Ecology of a fig ant–plant

Mutualistic interactions are embedded in networks of interactions that affect the benefits accruing to the mutualistic partners. Figs and their pollinating wasps are engaged in an obligate mutualism in which the fig is dependent on the fig pollinator for pollination services and the pollinator is dependent on fig ovules for brood sites. This mutualism is exploited by non-pollinating fig wasps that utilise the same ovules, but do not provide a pollination service. Most non-pollinating wasps oviposit from outside the inflorescence (syconium), where they are vulnerable to ant predation. Ficus schwarzii is exposed to high densities of non-pollinating wasps, but Philidris sp. ants patrolling the syconia prevent them from ovipositing. Philidris rarely catch wasps, but the fig encourages the patrolling by providing a reward through extra-floral nectaries on the surface of syconia. Moreover, the reward is apparently only produced during the phase when parasitoids are ovipositing. An ant-exclusion experiment demonstrated that, in the absence of ants, syconia were heavily attacked and many aborted as a consequence. Philidris was normally rare on the figs during the receptive phase or at the time of day when wasp offspring are emerging, so predation on pollinators was limited. However, Myrmicaria sp. ants, which only occurred on three trees, preyed substantially on pollinating as well as non-pollinating wasps. F. schwarzii occurs in small clusters of trees and has an exceptionally rapid crop turnover. These factors appear to promote high densities of non-pollinating wasps and, as a consequence, may have led to both a high incidence of ants on trees and increased selective pressure on fig traits that increase the payoffs of the fig–ant interaction for the fig. The fig receives no direct benefit from the reward it provides, but protects pollinating wasps that will disperse its pollen.     

Indirect mutualism: ants protect fig seeds and pollen dispersers from parasites

1. Mutualisms are ubiquitous and ecologically important, but may be particularly vulnerable to exploitation by species outside of the mutualism owing to a combination of an attractive reward and potentially limited defence options. For some mutualisms, ants can offer dynamic and relatively selective protection against herbivores and parasites. 2. The mutualism between fig trees and their pollinating wasps, a keystone mutualism in tropical forests, is particularly well suited for ant protection because pollinators are protected inside hollow inflorescences but parasites are exposed on the outside. 3. In the present study, it was shown that the presence of ants provides a fitness benefit for both the pollinators and the hosting fig tree. The presence of ants (i) reduced abortions of developing figs, (ii) reduced herbivory of figs, and (iii) reduced parasitic wasp loads, resulting in more pollinators and more seeds in ant‐protected figs. Even when taking costs such as ant predation on emerging pollinators into account, the total fitness increase of hosting ants was threefold for the tree and fivefold for the pollinators. 4. It was further shown that the seemingly most vulnerable parasitic wasps, of the genus Idarnes, have a specific behaviour that allows them to evade ant attack while continuing to oviposit. 5. Ants were present on 79% of surveyed Panamanian fig trees. Together with previous studies from the Old World, the results found here imply that ants are both powerful and common protectors of the fig mutualism worldwide.     

Complex interactions on fig trees: ants capturing parasitic wasps as possible indirect mutualists of the fig–fig wasp interaction

Like other mutualisms, pollination mutualisms attract parasites, as well as opportunistic and specialist predators of the pollinators and parasites. These associated species influence the evolutionary dynamics of pairwise mutualisms. Predatory ants are frequent associates of pollination mutualisms, but their effects on the complex interactions between plants, pollinators and parasites have not yet been clearly established, even in the case of the well-described obligate interaction between figs and fig wasps. We attempted to quantify such effects for ants associated with three fig species, two dioecious ( Ficus condensa [Bruneï], F . carica [France]) and one monoecious ( F . racemosa [India]). In all these cases, ant presence on a fig tree strongly reduced the number of parasitic wasps on the figs. Experimental exclusion of ants resulted in an increase in the number of non-pollinating fig wasps on F . condensa and F . racemosa . Experimental ant supplementation led to a decrease in the number of non-pollinating fig wasps on F . carica . Moreover, on F . condensa , the level of reduction of the number of parasitic wasps depended on the number and identity of the ants. On F . carica , non-pollinating fig wasps even avoided trees occupied by the dominant predatory ant. The consistency of the effect of ants in these three cases, representing a geographically, ecologically, and taxonomically broad sample of figs, argues for the generality of the effect we observed. Because reduction of parasitism benefits the pollinator, ants may be considered as indirect mutualists of plants and pollinators in the network of complex interactions supported by fig trees.     

