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.© 2013 Springer-Verlag Wien.
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Male insects rarely collaborate with each other, but pollinator fig wasps (Hymenoptera: Agaonidae) are said to be an exception. Immature fig wasps feed on galled ovules located inside figs, the inflorescences of Ficus species (Moraceae). After mating, adult pollinator males chew communal exit-holes that allow mated females (which are often also their siblings) to escape. Figs also support non-pollinating fig wasps (NPFWs), some of which produce exit-holes independently. We determined whether collaboration between pollinator males (Kradibia tentacularis from Ficus montana) was necessary for the release of their females, and used the relationship between male numbers and likelihood of success to measure the extent of cooperation during exit-hole production. These attributes were then compared with those of an NPFW (Sycoscapter sp.) from the same host plant. Pollinators were more abundant than NPFW, but their more female-biased sex ratio meant male pollinator densities were only slightly higher. Individual males of both species could produce an exit-hole. Single males of the NPFW were just as successful as single male pollinators, but only male pollinators cooperated effectively, becoming more successful as their numbers increased. The lack of cooperation among NPFW may be linked to their earlier period of intense inter-male aggression.
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Climatic oscillations during the last few million years had well-documented effects on the distributions and genomes of temperate plants and animals, but much less is known of their impacts on tropical and subtropical species. In contrast to Europe and North America, ice-sheets did not cover most of China during glacial periods, and the effects of glacial cycles were less dramatic. Fig trees are a predominantly tropical group pollinated by host-specific fig wasps. We employed partial mitochondrial COI (918 bp) and nuclear ITS2 (462 bp) gene sequences to investigate the genetic structure and demographic histories of the wasps that pollinate the subtropical Ficus pumila var. pumila in Southeastern China. Deep genetic divergence in both mitochondrial (7.2-11.6%) and nuclear genes (1.6-2.9%) indicates that three pollinator species are present and that they diverged about 4.72 and 6.00 Myr bp. This predates the Quaternary ice ages, but corresponds with the formation of the Taiwan Strait and uplifting of the Wuyi-Xianxia Mountains. The three pollinators have largely allopatric distribution patterns in China and display different postglacial demographic histories. Wiebesia spp. 1 and 2 occupy, respectively, the northern and southern regions of the mainland host range. Their populations both underwent significant postglacial spatial expansions, but at different times and at different rates.Wiebesia sp. 3 is largely restricted to northern islands and shows less evidence of recent population expansion. Their mainly allopatric distributions and different demographic histories are consistent with host plant postglacial expansion from three distinct refugia and suggest one mechanism whereby fig trees gain multiple pollinators.
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Figs are the inflorescences of fig trees (Ficus spp., Moraceae). They are shaped like a hollow ball, lined on their inner surface by numerous tiny female flowers. Pollination is carried out by host-specific fig wasps (Agaonidae). Female pollinators enter the figs through a narrow entrance gate and once inside can walk around on a platform generated by the stigmas of the flowers. They lay their eggs into the ovules, via the stigmas and styles, and also gall the flowers, causing the ovules to expand and their pedicels to elongate. A single pollinator larva develops in each galled ovule. Numerous species of non-pollinating fig wasps (NPFW, belonging to other families of Chalcidoidea) also make use of galled ovules in the figs. Some initiate galls, others make use of pollinator-generated galls, killing pollinator larvae. Most NPFW oviposit from the outside of figs, making peripherally-located pollinator larvae more prone to attack. Style length variation is high among monoecious Ficus spp. and pollinators mainly oviposit into more centrally-located ovules, with shorter styles. Style length variation is lower in male (wasp-producing) figs of dioecious Ficus spp., making ovules equally vulnerable to attack by NPFW at the time that pollinators oviposit. We recorded the spatial distributions of galled ovules in mature male figs of the dioecious Ficus hirta in Southern China. The galls contained pollinators and three NPFW that kill them. Pollinators were concentrated in galls located towards the centre of the figs, NPFW towards the periphery. Due to greater pedicel elongation by male galls, male pollinators became located in more central galls than their females, and so were less likely to be attacked. This helps ensure that sufficient males survive, despite strongly female-biased sex ratios, and may be a consequence of the pollinator females laying mostly male eggs at the start of oviposition sequences.© 2012 Yu, Compton.
