The Experts below are selected from a list of 14976 Experts worldwide ranked by ideXlab platform
Marion Valeix - One of the best experts on this subject based on the ideXlab platform.
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interspecific Interference Competition at the resource patch scale do large herbivores spatially avoid elephants while accessing water
Journal of Animal Ecology, 2016Co-Authors: Nicolas Ferry, Hervé Fritz, Stephane Dray, Marion ValeixAbstract:Animals may anticipate and try to avoid, at some costs, physical encounters with other competitors. This may ultimately impact their foraging distribution and intake rates. Such cryptic Interference Competition is difficult to measure in the field, and extremely little is known at the interspecific level. We tested the hypothesis that smaller species avoid larger ones because of potential costs of Interference Competition and hence expected them to segregate from larger competitors at the scale of a resource patch. We assessed fine-scale spatial segregation patterns between three African herbivore species (zebra Equus quagga, kudu Tragelaphus strepsiceros and giraffe Giraffa camelopardalis) and a megaherbivore, the African elephant Loxodonta africana, at the scale of water resource patches in the semi-arid ecosystem of Hwange National Park, Zimbabwe. Nine waterholes were monitored every two weeks during the dry season of a drought year, and observational scans of the spatial distribution of all herbivores were performed every 15 min. We developed a methodological approach to analyse such fine-scale spatial data. Elephants increasingly used waterholes as the dry season progressed, as did the probability of co-occurrence and agonistic interaction with elephants for the three study species. All three species segregated from elephants at the beginning of the dry season, suggesting a spatial avoidance of elephants and the existence of costs of being close to them. However, contrarily to our expectations, herbivores did not segregate from elephants the rest of the dry season but tended to increasingly aggregate with elephants as the dry season progressed. We discuss these surprising results and the existence of a trade-off between avoidance of interspecific Interference Competition and other potential factors such as access to quality water, which may have relative associated costs that change with the time of the year.
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the role of water abundance thermoregulation perceived predation risk and Interference Competition in water access by african herbivores
African Journal of Ecology, 2008Co-Authors: Marion Valeix, Hervé Fritz, Ruwadzano Matsika, Fadzai Matsvimbo, Hillary MadzikandaAbstract:In African savannas, surface water can become limiting and an understanding of how animals address the trade-offs between different constraints to access this resource is needed. Here, we describe water access by ten African herbivore species in Hwange National Park, Zimbabwe, and we explore four possible determinants of the observed behaviours: water abundance, thermoregulation, perceived predation risk and Interference Competition. On average, herbivores were observed to drink in 80% of visits to a waterhole. The probability of drinking was higher in 2003 (474 mm) than in 2004 (770 mm), and at the end of the dry season than at its beginning. For larger species, this probability may also be related to risks of Interference Competition with elephants or other herbivores. For smaller species, this probability may also be related to the perceived risk of predation. We also investigate the time spent accessing water to drink. The influence of herd size and the presence of young on the time spent accessing water for most species suggests that perceived predation risk plays a role. Thermoregulation also affects this time: during the hottest periods, herbivores spend less time in open areas, unless when wind is strong, probably owing to evapotranspired heat loss. Resume Dans les savanes africaines, l’eau de surface disponible peut devenir un facteur limitant et il est necessaire de comprendre comment les animaux agissent face aux differentes contraintes que pose l’acces a cette ressource. Nous decrivons ici l’acces a l’eau de dix herbivores africains du Parc National de Hwange, au Zimbabwe, et nous explorons quatre facteurs qui sont peut-etre determinants dans les comportements observes: l’abondance de l’eau, la thermoregulation, le risque de predation ressenti et la Competition/ Interference. En moyenne, on a observe que les herbivores buvaient lors de 80% de leurs visites au point d’eau. La probabilite qu’ils boivent etai plus forte en 2003 (474 mm) qu’en 2004 (770 mm), et a la fin de la saison seche qu’au debut. Pour les plus grandes especes, cette probabilite pourrait aussi etre liee aux risques de Competition par Interference avec les elephants ou d’autres herbivores. Pour les plus petites especes, cette probabilite pourrait aussi etre liee au risque de predation ressenti. Nous avons aussi etudie le temps passea se rendre au point d’eau pour y boire. L’influence de la taille du groupe et de la presence de jeunes sur le temps pris par la plupart des especes pour se rendre au point d’eau laisse penser que la perception du risque de predation joue un role. La thermoregulation affecte aussi cette duree: pendant les periodes les plus chaudes, les herbivores passent moins de temps dans les espaces ouverts, sauf si le vent est fort, probablement a cause de la perte de chaleur par evapotranspiration.