Variation in trophic cascade strength is triggered by top–down process in an ant–wasp‐fig system

Changes in the strength of trophic cascades over time have been associated with dramatic shifts in community structure and function. However, the pattern, process, and potential underlying mechanism of temporal variation in trophic cascades remains relatively unexplored. A top–down trophic cascade has been documented for the effects of predacious weaver ants Oecophylla smaragdina on the success of fig tree Ficus racemosa seed production. Ants cause high mortality of non‐pollinating fig wasps Sycophaga mayri that parasitize fruits, leading to greater success for the pollinating fig wasp–fig tree mutualists. Here, using a design in which pairs of branches were selected on a tree, and ants were excluded from one of each pair, we quantified the magnitude of the trophic cascade in the cool–dry, hot–dry and rainy (hot–wet) seasons in Xishuangbanna, southwest China. We also recorded the daily behavioral dynamics of ants and fig wasps in different seasons and analyzed the correlation between behavioral, activity and trophic cascade strength. We found that the strength of the trophic cascade was strong in the hot–dry season, diminished in the rainy season and disappeared in the cool–dry season in this system. The strength of species interactions between ants and non‐pollinating fig wasps, is positively correlated with trophic cascade strength, indicating that trophic cascade strength is determined by a top–down process when the community is well established. Moreover, because pollinating fig wasps, Ceratosolen fusciceps, play a central role in the establishment of fig wasp communities, when C. fusciceps wasps are absent, the community quickly disassembles as is the case in the cool–dry season. In summary, the strength of the trophic cascade is triggered by top–down processes, however, the occurrence of the trophic cascade is determined by a keystone species that plays a central role in assembly of the community.     

Quantitative tests of interaction between pollinating and non-pollinating fig wasps on dioecious Ficus hispida

Abstract.  1. The interaction between Ficus species and their pollinating wasps (Agaonidae) represents a striking example of a mutualism. Figs also shelter numerous non-pollinating chalcids that exploit the fig–pollinator mutualism.
2. Previous studies showed a weak negative correlation between numbers of pollinating and non-pollinating adults emerging from the same fruit. Little is known about the patterns and intensities of interactions between fig wasps. In the Xishuangbanna tropical rainforests of China, the dioecious Ficus hispida L. is pollinated by Ceratosolen solmsi marchali Mayr and is also exploited by the non-pollinators Philotrypesis pilosa Mayr, Philotrypesis sp., and Apocrypta bakeri Joseph. Here, the interaction of pollinator and non-pollinators on F. hispida is studied quantitatively.
3. The exact time of oviposition was determined for each species of fig wasp. Based on observational and experimental work it is suggested that (i) the relationship between pollinator and non-pollinators is a positive one, and that the genus Philotrypesis appears to have no significant impact on the pollinator population, whereas Apocrypta has a significant effect on both Philotrypesis and Ceratosolen ; (ii) gall numbers do not always increase with increasing number of foundresses, but developmental mortality of larvae correlates positively with the number of foundresses; and (iii) there is a positive correlation between non-pollinator numbers and their rates of parasitism, but the three species of non-pollinators differed in their rates of parasitism and show different effects on pollinator production.
4. The rates of parasitism when combined with the coexistent percentage and developmental mortality, underpin the way non-pollinating fig wasps successfully exploit and coexist stably in a fig–pollinator mutualism.     

Host-specificity and coevolution among pollinating and nonpollinating New World fig wasps

Figs (Ficus spp., Moraceae) and their pollinating wasps (Hymenoptera, Agaonidae, Chalcidoidea) constitute a classic example of an obligate plant-pollinator mutualism, and have become an ideal system for addressing questions on coevolution, speciation, and the maintenance of mutualisms. In addition to pollinating wasps, figs host several types of nonpollinating, parasitic wasps from a diverse array of Chalcid subfamilies with varied natural histories and ecological strategies (e.g. competitors, gallers, and parasitoids). Although a few recent studies have addressed the question of codivergence between specific genera of pollinating and nonpollinating fig wasps, no study has addressed the history of divergence of a fig wasp community comprised of multiple genera of wasps associated with a large number of sympatric fig hosts. Here, we conduct phylogenetic analyses of mitochondrial DNA sequences (COI) using 411 individuals from 69 pollinating and nonpollinating fig wasp species to assess relationships within and between five genera of fig wasps (Pegoscapus, Idarnes, Heterandrium, Aepocerus, Physothorax) associated with 17 species of New World Urostigma figs from section Americana. We show that host-switching and multiple wasp species per host are ubiquitous across Neotropical nonpollinating wasp genera. In spite of these findings, cophylogenetic analyses (TREEMAP 1.0, TREEMAP 2.02beta, and parafit) reveal evidence of codivergence among fig wasps from different ecological guilds. Our findings further challenge the classical notion of strict-sense coevolution between figs and their associated wasps, and mirror conclusions from detailed molecular studies of other mutualisms that have revealed common patterns of diffuse coevolution and asymmetric specialization among the participants.     

