Social Dynamics in Paper Wasps: The case of nest-drifting in Polistes canadensis

Le passage de la vie solitaire à la vie sociale représente une des principales transitions évolutives. La socialité a évolué au sein de plusieurs taxons du règne animal et notamment chez les insectes sociaux qui ont atteint son niveau le plus élevé : l'eusocialité. Les colonies d'insectes sociaux se composent d'une reine, qui monopolise la reproduction, et d'ouvrières, non-reproductrices ou parfois stériles, qui aident à élever la descendance de la reine. Selon la théorie de la sélection de parentèle, les ouvrières augmentent leur fitness (succès reproducteur) non pas à travers leur propre progéniture, mais en aidant des individus apparentés (leur reine) à produire davantage de descendants. Cette théorie prédit ainsi que les ouvrières ont un intérêt à rester fidèles à leur nid natal. Toutefois, chez la guêpe tropicale Polistes canadensis, de nombreuse ouvrières visitent d'autres nids que leur nid natal : un phénomène appelé « dérive des ouvrières ». Le but de ce doctorat est ainsi de mieux comprendre les mécanismes impliqués dans ce comportement particulier des ouvrières ainsi que ces implications pour la théorie de la sélection de parentèle. Nous avons examiné le comportement de dérive des ouvrières à travers une étude des dynamiques sociales chez la guêpe tropicale P. canadensis. Mes résultats montrent que les populations de P. canadensis se composent en différentes agrégations de nids. Malgré de précédentes suggestions, on n'observe qu'une faible viscosité génétique au sein des populations de P. canadensis étudiées. On retrouve toutefois un degré d'apparentement entre nids d'une même agrégation. Ceci suggère que les ouvrières dériveuses sont susceptibles de bénéficier de fitness indirect en aidant les nids proches géographiquement. De plus, ces échanges d'ouvrières ne semblent pas accidentels puisque l'on constate des variations de taux de dérive et puisque les déplacements observés entre nids persistent sur plusieurs périodes de temps. La charge de travail, qui correspond aux différences d'effort de fourragement entre nid visités et natals, est décrite dans notre étude comme potentiel facteur expliquant le comportement de dérive des ouvrières chez P. canadensis. Nos expériences de retrait d'ouvrières et de couvain ont révélées que les dériveuses ne semblent pas répondre aux changements de besoins en aide des nids visités. Les ouvrières dériveuses biaisent leur effort en aidant leur propre nid, par lequel elles bénéficient le plus en termes de fitness indirect, avant de se consacrer à tout autre nid. Dans l'ensemble, ces résultats sur la dérive des ouvrières chez P. canadensis sont cohérents et suggèrent que ce comportement est une importante stratégie de reproduction alternative chez cette espèce qui contribue à la fitness indirecte de ces ouvrières non-reproductrices. De plus, ce doctorat apporte des informations sur la structure génétique des populations de guêpes Polistes et décrit le rôle des ouvrières inactives. Celles-ci semblent servir de réserve en ouvrières apportant du support à la colonie dans l'éventualité d'une perte d'individus. Plus généralement, ce travail met l'accent sur l'organisation complexe et l'adaptabilité des individus dans les sociétés d'insectes. - One major transition in evolution is the shift from solitary to social life. Sociality has evolved in a few taxa of the animal kingdom, most notably in the social insects which have achieved the highest level of sociality: eusociality. Colonies of social insects are formed by a reproductive queen, and many non-reproductive or sterile workers who help raise their mother queen's offspring. Kin selection theory explains worker behaviour in terms of the indirect fitness they gain from raising non-offspring kin. It therefore predicts that workers should stay faithful to their natal nests, to which they are the more related. However, in the tropical paper wasps Polistes canadensis, high levels of nest-drifting, whereby workers spend time on other neighbouring nests, has been reported. This PhD aimed at understanding the mechanisms involved in this peculiar behaviour as well as its implications for kin selection theory. I examined nest-drifting through the study of the social dynamics of the tropical paper wasp P. canadensis. My results showed that populations of this species of paper wasps are composed of different aggregations of nests. The studied populations showed little limited dispersal (viscosity), despite previous suggestion, but nests within these aggregations were more related to each other than nests outside of aggregations. This suggested that drifters may benefit from indirect fitness when helping on neighbouring nests. Drifting was unlikely to be accidental since we found drifting patterns at various rates and consistently over several time periods during monitoring. Workload (differences in colony-level foraging effort) was also a potential factor explaining nest-drifting in P. canadensis. Worker and brood removal experiments revealed that drifters do not respond to any changes in the need for help in the non-natal nests they visit. Drifters thus bias their help in their natal nests, from which they may benefit the most in terms of indirect fitness, before investing in others. Altogether, these results on nest-drifting in P. canadensis are consistent and suggest that nest-drifting is an important alternative reproductive strategy, contributing to the indirect fitness benefits gained by non-reproductive wasps. Additionally, this PhD provides information on the genetic structure of paper wasps' populations and demonstrates the role of inactive or lazy wasps as a "reserve worker force", which provides resilience to the colony in the event of worker mortality. More generally, this work further highlights the complex organization and adaptability of individuals in insect societies.