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The role of water abundance, thermoregulation, perceived predation risk and Interference Competition in water access by African herbivores
African Journal of Ecology, 2008Co-Authors: Marion Valeix, Hervé Fritz, Ruwadzano Matsika, Fadzai Matsvimbo, Hillary MadzikandaAbstract:In African savannas, surface water can become limiting and an understanding of how animals address the trade-offs between different constraints to access this resource is needed. Here, we describe water access by ten African herbivore species in Hwange National Park, Zimbabwe, and we explore four possible determinants of the observed behaviours: water abundance, thermoregulation, perceived predation risk and Interference Competition. On average, herbivores were observed to drink in 80% of visits to a waterhole. The probability of drinking was higher in 2003 (474 mm)than in 2004 (770 mm), and at the end of the dry season than at its beginning. For larger species, this probability may also be related to risks of Interference Competition with elephants or other herbivores. For smaller species, this probability may also be related to the perceived risk of predation. Wealso investigate the time spent accessing water to drink. The influence of herd size and the presence of young on the time spent accessing water for most species suggests that perceived predation risk plays a role. Thermoregulation also affects this time: during the hottest periods, herbivores spend less time in open areas, unless when wind is strong, probably owing to evapotranspired heat loss.
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Interference Competition and temporal niche shifts: elephants and herbivore communities at waterholes
Oecologia, 2007Co-Authors: Marion Valeix, Simon Chamaillé-jammes, Hervé FritzAbstract:Scarcity of resources may result in high levels of animal aggregation; Interference Competition can occur in such a scenario and play a role in resource acquisition. Here, we test the hypothesis that animals could minimize Interference Competition by shifting their temporal niches in relation to competitors. In Hwange National Park, Zimbabwe, we monitored waterholes in order to study agonistic interactions between elephants and other herbivore species. We also used a long-term data set from a yearly survey of waterhole attendance by herbivores to evaluate the influence of the presence of elephants on the use of waterholes by other herbivore species. Our results show that in drier years, waterholes are crowded with elephants early in the afternoon. In general, the species most affected by Interference Competition with elephants shift their temporal niches at the waterholes, thus maintaining a constant temporal overlap with elephants. The species less affected by Interference Competition with elephants show no temporal niche shifts and increase their temporal overlaps with elephants at waterholes, as predicted from a nonCompetition hypothesis. This study provides evidence that Interference Competition with a behaviorally dominant large species influences the temporal niches of smaller species, and suggests that the potential costs associated with Interference between elephants and other herbivores at waterholes are linked to shifts in diurnal activities rather than interactions and water acquisition itself.
Douglas W. Yu - One of the best experts on this subject based on the ideXlab platform.
