Under local mate competition, sex ratio theory predicts that increasing numbers of ovipositing fe... more Under local mate competition, sex ratio theory predicts that increasing numbers of ovipositing females (foundresses) on a site should lead to higher proportions of males in their broods. Fig pollinators have confirmed this prediction. It is also predicted that with decreasing clutch size, solitary foundresses should produce increasing proportions of sons. We show this to be true. Further, when several females compete, brood size decreases. As a result, the proportion of males increases, and this could provide a mechanistic explanation of sex ratio response to numbers of colonizing females. Therefore, sex ratio data on fig wasps need to be reassessed to determine whether females 'count' other foundresses, as is generally accepted, or whether they simply 'count' the number of eggs that they lay. To cite this article:
Acta Oecologica-international Journal of Ecology, Jul 1, 2018
The mutualism of figs and their pollinating fig wasps is widely regarded as a model for coevolved... more The mutualism of figs and their pollinating fig wasps is widely regarded as a model for coevolved mutualism. A high degree of host specificity is ensured by female wasps only being attracted by their specific fig tree species through the volatile organic compounds (VOCs) released by the figs when they are ready to be pollinated. However, very little is known about the molecular mechanisms underlying the production of VOCs and how pollinators respond to these VOCs. Here we present transcriptome sequencing data from VOC-treated fig wasps and control fig wasps. Using Illumina paired-end sequencing, approximately 6.47 Gbp and 6.48 Gbp high quality reads were generated for fig wasps that had been exposed or not to VOCs of their host fig. After read trimming, the de novo assembly of both types of reads produced 58,192 unigenes with an average length of 817 bp. Then functional annotation and GO enrichment analysis was performed by aligning all-unigenes with public protein databases including NR, SwissProt, and KEGG. Differentially expressed genes (DEGs) were investigated using the RPKM method. Overall, 16 up-regulated genes and 13 down-regulated genes were identified. We further performed GO enrichment and metabolic pathway enrichment analyses. One gene involved in the synoptic vesicle cycle and two genes coding for odorant binding proteins (OBP) are likely to have potential impacts on the response of fig wasps to the VOCs emitted by their host figs. This is the first transcriptome sequencing of a fig wasp in the presence of VOCs of its host figs using the next-generation sequencing technology. Our studies suggest that the expression of some genes in the olfactory neural system of the fig wasps is affected by the VOCs released from the figs. This suggests the presence of a dynamic molecular system of detection and hence response to host plant VOCs. As such our findings provide indications for further mechanistic studies on the fig-fig wasp interactions.
Genetic Differentiation and Dispersal in Plants, 1985
ABSTRACT The caprifig tree, which is the male form of the common fig (Ficus carica L.),must produ... more ABSTRACT The caprifig tree, which is the male form of the common fig (Ficus carica L.),must produce the pollen but also permit the completion of the life cycle of th pollinator...........please see full-text
Fig trees (Ficus) have closed inflorescences. Closure is an efficient protection of flowers again... more Fig trees (Ficus) have closed inflorescences. Closure is an efficient protection of flowers against nonspecialist predators and harsh external environmental conditions. Each Ficus species is pollinated by a single insect species, an agaonid wasp, capable of forcing its way through a bract-covered pore, the ostiole, to gain access to the flowers. Figs also provide oviposition sites for the wasps. The fig/pollinator interaction is a classic example of mutualism. It has been widely assumed that, once pollinators have entered a fig, oviposited and pollinated, they die trapped within the fig. In this paper, we present observations under natural conditions and results of field experiments on three very different fig species (Ficus aurea Nutt., l? carica L. and F nzicrocarpa L.) showing that some pollinators do exit or try to exit from the fig after pollination and oviposition.
