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Joachim Offenberg - One of the best experts on this subject based on the ideXlab platform.
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Oecophylla longinoda hymenoptera formicidae lead to increased cashew kernel size and kernel quality
Journal of Economic Entomology, 2017Co-Authors: Florence M Anato, Joachim Offenberg, Antonio Sinzogan, Jean-françois Vayssières, Appolinaire Adandonon, Rosine Wargui, J M Deguenon, P M Ayelo, Dansou KossouAbstract:Weaver ants, Oecophylla spp., are known to positively affect cashew, Anacardium occidentale L., raw nut yield, but their effects on the kernels have not been reported. We compared nut size and the proportion of marketable kernels between raw nuts collected from trees with and without ants. Raw nuts collected from trees with weaver ants were 2.9% larger than nuts from control trees (i.e., without weaver ants), leading to 14% higher proportion of marketable kernels. On trees with ants, the kernel: raw nut ratio from nuts damaged by formic acid was 4.8% lower compared with nondamaged nuts from the same trees. Weaver ants provided three benefits to cashew production by increasing yields, yielding larger nuts, and by producing greater proportions of marketable kernel mass. (Resume d'auteur)
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mating strategy of Oecophylla smaragdina hymenoptera formicidae in northern australia
Australian Journal of Entomology, 2016Co-Authors: Mogens Nielsen, Renkang Peng, Joachim Offenberg, Dorthe BirkmoseAbstract:The aim of this study was to elucidate the mating strategy of Oecophylla smaragdina (Fabricius, 1775) and to clarify the factors that related to the nuptial flight. The nuptial flight was investigated over three seasons in the Darwin area, Australia, in which a total of 19 swarmings were observed. All swarmings were observed on days where no rain fell before 15:00 h, and with wind speed ≤18 km/h. On days of swarming air pressure was significantly higher (mean ± SD: 1009.3 ± 1.6 hPa) than on rainless days without swarming (mean ± SD: 1006.9 ± 1.2 hPa). Several swarmings took place during the season, and the production of alate queens occurred more or less continuously over a period of at least 2 months. Therefore, the number of individuals in each swarming depends on the time elapsed since the last swarming. Swarming commenced with males gathering on the external surfaces of nests at sunrise, and about 15 min later they started departing, which took about 10 min. When the males commenced flying the females came out of the nests. When most males had flown, the females started flying, which also took about 10 min. Both males and females flew straight up towards an opening in the canopy. After swarming, alate queens were observed coming down to the canopy after 15–20 min. No queens were found in artificial queen traps 2 h after swarming. A few queens were observed flying around 13:00 h, and later in the afternoon many fertilised queens were found in queen traps. From field observation and laboratory experiments, we conclude that it is most plausible that alate queens meet the males in the air, proceed to the tree canopy to conclude the mating, and then after midday the mated alate queens fly individually to find a nesting site.
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mating behavior of the african weaver ant Oecophylla longinoda latreille hymenoptera formicidae
Sociobiology, 2015Co-Authors: W. A. Nene, Joachim Offenberg, Gration M. Rwegasira, M Mwatawala, Mogens NielsenAbstract:Mating in most species of ants occurs during nuptial flights. In the African weaver ant , Oecophylla longinoda Latreille, mating has previously been hypothesized to take place within the nest before the nuptial flight. However, several researchers disagree with this supposition particularly with reference to the closely related species Oecopylla smaragdina (Fabricius) whose mating occur during nuptial flights. Understanding the mating strategy of O. longinoda is of importance for its successful application in biological control programs. We conducted field and screen house experiments during two mating seasons to determine whether the mating occur prior to the dispersal flight. We examined winged O. longinoda queens on the nest surface before taking flight, immediately after leaving the nest, up to twelve hours (12h) after leaving the nest and after settling naturally following the dispersal flights. Mating in captivity between different number of males and queens were also assessed. Only eggs produced by queens (N=65) collected after their natural settling hatched into larvae. No eggs hatched from any of the 527 winged queens that were collected prior to their dispersal flights and no mating attempts in captivity lead to viable offspring. Findings from the current study suggest that mating of O. longinoda queens take place during a nuptial flight and does not take place within the nest, as previously suggested.
