高榕雌花期传粉榕小蜂和欺骗性小蜂的繁殖特点

榕树及其专一性传粉榕小蜂组成了动植物界最为经典的协同进化关系,传粉榕小蜂演化出欺骗性是非常罕见的。在雌雄同株的高榕隐头果内,共存着一种传粉榕小蜂Eupristina altissima和一种欺骗性的小蜂Eupristina sp.,两种小蜂在雌花期进入隐头果内繁殖,但有不同的繁殖特点。对比研究了两种小蜂从成虫羽化到产卵和传粉这个阶段的雌蜂个体大小、孕卵量及繁殖差异,结果表明:羽化期两种雌蜂的平均个体小,经飞行小个体的雌蜂易死亡,大个体雌蜂到达接受树,但通过苞片通道,一些个体较大的传粉榕小蜂被夹死导致进入果腔的雌蜂相对小,而欺骗性小蜂易通过苞片以至进入果腔的雌蜂个体较大。两种未产卵雌蜂均表现为个体大者孕卵量较多,但两种雌蜂的平均孕卵量没有差异。即使有充足雌花资源产卵,两种雌蜂均未产完所有卵,产卵后两种雌蜂卵巢中的卵量均显著减少,遗留下的卵量两种小蜂间没有差异。传粉榕小蜂只有部分个体传完所携带花粉,并表现为传粉越成功的雌蜂,产卵越多。存在种内竞争时,两种小蜂的产卵量均减少,传粉榕小蜂的传粉效率也降低。在种间竞争背景下,欺骗性小蜂产卵更成功,传粉榕小蜂的产卵和传粉量均受到极大抑制。研究结果说明雌花期隐头果内传粉榕小蜂只适量利用雌花资源产卵繁殖后代,更有效地传粉繁殖榕树种子,这可能是维持榕-蜂互惠系统稳定共存的重要机制之一;欺骗者稳定存在需降低与传粉者的直接竞争,而欺骗者和传粉者分散在不同果内,甚至是不同的树上繁殖是理想的繁殖策略。     

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.     

The dominant exploiters of the fig/pollinator mutualism vary across continents,but their costs fall consistently on the male reproductive function of figs

1. Fig trees (Moraceae: Ficus) are keystone species, whose ecosystem function relies on an obligate mutualism with wasps (Chalcidoidea: Agaonidae) that enter fig syconia to pollinate. Each female flower produces one seed (fig female reproductive function), unless it also receives a wasp egg, in which case it supports a wasp. Fig male reproductive function requires both male flowers and pollinator offspring, which are the only vectors of fig pollen. 2. The mutualism is exploited by other wasps that lay eggs but provide no pollination service. Most of these non‐pollinating fig wasps (NPFWs) do not enter syconia, but lay eggs through the wall with long ovipositors. Some are gall‐makers, while others are parasitoids or lethal inquilines of other wasps. 3. Ficus is pan‐tropical and contains >750 fig species. However, NPFW communities vary across fig lineages and continents and their effects on the mutualism may also vary. This provides a series of natural experiments to investigate how the costs to a keystone mutualism vary geographically. 4. We made the first detailed study of the costs of NPFWs in a fig (Ficus obliqua G. Forst) from the endemic Australasian section Malvanthera. In contrast to the communities associated with section Americana in the New World, wasps from the subfamily Sycoryctinae (Chalcidoidea: Pteromalidae) dominated this community. 5. These sycoryctine wasps have a negative impact on pollinator offspring numbers, but not on seed production. Consequently, while the NPFW fauna varies greatly at high taxonomic levels across continents, we show that the consistent main effect of locally dominant exploiters of the mutualism is to reduce fig male reproductive function.     