In plant species with an obligate species‐specific pollinator, gamete encounter is a critical pha... more In plant species with an obligate species‐specific pollinator, gamete encounter is a critical phase in the success of reproductive strategies. One of the key factors in the success of gamete encounter, the length of female receptivity, has been rarely studied experimentally. In Ficus species (Moraceae), each exclusively associated with its specific pollinating wasp, the receptive female phase of individual syconia was believed to last only a few days. This estimate, based on field observations of pollinator arrivals, neglected the possibility that unpollinated syconia may remain receptive for a prolonged period. In two distantly related fig species (F. carica and F. aurea), we measured experimentally the duration of receptivity of individual syconia protected from pollinator visits. For these two species, receptivity lasted from 2 to 3 wk. Syconia pollinated at any time during this period of receptivity are capable of setting seeds. Furthermore, it has been assumed that female syconium receptivity stops quickly after pollinator visitation. Our experiments showed that syconia of both species are able to extend their receptive period for a few days longer when visited only by a single wasp. The demonstration of a long duration of female receptivity has important consequences for understanding the maintenance of the fig‐wasp mutualism.
Proceedings of The Royal Society B: Biological Sciences, Nov 30, 2011
Combining biogeographic, ecological, morphological, molecular and chemical data, we document depa... more Combining biogeographic, ecological, morphological, molecular and chemical data, we document departure from strict specialization in the fig-pollinating wasp mutualism. We show that the pollinating wasps Elisabethiella stuckenbergi and Elisabethiella socotrensis form a species complex of five lineages in East and Southern Africa. Up to two morphologically distinct lineages were found to co-occur locally in the southern African region. Wasps belonging to a single lineage were frequently the main regional pollinators of several Ficus species. In South Africa, two sister lineages, E. stuckenbergi and E. socotrensis, pollinate Ficus natalensis but only E. stuckenbergi also regularly pollinates Ficus burkei. The two wasp species co-occur in individual trees of F. natalensis throughout KwaZulu-Natal. Floral volatile blends emitted by F. natalensis in KwaZulu-Natal were similar to those emitted by F. burkei and different from those produced by other African Ficus species. The fig odour similarity suggests evolutionary convergence to attract particular wasp species. The observed pattern may result from selection for pollinator sharing among Ficus species. Such a process, with one wasp species regionally pollinating several hosts, but several wasp species pollinating a given Ficus species across its geographical range could play an important role in the evolutionary dynamics of the Ficus-pollinating wasp association.
Despite their ecological and evolutionary importance as key components of tropical ecosystems, th... more Despite their ecological and evolutionary importance as key components of tropical ecosystems, the phylogeny of fig trees is still unresolved. We use restriction-site-associated DNA (RAD) sequencing (ca 420kb) and 102 morphological characters to elucidate the relationships between 70 species of Ficus representing all known subgenera and sections and five outgroups. We compare morphological and molecular results to highlight discrepancies and reveal possible inference bias. We analyse marker and taxon properties that may bias molecular inferences, with existing softwares and a new approach based on iterative principal component analysis to reduce variance between clusters of samples. For the first time, with both molecular and morphological data, we recover a monophyletic subgenus Urostigma and a clade with all gynodioecious fig trees. However, our analyses show that it is not possible to homogenize evolutionary rates and GC content for all taxa prior to phylogenetic inference and that four competing positions for the root of the molecular tree are possible. The placement of the long-branched section Pharmacosycea as sister to all other fig trees is not supported by morphological data and considered as a result of a long branch attraction artefact to the outgroups. Regarding morphological features and indirect evidence from the pollinator tree of life, the topology that divides the genus Ficus into monoecious versus gynodioecious species appears most likely. Active pollination is inferred as the ancestral state for all topologies, ambiguity remains for ancestral breeding system including for the favored topology, and it appears most likely that the ancestor of fig trees was a freestanding tree. Increasing sampling may improve results and would be at least as relevant as maximizing the number of sequenced regions given the strong heterogeneity in evolutionary rates, and to a lesser extent, base composition among species. Despite morphological plasticity and frequent homoplasy of multiple characters, we advocate giving a central role to morphology in our understanding of the evolution of Ficus, especially as it can help detect insidious systematic errors that tend to .