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effect of supplementary feeding of Oecophylla longinoda on their abundance and predatory activities against cashew insect pests
Biocontrol Science and Technology, 2015Co-Authors: Nassor Rashid Abdulla, Karl-martin Vagn Jensen, Gration M. Rwegasira, M Mwatawala, Joachim OffenbergAbstract:Many studies have shown the efficiency of using weaver ants (Oecophylla species) as natural biocontrol agents against agricultural pests. Supplementary feeding could promote fast growth of this ant's population and discourage them from moving away. However, such artificial feeding might slow down ants search rates and in this way make them less efficient bio-agents. The experiments were conducted for two consecutive seasons at Naliendele Research Station. Cashew trees planted at a spacing of 12 m × 12 m in 2002 were used to investigate whether supplementary feeding could enhance foraging behaviour of Oecophylla longinoda. Fed O. longinoda colonies fed weaver ants (FWA) were supplemented with a 30% sugar solution and approximately 22 g of finely ground fish meat at two-week intervals while the unfed colonies unfed weaver ants (UWA) had access to only naturally occurring food sources. Weaver ant densities and pest damage were monitored fortnightly on newly damaged shoots, panicles and fruits and nut yields ...
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Pupae transplantation to boost early colony growth in the weaver ant Oecophylla longinoda Latreille (Hymenoptera: Formicidae)
Sociobiology, 2013Co-Authors: Issa Ouagoussounon, Joachim Offenberg, Antonio Sinzogan, Jean-françois Vayssières, Appolinaire Adandonon, Dansou KossouAbstract:Oecophylla ants are currently used for biological control in fruit plantations in Australia, Asia and Africa and for protein production in Asia. To further improve the technology and implement it on a large scale, effective and fast production of live colonies is desirable. Early colony development may be artificially boosted via the use of multiple queens (pleometrosis) and/or by adoption of foreign pupae in developing colonies. In the present experiments, we tested if multiple queens and transplantation of pupae could boost growth in young Oecophylla longinoda colonies. Colonies with two queens artificially placed in the same nest, all perished due to queen fighting, suggesting that pleometrosis is not used by O. longinoda in Benin. In contrast, pupae transplantation resulted in highly increased growth rates, as pupae were readily adopted by the queens and showed high survival rates (mean = 92%). Within the 50-day experiment the total number of individuals in colonies with 50 and 100 pupae transplanted, increased with 169 and 387 %, respectively, compared to colonies receiving no pupae. This increase was both due to the individuals added in the form of pupae but also due to an increased per capita brood production by the resident queen, triggered by the adopted pupae. Thus pupae transplantation may be used to shorten the time it takes to produce weaver ant colonies in ant nurseries, and may in this way facilitate the implementation of weaver ant biocontrol in West Africa.
Mark A Elgar - One of the best experts on this subject based on the ideXlab platform.
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density of antennal sensilla influences efficacy of communication in a social insect
The American Naturalist, 2013Co-Authors: Katherine P Gill, Ellen Van Wilgenburg, David L Macmillan, Mark A ElgarAbstract:AbstractEffective communication requires reliable signals and competent receptors. Theoretical and empirical accounts of animal signaling focus overwhelmingly on the capacity of the signaler to convey the message. Nevertheless, the intended receiver’s ability to detect a signal depends on the condition of its receptor organs, as documented for humans. The impact of receptor organ condition on signal reception and its consequences for functional behavior are poorly understood. Social insects use antennae to detect chemical odors that distinguish between nestmates and enemies, reacting aggressively to the latter. We investigated the impact of antennal condition, determined by the density of sensilla, on the behavior of the weaver ant Oecophylla smaragdina. Worker aggression depended upon the condition of their antennae: workers with fewer sensilla on their antennae reacted less aggressively to nonnestmate enemies. These novel data highlight the largely unappreciated significance of receptor organ condition ...