Non‐pollinating Fig Wasps Decrease Pollinator and Seed Production in Ficus andicola (Moraceae)

Fig trees ( Ficus spp.) and Agaonine fig‐wasps participate in an obligate mutualism. Fig wasps can only develop within fig inflorescences (syconia) and they are the only organisms capable of pollinating fig flowers. Other non‐pollinating wasps that lay eggs by inserting their ovipositors from the outside can also develop in syconia. These parasitic wasps may be parasitoids of either pollinating or other non‐pollinating wasps, or form galls in fig flowers or other tissues. Depending on this interaction, parasitic wasps may have various effects on the production of pollinating wasps and seeds. Wasps in the genus Idarnes, which parasitize New World figs (subgenus Urostigma), have an effect on wasp production but not on seed production. Heterandrium spp., which have short ovipositors and lay on external flowers, are infrequent and no effect on seed production has been documented. In the Colombian Andes, Idarnes spp. and Heterandrium spp. are the most frequent parasites of the Ficus andicola — Pegoscapus sp. mutualism, affecting 62 and 43 percent of syconia, respectively. Controlling for other factors that influence wasp and seed production, such as number of foundresses, syconium size and tree, we found that Idarnes reduced pollinator production by almost half but did not reduce seed production, whereas Heterandrium reduced seed production by 40 percent, and marginally affected pollinator production. Our results provide the first clear documentation of Heterandrium spp. impact on fig seed production. Whether the relative abundance of this genus is a generalized phenomenon in montane forest remains to be determined.     

Plasticity and diversity of the phenology of dioecious Ficus species in Taiwan

While Ficus present a series of traits often associated with dioecy, the prevalence of dioecy in Ficus is atypical. In Asian floras, dioecious Ficus species generally outnumber monoecious ones. Further this is also true in relatively northerly locations for Ficus such as the island of Taiwan. Ficus are pollinated by species-specific wasps that use fig flowers as breeding sites. In dioecious fig species, pollinators develop only in the inflorescences of male fig trees. In this study, we investigated the reproductive phenology of four dioecious Ficus species with distinct ecologies in several locations in northern and southern Taiwan. The two first species (Ficus erecta and Ficus septica) were investigated in four locations. Reproductive phenology was quite different among sites, even within a single species. For example, F. erecta presented well-defined crops at the population level in its usual high-elevation habitat but continuous fig production at low elevations, especially in South Taiwan. The two other fig species (Ficus pedunculosa var. mearnsii and Ficus tinctoria subsp. swinhoei), are shrubs growing together along seashores in exposed locations on coral reef remnants. These two species presented quite different traits allowing the survival of pollinating wasp populations. Ficus pedunculosa var. mearnsii produced figs continuously so that fresh receptive figs were always available for the pollinating wasps while F. tinctoria subsp. swinhoei extended the period of receptivity of its figs, so that receptive figs that had been waiting for pollinating wasps were almost always available. In summary, dioecious figs in Taiwan showed remarkable variation in their phenology, within species among locations or among species within location. Nevertheless, despite this variation, the phenology of the trees always allowed survival of pollinating wasp populations. Dioecious figs seem to have adopted a differentiated set of strategies which result in high resilience of pollinator populations. This resilience could help explain the atypical prevalence of dioecy in Ficus.     

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.     

Age at pollination modifies relative male and female reproductive success in a monoecious fig tree

Plants that depend on a single species of insect pollinator must often contend with infrequent and unpredictable visitation. Prolongation of floral receptivity comes at the cost of reduced male and/or female reproductive success among older flowers. Fig trees (Ficus spp.) have a highly specific pollination symbiosis and individual inflorescences (syconia) that remain receptive for days or weeks. Reproductive success in monoecious fig trees involves production of both seeds and fig wasp offspring. We assessed whether the reproductive output of individual syconia changes with the length of time they waited for pollination, and whether the relative female and male reproductive success also changes. A pollination experiment was conducted in an SE Asian monoecious fig tree Ficus curtipes, in which receptive syconia were covered with mesh bags to exclude wasps and pollinated by single pollinators of this fig tree at their different receptive ages. When the syconia matured their size and contents were recorded. Seed quality was also assessed. The results showed that pollinators entered syconia that had been waiting for up to 36?days. The frequencies of abortions among syconia pollinated at different ages were low throughout. The number of un-utilised flowers increased progressively in older syconia. Seed production was highest in syconia entered on the first day of receptivity, whereas pollinator production peaked in syconia pollinated on day 12, then declined in older syconia. Consequently, overall reproductive efficiency declined with syconium age and floral sex allocation became more male-biased in older syconia. Older syconia also produced lighter seeds. These results suggest that un-pollinated syconia of F. curtipes can remain receptive for several weeks. This makes pollination of each syconium more likely, but at the cost of reduced productivity and with more ovules allocated to male function. However, the prolongation of floral receptivity has significance for the co-adaptation between syconia and fig wasps and for the evolution of the fig tree-fig wasp symbiosis.     