Acta Oecologica-international Journal of Ecology, May 1, 2014
Understanding the ecology of non-pollinating fig-wasp communities depends on a good knowledge of ... more Understanding the ecology of non-pollinating fig-wasp communities depends on a good knowledge of larval feeding habits of the species involved, which can be gall inducers, kleptoparasites, parasitoids or seed eaters. However, larval feeding habits are poorly known and most community ecology studies on NPFW are based on hypothetical feeding habits or data analyzed independently of feeding habit. Here we take advantage of the particular situation in Ficus guianensis whose community is dominated by large NPFW, i.e. species that are obviously larger than pollinators, to establish the community structure and feeding habits of the most frequent wasps. We provide the first non-ambiguous negative correlation between the number of NPFW and the production of pollinators and seeds. Each developing large NPFW represents a disproportionate cost to the mutualism as it is responsible for the loss of about ten seeds plus pollinators, i.e. about 10% of the production of a fig.
Active pollination, although rare, has been documented in a few pollination mutualisms. Such beha... more Active pollination, although rare, has been documented in a few pollination mutualisms. Such behaviour can only evolve if it benefits the pollinator in some way. The wasps that pollinate Ficus inflorescences can be active or passive pollinators. They lay their eggs in fig flowers, so that a proportion of flowers will host a wasp larva instead of a seed. We show in an actively pollinated monoecious fig that lack of pollination does not induce fig abortion or affect wasp offspring size but results in smaller numbers of offspring. Hence, conversely to other active pollination systems, seed formation is not obligatory to sustain developing pollinator larvae; however there is a direct fitness cost to active pollinators not to pollinate. We then compared the locations of eggs and fertilised flowers of three actively pollinated Ficus species and one passively pollinated species. We found that more flowers containing wasp eggs were fertilised in the actively pollinated species relative to those of the passively pollinated one. These results along with comparison with similar studies on dioecious figs, support the hypothesis that active pollination has evolved in fig wasps to ensure that more flowers containing wasp eggs are fertilised as this may increase the chances of successful gall development. The stigmatic platform characterising actively pollinated figs is probably an adaptation to increase pollen dispersion within the fig.
HAL (Le Centre pour la Communication Scientifique Directe), 1998
Flower fragrances are important stimuli in attracting insect pollinators. Different odours attrac... more Flower fragrances are important stimuli in attracting insect pollinators. Different odours attract different pollinators and can, in some cases, achieve specific relationships. Among highly specific pollination systems, the genus Ficus (Moraceae) represents one extreme example, as each Ficus is pollinated by its specific wasp species. The identification of a receptive fig occurs in two steps and chemical information appears to be important in both stages. First, all figs of a tree develop synchronously, so that when the wasps emerge, their natal tree only bears mature figs. Therefore the wasps must locate another tree, bearing receptive figs. This long-distance attraction suggests olfactory signals. Second, once on the fig, fig wasps explore its surface by tapping their antennae on the surface (antennating) as they walk over it. This behaviour suggests contact chemostimulation. The fragrance of receptive Ficus carica figs was extracted using pentane, and the extracts tested on its pollinator wasp (Blastophaga psenes). The results from both distance attraction and contact stimulation experiments indicate that chemical compounds are sufficient to mediate these two steps. Visual cues are not sufficient to attract and stimulate fig pollinators and are probably only minor stimuli compared to the chemical signature of the fig. In this way, Ficus pollination is strikingly different from other specific pollination systems such as Trollius and Yucca, where visual cues are important in attraction to flowers.