Aspectos bionômicos da vespa social Neotropical Polistes canadensis canadensis (Linnaeus) (Hymenoptera, Vespidae

Aspectos bionômicos da vespa social Neotropical Polistes canadensis canadensis (Linnaeus) (Hymenoptera, Vespidae). O objetivo deste trabalho foi estudar alguns aspectos bionômicos da vespa social neotropical Polistes canadensis canadensis (Linnaeus, 1758). Vinte e seis colônias foram acompanhadas entre abril de 2004 e julho de 2006, no município de Mundo Novo, estado de Mato Grosso do Sul, região Centro-Oeste do Brasil. Os resultados encontrados nesse estudo sugerem que o padrão fenológico de Polistes canadensis canadensis é assincrônico nessa região, com fundações e abandonos podendo ocorrer o ano todo. A duração média dos estágios imaturos foi diferente entre as estações climáticas fria-seca e úmida-quente. Diferentes substratos foram escolhidos para nidificação, contudo em ambientes que forneceram condições físicas mais homogêneas durante o dia foram encontradas as maiores freqüências de sucesso. Colônias nessa espécie são fundadas por haplometrose ou pleometrose, no entanto, o sucesso tem sido maior para colônias pleometróticas.

Divisão de trabalho em colônias da vespa social neotropical Polistes canadensis canadensis Linnaeus (Hymenoptera, Vespidae)

Foram realizadas 100 horas de observação usando o método "scanning sample" para a qualificação e quantificação dos atos comportamentais de rainhas e operárias de quinze colônias de Polistes canadensis canadensis. Foi descrito um repertório comportamental com 28 atos, no qual rainhas executam 19 atos na colônia, enquanto operárias 26, ocorrendo 17 atos em comum entre as duas castas. Dentre esses atos, dois foram exclusivos do repertório de rainhas e nove de operárias. O resultado do teste do qui-quadrado apontou diferenças significativas entre os repertórios das duas castas, sendo que rainhas permanecem mais tempo no ninho e executam com maior freqüência atividades intra-nidais, ligadas à reprodução, enquanto que as operárias executam mais freqüentemente atividades relacionadas à manutenção das colônias, como a atividade de forrageamento que demanda um maior risco e alto custo energético.

Uso da vespa social Polistes versicolor no controle de desfolhadores de eucalipto

O objetivo deste trabalho foi determinar os recursos forrageados por Polistes versicolor em área de reflorestamento com eucalipto e identificar as presas forrageadas. No período de janeiro a dezembro de 2007, foram realizadas 24 observações da atividade forrageadora de colônias de P. versicolor presentes em um reflorestamento de eucalipto, em Juiz de Fora, MG, totalizando 240 horas de registros. Durante as dez horas de observação diária, foram registrados e qualificados, a cada 30 minutos, os retornos das operárias para a colônia. Foram registrados 1.809 retornos, dos quais 51,63% foram com néctar; 6,85%, com água; 4,7%, com fibra vegetal; 17,41%, com presas; e 19,40%, sem recurso forrageado (improdutivos). As operárias de P. versicolor predaram exclusivamente lagartas de lepidópteros, que foram a única fonte de proteína animal oferecida aos insetos imaturos, na colônia. Dessa forma, a espécie estudada apresenta potencial como agente controlador biológico de herbívoros desfolhadores de eucalipto.

Clypeal patterning in the paper wasp Polistes dominulus: no evidence of adaptive value in the wild

Status signals function in a number of species to communicate competitive ability to conspecific rivals during competition for resources. In the paper wasp Polistes dominulus, variable black clypeal patterns are thought to be important in mediating competition among females. Results of previous behavioral experiments in the lab indicate that P dominulus clypeal patterns provide information about an individual's competitive ability to rivals during agonistic interactions. To date, however, there has been no detailed examination of the adaptive value of clypeal patterns in the wild. To address this, we looked for correlations between clypeal patterning and various fitness measures, including reproductive success, hierarchical rank, and survival, in a large, free-living population of P. dominulus in southern Spain. Reproductive success over the nesting season was not correlated with clypeal patterning. Furthermore, there was no relationship between a female's clypeal patterning and the rank she achieved within the hierarchy or her survival during nest founding. Overall, we found no evidence that P dominulus clypeal patterns are related to competitive ability or other aspects of quality in our population. This result is consistent with geographical variation in the adaptive value of clypeal patterns between P. dominulus populations; however, data on the relationship between patterning and fitness from other populations are required to test this hypothesis.