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Pollinator fig wasps (Agaonidae) are a model system for studies of sex ratio evolution. They lay their eggs in galled ovules within figs. Only one adult emerges from each gall, suggesting that only one egg is always laid per ovule, but if double oviposition occurs then the assumption that adult (realised) sex ratios of fig wasps are representative of primary sex ratios may be violated. Many galls also fail to produce any wasps. If they initially contained eggs then differential mortality rates may also modify realized sex ratios. We investigated whether Kradibia (= Liporrhopalum) tentacularis foundresses in Ficus montana figs avoid laying in ovules that already contain eggs. Comparisons of oviposition frequencies and wasp emergence frequencies showed that most galls that failed to produce wasps will have had eggs laid in them, but few occupied ovules contained two eggs. Realised sex ratios therefore do not necessarily reflect primary sex ratios in this species, but double oviposition is not responsible.© 2011 Springer Science+Business Media, LLC.
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In ecological situations where interactions between two species are to their mutual benefit, traits are expected to evolve to maximise the value of the timing of their encounters. Plants that depend on animals for pollination vary in the longevity of their flowers and also in how the quality of the rewards they offer varies in flowers of different ages. However, costs of floral longevity are rarely studied. Using field experiments with Ficus semicordata, a SE Asian dioecious fig tree, we examined sexual differences in syconium ageing, how the reproductive success of the plant and its pollinator change with syconium age and whether these changes are reflected in pollinator preferences. Un-pollinated syconia remained receptive to their host-specific pollinators for long periods, but eventually abort. Compared with male syconia, un-pollinated female syconia aborted more quickly and lost their ability to attract pollinators more quickly. Older pollinated female syconia were also more likely to abort. Further, declines in productivity with syconium age were also more apparent in female syconia, though older male syconia also produced fewer, smaller wasp offspring. The longevity costs are reflected in pollinator preferences. This suggests that sexual differences in duration of receptivity may be adaptive and a component of the reproductive strategies. It also indicates that placing fig wasps onto older syconia over-estimates their likelihood of being pollinated under natural conditions and prolonged receptivity increases the likelihood of pollination at the cost of reduced productivity with syconium age. This opens interesting perspectives on the co-evolution of this inter-specific interaction.© 2011 Springer Science+Business Media B.V.
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Females of the pollinator fig wasp Elisabethiella baijnathi Wiebes carry mites (Tarsonemella sp. nr. africanus) and nematodes (Parasitodiplogaster sp.) between figs of Ficus burtt-davyi in Grahamstown, South Africa. The mites are phoretic on the outside of the wasps and phytophagous, feeding on galled flowers. The nematodes are transported inside the wasps and eventually eat them. Both mites and nematodes were present throughout the year. The prevalence (fig occupancy rates) of mites and nematodes in different crops ranged between zero and 100 %. Crop size did not influence the prevalence of either mites or nematodes. Contrasting dispersion patterns and relationships with fig wasp foundress numbers indicate that the mites, but not the nematodes, disperse between figs after being carried there by the pollinators, and they may also utilize non-pollinating fig wasps as vectors.
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In the specific mutualism between fig trees (Ficus) and their obligate pollinating fig wasps (Agaonidae), it is crucial that fig wasps can recognize the developmental stages of their host figs. However, the responses of fig wasps to volatiles released from figs during their developmental phases are less clearly understood and are the focus of this study. We extracted and identified the volatiles released from the figs of Ficus curtipes throughout their development. Using Y-tube choice experiments, we also compared the behavioural responses of the tree's pollinator (Eupristina sp.) to figs at different developmental stages, and compared these results to those obtained by trapping fig wasps as they arrived at a tree with a developing fig crop. The chemical composition of the fig volatiles changed during fig development with the blends exhibiting clear segregation among figs at different developmental phases. Male phase figs had the most distinct blend. Fig wasp females were preferentially attracted to receptive figs, but figs at most other developmental phases were also attractive. Conversely, male phase figs had a repellent effect. These results were supported by the behaviour of the wasps under natural conditions, with small numbers of fig wasps arriving at the tree before and after receptive figs were present. These results indicate a more complex relationship between fig volatiles and fig wasp behaviour than previously realized, with volatiles mediating both the initial meeting of the mutualists to achieve pollination and egg laying and the subsequent departure of the next generation of fig wasps. This offers an explanation for the specialization and long-term coexistence of figs and fig wasps.© 2012 Springer Basel AG.