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Mimicry of Host Cuticular Hydrocarbons by Salticid Spider Cosmophasis bitaeniata That Preys on Larvae of Tree Ants Oecophylla smaragdina
Journal of Chemical Ecology, 2002Co-Authors: Rachel A Allan, Robert J. Capon, W. Vance Brown, Mark A ElgarAbstract:The salticid spider Cosmophasis bitaeniata preys on the larvae of the green tree ant Oecophylla smaragdina . Gas chromatography (GC) and gas chromatography–mass spectrometry (GC-MS) reveal that the cuticle of C. bitaeniata mimics the mono- and dimethylalkanes of the cuticle of its prey. Recognition bioassays with extracts of the cuticular hydrocarbons of ants and spiders revealed that foraging major workers did not respond aggressively to the extracts of the spiders or conspecific nestmates, but reacted aggressively to conspecific nonnestmates. Typically, the ants either failed to react (as with control treatments with no extracts) or they reacted nonaggressively as with conspecific nestmates. These data indicate that the qualitative chemical mimicry of ants by C. bitaeniata allows the spiders to avoid detection by major workers of O. smaragdina.
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exploitation of the green tree ant Oecophylla smaragdina by the salticid spider cosmophasis bitaeniata
Australian Journal of Zoology, 2001Co-Authors: Rachel A Allan, Mark A ElgarAbstract:The salticid spider Cosmophasis bitaeniata is a myrmecophilic associate of the green tree ant, Oecophylla smaragdina. The abundance of C. bitaeniata on a tree or shrub is positively correlated with the number of nests of O. smaragdina on that vegetation. Experiments with captive spiders confirmed that the spiders prey on the larvae of their highly territorial and aggressive ant host, typically by removing the larvae from the mandibles of minor workers. C. bitaeniata avoids direct contact with major workers of O. smaragdina in daylight, but congeners elicited higher activity levels of major workers than either nestmate workers or C. bitaeniata. These data suggest thatC. bitaeniata may be an exploitative chemical mimic of its host.
Jean-françois Vayssières - One of the best experts on this subject based on the ideXlab platform.
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Oecophylla longinoda hymenoptera formicidae lead to increased cashew kernel size and kernel quality
Journal of Economic Entomology, 2017Co-Authors: Florence M Anato, Joachim Offenberg, Antonio Sinzogan, Jean-françois Vayssières, Appolinaire Adandonon, Rosine Wargui, J M Deguenon, P M Ayelo, Dansou KossouAbstract:Weaver ants, Oecophylla spp., are known to positively affect cashew, Anacardium occidentale L., raw nut yield, but their effects on the kernels have not been reported. We compared nut size and the proportion of marketable kernels between raw nuts collected from trees with and without ants. Raw nuts collected from trees with weaver ants were 2.9% larger than nuts from control trees (i.e., without weaver ants), leading to 14% higher proportion of marketable kernels. On trees with ants, the kernel: raw nut ratio from nuts damaged by formic acid was 4.8% lower compared with nondamaged nuts from the same trees. Weaver ants provided three benefits to cashew production by increasing yields, yielding larger nuts, and by producing greater proportions of marketable kernel mass. (Resume d'auteur)
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seasonal pattern in food gathering of the weaver ant Oecophylla longinoda hymenoptera formicidae in mango orchards in benin
Biocontrol Science and Technology, 2015Co-Authors: Jean-françois Vayssières, Antonio Sinzogan, Issa Ouagoussounon, Appolinaire Adandonon, Sam Korie, Raymond Todjihounde, Seidou Alassane, Rosine Wargui, Florence M Anato, Georg GoergenAbstract:Prey capture and food scavenging activities of Oecophylla longinoda were monitored through regular weekly samplings during two consecutive years (2009–2010) in a large mango orchard of the Borgou Department of Benin, West Africa, a main mango production area located in the Sudan agro-ecological zone. In both years, interspecific competition with other ants occurred mainly during the dry season (January to March) resulting in increased captures of Formicinae, Myrmicinae and Ponerinae. More prey was caught during the rainy season (end April to end October) than during the rest of the year, with Diptera and Coleoptera prey peaking in May and June, respectively, along with the mango season. As insect prey quickly decreased during November to December weaver ants increasingly collected seeds and plant debris. A total of 241 species of insects were captured including 61 species (25.3%) associated with mango and a few with cashew, among which 48 mango pest species (78.7% of species associated with mango tree). O...