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。     

Non-pollinating wasps distort the sex ratio of pollinating fig wasps

In fig wasps, mating occurs among the offspring of one or a few foundress mothers within the fig, from which the mated females disperse to found new broods. Under these conditions, males will compete with each other for mating, and such local mate competition can result in female-biased sex ratios. In addition to pollinating wasps, non-pollinating wasp species are also associated with figs and develop in flower ovaries or parasitize the larvae of primary galling wasps. While studying the fig wasp Pegoscapus tonduzi , which pollinates Ficus citrifolia in Brazil, we examined the influence of non-pollinating fig wasps on the sex ratio of species that pollinate F. citrifolia to determine whether the presence of non-pollinating wasps resulted in a distorted sex ratio. There was a positive relationship between the sex ratio of P. tonduzi and the number of non-pollinating wasps that was independent of the number of foundresses and brood size. In addition, the number of non-pollinating wasps correlated negatively with the number of pollinating females, but was not significantly related to the number of pollinating males. This finding suggested that non-pollinating wasps had a direct effect in distorting the sex ratio of P. tonduzi broods. Our results indicate that the secondary sex ratio may not precisely reflect the primary sex ratio when there is a high infestation of non-pollinating fig wasps.     

细叶榕榕小蜂群落结构及动态变化

细叶榕为桑科榕属植物,雌雄异株,广泛分布于印度-澳大利亚(Asia-Australasia)榕树植物分布中心区,它既是热带雨林的主要树种,也是庭院和行道绿化的常见树种。通过全年定时、定点、定株观察与采集,对福州2个样地19株细叶榕隐头果内小蜂群落结构及其动态进行研究。全年在两个样地530个隐头果内共收集到小蜂26318只。发现细叶榕隐头果内有17种小蜂,隶属小蜂总科Chalcidoidae中的榕小蜂科(Agaonidae)、隐针榕小蜂亚科(Epichrysomallinae)、金小蜂科(Pteromalidae)、广肩小蜂科(Eurytomidae)和刻腹小蜂科(Ormyridae),其中榕小蜂科的Eupristina verticillata是细叶榕唯一的传粉者,传粉方式为主动传粉,其性比为0.16,具明显偏雌现象;非传粉小蜂中,有翅雄蜂的榕小蜂(Odontofroggatia galili,O.quinifuniculus,O.corneri,Sycophila sp.1,Sycophila sp.2,Meselatus bicolor)的性比(0.46—0.55)较高,无翅雄蜂的榕小蜂(P.taiwanensis,Sycoscaptergajimaru,W.microcarpae)的性比(0.31—0.37)较低,而既具有翅雄蜂又具无翅雄蜂的非传粉榕小蜂(P.okinavensis)性比(0.47)居中。榕小蜂的性比可能与其交配行为策略有关。在细叶榕小蜂群落结构中,传粉小蜂E.verticillata的重要值占绝对优势,非传粉小蜂O.galili和Sycophila sp.2的重要值仅次于传粉小蜂。根据榕小蜂发生数量及连续性,可将细叶榕隐头果中的榕小蜂分为常见种和偶见种,E.verticillata、Odontofroggatia galili、Walkerella microcarpae、Sycophila sp.1、Sycophila sp.2和Philotrypesis okinavensis为常见种,其余11个种为偶见种。传粉小蜂和非传粉小蜂的种类和数量呈现明显的季节性变化。2月至6月期间,每月出现的榕小蜂种类较少,仅3—4种,单果内平均有传粉小蜂48.88只,非传粉小蜂13.64只;7月至翌年1月间,每月出现的榕小蜂种类较多,达6—13种,单果内平均有传粉小蜂24.38只,非传粉小蜂18.89只,表明,7月—翌年1月单果内传粉小蜂数量比较于2—6月极显著降低(P<0.001),而单果内非传粉小蜂数量极显著提高(P=0.001),同时种类也显著增加。雄花期榕小蜂的种类与数量取决于雌花期产卵榕小蜂的种类与数量,而雨量、气温以及雌花期花序果数量对产卵小蜂的数量,以及小蜂产卵行为都可能产生影响。本研究结果可为城市绿化和热带雨林生物多样性保护提供科学依据。     

Reconstruction of fig wasp mating structure: how many mothers share a fig?