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Climatic oscillations during the last few million years had well-documented effects on the distributions and genomes of temperate plants and animals, but much less is known of their impacts on tropical and subtropical species. In contrast to Europe and North America, ice-sheets did not cover most of China during glacial periods, and the effects of glacial cycles were less dramatic. Fig trees are a predominantly tropical group pollinated by host-specific fig wasps. We employed partial mitochondrial COI (918 bp) and nuclear ITS2 (462 bp) gene sequences to investigate the genetic structure anddemographic histories of the wasps that pollinate the subtropical Ficus pumila var. pumila in Southeastern China. Deep genetic divergence in both mitochondrial (7.2-11.6%) and nuclear genes (1.6-2.9%) indicates that three pollinator species are present and that they diverged about 4.72 and 6.00 Myr bp. This predates the Quaternary ice ages, but corresponds with the formation of the Taiwan Strait and uplifting of the Wuyi-Xianxia Mountains. The three pollinators have largely allopatric distribution patterns in China and display different postglacial demographic histories. Wiebesia spp. 1 and 2 occupy, respectively, the northern and southern regions of the mainland host range. Their populations both underwent significant postglacial spatial expansions, but at different times and at different rates. Wiebesia sp. 3 is largely restricted to northern islands and shows less evidence of recent population expansion. Their mainly allopatric distributions and different demographic histories are consistent with host plant postglacial expansion from three distinct refugia and suggest one mechanism whereby fig trees gain multiple pollinators.© 2012 Blackwell Publishing Ltd.
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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 figwasps and for the evolution of the fig tree-fig wasp symbiosis. © 2012 Springer Science+Business Media B.V.
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Gene flow strongly influences the regional genetic structuring of plant populations. Seed and pollen dispersal patterns can respond differently to the increased isolation resulting from habitat fragmentation, with unpredictable consequences for gene flow and population structuring. In a recently fragmented landscape we compared the pre- and post-fragmentation genetic structure of populations of a tree species where pollen and seed dispersal respond differentially to forest fragmentation generated by flooding. Castanopsis sclerophylla is wind-pollinated, with seeds that are dispersed by gravity and rodents. Using microsatellites, we found no significant difference in genetic diversity between pre- and post-fragmentation cohorts. Significant genetic structure was observed in pre-fragmentation cohorts, due to an unknown genetic barrier that had isolated one small population. Among post-fragmentation cohorts this genetic barrier had disappeared and genetic structure was significantly weakened. The strengths of genetic structuring were at a similar level in both cohorts, suggesting that overall gene flow of C. sclerophylla has been unchanged by fragmentation at the regional scale. Fragmentation has blocked seed dispersal among habitats, but this appears to have been compensated for by enhanced pollen dispersal, as indicated by the disappearance of a genetic barrier, probably as a result of increased wind speeds and easier pollen movement over water. Extensive pollen flow can counteract some negative effects of fragmentation and assist the long-term persistence of small remnant populations.
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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.© Springer Science+Business Media B.V. 2012.
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In the specific mutualism between fig trees (Ficus) and their obligate pollinating fig wasps (Agaonidae), it is crucial that fig wasps can recognize the developmental stages of their host figs. However, the responses of fig wasps to volatiles released from figs during their developmental phases are less clearly understood and are the focus of this study. We extracted and identified the volatiles released from the figs of Ficus curtipes throughout their development. Using Y-tube choice experiments, we also compared the behavioural responses of the tree's pollinator (Eupristina sp.) to figs at different developmental stages, and compared these results to those obtained by trapping fig wasps as they arrived at a tree with a developing fig crop. The chemical composition of the fig volatiles changed during fig development with the blends exhibiting clear segregation among figs at different developmental phases. Male phase figs had the most distinct blend. Fig wasp females were preferentially attracted to receptive figs, but figs at most other developmental phases were also attractive. Conversely, male phase figs had a repellent effect. These results were supported by the behaviour of the wasps under natural conditions, with small numbers of fig wasps arriving at the tree before and after receptive figs were present. These results indicate a more complex relationship between fig volatiles and fig wasp behaviour than previously realized, with volatiles mediating both the initial meeting of the mutualists to achieve pollination and egg laying and the subsequent departure of the next generation of fig wasps. This offers an explanation for the specialization and long-term coexistence of figs and fig wasps.© 2012 Springer Basel AG.