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Pupae transplantation to boost early colony growth in the weaver ant Oecophylla longinoda Latreille (Hymenoptera: Formicidae)
Sociobiology, 2013Co-Authors: Issa Ouagoussounon, Joachim Offenberg, Antonio Sinzogan, Jean-françois Vayssières, Appolinaire Adandonon, Dansou KossouAbstract:Oecophylla ants are currently used for biological control in fruit plantations in Australia, Asia and Africa and for protein production in Asia. To further improve the technology and implement it on a large scale, effective and fast production of live colonies is desirable. Early colony development may be artificially boosted via the use of multiple queens (pleometrosis) and/or by adoption of foreign pupae in developing colonies. In the present experiments, we tested if multiple queens and transplantation of pupae could boost growth in young Oecophylla longinoda colonies. Colonies with two queens artificially placed in the same nest, all perished due to queen fighting, suggesting that pleometrosis is not used by O. longinoda in Benin. In contrast, pupae transplantation resulted in highly increased growth rates, as pupae were readily adopted by the queens and showed high survival rates (mean = 92%). Within the 50-day experiment the total number of individuals in colonies with 50 and 100 pupae transplanted, increased with 169 and 387 %, respectively, compared to colonies receiving no pupae. This increase was both due to the individuals added in the form of pupae but also due to an increased per capita brood production by the resident queen, triggered by the adopted pupae. Thus pupae transplantation may be used to shorten the time it takes to produce weaver ant colonies in ant nurseries, and may in this way facilitate the implementation of weaver ant biocontrol in West Africa.
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ovipositional behaviour of two mango fruit fly species diptera tephritidae in relation to Oecophylla cues hymenoptera formicidae as compared to natural conditions without ant cues
International Journal of Biological and Chemical Sciences, 2013Co-Authors: Jean-françois Vayssières, Antonio Sinzogan, P. Van Mele, Appolinaire Adandonon, Sam KorieAbstract:The tritrophic interactions between mangoes ( Mangifera indica ), two frugivorous fly species of great economic significance, Bactrocera invadens and Ceratitis cosyra , and weaver ants ( Oecophylla longinoda ) were studied in Benin. We investigated whether Oecophylla cues affect B. invadens and C. cosyr a oviposition behaviour compared to natural conditions. Results show that on un-marked fruits, both C. cosyra and B. invadens adults have different active periods and length of oviposition, both under laboratory and field conditions. Compared to their landing on unmarked fruits at 7h after confinement, 46% of B. invadens refrained from landing on fruits marked with Oecophylla cues, while C. cosyra reduced its landing by 73%. In contrast to the un-marked fruit, both tephritid species significantly reduce oviposition duration and oviposited less in fruits when weaver ants had patrolled on them before. Moreover, no significant difference was detected between C. cosyra and B. invadens, in number of pupae produced, when confined with ant-marked fruits. Ecological and behavioural implications of our observations are discussed. Keywords: Mango fruit flies, oviposition duration, predator avoidance, weaver ants, biocontrol.
