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。     

Biogeography and divergence times in the mulberry family (Moraceae)

The biogeographical history of the mulberry family (Moraceae) was investigated using phylogenetic inferences from nuclear and chloroplast DNA, molecular dating with multiple fossil calibrations, and independent geological evidence. The Moraceae are centered in the tropics which has invited the hypothesis that the family has Gondwanan origins and extant distribution is the result of vicariance due to the break-up of Gondwana. However, the cosmopolitan distribution of Moraceae suggests a more complicated biogeographical history. The timing and location of Moraceae diversification also bears on the origin of the fig pollination mutualism, a model for the study of coevolution and specialization. Recent molecular dating of pollinating fig wasps suggested that an ancient Gondwanan origin coupled with vicariance and dispersal could account for the present day distribution of the mutualism. Here, we provide the first assessment of this hypothesis based on dating of figs and their relatives. Minimum age estimates suggest that the Moraceae had diversified by at least the mid-Cretaceous and major clades including the figs may have radiated during the Tertiary after the break-up of Gondwanaland. Molecular evidence together with Eurasian fossils suggest that the early diversification of Moraceae in Eurasia and subsequent migration into the southern hemisphere is at least as plausible as the Gondwanan hypothesis. These findings invite a reevaluation of the biogeography of fig pollination and highlight the need for incorporating multiple sources of evidence in biogeographical reconstructions.     

西双版纳聚果榕隐头果内小蜂群落结构及种间关系

聚果榕Ficus racemosa Linn.是雌雄同株榕树,它是西双版纳热带雨林生态系统中的一个常见种群。聚果榕必须依靠聚果榕小蜂Ceratosolen fusciceps Mayr传粉才能获得有性繁殖,而聚果榕小蜂又必须依靠聚果榕隐头果内短柱花繁衍后代,两者间形成了种间专一的互惠共生体系。同时,在其隐头果内还存在一个复杂的非传粉小蜂功能群,它们主要是榕树种子和传粉榕小蜂的寄生者。在云南省西双版纳自治州勐腊县勐仑镇选取了5个样地,对聚果榕单果内小蜂群落组成和种间相互关系进行研究。在不同时间段采集聚果榕单果242个,共收集小蜂366660头。聚果榕隐头果内有6种小蜂,隶属小蜂总科Chalcidoidae中的榕小蜂科Agaonidae、长尾小蜂科Caliimomidae、金小蜂科Pteromalidae,其中榕小蜂科中的C．fusciceps是聚果榕唯一的传粉者。金小蜂科中的Apocryta westwoodi Grandi和Apocryta sp.两个种是榕小蜂的寄生者,它们的寄生是传粉榕小蜂的种群数量减少因素之一。长尾小蜂科中Platyneura agraensis Joseph,Platyneura mayri Rasplus和Platyneura testacea Motschulsky3个种是寄生榕树种子或与榕小蜂争夺食物(瘿花)资源的小蜂类群,它们的出现与发生,致使聚果榕正在发育成种子的长柱小花形成瘿花,同时一部分种类把卵寄生在已被榕小蜂产卵的短柱小花子房中与榕小蜂争夺食物资源,致使榕小蜂食物资源的匮乏而死亡,对传粉小蜂种群有明显的影响。传粉小蜂从花托口钻入隐头果内,在隐头果内的长柱小花传粉和短柱小花子房中产卵,5种非传粉小蜂从隐头果外部把产卵器刺穿果肉把卵产在小花子房上。通过对5块样地隐头果内小蜂群落的综合分析发现,传粉榕小蜂为优势种群,而Apocryta sp.种的数量最少。在传粉及非传粉小蜂自然群体中各种类性比明显具有偏雌现象。小蜂群落表现异常的是聚果榕孤立株的样地,该样地传粉小蜂个体数量明显下降,非传粉小蜂个体数量则增加,各小蜂种群之间竞争激烈,出现C．fusciceps和P．mayri两个优势种。     