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Fragmentation reduces population sizes, increases isolation between habitats and can result in restricted dispersal of pollen and seeds. Given that diploid seed dispersal contributes more to shaping fine-scale spatial genetic structure (SGS) than haploid pollen flow, we tested whether fine-scale SGS can be sensitive to fragmentation even if extensive pollen dispersal is maintained. Castanopsis sclerophylla (Lindley&Paxton) Schottky (Fagaceae), a wind-pollinated and gravity seed-dispersed tree, was studied in an area of southeast China where its populations have been fragmented to varying extents by human activity. Using different age classes of trees in areas subject to varying extents of fragmentation, we found no significant difference in genetic diversity between prefragmentation vs. postfragmentation C. sclerophylla subpopulations. Genetic differentiation among postfragmentation subpopulations was also only slightly lower than among prefragmentation subpopulations. In the most fragmented habitat, selfing rates were significantly higher than zero in prefragmentation, but not postfragmentation, cohorts. These results suggest that fragmentation had not decreased gene flow among these populations and that pollen flow remains extensive. However, significantly greater fine-scale SGS was found in postfragmentation subpopulations in the most fragmented habitat, but not in less fragmented habitats. This alteration in SGS reflected more restricted seed dispersal, induced by changes in the physical environments and the prevention of secondary seed dispersal by rodents. An increase in SGS can therefore result from more restricted seed dispersal, even in the face of extensive pollen flow, making it a sensitive indicator of the negative consequences of population fragmentation.
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The responses of arthropod communities to an agroforestry landscape was studied at the Leeds University Field Station (Bramham), in northern England. The experimental design consisted of tree rows (containing four species of furniture timber trees, hazel bushes and grass alleys between the tree rows), forestry plots (comprising three species of timber trees and hazel bushes) and natural woodlots (consisting of mostly pine and beech trees). Forty tree sparrow nest-boxes with guards were constructed to study the structure of this model community. The material used for nest construction was determined based on a used tree sparrow nest obtained from a hedge at the field station. Numbers of arthropods found in tree rows were significantly higher compared to both the forest plots and woodlots. Similarly, the number of green lacewings, flies and beetles were all significantly higher in the tree rows than the forestry plots and woodlots. However, no significant difference between the varying resources of artificial nesting materials was found in total fauna. The common earwigs, Forficula auricularia were attacked by a tachinid fly, Triarthria. setipennis. The rate of parasitism was 43%. This tachinid fly was further parasitised by two hymenopteran, the pteromalids, Dibrachys. cavus and D. boarmiae. There were no significant differences observed between the brood sizes of the tachinid hyperparasitoids. Copyright 2010 Zoological Society of Pakistan.
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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.
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In the Cook Islands the population of Pteropus tonganus tonganus is thought to be declining, but a lack of knowledge of its status, feeding and roosting requirements has precluded effective conservation plans. We surveyed P. t. tonganus on the Cook Islands through observations, counts and interviews with local residents. We estimated the population to be c. 1,730 on Rarotonga and 78 on Mangaia. A lack of suitable habitat on Mangaia was the most important factor affecting abundance. Overhunting appears to have reduced the populations on both islands. All roost sites were found in undisturbed forest on steep slopes and ridges in the inner and most inaccessible parts of the islands, with roost preference determined by the relative safety from humans rather than food availability. The residents of the Cook Islands seem generally unaware of the serious threat the bats face, with little thought for sustainable hunting. For successful conservation it will be important to alter people's negative perception of these mammals, promoting the value of the bats both ecologically and as a potential source of income from tourists. Habitat protection and enhancement, particularly on Mangaia, will be essential.