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density of pheromone sources of the weaver ant Oecophylla longinoda affects oviposition behaviour and damage by mango fruit flies diptera tephritidae
International Journal of Pest Management, 2009Co-Authors: Appolinaire Adandonon, Antonio Sinzogan, Jean-françois Vayssières, Paul Van MeleAbstract:As damage by the fruit flies Bactrocera invadens and Ceratitis cosyra is significantly reduced in mango trees with weaver ants, but we rarely observed adult flies being captured, we investigated whether Oecophylla pheromones affect fruit fly oviposition behaviour. Mangoes were collected within 1 m and 1–3 m distance from ant nests, and from ant-free trees. Using both choice and no-choice tests, fruit flies were allowed to oviposit on fruits for 72 h in the absence of ants. Flies landed significantly more and spent more time on fruit from ant-free than from ant-colonized trees. The density of ant pheromone sources significantly affected the oviposition time and the number of fruit fly pupae collected per kg fruit under greenhouse conditions. However, field data did not show any difference in damage for fruit collected within 1 m and 1–3 m distance from ant nests, suggesting that physical or visual mechanisms complement the repellencey effect of ant pheromones against fruit flies.
Mogens Nielsen - One of the best experts on this subject based on the ideXlab platform.
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mating strategy of Oecophylla smaragdina hymenoptera formicidae in northern australia
Australian Journal of Entomology, 2016Co-Authors: Mogens Nielsen, Renkang Peng, Joachim Offenberg, Dorthe BirkmoseAbstract:The aim of this study was to elucidate the mating strategy of Oecophylla smaragdina (Fabricius, 1775) and to clarify the factors that related to the nuptial flight. The nuptial flight was investigated over three seasons in the Darwin area, Australia, in which a total of 19 swarmings were observed. All swarmings were observed on days where no rain fell before 15:00 h, and with wind speed ≤18 km/h. On days of swarming air pressure was significantly higher (mean ± SD: 1009.3 ± 1.6 hPa) than on rainless days without swarming (mean ± SD: 1006.9 ± 1.2 hPa). Several swarmings took place during the season, and the production of alate queens occurred more or less continuously over a period of at least 2 months. Therefore, the number of individuals in each swarming depends on the time elapsed since the last swarming. Swarming commenced with males gathering on the external surfaces of nests at sunrise, and about 15 min later they started departing, which took about 10 min. When the males commenced flying the females came out of the nests. When most males had flown, the females started flying, which also took about 10 min. Both males and females flew straight up towards an opening in the canopy. After swarming, alate queens were observed coming down to the canopy after 15–20 min. No queens were found in artificial queen traps 2 h after swarming. A few queens were observed flying around 13:00 h, and later in the afternoon many fertilised queens were found in queen traps. From field observation and laboratory experiments, we conclude that it is most plausible that alate queens meet the males in the air, proceed to the tree canopy to conclude the mating, and then after midday the mated alate queens fly individually to find a nesting site.
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mating behavior of the african weaver ant Oecophylla longinoda latreille hymenoptera formicidae
Sociobiology, 2015Co-Authors: W. A. Nene, Joachim Offenberg, Gration M. Rwegasira, M Mwatawala, Mogens NielsenAbstract:Mating in most species of ants occurs during nuptial flights. In the African weaver ant , Oecophylla longinoda Latreille, mating has previously been hypothesized to take place within the nest before the nuptial flight. However, several researchers disagree with this supposition particularly with reference to the closely related species Oecopylla smaragdina (Fabricius) whose mating occur during nuptial flights. Understanding the mating strategy of O. longinoda is of importance for its successful application in biological control programs. We conducted field and screen house experiments during two mating seasons to determine whether the mating occur prior to the dispersal flight. We examined winged O. longinoda queens on the nest surface before taking flight, immediately after leaving the nest, up to twelve hours (12h) after leaving the nest and after settling naturally following the dispersal flights. Mating in captivity between different number of males and queens were also assessed. Only eggs produced by queens (N=65) collected after their natural settling hatched into larvae. No eggs hatched from any of the 527 winged queens that were collected prior to their dispersal flights and no mating attempts in captivity lead to viable offspring. Findings from the current study suggest that mating of O. longinoda queens take place during a nuptial flight and does not take place within the nest, as previously suggested.