Cees, in that period, did not feel overly enthusiastic about going into the field. I remember, ho... more Cees, in that period, did not feel overly enthusiastic about going into the field. I remember, however, that after I had spent a year in Amazonian Brazil (1971) on several expeditions led by G.T. Prance, I suggested that Cees do the same. He then agreed and went to Brazil, only to become completely 'lost' to In memoriam Cees Berg (
Fig trees (Moraceae) have remarkable enclosed infl orescences called fi gs or syconia. The fl owe... more Fig trees (Moraceae) have remarkable enclosed infl orescences called fi gs or syconia. The fl owers are pollinated by host-specifi c fi g wasps that enter the fi g to lay their eggs. This nursery pollination system is one of the most studied of tropical mutualism interactions, but the source of the volatiles that attract fi g wasps to their specifi c host fi gs has not been confi rmed. The fragrance is the basis of host selection and, therefore, of reproductive isolation among sympatric Ficus species. This study locates and characterizes the glands likely to be responsible for pollinator attraction and also protection from herbivory in the fi gs of nine Ficus species representing all the major lineages within the genus. METHODS: Figs with receptive pistillate fl owers were examined using light and scanning electron microscopy. Tests for histolocalization of substances were employed to detect glandular activity throughout the fi gs. KEY RESULTS: A great diversity of glands is found throughout the fi g, and for the fi rst time, the sites producing fragrances are identifi ed. Scent glands are present on the ostiolar bracts and the outer layers of the fi g receptacle. Laticifers and phenolic-producing idioblasts, epidermis, and trichomes associated with fi g protection occur on the ostiolar bracts, the fi g receptacle, and fl oral tissues. CONCLUSIONS: The volatiles produced by glands on the ostiolar bracts are candidate sources for the long-distance attraction of pollinator fi g wasps. Scent glands on the outer layers of the receptacle may also play a role in chemical perception of the fi gs or may be related to their protection. The high cost to the plants if the fi gs are eaten and the temperature conditions required for nursery pollination are likely the factors that led to the selection of phenolic glands and laticifers during the group's evolution.
Studies investigating the evolution of flowering plants have long focused on isolating mechanisms... more Studies investigating the evolution of flowering plants have long focused on isolating mechanisms such as pollinator specificity. Some recent studies have proposed a role for introgressive hybridization between species, recognizing that isolating processes such as pollinator specialization may not be complete barriers to hybridization. Occasional hybridization may therefore lead to distinct yet reproductively connected lineages. We investigate the balance between introgression and reproductive isolation in a diverse clade using a densely sampled phylogenomic study of fig trees ( Ficus , Moraceae). Codiversification with specialized pollinating wasps (Agaonidae) is recognized as a major engine of fig diversity, leading to about 850 species. Nevertheless, some studies have focused on the importance of hybridization in Ficus , highlighting the consequences of pollinator sharing. Here, we employ dense taxon sampling (520 species) throughout Moraceae and 1,751 loci to investigate phyloge...
Under local mate competition, sex ratio theory predicts that increasing numbers of ovipositing fe... more Under local mate competition, sex ratio theory predicts that increasing numbers of ovipositing females (foundresses) on a site should lead to higher proportions of males in their broods. Fig pollinators have confirmed this prediction. It is also predicted that with decreasing clutch size, solitary foundresses should produce increasing proportions of sons. We show this to be true. Further, when several females compete, brood size decreases. As a result, the proportion of males increases, and this could provide a mechanistic explanation of sex ratio response to numbers of colonizing females. Therefore, sex ratio data on fig wasps need to be reassessed to determine whether females 'count' other foundresses, as is generally accepted, or whether they simply 'count' the number of eggs that they lay. To cite this article:
Acta Oecologica-international Journal of Ecology, Jul 1, 2018
The mutualism of figs and their pollinating fig wasps is widely regarded as a model for coevolved... more The mutualism of figs and their pollinating fig wasps is widely regarded as a model for coevolved mutualism. A high degree of host specificity is ensured by female wasps only being attracted by their specific fig tree species through the volatile organic compounds (VOCs) released by the figs when they are ready to be pollinated. However, very little is known about the molecular mechanisms underlying the production of VOCs and how pollinators respond to these VOCs. Here we present transcriptome sequencing data from VOC-treated fig wasps and control fig wasps. Using Illumina paired-end sequencing, approximately 6.47 Gbp and 6.48 Gbp high quality reads were generated for fig wasps that had been exposed or not to VOCs of their host fig. After read trimming, the de novo assembly of both types of reads produced 58,192 unigenes with an average length of 817 bp. Then functional annotation and GO enrichment analysis was performed by aligning all-unigenes with public protein databases including NR, SwissProt, and KEGG. Differentially expressed genes (DEGs) were investigated using the RPKM method. Overall, 16 up-regulated genes and 13 down-regulated genes were identified. We further performed GO enrichment and metabolic pathway enrichment analyses. One gene involved in the synoptic vesicle cycle and two genes coding for odorant binding proteins (OBP) are likely to have potential impacts on the response of fig wasps to the VOCs emitted by their host figs. This is the first transcriptome sequencing of a fig wasp in the presence of VOCs of its host figs using the next-generation sequencing technology. Our studies suggest that the expression of some genes in the olfactory neural system of the fig wasps is affected by the VOCs released from the figs. This suggests the presence of a dynamic molecular system of detection and hence response to host plant VOCs. As such our findings provide indications for further mechanistic studies on the fig-fig wasp interactions.