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.     

Some pollinators are more equal than others: Factors influencing pollen loads and seed set capacity of two actively and passively pollinating fig wasps

The nursery pollination system of fig trees (Ficus) results in the plants providing resources for pollinator fig wasp larvae as part of their male reproductive investment, with selection determining relative investment into pollinating wasps and the pollen they carry. The small size of Ficus pollen suggests that the quantities of pollen transported by individual wasps often limits male reproductive success. We assessed variation in fig wasp pollen loads and its influence on seed production in actively pollinated (Ficus montana) and passively pollinated (Ficus carica) dioecious fig trees.The ratios of number of male flowers on number of female flowers in a glasshouse-maintained F. montana population were highly variable. When fig wasps were introduced into receptive female figs, the resulting seed numbers were strongly linked to the numbers of pollinators that had been seeking access to pollen, relative to the number of anthers in their natal figs. In F. carica estimates of the amounts of pollen produced per fig and the quantities of pollen carried by emerging fig wasps suggest that less than 10% of the pollen is transported. Pollinators of F. carica that emerged earlier from figs carried more pollen, and also generated more seeds when introduced into receptive female figs.We show here that all pollinators are not equally valuable and producing more pollinators is not necessarily a good option in terms of Ficus male fitness. Previous results on F. montana figs showed that only around half of the flowers where pollinators lay eggs produced adult offspring. The amount of pollen collected by young female fig wasps may be a major determinant of their reproductive success.     

Finding hidden females in a crowd: Mate recognition in fig wasps

Multi-species mating aggregations are crowded environments within which mate recognition must occur. Mating aggregations of fig wasps can consist of thousands of individuals of many species that attain sexual maturity simultaneously and mate in the same microenvironment, i.e, in syntopy, within the close confines of an enclosed globular inflorescence called a syconium – a system that has many signalling constraints such as darkness and crowding. All wasps develop within individual galled flowers. Since mating mostly occurs when females are still confined within their galls, male wasps have the additional burden of detecting conspecific females that are “hidden” behind barriers consisting of gall walls. In Ficus racemosa, we investigated signals used by pollinating fig wasp males to differentiate conspecific females from females of other syntopic fig wasp species. Male Ceratosolen fusciceps could detect conspecific females using cues from galls containing females, empty galls, as well as cues from gall volatiles and gall surface hydrocarbons.In many figs, syconia are pollinated by single foundress wasps, leading to high levels of wasp inbreeding due to sibmating. In F. racemosa, as most syconia contain many foundresses, we expected male pollinators to prefer non-sib females to female siblings to reduce inbreeding. We used galls containing females from non-natal figs as a proxy for non-sibs and those from natal figs as a proxy for sibling females. We found that males preferred galls of female pollinators from natal figs. However, males were undecided when given a choice between galls containing non-pollinator females from natal syconia and pollinator females from non-natal syconia, suggesting olfactory imprinting by the natal syconial environment.     