Spatial genetic structure and restricted gene flow in a functionally dioecious fig, <Emphasis Type="Italic">Ficus pumila</Emphasis> L. var. <Emphasis Type="Italic">pumila</Emphasis> (Moraceae)

The mutualism between fig plants and fig wasps has been recognized as one of the most specialized systems of symbiosis. Figs are pollinated by their highly specific pollinating fig wasps, and the pollinating fig wasps are raised within the syconia of figs. Recent studies indicated a difference between monoecious and dioecious figs in the dispersal range of pollinating wasps, which has potential consequences for gene flow. In this study, we detected the gene-flow pattern of the dioecious climbing fig, Ficus pumila L. var. pumila, at both local and regional scales. At the local scale, spatial autocorrelation analysis indicated strong genetic structure at short distances, a pattern of limited gene flow. This result was also supported by a high inbreeding coefficient (F _IS = 0.287) and significant substructuring (F _ST = 0.060; P < 0.001). Further analysis indicated that the effective gene dispersal range was 1,211 m, and the relative contribution of seed dispersal was smaller than that of pollen dispersal. The inferred effective range of pollen dispersal ranged from 989 to 1,712 m, while the effective seed dispersal range was less than 989 m. Lack of long-distance dispersal agents may explain the limited seed dispersal. The high density of receptive fig trees was the most likely explanation for limited pollen dispersal, and the position of syconia and relatively low wind speed beneath the canopy may contribute to this phenomenon. At the regional scale, significant negative correlations (kinship coefficient F _ij ranging from −0.038 to −0.071) existed in all comparisons between the studied population and other populations, and the assignment test grouped almost all individuals of the studied population into a distinct cluster. Asynchronous flowering on the regional scale, which provides a barrier for the pollinating wasps to fly from the studied population to the other populations, is probably responsible for the limited gene flow on the regional scale.     

歪叶榕非传粉小蜂的繁殖策略及其对榕-蜂共生系统的影响

2004年8月至2005年8月在西双版纳热带植物园内,通过广泛收集歪叶榕榕小蜂标本、非传粉小蜂产卵行为学观察和阻止传粉者入果等实验方法,研究了我国西双版纳热带雨林下的一种榕树——歪叶榕Ficus cyrtophylla的榕小蜂群落组成结构、非传粉小蜂的繁殖策略以及它们对榕-蜂共生系统的影响。结果表明,歪叶榕中除了具有唯一传粉榕小蜂Blastophag sp.以外,还具有3种非传粉小蜂Platyneura sp.、Philotrypesis sp.和Sycoscapter sp.。在歪叶榕榕小蜂群落中,传粉榕小蜂占整个群落总数的92.21%,是群落的最主要组成者;主要的非传粉小蜂是Sycoscaptersp.,占5.78%; 其次是Philotrypesissp.,占1.84%,而Platyneurasp.仅占群落总数的0.17%。歪叶榕中的非传粉小蜂通过各自产卵时间和食性分化的策略来利用榕果中的资源繁殖后代。非传粉小蜂寄生使传粉榕小蜂的总数和其雌蜂数量都显著地降低,但是对传粉小蜂雄蜂数量没有显著影响,从而导致传粉榕小蜂的雄性性比显著地增加。这说明非传粉小蜂在选择寄居宿主时具有明显的倾向性,而且更多地将卵产于含有雌性传粉小蜂的瘿花之中。因此,非传粉小蜂通过减少雌性传粉小蜂的数量而降低了榕树的雄性适合度,从而在一定程度上对榕 蜂共生系统的稳定存在和发展产生了负面影响。     