Genetic Differentiation and Dispersal in Plants, 1985
ABSTRACT The caprifig tree, which is the male form of the common fig (Ficus carica L.),must produ... more ABSTRACT The caprifig tree, which is the male form of the common fig (Ficus carica L.),must produce the pollen but also permit the completion of the life cycle of th pollinator...........please see full-text
Fig trees (Ficus) have closed inflorescences. Closure is an efficient protection of flowers again... more Fig trees (Ficus) have closed inflorescences. Closure is an efficient protection of flowers against nonspecialist predators and harsh external environmental conditions. Each Ficus species is pollinated by a single insect species, an agaonid wasp, capable of forcing its way through a bract-covered pore, the ostiole, to gain access to the flowers. Figs also provide oviposition sites for the wasps. The fig/pollinator interaction is a classic example of mutualism. It has been widely assumed that, once pollinators have entered a fig, oviposited and pollinated, they die trapped within the fig. In this paper, we present observations under natural conditions and results of field experiments on three very different fig species (Ficus aurea Nutt., l? carica L. and F nzicrocarpa L.) showing that some pollinators do exit or try to exit from the fig after pollination and oviposition.
In plant species with an obligate species‐specific pollinator, gamete encounter is a critical pha... more In plant species with an obligate species‐specific pollinator, gamete encounter is a critical phase in the success of reproductive strategies. One of the key factors in the success of gamete encounter, the length of female receptivity, has been rarely studied experimentally. In Ficus species (Moraceae), each exclusively associated with its specific pollinating wasp, the receptive female phase of individual syconia was believed to last only a few days. This estimate, based on field observations of pollinator arrivals, neglected the possibility that unpollinated syconia may remain receptive for a prolonged period. In two distantly related fig species (F. carica and F. aurea), we measured experimentally the duration of receptivity of individual syconia protected from pollinator visits. For these two species, receptivity lasted from 2 to 3 wk. Syconia pollinated at any time during this period of receptivity are capable of setting seeds. Furthermore, it has been assumed that female syconium receptivity stops quickly after pollinator visitation. Our experiments showed that syconia of both species are able to extend their receptive period for a few days longer when visited only by a single wasp. The demonstration of a long duration of female receptivity has important consequences for understanding the maintenance of the fig‐wasp mutualism.
Proceedings of The Royal Society B: Biological Sciences, Nov 30, 2011
Combining biogeographic, ecological, morphological, molecular and chemical data, we document depa... more Combining biogeographic, ecological, morphological, molecular and chemical data, we document departure from strict specialization in the fig-pollinating wasp mutualism. We show that the pollinating wasps Elisabethiella stuckenbergi and Elisabethiella socotrensis form a species complex of five lineages in East and Southern Africa. Up to two morphologically distinct lineages were found to co-occur locally in the southern African region. Wasps belonging to a single lineage were frequently the main regional pollinators of several Ficus species. In South Africa, two sister lineages, E. stuckenbergi and E. socotrensis, pollinate Ficus natalensis but only E. stuckenbergi also regularly pollinates Ficus burkei. The two wasp species co-occur in individual trees of F. natalensis throughout KwaZulu-Natal. Floral volatile blends emitted by F. natalensis in KwaZulu-Natal were similar to those emitted by F. burkei and different from those produced by other African Ficus species. The fig odour similarity suggests evolutionary convergence to attract particular wasp species. The observed pattern may result from selection for pollinator sharing among Ficus species. Such a process, with one wasp species regionally pollinating several hosts, but several wasp species pollinating a given Ficus species across its geographical range could play an important role in the evolutionary dynamics of the Ficus-pollinating wasp association.