Laticifer distribution in fig inflorescence and its potential role in the fig-fig wasp mutualism

Although in Moraceae the presence of laticifers is considered to be a synapomorphy, little is known about the distribution and morphology of this type of secretory structure in the reproductive organs of its species. Ficus, the largest genus of Moraceae, is characterized by an inflorescence known as syconium and by an obligate mutualistic interaction with pollinating wasps. The objectives of the present study were to evaluate the distribution and morphology of laticifers in syconia of 36 species belonging to different Ficus sections and to survey traits of taxonomic and adaptive value for the group. Syconia containing flowers in a receptive state were collected, fixed and processed for anatomical analysis. All species studied have branched laticifers distributed in the syconium receptacle, in the ostiolar bracts and in the pedicel of staminate flowers. Almost all species show laticifers in the pedicel of shorter-styled flowers. Laticifers also occur in the pedicel of longer-styled flowers in most Ficus sections, except F. curtipes (Conosycea section) and more than 75% of the studied species of the Americanae section. Laticifers are observed in the sepals of 25 of the 36 species studied and occasionally in the pistil. The presence of laticifers in the pedicel of shorter-style flowers and its absence in the pistil suggest that the distribution of this secretory structure in the fig flower was selected by pressures imposed by the fig-fig wasp mutualism. The laticifers in the pedicel of shorter-styled flowers may confer protection to the developing wasp larvae against natural enemies. However, the absence of laticifers in the pistil of most Ficus species studied was probably selected by the mutualistic relationship with the agaonid pollinating wasps since the latex could interfere with oviposition through the style, with the larval development of the pollinating fig wasps, and the emergence of pollinator offspring from their galls.     

Seasonal change in the structure of fig-wasp community and its implication for conservation

Figs (Moraceae) and their pollinating wasps (Agaonidae) constitute a famous reciprocal mutualism in which figs provide some female flowers for the development of fig wasp offspring while the fig wasps pollinate fig flowers. However, figs also host many non-pollinating wasps which are either parasitoids or resource competitors of pollinators, and bring no benefit for figs and are detrimental to fig’ fitness. Our data onFicus racemosa in Xishuangbanna showed that the numbers of non-pollinators and the mature syconia without pollinator wasps increase in rainy season, especially in the highly fragmented forest. This might be because of the longer developing time of the syconia and thereby longer oviposition time to non-pollinators in the dry season. The galled flower and the viable seed percentages in dry seasons are also larger than in rainy seasons in both primary forest and fragmented forest, and the development of non-pollinators is mainly at the expense of pollinator wasps. Our results showed that there exists a discriminative seasonal impact of non-pollinators and fragmentation effects on population size of fig’s pollinators. This implies that fig/fig wasp mutualism is more fragile in dry season, and that the critical population size and breeding units of figs in seasonal area might be larger than previously estimated without considering the seasonal change of pollinator population.     

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.     

Phenology and Pollination Ecology of Three Brazilian Fig Species (Moraceae)

The phenology and pollination ecology of three native fig species were studied in southeastern Brazil. Populations displayed continual syconia production, with one species showing intra-tree flowering asynchrony. Pollination of the fig flowers was necessary for the development of the syconia; lack of pollination induced abortion of syconia. All three species follow the general pattern of pollination known for figs, but the behavior of the pollinator wasps, Pegoscapus spp., differed in some aspects from those of other neotropical and paleotropical fig wasps, mainly with respect to pollen loading and unloading during pollination. The longevity of Pegoscapus wasps outside the syconium was about two days.     

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.     

Extremely high proportions of male flowers and geographic variation in floral ratios within male figs of Ficus tikoua despite pollinators displaying active pollen collection

Most plants are pollinated passively, but active pollination has evolved among insects that depend on ovule fertilization for larval development. Anther‐to‐ovule ratios (A/O ratios, a coarse indicator of pollen‐to‐ovule ratios) are strong indicators of pollination mode in fig trees and are consistent within most species. However, unusually high values and high variation of A/O ratios (0.096–10.0) were detected among male plants from 41 natural populations of Ficus tikoua in China. Higher proportions of male (staminate) flowers were associated with a change in their distribution within the figs, from circum‐ostiolar to scattered. Plants bearing figs with ostiolar or scattered male flowers were geographically separated, with scattered male flowers found mainly on the Yungui Plateau in the southwest of our sample area. The A/O ratios of most F. tikoua figs were indicative of passive pollination, but its Ceratosolen fig wasp pollinator actively loads pollen into its pollen pockets. Additional pollen was also carried on their body surface and pollinators emerging from scattered‐flower figs had more surface pollen. Large amounts of pollen grains on the insects' body surface are usually indicative of a passive pollinator. This is the first recorded case of an actively pollinated Ficus species producing large amounts of pollen. Overall high A/O ratios, particularly in some populations, in combination with actively pollinating pollinators, may reflect a response by the plant to insufficient quantities of pollen transported in the wasps’ pollen pockets, together with geographic variation in this pollen limitation. This suggests an unstable scenario that could lead to eventual loss of wasp active pollination behavior.     