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Pollinating fig wasps are often used to study sex ratio evolution in structured mating populations. Theory predicts a female-biased sex ratio, becoming less female biased as female (foundress) density increases. We used Liporrhopalum tentacularis to test two mechanisms of sex-ratio control when foundresses oviposit simultaneously: (1) foundresses facultatively adjust the number,of males in clutches, and (2) they produce the same number of males regardless of clutch size, which, given limited numbers of oviposition sites, would lead to increases in sex ratio with increasing density. We then examined whether foundresses,can oviposit sequentially into figs. When oviposition was simultaneous, brood composition indicated facultative adjustment, although sex ratios were more female biased, than predicted. Instead, foundresses appeared to adjust their sex ratio in response to both others ovipositing and their own fecundity. We also found that foundresses are able to oviposit completely sequentially, with those arriving second adjusting their sex ratio in response to the previous oviposition. Hence, pollinating wasps may fail to fit, the predictions of classical sex ratio theory because the conditions under which foundresses oviposit, and their responses to changes in such conditions, are more complex than once assumed. (C) 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.
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This study uses DNA sequence and morphometric comparisons to investigate the systematic status of a broad-nosed weevil, Cathormiocerus brittanicus (Curculionidae; Entiminae), currently described as an endangered UK endemic. The nuclear marker ITS2 was sequenced from specimens of C. brittanicus, C. myrmecophilus, C. curvipes and C. maritimus. Little sequence differentiation was detected between C. brittanicus and C. myrmecophilus, although both species' sequences were different to those of the other two congeners under study. Multivariate analyses of eight morphometric characters also failed to distinguish C. brittanicus from C. myrmecophilus. The taxonomic status of the two species is therefore questionable. If they are the same species the endangered status of C. brittanicus shall need re-assessing and, because C. myrmecophilus also occurs in France, so will its status as a UK endemic. (C) 2001 Elsevier Science Ltd. All rights reserved.
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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.
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Seed dispersal and pollination by animals play a crucial role in the maintenance of forest ecosystems worldwide. Frugivorous bats are important pollen and seed dispersers in both the Palaeo- and Neotropics, and at least 300 plant species are known to rely on Old World fruit bats (Megachiroptera, Pteropodidae) for their propagation. However, rapid food transit times (generally less than 30 minutes) in frugivorous bats have been thought to limit their ability to disperse seeds to just a few tens of kilometres. Here we demonstrate regular daytime (>12 hours) retention of food and viable fig seeds (Ficus, Moraceae) in the gut of the Old World fruit bat Cynopterus sphinx : a behaviour not previously reported for any frugivorous bat. Field observations indicate that this behaviour also occurs in other genera. Old World fruit bats are highly mobile and many species undertake considerable foraging and migration flights. Our findings indicate that Old World fruit bats have the potential to disperse small seeds hundreds of kilometres. This necessitates a reappraisal of their importance in transporting zoochorous seeds to remote areas and facilitating gene flow between isolated populations of plants, both within mainlands and across ocean barriers.
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1. Female agaonine fig wasps enter Fic lts fruits (figs), where they pollinate the Flowers and oviposit into the ovaries of a proportion of the flowers via their styles. The fig trees are totally dependent on these fig wasps for sexual reproduction, as the wasps fertilize the figs' seeds and transfer pollen between trees, while the wasps need the fig trees' ovaries as feeding sites (galled seeds) for their progeny. Since the wasp progeny destroy seeds, the question arises as to why selection has not led to increasingly higher fig wasp fecundities and the eventual collapse of the mutualism. 2. The stability of the mutualism could be maintained by pollinators having short ovipositors, restricting oviposition to short-styled flowers so that long-styled flowers produce seeds. However, in most of the monoecious Ficus species where measurements were taken, pollinators generally possessed ovipositors of sufficient length to reach the ovaries of a large majority of the Rowers. This was confirmed bq! the presence of pollinator progeny in flowers with long styles. 3. Complete seed destruction may also be avoided by a proportion of fig ovaries being inviolate to oviposition by fig wasps. independent of their style lengths. However, experimental increases in pollinator foundresses per fig in F, burtt-davyi showed that all the ovaries that could be reached by the wasps' ovipositors were potentially exploitable by agaonine fig wasps. 4. Relative production of wasps and seeds was found to be largely dependent on the interplay between the number of eggs inside each wasp, the number of accessible ovaries in individual figs, and the average number of foundresses entering each fig. On average, there were not enough foundresses entering each fig to utilize all accessible ovaries. 5. Possible factors affecting the total entry numbers of wasps into figs include ostiolar closure rates and wasp population densities in the areas surrounding fig trees. As many ovaries remain unused because of a frequent shortage of wasp eggs per fig, fig trees can continue to produce enough seeds for the continued evolutionary stability of the fig-fig wasp mutualism.
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