Despite their ecological and evolutionary importance as key components of tropical ecosystems, th... more Despite their ecological and evolutionary importance as key components of tropical ecosystems, the phylogeny of fig trees is still unresolved. We use restriction-site-associated DNA (RAD) sequencing (ca 420kb) and 102 morphological characters to elucidate the relationships between 70 species of Ficus representing all known subgenera and sections and five outgroups. We compare morphological and molecular results to highlight discrepancies and reveal possible inference bias. We analyse marker and taxon properties that may bias molecular inferences, with existing softwares and a new approach based on iterative principal component analysis to reduce variance between clusters of samples. For the first time, with both molecular and morphological data, we recover a monophyletic subgenus Urostigma and a clade with all gynodioecious fig trees. However, our analyses show that it is not possible to homogenize evolutionary rates and GC content for all taxa prior to phylogenetic inference and that four competing positions for the root of the molecular tree are possible. The placement of the long-branched section Pharmacosycea as sister to all other fig trees is not supported by morphological data and considered as a result of a long branch attraction artefact to the outgroups. Regarding morphological features and indirect evidence from the pollinator tree of life, the topology that divides the genus Ficus into monoecious versus gynodioecious species appears most likely. Active pollination is inferred as the ancestral state for all topologies, ambiguity remains for ancestral breeding system including for the favored topology, and it appears most likely that the ancestor of fig trees was a freestanding tree. Increasing sampling may improve results and would be at least as relevant as maximizing the number of sequenced regions given the strong heterogeneity in evolutionary rates, and to a lesser extent, base composition among species. Despite morphological plasticity and frequent homoplasy of multiple characters, we advocate giving a central role to morphology in our understanding of the evolution of Ficus, especially as it can help detect insidious systematic errors that tend to .
Acta Oecologica-international Journal of Ecology, May 1, 2014
Understanding the ecology of non-pollinating fig-wasp communities depends on a good knowledge of ... more Understanding the ecology of non-pollinating fig-wasp communities depends on a good knowledge of larval feeding habits of the species involved, which can be gall inducers, kleptoparasites, parasitoids or seed eaters. However, larval feeding habits are poorly known and most community ecology studies on NPFW are based on hypothetical feeding habits or data analyzed independently of feeding habit. Here we take advantage of the particular situation in Ficus guianensis whose community is dominated by large NPFW, i.e. species that are obviously larger than pollinators, to establish the community structure and feeding habits of the most frequent wasps. We provide the first non-ambiguous negative correlation between the number of NPFW and the production of pollinators and seeds. Each developing large NPFW represents a disproportionate cost to the mutualism as it is responsible for the loss of about ten seeds plus pollinators, i.e. about 10% of the production of a fig.
Active pollination, although rare, has been documented in a few pollination mutualisms. Such beha... more Active pollination, although rare, has been documented in a few pollination mutualisms. Such behaviour can only evolve if it benefits the pollinator in some way. The wasps that pollinate Ficus inflorescences can be active or passive pollinators. They lay their eggs in fig flowers, so that a proportion of flowers will host a wasp larva instead of a seed. We show in an actively pollinated monoecious fig that lack of pollination does not induce fig abortion or affect wasp offspring size but results in smaller numbers of offspring. Hence, conversely to other active pollination systems, seed formation is not obligatory to sustain developing pollinator larvae; however there is a direct fitness cost to active pollinators not to pollinate. We then compared the locations of eggs and fertilised flowers of three actively pollinated Ficus species and one passively pollinated species. We found that more flowers containing wasp eggs were fertilised in the actively pollinated species relative to those of the passively pollinated one. These results along with comparison with similar studies on dioecious figs, support the hypothesis that active pollination has evolved in fig wasps to ensure that more flowers containing wasp eggs are fertilised as this may increase the chances of successful gall development. The stigmatic platform characterising actively pollinated figs is probably an adaptation to increase pollen dispersion within the fig.
