕果内小蜂种群数量和群落内种间关系。然而目前对榕小蜂温度耐受性的研究尚少, 榕小蜂的温度耐受能力如何影响榕果内小蜂的共存关系还未见报道。本文研究了分布于西双版纳的2种雌雄同株和1种雌雄异株榕树果内传粉榕小蜂和非传粉小蜂的温度耐受能力。结果表明: 3种传粉榕小蜂对高温的耐受性极差, 相对于雌雄同株的高榕(F. altissima)和聚果榕(F. racemosa)传粉榕小蜂, 雌雄异株的鸡嗉子榕(F. semicordata)传粉榕小蜂对低温有增强的耐受趋势。聚果榕小蜂群落结构显示: 在适宜其生长的西双版纳地区, 传粉榕小蜂的数量占绝对优势, 在温度较低的季节其数量显著减少; 而非传粉榕小蜂呈相反模式, 较强的温度耐受能力使其在低温的雾凉季维持了较高的种群数量。鸡嗉子榕果内非传粉小蜂Sycoscapter trifemmensis相对于Philotrypesis dunia有更强的温度耐受能力, 在种群数量和种间关系上有更多的竞争优势及数量。榕小蜂的温度耐受性差异在物种分布、种间关系的维持和共存上起了重要作用, 本研究结果为阐明榕小蜂种间共存的维持机制提供了科学依据。     

非传粉小蜂对榕-蜂共生系统的影响

榕-蜂共生系统是桑科榕属(Ficus)植物与传粉榕小蜂专一互惠形成的生态学关系。但是,也有一些非传粉的小蜂出现在这个系统中,对榕-蜂共生系统可能产生较大的影响。西双版纳的聚果榕(Ficus racemosa)树上主要有5种非传粉小蜂,分别在榕果发育的不同阶段从果外向果内产卵。在传粉榕小蜂进果之前的花前期,Platyneura testace、Apocrypta sp.和P. mayri这3种非传粉小蜂先后到果外产卵繁殖后代,对榕-蜂共生系统造成显著影响,尤其是影响传粉榕小蜂的繁殖。在传粉榕小蜂进果之后的间花期,P. mayri、A. westwoodi和P. agraensis这3种非传粉小蜂相继到果外产卵,它们虽然能减少种子形成和传粉榕小蜂繁殖的数量,但最终没有对榕-蜂共生系统造成显著的影响。造瘿类的P. mayri可在花前期和间花期产卵繁殖,在花前期产卵时它主要是影响传粉榕小蜂的繁殖,而在间花期产卵时它则更多地是影响种子的生产。     

Diversification in the use of resources by Idarnes species: bypassing functional constraints in the fig–fig wasp interaction

Mutualisms such as the fig–fig wasp mutualism are generally exploited by parasites. We demonstrate that amongst nonpollinating fig wasps (NPFWs) parasitic on Ficus citrifolia, a species of Idarnes galls flowers and another species feeds on galls induced by other wasps killing their larvae. The galling wasp inserts its ovipositor through the fig wall into the fig cavity. The ovipositor then follows a sinuous path and is introduced through the stigma and style of the flower. The egg is deposited between the integument and nucellus, in the exact location where the pollinating mutualistic wasp would have laid its egg. Gall induction is a complex process. In contrast, the path followed by the ovipositor of the other species is straightforward: attacking a larva within a developed gall poses different constraints. Shifts in feeding regime have occurred repeatedly in NPFWs. Monitoring traits associated with such repeated evolutionary shifts may help understand underlying functional constraints. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 114–122.     

Can fine-scale post-pollination variation of fig volatile compounds explain some steps of the temporal succession of fig wasps associated with Ficus racemosa?

Volatile organic compounds (VOCs) emitted by flowers play an essential role in mediating the attraction of pollinators. However, they also attract other species exploiting resources associated with flowers. For instance, VOCs emitted by figs play a major role in encounters between Ficus spp., their mutualistic pollinating wasps, and all the members of the community of non-pollinating fig wasps (NPFWs) that exploit the mutualistic interaction. Because pollinators might be in limited supply for a tree bearing many inflorescences, the plant might maximize its individual reproductive success by reducing the attractiveness of inflorescences once they are pollinated, so that pollinators orient only towards the tree's unpollinated figs. Changes in VOCs emission that bring this about could represent an important cue for NPFWs that exploit particular stages of fig development. In this study, by monitoring precisely the presence of fig-associated wasps on figs of F. racemosa, a common widespread fig species, we demonstrated that 4–5 days and 15 days following pollination represent two critical transitional steps in the succession of different wasp species. Then, focusing on the first one of these transitional steps, by investigating the composition of fig VOCs at receptivity and from 1 to 5 days following pollination, we detected progressive quantitative and qualitative variation of floral scent following pollination. These changes are significant at 5 days following pollination. The qualitative changes are mainly due to an increase in the relative proportions of two monoterpenes (α-pinene and limonene). These variations of the floral VOCs following pollination could explain why pollinating wasps stop visiting figs very shortly after the first pollinators enter receptive figs. They also possibly explain the succession of non-pollinating wasps on the figs following pollination.