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Interference Competition and high temperatures reduce the virulence of fig wasps and stabilize a fig wasp mutualism
PLOS ONE, 2009Co-Authors: Ruiwu Wang, Jo Ridley, Derek W. Dunn, Douglas W. Yu, Yaping Zhang, James M Cook, Qi ZhengAbstract:Fig trees are pollinated by fig wasps, which also oviposit in female flowers. The wasp larvae gall and eat developing seeds. Although fig trees benefit from allowing wasps to oviposit, because the wasp offspring disperse pollen, figs must prevent wasps from ovipositing in all flowers, or seed production would cease, and the mutualism would go extinct. In Ficus racemosa, we find that syconia (‘figs’) that have few foundresses (ovipositing wasps) are underexploited in the summer (few seeds, few galls, many empty ovules) and are overexploited in the winter (few seeds, many galls, few empty ovules). Conversely, syconia with many foundresses produce intermediate numbers of galls and seeds, regardless of season. We use experiments to explain these patterns, and thus, to explain how this mutualism is maintained. In the hot summer, wasps suffer short lifespans and therefore fail to oviposit in many flowers. In contrast, cooler temperatures in the winter permit longer wasp lifespans, which in turn allows most flowers to be exploited by the wasps. However, even in winter, only in syconia that happen to have few foundresses are most flowers turned into galls. In syconia with higher numbers of foundresses, Interference Competition reduces foundress lifespans, which reduces the proportion of flowers that are galled. We further show that syconia encourage the entry of multiple foundresses by delaying ostiole closure. Taken together, these factors allow fig trees to reduce galling in the wasp-benign winter and boost galling (and pollination) in the wasp-stressing summer. Interference Competition has been shown to reduce virulence in pathogenic bacteria. Our results show that Interference also maintains cooperation in a classic, cooperative symbiosis, thus linking theories of virulence and mutualism. More generally, our results reveal how frequency-dependent population regulation can occur in the fig-wasp mutualism, and how a host species can ‘set the rules of the game’ to ensure mutualistic behavior in its symbionts.
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Interference Competition and high temperature reduce the virulence of fig wasps and contribute to stability of a fig wasp mutualism
2009Co-Authors: R U Wang, Jo Ridley, Derek W. Dunn, Yaping Zhang, James M Cook, Qi Zheng, Douglas W. YuAbstract:Fig trees are pollinated by fig wasps, which also oviposit in female flowers. The wasp larvae gall and eat developing seeds. Although fig trees benefit from allowing wasps to oviposit, because the wasp offspring disperse pollen, figs must prevent wasps from ovipositing in all flowers, or seed production would cease, and the mutualism would go extinct. In Ficus racemosa, we find that syconia (‘figs’) that have few foundresses (ovipositing wasps) are underexploited in the summer (few seeds, few galls, many empty ovules) and are overexploited in the winter (few seeds, many galls, few empty ovules). Conversely, syconia with many foundresses produce intermediate numbers of galls and seeds, regardless of season. We use experiments to explain these patterns, and thus, to explain how this mutualism is maintained. In the hot summer, wasps suffer short lifespans and therefore fail to oviposit in many flowers. In contrast, cooler temperatures in the winter permit longer wasp lifespans, which in turn allows most flowers to be exploited by the wasps. However, even in winter, only in syconia that happen to have few foundresses are most flowers turned into galls. In syconia with higher numbers of foundresses, Interference Competition reduces foundress lifespans, which reduces the proportion of flowers that are galled. We further show that syconia encourage the entry of multiple foundresses by delaying ostiole closure. Taken together, these factors allow fig trees to reduce galling in the wasp-benign winter and boost galling (and pollination) in the wasp-stressing summer. Interference Competition has been shown to reduce virulence in pathogenic bacteria. Our results show that Interference also maintains cooperation in a classic, cooperative symbiosis, thus linking theories of virulence and mutualism. More generally, our results reveal how frequency-dependent population regulation can occur in the fig-wasp mutualism, and how a host species can ‘set the rules of the game’ to ensure mutualistic behavior in its symbionts.
Hervé Fritz - One of the best experts on this subject based on the ideXlab platform.