N:P stoichiometry in Ficus racemosa and its mutualistic pollinator

Aims Nitrogen (N) and phosphorus (P) are limiting nutrients to life across a variety of ecosystems. N:P stoichiometry, concerning the balance of these two elements, has recently received great attention. However, little is known about the nature of N:P stoichiometry in obligate mutualism.Methods N:P stoichiometry of Ficus racemosa and its pollinating wasp Ceratosolen fusciceps, an example of coevolving obligate mutualism, was investigated, and the N:P stoichiometric traits of male versus female wasps were compared.Important findings Nutrient concentrations in C. fusciceps were much higher than in its host. N enrichment in fig wasp was evidently stronger than phosphorus. N concentrations of male fig wasps were significantly higher than those of females, while P concentrations of female fig wasps were remarkably higher than those of male ones. Therefore, N:P ratios in male fig wasps were significantly greater than in female fig wasps. N:P ratio in fig-pollinating wasp displayed linear functions to fig N contents, suggesting that N limitation in fig wasps may dominate the nutritional relationship between fig pollinator and its host. Fig wasp population size had significant influences on N concentrations in host fig and female wasp per se. Driven by the nutritional stress of pollinating and parasite insects, fig fruit preferred increasing its diameter first but not nutrient richness. Values for N and P contents of fig pollinators showed seasonal differences with greater N:P ratios in dry season than in rainy season. The observations suggest that tropical climate change would result in more severe N limitation to fig-pollinating wasp and may further influence the stability of fig–fig wasp mutualism.     

Phylogenetic relationships, historical biogeography and character evolution of fig-pollinating wasps

Nucleotide sequences from the cytochrome oxidase I (COI) gene were used to reconstruct phylogenetic relationships among 15 genera of fig-pollinating wasps. We present evidence supporting broad-level co-cladogenesis with respect to most but not all of the corresponding groups of figs. Using fossil evidence for calibrating a molecular clock for these data, we estimated the origin of the fig-wasp mutualism to have occurred ca. 90 million years ago. The estimated divergence times among the pollinator genera and their current geographical distributions corresponded well with several features of the break-up of the southern continents during the Late Cretaceous period. We then explored the evolutionary trajectories of two characteristics that hold profound consequences for both partners in the mutualism: the breeding system of the host (monoecious or dioecious) and pollination behaviour of the wasp (passive or active). The fig wasp mutualism exhibits extraordinarily long-term evolutionary stability despite clearly identifiable conflicts of interest between the interactors, which are reflected by the very distinct variations found on the basic mutualistic theme.     

薜荔榕小蜂对薜荔和爱玉子雌花期榕果挥发物的行为反应

薜荔和爱玉子均属雌雄异株桑科榕属植物,两者互为原变种与变种的关系,分别与薜荔传粉小蜂和爱玉子传粉小蜂(二者互为隐存种)建立了专性共生关系,榕树榕果挥发物在维系传粉小蜂与其寄主的共生关系上起着重要作用。利用Y型嗅觉仪测定薜荔榕小蜂(薜荔和爱玉子的传粉小蜂)对薜荔和爱玉子雌花期榕果挥发物的行为反应。结果表明:(1)雌花期果型的大小对薜荔榕小蜂行为反应无显著影响,薜荔大、小果型雌花期雌(雄)榕果挥发物对其传粉小蜂均具有强烈的吸引作用;(2)榕果挥发物浓度影响薜荔榕小蜂行为反应,薜荔、爱玉子雌花期雌(雄)榕果挥发物对其传粉小蜂的吸引作用均可能存在阈值反应,即榕果挥发物浓度未超过阈值时,雌花期榕果挥发物对传粉小蜂的吸引作用与挥发物浓度成正相关关系,而一旦超过阈值,榕果挥发物对传粉蜂的吸引作用显著下降,表明寄主榕果挥发物浓度影响传粉小蜂的寄主定位;(3)薜荔传粉小蜂对低浓度爱玉子雌花期雌(雄)榕果挥发物、爱玉子传粉小蜂对低浓度薜荔雌花期雌(雄)榕果挥发物均既无趋向也无驱避行为;薜荔传粉小蜂对高浓度的爱玉子雌花期雌(雄)榕果挥发物表现为显著的驱避行为,而爱玉子传粉小蜂对高浓度薜荔雌(雄)雌花期榕果挥发物表现为显著的趋向行为,因此,薜荔传粉小蜂与爱玉子传粉小蜂存在寄主专一性不对称现象,爱玉子传粉小蜂进入薜荔雌(雄)果内传粉或产卵的可能性较大,而福州地区的薜荔传粉小蜂可能难以进入爱玉子雌(雄)果内传粉或产卵。本研究结果将为榕-蜂共生体系的化学生态学理论研究以及爱玉子栽培提供科学依据。     