Abstract.  1. Fig wasps (Hymenoptera: Agaonidae) represent an important model system for studies of sex ratio evolution, mainly because they may adjust their sex ratios in response to the numbers of ovipositing females (foundresses) that enter a fig and their clutch size.
2. Until recently, it was assumed that all foundresses fail to re-emerge from the figs that they have entered to oviposit, but there is increasing evidence that such re-emergence may be routine. The common practice of counting the number of dead foundresses present in a fig in order to deduce the number of foundresses is therefore questionable in species where failure to re-emerge has not been confirmed.
3. In this study, the alternative approach of microsatellite markers was used to reconstruct the within-fig breeding structure of a pollinating fig wasp by genetic analysis of the offspring. Broods of Liporrhopalum tentacularis , a species where foundresses regularly re-emerge from figs, were collected from figs of Ficus montana in their natural habitat in Indonesia as well as from an experimental glasshouse population in Leeds (U.K.).
4. The estimated foundress densities in the glasshouse population were similar to those in the field and ranged from one to six foundresses per brood.
5. Nearly 40% of all broods were produced by a single foundress, indicating that mating in these broods occurs exclusively between full siblings. High levels of inbreeding are therefore common in this species.     

Contrasting patterns of fig wasp communities along Mt. Wilhelm,Papua New Guinea

The fig (Moraceae) and pollinating fig wasp (Agaonidae) mutualism is best known as a model system for the study of coevolution in plant–pollinator interactions and its central role in shaping vertebrate communities in tropical forests. Figs also host myriad antagonistic parasitic fig wasps which impose costs on both partners threatening mutualism stability. Spatiotemporal variation in parasitic wasp abundance is a key factor in mitigating these effects. Because fig wasps are temperature sensitive and likely vary in their ability to traverse environmental gradients, we expect community assemblages and abundance of both pollinating and non-pollinating fig wasps to respond to changes along an elevational gradient. In the present study, we compare the fig wasp communities and abundance of three fig species growing along the slopes of the Mount Wilhelm altitudinal gradient in Papua New Guinea. We quantified wasps from over 100 male fig trees and calculated seed set for 55 female trees along each of the species’ distribution on the transect. Our results show that the abundance of both pollinating and non-pollinating fig wasps follow a mid-elevation peak, consistent with fig species richness found in the same transect. The patterns, however, are different according to the host's species distribution. Seed set remained relatively constant along the gradient for all species with some decrease along higher elevations, potentially affecting connectivity along the gradient. As suggested for insects in general, temperature and habitat diversity appear to play a fundamental role in the species richness and abundance of fig wasps.     

Measuring the discrepancy between fecundity and lifetime reproductive success in a pollinating fig wasp

Lifetime reproductive success in female insects is often egg‐ or time‐limited. For instance in pro‐ovigenic species, when oviposition sites are abundant, females may quickly become devoid of eggs. Conversely, in the absence of suitable oviposition sites, females may die before laying all of their eggs. In pollinating fig wasps (Hymenoptera: Agaonidae), each species has an obligate mutualism with its host fig tree species [Ficus spp. (Moraceae)]. These pro‐ovigenic wasps oviposit in individual ovaries within the inflorescences of monoecious Ficus (syconia, or ‘figs’), which contain many flowers. Each female flower can thus become a seed or be converted into a wasp gall. The mystery is that the wasps never oviposit in all fig ovaries, even when a fig contains enough wasp females with enough eggs to do so. The failure of all wasps to translate all of their eggs into offspring clearly contributes to mutualism persistence, but the underlying causal mechanisms are unclear. We found in an undescribed Brazilian Pegoscapus wasp population that the lifetime reproductive success of lone foundresses was relatively unaffected by constraints on oviposition. The number of offspring produced by lone foundresses experimentally introduced into receptive figs was generally lower than the numbers of eggs carried, despite the fact that the wasps were able to lay all or most of their eggs. Because we excluded any effects of intraspecific competitors and parasitic non‐pollinating wasps, our data suggest that some pollinators produce few offspring because some of their eggs or larvae are unviable or are victims of plant defences.     