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heterogeneity of water physico chemical characteristics in artificially pumped waterholes do african herbivores drink at the same locations and does it lead to Interference Competition
Journal of Arid Environments, 2020Co-Authors: Nicolas Ferry, Stephane Dray, Marion Cordonnier, Florence D Hulot, Farisayi Dakwa, Lovelater Sebele, Hervé FritzAbstract:Abstract In many semi-arid savanna ecosystems, surface water is scarce and only found in artificially pumped waterholes at the end of the dry season, leading to high large mammal densities and Competition. Further, the modification of the physico-chemical characteristics of the drinking water over the dry season (e.g. through faeces accumulation) could enhance Competition. Indeed, elephants, considered as key-competitors, and other herbivores by aggregating near the trough where clear water arrives could compete for this resource. We studied the drinking locations of eight herbivore species around pumped waterholes in relation to these water characteristics in Hwange National Park, Zimbabwe. We identified differences of the physico-chemical characteristics of the water in different sections of pumped waterholes at the end of the dry season. Elephants drank the water in or close to the trough, whereas other species drank further in the waterhole, except roan and sable antelopes which were indifferent about where they drank. Interference Competition with elephants for the access to water close to the trough was not detected for zebras and kudus. We discuss possible directions for future research to enhance our understanding of waterhole use by herbivores.
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interspecific Interference Competition at the resource patch scale do large herbivores spatially avoid elephants while accessing water
Journal of Animal Ecology, 2016Co-Authors: Nicolas Ferry, Hervé Fritz, Stephane Dray, Marion ValeixAbstract:Animals may anticipate and try to avoid, at some costs, physical encounters with other competitors. This may ultimately impact their foraging distribution and intake rates. Such cryptic Interference Competition is difficult to measure in the field, and extremely little is known at the interspecific level. We tested the hypothesis that smaller species avoid larger ones because of potential costs of Interference Competition and hence expected them to segregate from larger competitors at the scale of a resource patch. We assessed fine-scale spatial segregation patterns between three African herbivore species (zebra Equus quagga, kudu Tragelaphus strepsiceros and giraffe Giraffa camelopardalis) and a megaherbivore, the African elephant Loxodonta africana, at the scale of water resource patches in the semi-arid ecosystem of Hwange National Park, Zimbabwe. Nine waterholes were monitored every two weeks during the dry season of a drought year, and observational scans of the spatial distribution of all herbivores were performed every 15 min. We developed a methodological approach to analyse such fine-scale spatial data. Elephants increasingly used waterholes as the dry season progressed, as did the probability of co-occurrence and agonistic interaction with elephants for the three study species. All three species segregated from elephants at the beginning of the dry season, suggesting a spatial avoidance of elephants and the existence of costs of being close to them. However, contrarily to our expectations, herbivores did not segregate from elephants the rest of the dry season but tended to increasingly aggregate with elephants as the dry season progressed. We discuss these surprising results and the existence of a trade-off between avoidance of interspecific Interference Competition and other potential factors such as access to quality water, which may have relative associated costs that change with the time of the year.
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the role of water abundance thermoregulation perceived predation risk and Interference Competition in water access by african herbivores
African Journal of Ecology, 2008Co-Authors: Marion Valeix, Hervé Fritz, Ruwadzano Matsika, Fadzai Matsvimbo, Hillary MadzikandaAbstract:In African savannas, surface water can become limiting and an understanding of how animals address the trade-offs between different constraints to access this resource is needed. Here, we describe water access by ten African herbivore species in Hwange National Park, Zimbabwe, and we explore four possible determinants of the observed behaviours: water abundance, thermoregulation, perceived predation risk and Interference Competition. On average, herbivores were observed to drink in 80% of visits to a waterhole. The probability of drinking was higher in 2003 (474 mm) than in 2004 (770 mm), and at the end of the dry season than at its beginning. For larger species, this probability may also be related to risks of Interference Competition with elephants or other herbivores. For smaller species, this probability may also be related to the perceived risk of predation. We also investigate the time spent accessing water to drink. The influence of herd size and the presence of young on the time spent accessing water for most species suggests that perceived predation risk plays a role. Thermoregulation also affects this time: during the hottest periods, herbivores spend less time in open areas, unless when wind is strong, probably owing to evapotranspired heat loss. Resume Dans les savanes africaines, l’eau de surface disponible peut devenir un facteur limitant et il est necessaire de comprendre comment les animaux agissent face aux differentes contraintes que pose l’acces a cette ressource. Nous decrivons ici l’acces a l’eau de dix herbivores africains du Parc National de Hwange, au Zimbabwe, et nous explorons quatre facteurs qui sont peut-etre determinants dans les comportements observes: l’abondance de l’eau, la thermoregulation, le risque de predation ressenti et la Competition/ Interference. En moyenne, on a observe que les herbivores buvaient lors de 80% de leurs visites au point d’eau. La probabilite qu’ils boivent etai plus forte en 2003 (474 mm) qu’en 2004 (770 mm), et a la fin de la saison seche qu’au debut. Pour les plus grandes especes, cette probabilite pourrait aussi etre liee aux risques de Competition par Interference avec les elephants ou d’autres herbivores. Pour les plus petites especes, cette probabilite pourrait aussi etre liee au risque de predation ressenti. Nous avons aussi etudie le temps passea se rendre au point d’eau pour y boire. L’influence de la taille du groupe et de la presence de jeunes sur le temps pris par la plupart des especes pour se rendre au point d’eau laisse penser que la perception du risque de predation joue un role. La thermoregulation affecte aussi cette duree: pendant les periodes les plus chaudes, les herbivores passent moins de temps dans les espaces ouverts, sauf si le vent est fort, probablement a cause de la perte de chaleur par evapotranspiration.