Dispersal and fighting in male pollinating fig wasps

For more than two decades, it has been the dogma that the males of pollinating fig wasps do not fight and that they only mate in their native fig. Their extreme degree of local mating leads to highly female biased sex ratios that should eliminate the benefits of fighting and dispersal by males. Furthermore, males sharing a fig are often brothers, and fighting may be barred by kin selection. Therefore, theory supported the presumed absence of fighting and dispersal in pollinating fig wasp males. However, we report here that in pollinating fig wasps, fighting between brothers evolved at least four and possibly six time, and dispersal by males at least twice. This finding supports the idea that competition between relatives can cancel the ameliorating effects of relatedness. The explanation to this evolutionary puzzle, as well as the consequences of male dispersal and fighting, opens the doors to exciting new research.     

Physiological determinants of Ficus fruit temperature and implications for survival of pollinator wasp species: comparative physiology through an energy budget approach

Figs are completely dependent for pollen dispersal on species-specific fig-pollinating wasps that develop within developing fig fruits. These wasps are very sensitive to heat and die at temperatures only a few degrees above ambient. Such temperatures are expected and observed in objects exposed to full sunlight, as fig fruits frequently are. In detailed field and experimental studies of 11 species of Panamanian figs with fruit ranging in size from 5 mm to 50 mm in diameter, we found that both the relative and absolute contribution of transpiration to maintaining non-lethal fruit temperatures increased with fruit size. Small and large fruits reached temperatures of 3 and 8°C, respectively, above air temperature in full sunlight when transpiration was prevented by grease. The temperature reached by large, nontranspiring fruits was sufficient to kill their pollinators. Control fruits which transpired reached temperatures of 2–3°C above air temperature in sunlight, regardless of size. An analysis of the solar energy budget of fruit revealed that large fruits must transpire to maintain tolerable temperatures for the wasps because heat diffusion from fruit to air was too low to balance net radiation in sunlight. By contrast, small fruits do not need to transpire to maintain tolerable temperatures for the pollinators.     

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。     

榕树传粉昆虫榕小蜂染色体制备方法研究

榕树与其传粉昆虫榕小蜂之间具有高度专一的互惠共生关系,榕小蜂为榕树传粉的同时又在榕果内营寄生生活,直至完成其整个生活史,因此一直以来对榕小蜂的染色体研究存在很大困难。本文以对叶榕Ficus hispida传粉榕小蜂Ceratosolen solmsi和鸡嗉子榕F.semicordata传粉榕小蜂C.gravelyi为材料,摸索出一套适合于榕树传粉昆虫榕小蜂染色体研究的详细、有效的技术和方法。应用该法对对叶榕传粉榕小蜂C.solmsi和鸡嗉子榕传粉榕小蜂C.gravelyi的染色体核型进行了研究,结果表明两种榕小蜂的染色体核型特征非常相似,具有相同的染色体数目2n(♀)=10,染色体类型全部为中着丝粒染色体,臂数NF=20。此外,在相对长度方面两者也没有明显的差异。最后与Imai等1988年研究蚂蚁染色体时提出的方法进行了比较。利用本文介绍的方法进行榕小蜂染色体制备,操作过程简单、重复性强,不仅能够得到大量的染色体分裂相,而且染色体细胞界限明确、形态清晰、分散良好。     

Geographic structuring into vicariant species-pairs in a wide-ranging,high-dispersal plant–insect mutualism: the case of <Emphasis Type="Italic">Ficus racemosa</Emphasis> and its pollinating wasps