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The effect of cooling on mortality of the Asian weaver ant Oecophylla smaragdina
Insectes Sociaux, 2010Co-Authors: Henrik Lauridsen, Mogens Nielsen, Joachim OffenbergAbstract:Cooling is an efficient method to immobilise insects for handling, but it is known that fast cooling to temperatures above freezing can cause chill injury and/or death. The mortality of Asian weaver ants, Oecophylla smaragdina, a tropical species that does not normally encounter near freezing temperatures, was investigated in experiments with cooling temperatures of 0 and 5°C and duration of cooling periods of 45 and 150 min. No significant difference in mortality was found between ants cooled to 5 and 0°C; however, cooling to these temperatures led to higher mortalities compared to non-cooled control ants. Following both 45 and 150 min of cold treatment, a significant excessive mortality of cooled ants (compared to uncooled ants) was observed, indicating that effects of cooling on mortality should be considered when performing studies on Asian weaver ants.
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intercolony transplantation of Oecophylla smaragdina hymenoptera formicidae larvae
Journal of Asia-pacific Entomology, 2010Co-Authors: Kristian Krag, Mogens Nielsen, Joachim Offenberg, Rasmus Lundegaard, Decha WiwatwittayaAbstract:Oecophylla ants are utilized for biological control in fruit plantations in Australia and Asia. In Asia, queen larvae and alates are sold on commercial markets for human and animal consumption. This double utilization has induced an increasing interest in the domestication of these ants, but attempts to rear live colonies have been hindered partly by the length of time it takes from the founding of a colony until it can be utilized commercially. Early growth of a colony may be increased if ants from other colonies are adopted. The present experiments show that Oecophylla smaragdina larvae transplanted from other colonies are readily tolerated by non-nestmate workers and are reared to imagos. These results are fundamental for the future domestication of Oecophylla and elucidate the need for further studies of chemical nestmate recognition.
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evidence that insect herbivores are deterred by ant pheromones
Proceedings of The Royal Society B: Biological Sciences, 2004Co-Authors: Joachim Offenberg, Mogens Nielsen, Sopon Havanon, Donald J Macintosh, Sanit AksornkoaeAbstract:It is well documented that ants can protect plants against insect herbivores, but the underlying mechanisms remain almost undocumented. We propose and test the pheromone avoidance hypothesis—an indirect mechanism where insect herbivores are repelled not only by ants but also by ant pheromones. Herbivores subjected to ant predation will experience a selective advantage if they evolve mechanisms enabling them to avoid feeding within ant territories. Such a mechanism could be based on the ability to detect and evade ant pheromones. Field observations and data from the literature showed that the ant Oecophylla smaragdina distributes persistent pheromones throughout its territory. In addition, a laboratory test showed that the beetle Rhyparida wallacei , which this ant preys on, was reluctant to feed on leaves sampled within ant territories compared with leaves sampled outside territories. Thus, this study provides an example of an ant–herbivore system conforming to the pheromone avoidance hypothesis.
Bo Wang - One of the best experts on this subject based on the ideXlab platform.