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The role of water abundance, thermoregulation, perceived predation risk and Interference Competition in water access by African herbivores
African Journal of Ecology, 2008Co-Authors: Marion Valeix, Hervé Fritz, Ruwadzano Matsika, Fadzai Matsvimbo, Hillary MadzikandaAbstract:In African savannas, surface water can become limiting and an understanding of how animals address the trade-offs between different constraints to access this resource is needed. Here, we describe water access by ten African herbivore species in Hwange National Park, Zimbabwe, and we explore four possible determinants of the observed behaviours: water abundance, thermoregulation, perceived predation risk and Interference Competition. On average, herbivores were observed to drink in 80% of visits to a waterhole. The probability of drinking was higher in 2003 (474 mm)than in 2004 (770 mm), and at the end of the dry season than at its beginning. For larger species, this probability may also be related to risks of Interference Competition with elephants or other herbivores. For smaller species, this probability may also be related to the perceived risk of predation. Wealso investigate the time spent accessing water to drink. The influence of herd size and the presence of young on the time spent accessing water for most species suggests that perceived predation risk plays a role. Thermoregulation also affects this time: during the hottest periods, herbivores spend less time in open areas, unless when wind is strong, probably owing to evapotranspired heat loss.
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Interference Competition and temporal niche shifts: elephants and herbivore communities at waterholes
Oecologia, 2007Co-Authors: Marion Valeix, Simon Chamaillé-jammes, Hervé FritzAbstract:Scarcity of resources may result in high levels of animal aggregation; Interference Competition can occur in such a scenario and play a role in resource acquisition. Here, we test the hypothesis that animals could minimize Interference Competition by shifting their temporal niches in relation to competitors. In Hwange National Park, Zimbabwe, we monitored waterholes in order to study agonistic interactions between elephants and other herbivore species. We also used a long-term data set from a yearly survey of waterhole attendance by herbivores to evaluate the influence of the presence of elephants on the use of waterholes by other herbivore species. Our results show that in drier years, waterholes are crowded with elephants early in the afternoon. In general, the species most affected by Interference Competition with elephants shift their temporal niches at the waterholes, thus maintaining a constant temporal overlap with elephants. The species less affected by Interference Competition with elephants show no temporal niche shifts and increase their temporal overlaps with elephants at waterholes, as predicted from a nonCompetition hypothesis. This study provides evidence that Interference Competition with a behaviorally dominant large species influences the temporal niches of smaller species, and suggests that the potential costs associated with Interference between elephants and other herbivores at waterholes are linked to shifts in diurnal activities rather than interactions and water acquisition itself.
Qi Zheng - One of the best experts on this subject based on the ideXlab platform.
