Phenological Adaptations in Ficus tikoua Exhibit Convergence with Unrelated Extra-Tropical Fig Trees

Flowering phenology is central to the ecology and evolution of most flowering plants. In highly-specific nursery pollination systems, such as that involving fig trees (Ficus species) and fig wasps (Agaonidae), any mismatch in timing has serious consequences because the plants must balance seed production with maintenance of their pollinator populations. Most fig trees are found in tropical or subtropical habitats, but the dioecious Chinese Ficus tikoua has a more northerly distribution. We monitored how its fruiting phenology has adapted in response to a highly seasonal environment. Male trees (where fig wasps reproduce) had one to three crops annually, whereas many seed-producing female trees produced only one fig crop. The timing of release of Ceratosolen fig wasps from male figs in late May and June was synchronized with the presence of receptive figs on female trees, at a time when there were few receptive figs on male trees, thereby ensuring seed set while allowing remnant pollinator populations to persist. F. tikoua phenology has converged with those of other (unrelated) northern Ficus species, but there are differences. Unlike F. carica in Europe, all F. tikoua male figs contain male flowers, and unlike F. pumila in China, but like F. carica, it is the second annual generation of adult wasps that pollinate female figs. The phenologies of all three temperate fig trees generate annual bottlenecks in the size of pollinator populations and for female F. tikoua also a shortage of fig wasps that results in many figs failing to be pollinated.     

Variation in reproductive success within a subtropical fig/pollinator mutualism

Abstract. Plants pollinated by specialists are often thought to receive exceptionally high-quality pollinator service, but in relatively low and unpredictable quantities. We examine and reject this hypothesis for an obligate mutualism between a subtropical New World fig ( Ficus aurea ) and its species-specific pollinator ( Pegoscapus jimenezi ). Fig wasps lay eggs within the flowers they pollinate; their offspring destroy a large proportion of fig's seeds. In a 6-year study of this interaction in Florida, U.S.A., we found that pollination intensity was in fact relatively high. Also contrary to expectations, reproductive success of both mutualists (as well as other wasps cohabiting the figs) was extremely variable and generally low, at three different scales of sampling: among figs from a single crop of one tree (thirty-four figs), among crops produced at different times by that tree (126 figs), and across trees over a 1-year period (379 figs). Although variable, fig contents were not completely unpredictable. For example, seed and wasp numbers increased with the number of flowers in a fig, and female and male flower numbers increased together. Little is yet known about the causes either of these relationships or of the massive fig-to-fig variation itself, although there is some evidence that they exist in other fig species as well. Further investigations of these patterns should shed new light on the ecology and evolution of this mutualism.     

榕树–榕小蜂协同进化中的非对称性相互作用及其集合种群效应

在协同进化研究中,传统观点认为物种之间的相互作用是对称性的,在进化过程中将形成一个稳定的均衡状态或进化稳定策略。然而,近来的观测和实验数据表明,物种间的协同进化可能存在非对称性相互作用,而且这种非对称性可能造成集合种群效应(metapopulation effect)或形成非均衡状态(例如混沌,chaos)。本文利用"榕树–榕小蜂"这一经典的协同进化模式系统来介绍协同进化过程中的非对称性相互作用,以及这种非对称性如何产生集合种群效应。在榕–蜂共生系统中,栖身于榕果中的榕小蜂除了传粉小蜂之外,还有一些"投机"的非传粉小蜂。非传粉小蜂比传粉小蜂具有更强的竞争力,而榕树则可惩罚不合作的非传粉蜂,同时奖励合作的传粉小蜂,从而形成了复杂的非对称性种间相互作用。在某个斑块生境中,非传粉小蜂通过竞争作用排斥传粉小蜂,然而随着非传粉小蜂在蜂群中的比例不断升高,榕树惩罚作用(如落果等)常常会导致整个非传粉蜂群的数量急剧下降,甚至局域性灭绝。随后,其他斑块的传粉小蜂则迁移过来填补空白。然而,随着传粉小蜂种群的数量增长,该斑块又会集聚更多的投机性非传粉小蜂,进而诱发榕树再次进行惩罚。这样的非对称性相互作用导致了非传粉小蜂、传粉小蜂以及榕树种群的集合效应,其种群大小呈现周期性的"此消彼长"式的循环。     

Variation in inflorescence size in a dioecious fig tree and its consequences for the plant and its pollinator fig wasp