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Variation in trophic cascade strength is triggered by top-down process in an ant-wasp-fig system
2018Co-Authors: Bo Wang, Simon T. Segar, Gui-zhong Deng, Tian-xun Luo, Hua Lin, Yan-qiong PengAbstract:R code and Original data for:Figure 2: Number of wasps from branches with weaver ants or without ants in the cool-dry (A), hot-dry (B), and rainy (C) seasons. Species composition is shown on the top of bar plot for each season, left pie (with ants), right pie (ants excluded). Syconia in the cool-dry season in ant exclusion treatments were all aborted. Linear mixed-effects models were fitted, with the number of fig wasps as the response variable, with treatment (trees with or without Oecophylla smaragdina ) as the fixed factor, tree as a random factor. * (P < 0.05), ** (P < 0.01), *** (P < 0.001), NS = not significant. CF = Ceratosolen fusciceps; SM = Sycophaga mayri; ST = S. testacea; SA = S. agraensis; AS = Apocrypta sp.; AW = A. westwoodi. Columns and bars show mean ± SD. # represent pollinating fig wasp. Numbers under the pie represent replications of syconium sampled.Figure 3: Number of seed from branches with weaver ants or ants excluded in cool-dry, hot-dry, and rainy seasons. * (P < 0.05), *** (P < 0.001). Numbers in the box represent replications of syconium sampled.Figure 4: Mean (±SD) interaction strength (A) of weaver ant, Oecophyla smaragdina, on the gall making fig wasp, Sycophagus mayri, and the strength of the trophic cascade (B) in different seasons. * (P < 0.05), *** (P < 0.001). Numbers in the brackets represent replications of with ants/ant exclusion branchlets pairs.Figure 5: Box plot of the number of weaver ant nests (A), number of weaver ants foraging in fig-bearing branchlets (B), foundress number (C), and oviposition scars of non-pollinating fig wasps (D) in the fruits of Ficus racemosa after receptive stage of Ficus racemosa in different seasons. Different letters represent significant differences between each season, pairwise comparisons conducted using Tukey and Kramer test. Each circle represents a data point. Figure 6: Number (mean ± SD) of weaver ants, Oecophyla smaragdina (A), pollinating fig wasp activity, Ceratosolen fusciceps (B), and gall making fig wasp, Sycophagus mayri activity (C) from 6:00 to 20:00 in different seasons. Symbols represent means and drop lines show the standard deviation. Different letters represent significant differences between each season, significance derived using nonparametric rank-based analysis of longitudinal data with ANOVA-type statistics (ATS).
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Chemical camouflage: a key process in shaping an ant-treehopper and fig-fig wasp mutualistic network
2017Co-Authors: Bo Wang, James Cook, Da-rong Yang, Derek W. Dunn, Ruiwu WangAbstract:Digital appendix 1: Tending behavior of weaver ants, Oecophylla smaragdina, to treehoppers, Tricentrus sp. Digital appendix 2: Predation by weaver ants, Oecophylla smaragdina, of a non-pollinating fig wasp, Platyneura mayri.
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a trophic cascade induced by predatory ants in a fig fig wasp mutualism
Journal of Animal Ecology, 2014Co-Authors: Xiangzong Geng, James M Cook, Bo Wang, Ruiwu WangAbstract:1. A trophic cascade occurs when predators directly decrease the densities, or change the behaviour, of herbivores and thus indirectly increase plant productivity. The predator-herbivore-plant context is well known, but some predators attack species beneficial to plants (e. g. pollinators) and/or enemies of herbivores (e.g. parasites), and their role in the dynamics of mutualisms remains largely unexplored. 2. We surveyed the predatory ant species and studied predation by the dominant ant species, the weaver ant Oecophylla smaragdina, associated with the fig tree Ficus racemosa in southwest China. We then tested the effects of weaver ants on the oviposition behaviour of pollinating and non-pollinating fig wasps in an ant-exclusion experiment. The effects of weaver ants on fig wasp community structure and fig seed production were then compared between trees with and without O. smaragdina. 3. Oecophylla smaragdina captured more non-pollinating wasps (Platyneura mayri) than pollinators as the insects arrived to lay eggs. When ants were excluded, more non-pollinators laid eggs into figs and fewer pollinators entered figs. Furthermore, trees with O. smaragdina produced more pollinator offspring and fewer non-pollinator offspring, shifting the community structure significantly. In addition, F. racemosa produced significantly more seeds on trees inhabited by weaver ants. 4. Oecophylla smaragdina predation reverses the dominance of the two commonest wasp species at the egg-laying stage and favours the pollinators. This behavioural pattern is mirrored by wasp offspring production, with pollinators' offspring dominating figs produced by trees inhabited by weaver ants, and offspring of the non-pollinator P. mayri most abundant in figs on trees inhabited by other ants. 5. Overall, our results suggest that predation by weaver ants limits the success of the non-pollinating P. mayri and therefore indirectly benefits the mutualism by increasing the reproductive success of both the pollinators and the plant. Predation is thus a key functional factor that can shape the community structure of a pollinator-plant mutualistic system.