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Interference Competition and high temperatures reduce the virulence of fig wasps and stabilize a fig wasp mutualism
PLOS ONE, 2009Co-Authors: Ruiwu Wang, Jo Ridley, Derek W. Dunn, Douglas W. Yu, Yaping Zhang, James M Cook, Qi ZhengAbstract:Fig trees are pollinated by fig wasps, which also oviposit in female flowers. The wasp larvae gall and eat developing seeds. Although fig trees benefit from allowing wasps to oviposit, because the wasp offspring disperse pollen, figs must prevent wasps from ovipositing in all flowers, or seed production would cease, and the mutualism would go extinct. In Ficus racemosa, we find that syconia (‘figs’) that have few foundresses (ovipositing wasps) are underexploited in the summer (few seeds, few galls, many empty ovules) and are overexploited in the winter (few seeds, many galls, few empty ovules). Conversely, syconia with many foundresses produce intermediate numbers of galls and seeds, regardless of season. We use experiments to explain these patterns, and thus, to explain how this mutualism is maintained. In the hot summer, wasps suffer short lifespans and therefore fail to oviposit in many flowers. In contrast, cooler temperatures in the winter permit longer wasp lifespans, which in turn allows most flowers to be exploited by the wasps. However, even in winter, only in syconia that happen to have few foundresses are most flowers turned into galls. In syconia with higher numbers of foundresses, Interference Competition reduces foundress lifespans, which reduces the proportion of flowers that are galled. We further show that syconia encourage the entry of multiple foundresses by delaying ostiole closure. Taken together, these factors allow fig trees to reduce galling in the wasp-benign winter and boost galling (and pollination) in the wasp-stressing summer. Interference Competition has been shown to reduce virulence in pathogenic bacteria. Our results show that Interference also maintains cooperation in a classic, cooperative symbiosis, thus linking theories of virulence and mutualism. More generally, our results reveal how frequency-dependent population regulation can occur in the fig-wasp mutualism, and how a host species can ‘set the rules of the game’ to ensure mutualistic behavior in its symbionts.
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Interference Competition and high temperature reduce the virulence of fig wasps and contribute to stability of a fig wasp mutualism
2009Co-Authors: R U Wang, Jo Ridley, Derek W. Dunn, Yaping Zhang, James M Cook, Qi Zheng, Douglas W. YuAbstract:Fig trees are pollinated by fig wasps, which also oviposit in female flowers. The wasp larvae gall and eat developing seeds. Although fig trees benefit from allowing wasps to oviposit, because the wasp offspring disperse pollen, figs must prevent wasps from ovipositing in all flowers, or seed production would cease, and the mutualism would go extinct. In Ficus racemosa, we find that syconia (‘figs’) that have few foundresses (ovipositing wasps) are underexploited in the summer (few seeds, few galls, many empty ovules) and are overexploited in the winter (few seeds, many galls, few empty ovules). Conversely, syconia with many foundresses produce intermediate numbers of galls and seeds, regardless of season. We use experiments to explain these patterns, and thus, to explain how this mutualism is maintained. In the hot summer, wasps suffer short lifespans and therefore fail to oviposit in many flowers. In contrast, cooler temperatures in the winter permit longer wasp lifespans, which in turn allows most flowers to be exploited by the wasps. However, even in winter, only in syconia that happen to have few foundresses are most flowers turned into galls. In syconia with higher numbers of foundresses, Interference Competition reduces foundress lifespans, which reduces the proportion of flowers that are galled. We further show that syconia encourage the entry of multiple foundresses by delaying ostiole closure. Taken together, these factors allow fig trees to reduce galling in the wasp-benign winter and boost galling (and pollination) in the wasp-stressing summer. Interference Competition has been shown to reduce virulence in pathogenic bacteria. Our results show that Interference also maintains cooperation in a classic, cooperative symbiosis, thus linking theories of virulence and mutualism. More generally, our results reveal how frequency-dependent population regulation can occur in the fig-wasp mutualism, and how a host species can ‘set the rules of the game’ to ensure mutualistic behavior in its symbionts.
Derek W. Dunn - One of the best experts on this subject based on the ideXlab platform.