Foundress Fig Wasps are More Likely to Re-emerge From Older Figs

The mutualistic interaction between Ficus spp. and their pollinating fig wasps (Agaonidae) centres on the plants’ unique inflorescences—their figs. Each Ficus species is pollinated by foundresses of host-specific fig wasps which enter figs to lay eggs in the female flowers. Most foundresses are trapped in the first figs they enter, but in some species wingless foundresses can re-emerge and subsequently enter and oviposit into further figs. We investigated whether number of potential oviposition sites, age of the fig and age of the wasp influence the likelihood of re-emergence of lone foundresses of the Asian fig wasp Kradibia (=Liporrhopalum) tentacularis from previously un-entered figs of Ficus montana. Likelihood of re-emergence was not influenced by wasp age or flower numbers (resource abundance), but was more frequent from older figs that had waited longer to be pollinated. Laying eggs in several figs offers clear advantages, but foundresses often failed to re-emerge despite being unable to lay all their eggs. Resource quality not quantity appears to be the main influence on the fig wasp’s oviposition decisions. The physical difficulty that the wasps experience when trying to re-emerge may prevent it, even when re-emergence would be advantageous for both the insect and its host plant, but older fig wasps were not detectably ‘weaker’ than younger individuals.     

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。     

Mutualism from the inside: coordinated development of plant and insect in an active pollinating fig wasp

Recent studies on the obligate interaction between fig trees and their pollinating agaonid wasps have focused on population aspects and wasp?Cseed exploitation at the level of the inflorescence. Detailed studies on larval and gall development are required to more fully understand how resources are exploited and adaptations fine-tuned by each partner in nursery pollination mutualisms. We studied the larval development of the active pollinating fig wasp, Pegoscapus sp., and the galling process of individual flowers within the figs of its monoecious host, Ficus citrifolia, in Brazil. The pollinator development is strongly dependent on flower pollination. Figs entered by pollen-free wasps were in general more likely to abort. Retained, unpollinated figs had both higher larval mortality and a lower number of wasps. Pegoscapus sp. larvae are adapted to plant development, with two contrasting larval feeding strategies proceeding alongside gall development. The first two larval stages behave as ovary parasites. Later larval stages feed on hypertrophied endosperm. This indicates that a successful galling process relies on endosperm, and also reveals why pollination would be a prerequisite for the production of high-quality galls for this Pegoscapus species.     

Genome‐wide sequence data suggest the possibility of pollinator sharing by host shift in dioecious figs (Moraceae,Ficus)

The obligate mutualism of figs and fig‐pollinating wasps has been one of the classic models used for testing theories of co‐evolution and cospeciation due to the high species‐specificity of these relationships. To investigate the species‐specificity between figs and fig pollinators and to further understand the speciation process in obligate mutualisms, we examined the genetic differentiation and phylogenetic relationships of four closely related fig‐pollinating wasp species (Blastophaga nipponica, Blastophaga taiwanensis, Blastophaga tannoensis and Blastophaga yeni) in Japan and Taiwan using genome‐wide sequence data, including mitochondrial DNA sequences. In addition, population structure was analysed for the fig wasps and their host species using microsatellite data. The results suggest that the three Taiwanese fig wasp species are a single panmictic population that pollinates three dioecious fig species, which are sympatrically distributed, have large differences in morphology and ecology and are also genetically differentiated. Our results illustrate the first case of pollinator sharing by host shift in the subgenus Ficus. On the other hand, there are strict genetic codivergences between allopatric populations of the two host–pollinator pairs. The possible processes that produce these pollinator‐sharing events are discussed based on the level and pattern of genetic differentiation in these figs and fig wasps.