How to be an ant on figs

Mutualistic interactions are open to exploitation by one or other of the partners and a diversity of other organisms, and hence are best understood as being embedded in a complex network of biotic interactions. Figs participate in an obligate mutualism in that figs are dependent on agaonid fig wasps for pollination and the wasps are dependent on fig ovules for brood sites. Ants are common insect predators and abundant in tropical forests. Ants have been recorded on approximately 11% of fig species, including all six subgenera, and often affect the fig–fig pollinator interaction through their predation of either pollinating and parasitic wasps. On monoecious figs, ants are often associated with hemipterans, whereas in dioecious figs ants predominantly prey on fig wasps. A few fig species are true myrmecophytes, with domatia or food rewards for ants, and in at least one species this is linked to predation of parasitic fig wasps. Ants also play a role in dispersal of fig seeds and may be particularly important for hemi-epiphytic species, which require high quality establishment microsites in the canopy. The intersection between the fig–fig pollinator and ant–plant systems promises to provide fertile ground for understanding mutualistic interactions within the context of complex interaction networks.     

Egg deposition patterns of fig pollinating wasps: implications for studies on the stability of the mutualism

1. Fig pollinating wasps (Agaonidae) enter Ficus inflorescences (figs), oviposit in some of the flowers, and pollinate in the process. Each larva completes its development within a single flower. In most cases, an inflorescence entered by a wasp will represent its only egg‐laying site. The mechanisms that prevent pollinating wasps from exploiting all the flowers inside a fig are not understood. In this study, hypotheses about flower use by pollinating fig wasps were tested by investigating egg deposition patterns in three species. 2. Either one or three wasps were introduced into figs. The figs were then harvested. Serial sections allowed assessment of the presence or absence of a wasp egg in a sample of flowers in each fig. The overall proportion of flowers with eggs and the spatial distribution of eggs were then compared in single wasp figs and three foundress figs. 3. In all species, the proportion of flowers with a wasp egg increased with foundress number but less than three‐fold. 4. In all species, at least in single foundress figs, flowers near the fig cavity were more likely to receive a wasp egg than were flowers near the fig wall. 5. In two species, when the number of foundresses was multiplied by three, there was an increase in the use of flowers near the fig wall, while in the third species, the increase was spread evenly among flowers. 6. Factors affecting wasp egg deposition patterns and the potential of investigating such patterns for studying the stability of the mutualism are discussed.     

榕果挥发物对传粉榕小蜂的吸引作用

榕树 /榕小蜂专一性共生系统的维持 ,与榕树开花期释放的特殊的挥发性化合物以及榕小蜂对其寄主榕树的化学识别和定位紧密相关。研究选取了西双版纳地区常见的 3种榕树 ,即对叶榕 Ficus hispida、木瓜榕 F.auriculata和鸡嗉子榕F.semicordata的榕果作为实验材料 ,利用野外诱捕实验、室内生物检测实验检测传粉榕小蜂 Hymenoptera:ChalcidoidaeAgaonidae对 12种信息化合物及榕果的二氯甲烷浸提物的趋向性反应 ,研究不同榕属植物的传粉榕小蜂对相同的信息化合物的反应差异 ,以及传粉榕小蜂受不同发育时期榕果浸提物吸引的显著性程度。诱捕实验中对叶榕小蜂 Ceratosolen solmsimarchali对香叶醇的趋向性反应显著 ,大果榕小蜂 C.emarginatus对接受期榕果浸提物和芳樟醇都有明显的趋向性反应 ,而对间花期榕果浸提物则无显著反应。嗅觉仪生物检测实验中 ,鸡嗉果榕小蜂 C.gravelyi对香叶醇和松油醇都表现出显著的趋向性反应。结果表明 ,对叶榕、鸡嗉子榕传粉榕小蜂对 12种信息化合物的反应存在一定的差异 ,木瓜榕传粉榕小蜂对香叶醇和木瓜榕接受期榕果浸提物的趋向性反应比间花期榕果强得多     

Virginity in haplodiploid populations: a study on fig wasps

ABSTRACT.