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Interference Competition and high temperatures reduce the virulence of fig wasps and stabilize a fig wasp mutualism
PLOS ONE, 2009Co-Authors: Ruiwu Wang, Jo Ridley, Derek W. Dunn, Douglas W. Yu, Yaping Zhang, James M Cook, Qi ZhengAbstract:Fig trees are pollinated by fig wasps, which also oviposit in female flowers. The wasp larvae gall and eat developing seeds. Although fig trees benefit from allowing wasps to oviposit, because the wasp offspring disperse pollen, figs must prevent wasps from ovipositing in all flowers, or seed production would cease, and the mutualism would go extinct. In Ficus racemosa, we find that syconia (‘figs’) that have few foundresses (ovipositing wasps) are underexploited in the summer (few seeds, few galls, many empty ovules) and are overexploited in the winter (few seeds, many galls, few empty ovules). Conversely, syconia with many foundresses produce intermediate numbers of galls and seeds, regardless of season. We use experiments to explain these patterns, and thus, to explain how this mutualism is maintained. In the hot summer, wasps suffer short lifespans and therefore fail to oviposit in many flowers. In contrast, cooler temperatures in the winter permit longer wasp lifespans, which in turn allows most flowers to be exploited by the wasps. However, even in winter, only in syconia that happen to have few foundresses are most flowers turned into galls. In syconia with higher numbers of foundresses, Interference Competition reduces foundress lifespans, which reduces the proportion of flowers that are galled. We further show that syconia encourage the entry of multiple foundresses by delaying ostiole closure. Taken together, these factors allow fig trees to reduce galling in the wasp-benign winter and boost galling (and pollination) in the wasp-stressing summer. Interference Competition has been shown to reduce virulence in pathogenic bacteria. Our results show that Interference also maintains cooperation in a classic, cooperative symbiosis, thus linking theories of virulence and mutualism. More generally, our results reveal how frequency-dependent population regulation can occur in the fig-wasp mutualism, and how a host species can ‘set the rules of the game’ to ensure mutualistic behavior in its symbionts.
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Interference Competition and high temperature reduce the virulence of fig wasps and contribute to stability of a fig wasp mutualism
2009Co-Authors: R U Wang, Jo Ridley, Derek W. Dunn, Yaping Zhang, James M Cook, Qi Zheng, Douglas W. YuAbstract:Fig trees are pollinated by fig wasps, which also oviposit in female flowers. The wasp larvae gall and eat developing seeds. Although fig trees benefit from allowing wasps to oviposit, because the wasp offspring disperse pollen, figs must prevent wasps from ovipositing in all flowers, or seed production would cease, and the mutualism would go extinct. In Ficus racemosa, we find that syconia (‘figs’) that have few foundresses (ovipositing wasps) are underexploited in the summer (few seeds, few galls, many empty ovules) and are overexploited in the winter (few seeds, many galls, few empty ovules). Conversely, syconia with many foundresses produce intermediate numbers of galls and seeds, regardless of season. We use experiments to explain these patterns, and thus, to explain how this mutualism is maintained. In the hot summer, wasps suffer short lifespans and therefore fail to oviposit in many flowers. In contrast, cooler temperatures in the winter permit longer wasp lifespans, which in turn allows most flowers to be exploited by the wasps. However, even in winter, only in syconia that happen to have few foundresses are most flowers turned into galls. In syconia with higher numbers of foundresses, Interference Competition reduces foundress lifespans, which reduces the proportion of flowers that are galled. We further show that syconia encourage the entry of multiple foundresses by delaying ostiole closure. Taken together, these factors allow fig trees to reduce galling in the wasp-benign winter and boost galling (and pollination) in the wasp-stressing summer. Interference Competition has been shown to reduce virulence in pathogenic bacteria. Our results show that Interference also maintains cooperation in a classic, cooperative symbiosis, thus linking theories of virulence and mutualism. More generally, our results reveal how frequency-dependent population regulation can occur in the fig-wasp mutualism, and how a host species can ‘set the rules of the game’ to ensure mutualistic behavior in its symbionts.