The host-specific relationship between fig trees (Ficus) and their pollinator wasps (Agaonidae) is a classic case of obligate mutualism. Pollinators reproduce within highly specialised inflorescences (figs) of fig trees that depend on the pollinator offspring for the dispersal of their pollen. About half of all fig trees are functionally dioecious, with separate male and female plants responsible for separate sexual functions. Pollen and the fig wasps that disperse it are produced within male figs, whereas female figs produce only seeds. Figs vary greatly in size between different species, with female flower numbers varying from tens to many thousands. Within species, the number of female flowers present in each fig is potentially a major determinant of the numbers of pollinator offspring and seeds produced. We recorded variation in female flower numbers within male and female figs of the dioecious Ficus montana growing under controlled conditions, and assessed the sources and consequences of inflorescence size variation for the reproductive success of the plants and their pollinator (Kradibia tentacularis). Female flower numbers varied greatly within and between plants, as did the reproductive success of the plants, and their pollinators. The numbers of pollinator offspring in male figs and seeds in female figs were positively correlated with female flower numbers, but the numbers of male flowers and a parasitoid of the pollinator were not. The significant variation in flower number among figs produced by different individuals growing under uniform conditions indicates that there is a genetic influence on inflorescence size and that this character may be subject to selection.     

Adaptive phenology of Ficus subpisocarpa and Ficus caulocarpa in Taipei,Taiwan

Insect pollination is the main strategy used by Angiosperm plants to transport pollen to another individual. The interaction between entomophilous plants and their pollinators is often mutualistic, with many species pairs being interdependent. In obligate pollination mutualism, the plant relies on its partner for pollination, whereas the pollen vector relies on plant resources. In the mutualism between Ficus (Moraceae) and the fig wasps (Hymenoptera, Agaonidae), the plant provides oviposition sites to its exclusive pollinator, which has an extremely short lifespan (a maximum lifespan of few days). This study examined how fig trees maintain their associated pollinator populations by conducting a 45-month phenological survey of 27 and 64 trees belonging to the species Ficus caulocarpa and F. subpisocarpa in Taipei, Taiwan. The observations indicated that the trees produce figs year-round with no clear seasonal pattern, and are not affected by meteorological factors. On average, about 30% of the trees of both species were bearing figs during the survey. The duration of the fig development was longer during the winter-spring period than during the summer-fall period. The trees displayed strong asynchrony among trees in the population but each crop was synchronous within a tree. However, after wasp emergence, crops lost their synchrony with part of the figs ripening within few days whereas some figs only ripened eight weeks later for F. subpisocarpa and four weeks later for F. caulocarpa. This study also discusses the implications of fig frugivory and mutualism.     

鸡嗉子榕隐头果雌花期特征对传粉榕小蜂选择的影响

为了探讨榕树隐头果的发育期、性别、大小等外部特征对传粉榕小蜂选择的影响,采取人为控制雌花期的方法,对鸡嗉子榕(Ficus sermicordata)及其传粉榕小蜂(Ceratosolen gravelyi)的选择行为进行研究。结果表明,在隐头花序发育到雌花期后,如果阻止传粉小蜂进入,隐头果会继续生长。直径较小的雌果和雄果的进蜂量较多,且在雌雄果同时存在时,小蜂仍然会选择进入雌果,但进蜂量显著低于雄果。小蜂优先选择进入雌花期前期的隐头花序,雌雄果皆有此特点。对于相同发育期的隐头果,果径和进蜂量呈正相关关系,说明对于相同发育期的隐头果,小蜂更倾向于进入较大的隐头果。因此,真正控制小蜂行为的是隐头花序所处的发育期,以及不同发育期所产生的化学挥发物,而非隐头果直径大小。这为进一步研究榕-蜂系统的稳定机制提供依据。     

Making the most of your pollinators: An epiphytic fig tree encourages its pollinators to roam between figs