• 1 The fig wasps inhabiting the figs of Ficus hispidioides S. Moore in New Guinea were investigated. The galls formed by the pollinating agaonid were also inhabited by two other non-pollinating species of wasp; a third non-pollinating wasp caused the production of a different type of gall, and was itself parasitized by a fourth species. In all species, males were wingless and all matings occurred within the fig.
• 2 It was estimated that 2% of the pollinating fig wasps left the fig unmated. The equivalent figures for three of the non-pollinating wasps were 2%, 4% and 23%. The significance of oviposition by virgin females to the sex allocation strategy of mated females is discussed.
• 3 The absence of fighting and male wing dimorphism were studied in the context of the predictions of their occurrence by Hamilton (1979).

     

Direct evidence for the cycling of fig wasps within one male fig tree

Fig wasps can only survive when flowering fig trees are present all the year around. Ficus trees can only reproduce if they are pollinated by highly specific wasps. In highly seasonal habitats, when only few trees occur at a specific site, gaps in fruiting may lead to the extinction of the local pollinator population. This paper demonstrates that in a dioecious fig tree, Ficus hirta , the fig wasp population can be maintained successfully within an individual plant, through the strong intra-tree asynchrony in flowering. By experimentally bagging trees, we showed that the pollinating wasps ( Blastophaga javana hilli ) could live for two generations, and the non-pollinating wasps ( Sycoscapter sp.) for up to three generations in a closed intra-tree system. However, there was a sharp decline in wasp abundance, deviating sex ratios and decreasing flower occupancy before their ultimate extinction, indicating that the wasp populations were not sustainable. This phenological strategy may enable dioecious figs, which are not constrained by the cost of selfing, to occupy a wider breadth of niches in both tropical and seasonal habitats.     

传粉榕小蜂与榕树的繁衍

榕树传粉现象被广泛地作为研究协同进化特别是互惠共生的重要模式之一。本文总结了榕果与传粉榕小蜂的有关研究,试图解释其形态结构之间的相互适应,总结传粉榕小蜂的传粉行为,探讨传粉榕小蜂在雌雄同株及雌雄异株榕树上的传粉模式,讨论传粉榕小蜂的寄主专一性,并展望中国在榕小蜂方面的研究前景。     

Ant mutualists alter the composition and attack rate of the parasitoid community for the gall wasp Disholcaspis eldoradensis (Cynipidae)

Abstract.  1. The strength or density dependence of pairwise species interactions can depend on the presence or absence of other species, especially potential mutualists.
2. The gall wasp Disholcaspis eldoradensis induces plant galls that secrete a sweet honeydew from their top surfaces while the wasp larvae are active. These galls are actively tended by Argentine ants, which collect the honeydew and drive off parasitoids attempting to attack the gall wasp.
3. When ants were excluded, the total rate of parasitism by seven species of parasitoids increased by 36%, and the rate of gall-wasp emergence decreased by 54%.
4. The total percentage parasitism was affected by gall density when ants were excluded but not when ants were unmanipulated, suggesting a change in parasitoid functional responses due to ant tending.
5. In addition, excluding ants significantly altered the proportions of different parasitoid species that emerged from galls; one parasitoid species increased from 1% to 34%, and another decreased from 46% to 19%.
6. The invasive Argentine ants studied are capable of maintaining the mutualism with the gall wasps that evolved in the presence of different ant species and also act as a selective filter for the local community of generalist parasitoids trying to attack this gall species.     

Between‐species facilitation by male fig wasps in shared figs

1. Facilitation is recorded from diverse plant–insect interactions, including pollination and herbivory. 2. The significance of facilitation resulting from the behavior of males of multiple fig wasp species inside figs was investigated. Female fig wasps emerge from natal figs via exit holes dug by males, especially male pollinators. When no males are present, the females struggle to escape and may die. 3. Ficus microcarpa L. is a widely‐established invasive fig tree from Southeast Asia. Its pollinator is absent in South Africa, so the tree cannot reproduce, but two Asian non‐pollinating fig wasps (NPFW) Walkerella microcarpae and Odontofroggatia galili occupy its figs. Abundance patterns of the two NPFW and the proportion of male‐free figs in South Africa, Spain (where the pollinator is introduced), and in China, where the native fig wasp community is diverse, were compared to determine the consequences of reduced species richness for insect survival. 4. Female fig wasps in male‐free figs were found to be trapped, and small clutch sizes contributed to the absence of males in both species. The presence of pollinators in Spain allowed most NPFW to develop in figs containing males. Far more male‐free figs were present in South Africa, elevating mortality rates among female NPFW. Facilitation of female release by males of other NPFW species nonetheless benefitted the rarer species. 5. Selection pressures in South Africa currently favour greater aggregation of NPFW offspring and/or less female biased sex ratios.