Ficus and their mutualistic pollinating wasps provide a unique model to investigate joint diversification in a high dispersal system. We investigate genetic structuring in an extremely wide-ranging Ficus species, Ficus racemosa, and its pollinating wasp throughout their range, which extends from India to Australia. Our samples were structured into four large, vicariant populations of figs and wasps which may correspond to distinct (sub)species, located in India, China-Thailand, Borneo, and Australia. However, the genetically most divergent group was the Indian population for the figs and the China-Thailand population for the wasps, suggesting different evolutionary histories of populations. Molecular dating for the wasps shows that diversification of the pollinator clade is surprisingly old, beginning about 13.6 Ma. Data on both the host fig species and its pollinating wasps suggest that strong genetic flow within biogeographic groups over several hundreds of kilometers has limited genetic and morphological differentiation and, potentially, local adaptation. This is probably due to long-distance dispersal of pollinating wasps. The genetic clustering into large geographic units observed in F. racemosa and its pollinators is reminiscent of what can be observed in some other high-dispersal organisms characterized by morphology that varies little over huge distances. The implications of strong gene flow for diversification processes and adaptation to different ecological conditions in Ficus and their pollinating wasps are just beginning to emerge.     

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.     

Molecular phylogenies of figs and fig-pollinating wasps in the Ryukyu and Bonin (Ogasawara) islands, Japan

The interaction between figs (Ficus, Moraceae) and fig-pollinating wasps (Chalcidoidea, Agaonidae) is one of the most specific mutualisms, and thus is a model system for studying coevolution and cospeciation. In this study we focused on figs and their associated fig-wasps found in the Ryukyu and Bonin (Ogasawara) Islands, Japan, because it has been suggested that breakdown in the specificity may occur in islands or at edge of a species' distribution. We collected 136 samples of 15 native fig species and 95 samples of 13 associated fig-wasps from all major islands in the Ryukyu Islands, including two fig species and one fig-wasp species endemic to the Bonin Islands. We performed molecular phylogenetic analyses using plastid DNA and nuclear ITS sequences for the figs and nuclear 28S rRNA and mitochondrial COI genes for the fig-wasps to investigate the interspecific phylogenies and intraspecific variation within the mutualism. Our phylogenetic analyses using multiple samples per species show the single clade of each fig (except the Bonin endemic species) and fig-pollinating wasp species. Fig species belonging to the same subgenera formed well-supported clades in both plastid and ITS trees, except for the subgenus Urostigma. Likewise, fig wasps emerging from host fig species belonging to the same subgenera formed mostly well supported clades in both 28S and COI trees. Host specificity between the figs and fig-wasps functions strictly in these islands. There was very little sequence variation within species, and that no major geographic structure was found. The two Bonin endemic species (F. boninsimae and F. nishimurae) or their common ancestor and the associated fig-wasps (Blastophaga sp.) are apparently derived from F. erecta and its associated fig-wasps (B. nipponica), respectively, and probably migrated from the Ryukyu Islands.     

Culture-Free Survey Reveals Diverse and Distinctive Fungal Communities Associated with Developing Figs (Ficus spp.) in Panama

The ancient association of figs (Ficus spp.) and their pollinating wasps (fig wasps; Chalcidoidea, Hymenoptera) is one of the most interdependent plant–insect mutualisms known. In addition to pollinating wasps, a diverse community of organisms develops within the microcosm of the fig inflorescence and fruit. To better understand the multipartite context of the fig–fig wasp association, we used a culture-free approach to examine fungal communities associated with syconia of six species of Ficus and their pollinating wasps in lowland Panama. Diverse fungi were recovered from surface-sterilized flowers of all Ficus species, including gall- and seed flowers at four developmental stages. Fungal communities in syconia and on pollinating wasps were similar, dominated by diverse and previously unknown Saccharomycotina, and distinct from leaf- and stem endophyte communities in the same region. Before pollination, fungal communities were similar between gall- and seed flowers and among Ficus species. However, fungal communities differed significantly in flowers after pollination vs. before pollination, and between anciently diverged lineages of Ficus with active vs. passive pollination syndromes. Within groups of relatively closely related figs, there was little evidence for strict-sense host specificity between figs and particular fungal species. Instead, mixing of fungal communities among related figs, coupled with evidence for possible transfer by pollinating wasps, is consistent with recent suggestions of pollinator mixing within syconia. In turn, changes in fungal communities during fig development and ripening suggest an unexplored role of yeasts in the context of the fig–pollinator wasp mutualism.     