Ficus species are characterized by their unusual enclosed inflorescences (figs) and their relationship with obligate pollinator fig wasps (Agaonidae). Fig trees have a variety of growth forms, but true epiphytes are rare, and one example is Ficus deltoidea of Southeast Asia. Presumably as an adaptation to epiphytism, inflorescence design in this species is exceptional, with very few flowers in female (seed‐producing) figs and unusually large seeds. Figs on male (pollinator offspring‐generating) trees have many more flowers. Many fig wasps pollinate one fig each, but because of the low number of flowers per fig, efficient utilization by F. deltoidea''s pollinators depends on pollinators entering several female figs. We hypothesized that it is in the interest of the plants to allow pollinators to re‐emerge from figs on both male and female trees and that selection favors pollinator roaming because it increases their own reproductive success. Our manipulations of Blastophaga sp. pollinators in a Malaysian oil palm plantation confirmed that individual pollinators do routinely enter several figs of both sexes. Entering additional figs generated more seeds per pollinator on female trees and more pollinator offspring on male trees. Offspring sex ratios in subsequently entered figs were often less female‐biased than in the first figs they entered, which reduced their immediate value to male trees because only female offspring carry their pollen. Small numbers of large seeds in female figs of epiphytic F. deltoidea may reflect constraints on overall female fig size, because pollinator exploitation depends on mutual mimicry between male and female figs.     

Sexual differences in the attractiveness of figs to pollinators: females stay attractive for longer

1. Figs on male dioecious fig trees (Ficus, Moraceae) are breeding sites for pollinator fig wasps (Hymenoptera, Agaonidae), but figs on female plants are traps that produce only seeds. As the short‐lived fig wasps cannot reproduce in female figs, natural selection should favour individuals that avoid them. Several studies have failed to detect such discrimination, a result attributed to inter‐sexual mimicry and ‘selection to rush’ in the wasps, but their experiments failed to explicitly take into account fig age (how long they had been waiting to be pollinated). 2. We compared the relative attraction of male and female figs of known ages of the South East Asian Ficus montana Burm. f. to its pollina tor Liporrhopalum tentacularis Grandi and examined how the reproductive success of the plant and its pollinator change with the age of the figs. 3. Mean retention time for un‐pollinated figs on female plants was 16 days whereas in male figs it was 12 days. Female figs remained attractive for up to 2 weeks, although the wasps were less willing to enter older figs. After pollinator entry, receptivity continued for several days, lasting longer in figs entered by a single wasp. Consistent with abortion rates, attractiveness persisted longer in female figs. Older figs produced fewer fig wasp offspring, but similar numbers of seeds. 4. The sexual differences in floral longevity in F. montana may represent part of a previously un‐recognised reproductive strategy in some fig trees that allows male plants to ‘export’ pollinators while also maintaining a resident fig wasp population.     

Pollinators entering female dioecious figs: why commit suicide?

In the dioecious fig/pollinator mutualism, the female wasps that pollinate figs on female trees die without reproducing, whereas wasps that pollinate figs on male trees produce offspring. Selection should strongly favour wasps that avoid female figs and enter only male figs. Consequently, fig trees would not be pollinated and fig seed production would ultimately cease, leading to extinction of both wasp and fig. We experimentally presented pollinators in the wild (southern India) with a choice between male and female figs of a dioecious fig species, Ficus hispida L. Our results show that wasps do not systematically discriminate between sexes of F. hispida. We propose four hypotheses to explain why wasp choice has not evolved, and how a mutualism is thus maintained in which all wasps that pollinate female figs have zero fitness.     

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.     

Can chemical signals,responsible for mutualistic partner encounter,promote the specific exploitation of nursery pollination mutualisms? – The case of figs and fig wasps

In nursery pollination mutualisms, where pollinators reproduce within the inflorescence they pollinate, floral scents often play a major role in advertizing host location and rewards for the pollinator. However, chemical messages emitted by the plant that are responsible for the encounter of mutualist partners can also be used by parasites of these mutualisms to locate their host. Each species of Ficus (Moraceae) is involved in an obligatory nursery pollination mutualism with usually one pollinating fig wasp (Hymenoptera: Chalcidoidea: Agaonidae). In this interaction, volatile compounds emitted by receptive figs are responsible for the attraction of their specific pollinator. However, a large and diverse community of non-pollinating chalcidoid wasps can also parasitize this mutualism. We investigated whether the chemical message emitted by figs to attract their pollinator can promote the host specificity of non-pollinating fig wasps. We analysed the volatile compounds emitted by receptive figs of three sympatric Ficus species, namely, Ficus hispida L., Ficus racemosa L., and Ficus tinctoria G. Forster, and tested the attraction of the pollinator of F. hispida ( Ceratosolen solmsi marchali Mayr), and of one species of non-pollinating fig wasp [ Philotrypesis pilosa Mayr (Hymenoptera: Chalcidoidea: Pteromalidae)] to scents emitted by receptive figs of these three Ficus species. Analysis of the volatile compounds emitted by receptive figs revealed that the three Ficus species could be clearly distinguished by their chemical composition. Behavioural bioassays performed in a Y-tube olfactometer showed that both pollinator and parasite were attracted only by the specific odour of F. hispida . These results suggest that the use by non-pollinating fig wasps of a specific chemical message produced by figs could limit host shifts by non-pollinating fig wasps.     