HAL (Le Centre pour la Communication Scientifique Directe), 1998
Flower fragrances are important stimuli in attracting insect pollinators. Different odours attrac... more Flower fragrances are important stimuli in attracting insect pollinators. Different odours attract different pollinators and can, in some cases, achieve specific relationships. Among highly specific pollination systems, the genus Ficus (Moraceae) represents one extreme example, as each Ficus is pollinated by its specific wasp species. The identification of a receptive fig occurs in two steps and chemical information appears to be important in both stages. First, all figs of a tree develop synchronously, so that when the wasps emerge, their natal tree only bears mature figs. Therefore the wasps must locate another tree, bearing receptive figs. This long-distance attraction suggests olfactory signals. Second, once on the fig, fig wasps explore its surface by tapping their antennae on the surface (antennating) as they walk over it. This behaviour suggests contact chemostimulation. The fragrance of receptive Ficus carica figs was extracted using pentane, and the extracts tested on its pollinator wasp (Blastophaga psenes). The results from both distance attraction and contact stimulation experiments indicate that chemical compounds are sufficient to mediate these two steps. Visual cues are not sufficient to attract and stimulate fig pollinators and are probably only minor stimuli compared to the chemical signature of the fig. In this way, Ficus pollination is strikingly different from other specific pollination systems such as Trollius and Yucca, where visual cues are important in attraction to flowers.
Cees, in that period, did not feel overly enthusiastic about going into the field. I remember, ho... more Cees, in that period, did not feel overly enthusiastic about going into the field. I remember, however, that after I had spent a year in Amazonian Brazil (1971) on several expeditions led by G.T. Prance, I suggested that Cees do the same. He then agreed and went to Brazil, only to become completely 'lost' to In memoriam Cees Berg (
Fig trees (Moraceae) have remarkable enclosed infl orescences called fi gs or syconia. The fl owe... more Fig trees (Moraceae) have remarkable enclosed infl orescences called fi gs or syconia. The fl owers are pollinated by host-specifi c fi g wasps that enter the fi g to lay their eggs. This nursery pollination system is one of the most studied of tropical mutualism interactions, but the source of the volatiles that attract fi g wasps to their specifi c host fi gs has not been confi rmed. The fragrance is the basis of host selection and, therefore, of reproductive isolation among sympatric Ficus species. This study locates and characterizes the glands likely to be responsible for pollinator attraction and also protection from herbivory in the fi gs of nine Ficus species representing all the major lineages within the genus. METHODS: Figs with receptive pistillate fl owers were examined using light and scanning electron microscopy. Tests for histolocalization of substances were employed to detect glandular activity throughout the fi gs. KEY RESULTS: A great diversity of glands is found throughout the fi g, and for the fi rst time, the sites producing fragrances are identifi ed. Scent glands are present on the ostiolar bracts and the outer layers of the fi g receptacle. Laticifers and phenolic-producing idioblasts, epidermis, and trichomes associated with fi g protection occur on the ostiolar bracts, the fi g receptacle, and fl oral tissues. CONCLUSIONS: The volatiles produced by glands on the ostiolar bracts are candidate sources for the long-distance attraction of pollinator fi g wasps. Scent glands on the outer layers of the receptacle may also play a role in chemical perception of the fi gs or may be related to their protection. The high cost to the plants if the fi gs are eaten and the temperature conditions required for nursery pollination are likely the factors that led to the selection of phenolic glands and laticifers during the group's evolution.
Studies investigating the evolution of flowering plants have long focused on isolating mechanisms... more Studies investigating the evolution of flowering plants have long focused on isolating mechanisms such as pollinator specificity. Some recent studies have proposed a role for introgressive hybridization between species, recognizing that isolating processes such as pollinator specialization may not be complete barriers to hybridization. Occasional hybridization may therefore lead to distinct yet reproductively connected lineages. We investigate the balance between introgression and reproductive isolation in a diverse clade using a densely sampled phylogenomic study of fig trees ( Ficus , Moraceae). Codiversification with specialized pollinating wasps (Agaonidae) is recognized as a major engine of fig diversity, leading to about 850 species. Nevertheless, some studies have focused on the importance of hybridization in Ficus , highlighting the consequences of pollinator sharing. Here, we employ dense taxon sampling (520 species) throughout Moraceae and 1,751 loci to investigate phyloge...
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