Do Fig Wasps Produce Mixed Paternity Clutches?

Pollinating fig wasps (Hymenoptera, Agaonidae) have been the focus of numerous studies examining sex ratio evolution. Recently, molecular genetic techniques have been introduced that assume single matings in fig wasps, yet their mating biology has not been investigated genetically. We used recently developed microsatellite markers to investigate whether a pollinating fig wasp (Liporrhopalum tentacularis Grandi) produces single or mixed paternity clutches. The clutches of 12 females which had had the opportunity to mate with males of different genotypes were investigated. The results suggest that, at least in this species of fig wasp, single paternity clutches are the norm. Based on our behavioural observations, this appears to be due to mating with a single male rather than sperm competition.     

Digest: Process‐based phylogenetic models provide unique insights into the evolution of mutualistic networks*

Figs and their pollinating fig wasps are a classic example of long‐term obligate associations between different species. Satler et al. use a process‐based model adopted from molecular evolution to identify the major processes that affect cophylogenetic matching between figs and fig wasps. They find that host‐switching is one of the most important evolutionary processes contributing to current cophylogenetic patterns, illustrating the value of probabilistic approaches to studying the evolutionary history of mutualisms.     

榕树高度专性共生体系内影响传粉蜂子代繁殖的因素

为探讨影响传粉蜂子代数量及性比的因素,以广州地区分布的粗叶榕(Ficus hirta Vahl)及其传粉小蜂爪哇榕小蜂(Valasia javana Mayr)为材料,采用自然收蜂与控制放蜂试验进行研究。结果表明,果内的榕小蜂群落随季节更替发生显著变化,非传粉蜂的介入、季节差异使雌蜂间的干扰强度不同,导致传粉蜂子代数量发生变化,其中雌蜂间的干扰会使传粉蜂性比显著升高,而非传粉蜂的介入对传粉蜂性比的影响不大,传粉蜂仍能正常地进行繁殖。另外,传粉蜂在雌花期雄花序内的产卵和存活时间一般较短,约为15 h;传粉蜂子代在干、湿季的雄花序内的发育时间差异显著,干季时间长,湿季时间短。这表明传粉榕小蜂进化出了适应广州地区季节变化的繁殖策略。     

Restructuring of a mutualism following introduction of Australian fig trees and pollinating wasps to Europe and the USA

Figs and fig-pollinating wasps are obligate mutualists that require each other to complete sexual reproduction. However, landscapers can establish populations of fig trees outside their native ranges by propagation through exported seeds, seedlings or cuttings. Once mature, these trees could be colonized by pollinating wasps and/or various non-pollinating wasps that also develop in figs. In recent decades, the Australian endemic Ficus rubiginosa has been planted widely in the Mediterranean region and in parts of the USA. Observation of ripe fruit production suggested that a pollination mutualism has been re-established by pollinating wasps colonizing trees in the plant’s introduced range. We therefore used sampling of pollinators from mainland Spain, Tenerife and California (USA) and molecular studies to characterize the restructured mutualism and compare it with the native range. In the native range, the plant is pollinated by five wasp species that form the Pleistodontes imperialis complex. However, all wasps in the introduced ranges belonged to just one of these species (P. imperialis sp. 1). Moreover, their mtDNA diversity was close to zero and the sequences clearly link them with the native southern population of this species. None of the?>?20 non-pollinating wasp species from the native range were found in the introduced ranges. In summary, the restructured mutualism has been dramatically simplified, lacking all non-pollinating wasps and all but one pollinator species from the native range. Moreover, the one pollinator species to establish successfully shows a drastic reduction in genetic diversity relative to its source population.