First record of an apparently rare fig wasp feeding strategy: obligate seed predation

1. Fig trees require host‐specific agaonid fig wasps for pollination, but their figs also support numerous non‐pollinating fig wasps (NPFW) that gall fig tissues or develop as parasitoids. 2. Ficus microcarpa L. is widely naturalised outside its native range and the most invasive fig tree species. Seed predators are widely used for the biological control of invasive plants, but no obligate seed predatory (as opposed to ovule or fig wall galling) NPFW have been recorded previously from any fig trees. 3. Philotrypesis NPFW are usually regarded as parasitoids or ‘inquilines’ (parasitoids that also eat plant material) of pollinator fig wasps, but the present study provides evidence that Philotrypesis taiwanensis, a NPFW associated with F. microcarpa, is an obligate seed predator: (i) adults emerge from seeds of typical appearance, with a surrounding elaiosome; (ii) it shows no preference for figs occupied by fig wasp species, other than the pollinator; (iii) it only develops in figs that contain pollinated ovules, avoiding figs occupied by an agaonid that fails to pollinate; (iv) larvae are distributed in layers where seeds are concentrated and (v) it has a negative impact on seed but not pollinator offspring numbers. 4. Philotrypesis is a large genus, and further species are likely to be seed predators.     

Floral constraint resulting from intersexual mimicry in a gynodioecious fig tree

Fig trees (Ficus: Moraceae) are pollinated by female fig wasps (Agaonidae) whose larvae develop inside galled flowers of unusual inflorescences (figs). Most fig trees also support communities of non‐pollinating fig wasps. Figs of different species display great size variation and contain tens to tens of thousands of flowers. Around one‐half the species of fig trees have the gynodioecious breeding system, where female trees have figs that produce seeds and male trees have figs that support development of pollinators. Mutual mimicry between receptive male and female figs ensures that pollinators enter female figs, even though the insects will die without reproducing, but the need to give no sex‐specific cues to the pollinators may constrain differences in size between receptive male and female figs. We compared relationships between inflorescence size and some measures of reproductive success in male and female figs of Ficus montana grown under controlled conditions in the presence of the pollinator Kradibia tentacularis and its main parasitoid Sycoscapter sp. indesc. Female figs that contained more flowers produced more seeds, but male figs did not increase the production of female pollinator K. tentacularis fig wasps in proportion of the flower number. Although more flowers were galled by the pollinators in male figs containing more female flowers, the high larval mortality caused by parasitism and nutritional limitation prevented the increase in the production of adult female offspring. Selection may favor the increase in flower numbers within figs in female plants of F. montana, but contrarily constrain this attribute in male plants.     

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.     

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。     

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.     

钝叶榕(Ficus curtipes)非传粉小蜂交配行为

榕树及其传粉榕小蜂繁殖上相互依存,被认为是生物界中协同进化时间最悠久,相互关系最密切的一对生物;在大多数榕树种类的隐头花序内,除了传粉榕小蜂外,还共存着多种非传粉小蜂,它们的繁殖行为直接影响着榕树和传粉榕小蜂的繁殖和互惠稳定。钝叶榕(Ficus curtipes Corner),是一种雌雄同株的绞杀性榕树。研究在西双版纳热带植物园里共收集钝叶榕100个隐头果内的榕小蜂,获得9493号标本;其中,包括1种传粉小蜂和5种非传粉小蜂,钝叶榕传粉小蜂Eupristina sp.占总数的4466%,杨氏榕树金小蜂Diaziella yangi 占46.13%,而其它4种非传粉小蜂（Lipothymus sp., Sycobia sp., Philotrypesis sp.和Sycoscopter sp.）仅占9.20%。前3种榕小蜂雌蜂进到果腔产卵,其余3种在果外产卵。观测23个钝叶榕榕果出蜂情况发现,6种榕小蜂在钝叶榕隐头花序内遵循严格的羽化出蜂顺序,首先是Sycobia sp.,次之是Lipothymus sp.,再次之是杨氏榕树金小蜂,最后是钝叶榕传粉小蜂、Philotrypesis sp.和Sycoscopter sp.。5种非传粉小蜂的交配场所与雄蜂翅型无关,雄蜂有翅型的杨氏榕树金小蜂大部分交配在果内完成,而且它们的雄蜂为争夺交配机会存在激烈的打斗行为;雄蜂无翅型的Lipothymus sp.有部分雄蜂爬出隐头果,在果壁和附近的叶片背面交配;雄蜂有翅型的Sycobia sp.,其所有交配都发生在果外;Philotrypesis sp.和Sycoscopter sp. 雄蜂均无翅,它们的交配全发生在果内。局域配偶竞争使榕小蜂性比偏雌,杨氏榕树金小蜂雄蜂虽然有翅,但大部分交配发生在榕果内,这将影响其最佳的性比率。因此,依赖雄蜂翅型并不能很好地预测榕小蜂的交配场所和性比率。     

Putting your eggs in several baskets: oviposition in a wasp that walks between several figs

The interaction between figs (Ficus spp., Moraceae) and their pollinator fig wasps (Hymenoptera: Agaonidae) is an obligate mutualism, but females of dioecious fig trees exploit fig wasps without providing rewards. Figs are closed inflorescences that typically trap pollinator females after entry, but some fig wasp species can re‐emerge (although wingless) and subsequently oviposit in and pollinate further figs. Using glasshouse populations, we examined the sex ratios and clutches laid by single foundresses of Kradibia tentacularis (Grandi) in their first and subsequent male figs of Ficus montana Blume, and how the probability of emergence and entering a second fig varied between seasons. A maximum of four figs were entered by any one foundress. Wingless foundresses were able to locate and enter figs up to 60 cm from the first fig they entered, but the probability of entry declined sharply with distance from that fig. The foundresses that re‐emerged produced slightly higher adult offspring totals than those that failed to re‐emerge. Clutch sizes of a single foundress in its first fig equalled those in all the subsequent figs combined, with clutch size per fig decreasing when more figs were entered. Smaller clutches had less female‐biased sex ratios. Figs were more numerous in summer than in winter, but the proportion of figs entered by only wingless foundresses remained unchanged. Movement between figs increases pollinator reproductive success in male figs, thereby encouraging foundresses that encounter a female tree to also move between and pollinate several female figs.     

Fig choice by the pollinator of a gynodioecious fig: selection to rush,or intersexual mimicry?

Due to selection to maximise the benefits accrued, conflicts of interest exist between mutualists. An extreme conflict occurs between gynodioecious fig trees and their pollinating wasps. Female wasps, which are required for pollination, cannot reproduce in female figs and should be selected to avoid them. We investigate fig choice in Liporrhopalum tentacularis , pollinator of Ficus montana . We show that entry rates are independent of fig sex and diameter, with wasps instead entering the first fig encountered (although significant between-tree differences in entry rates to figs were observed). This suggests that wasps are unable to discriminate between the sexes because of selection for inter-sexual fig mimicry. In conjuction with data on other species pairs, these findings imply that that the resolution of the conflict is ultimately under the tree's control, with the level of mimicry evolving in response to both the propensity of wasps to discriminate and the costs of them doing so.     

Ability to gall: the ultimate basis of host specificity in fig wasps?

1. Fig trees (Ficus spp.) and their host‐specific pollinator fig wasps (Agaonidae) are partners in an obligate mutualism. Receptive phase figs release specific volatiles to attract their pollinators, and this is generally effective in preventing pollinator species from entering figs of the wrong hosts. 2. If entry is attempted into atypical host figs, then ostiole size and shape and style length may also prevent reproduction. In spite of these barriers, there is increasing evidence that fig wasps enter atypical hosts, and that this can result in hybrid seed and fig wasp offspring. 3. This study examines the basis of pollinator specificity in two dioecious fig species from different geographical areas. Kradibia tentacularis pollinates Ficus montana in Asia. Ficus asperifolia from East Africa is closely related but is pollinated by a different species of Kradibia. 4. In glasshouses, K. tentacularis was attracted to its normal host, F1s and backcrosses, but only rarely entered figs of F. asperifolia. Foundresses were able to lay eggs in hybrids, backcrosses, and F. asperifolia, although flower occupancy was lowest in F. asperifolia figs and intermediate in hybrids. 5. The fig wasp failed to reproduce in female F. montana, male F. asperifolia, and male F1s, and most but not all backcrosses to F. montana. This was a result of the failure to initiate gall production. 6. Host specificity in this fig wasp is strongly influenced by host volatiles, but the ability to gall may be the ultimate determinant of whether it can reproduce.