Characterization of the mechanisms underlying the inflammatory response to Polistes lanio lanio (paper wasp) venom in mouse dorsal skin

Stings by Polistes wasps can cause life-threatening allergic reactions, pain and inflammation. We examined the changes in microvascular permeability and neutrophil influx caused by the venom of Polistes lanio a paper wasp found in southeastern Brazil. The intradermal injection of wasp venom caused long-lasting paw oedema and dose-dependently increased microvascular permeability in mouse dorsal skin. SR140333, an NK(1) receptor antagonist, markedly inhibited the response, but the NK(2) receptor antagonist SR48968 was ineffective. The oedema was reduced in capsaicin-treated rats, indicating a direct activation of sensory fibres. Dialysis of the venom partially reduced the oedema and the remaining response was further inhibited by SR140333. Mass spectrometric analysis of the venom revealed two peptides (QPPTPPEHRFPGLM and ASEPTALGLPRIFPGLM) with sequence similarities to the C-terminal region of tachykinin-like peptides found in Phoneutria nigniventer spider venom and vertebrates. Wasp venom failed to release histamine from mast cells in vitro and spectrofluorometric assay of the venom revealed a negligible content of histamine in the usual dose of P.l. lanio venom (1 nmol of histamine/7 mu g of venom)that was removed by dialysis. The histamine H(1) receptor antagonist pyrilamine, but not bradykinin B(1) or B(2) receptor antagonists, inhibited venom-induced oedema. In conclusion, P. l. lanio venom induces potent oedema and increases vascular permeability in mice, primarily through activation of tachykinin NK(1) receptors by substance P released from sensory C fibres, which in turn releases histamine from dermal mast cells. This is the first description of a neurovascular mechanism for P. l. lanio venom-mediated inflammation. The extent to which the two tachykinin-like peptides identified here contribute to this neurogenic inflammatory response remains to be elucidated. (c) 2008 Elsevier Ltd. All rights reserved.

Prey captured and used in Polistes versicolor (Olivier) (Hymenoptera: Vespidae) Nourishment

As vespas sociais são predadoras de muitas espécies de insetos e o estudo de suas presas pode revelar seu potencial para programas de controle biológico de pragas. Foram realizadas 240h de coleta de presas em 32 colônias de Polistes versicolor (Olivier) no município de Juiz de Fora, MG, de março de 2000 a fevereiro de 2001. As presas capturadas por P. versicolor foram, principalmente, das ordens Lepidoptera (95,4%) e Coleoptera (1,1%) além de 3,4% de indivíduos não identificados. A espécie mais coletada foi Chlosyne lacinia saundersii Doubleday & Hewitson (13,5%) (Lepidoptera: Nymphalidae) e o número total estimado de presas capturadas por colônia de P. versicolor foi de 4.015 indivíduos por ano. Isso mostra que a espécie pode ser utilizada em programas de manejo integrado de pragas de insetos herbívoros, principalmente lagartas desfolhadoras.

Biology of the wasp Polistes (Epicnemius) cinerascens Saussure (Hymenoptera: Vespidae)

Estudos dos ninhos da vespa social Polistes (Epicnemius) cinerascens Saussure apresentaram correlação entre o tamanho do favo e a largura do pedúnculo, bem como com a altura das células e número de gerações produzidas. Foi verificado o tempo de duração do ciclo biológico das colônias (199,3 dias), número de células construídas (102,9) e de adultos produzidos (94,2), além das taxas: 0,5 células/dia, 0,3 adultos/dia e 0,8 adultos/célula, da percentagem de células produtivas/ninho (55,2 %) e do número de gerações/colônia (até 4). O número de ínstares larvais foi 5, a taxa de crescimento 1,3, o tempo de duração dos estágios imaturos foi: ovos = 13,0 dias, larvas = 23,7, pupas - 22,2 e a duração total = 58,6 dias. A longevidade dos adultos foi 38,3 dias.

Morphological features and occurrence of degenerative characteristics in the hypopharyngeal glands of the paper wasp Polistes versicolor (Olivier) (Hymenoptera : Vespidae)

Different histochemical techniques were applied to examine the morphological features of the secretory cells of hypopharyngeal glands in the wasp Polistes versicolor. The results showed that most analyzed individuals present active glands with secretion stored in the cytoplasm. In some glands, morphological analyses revealed the presence of degenerative characteristics. Analyses of cellular integrity, however, did not detect dead cells. The results showed that, in P. versicolor, the development and regression of the hypopharyngeal glands were not age related, unlike glands of social bees. (c) 2006 Elsevier Ltd. All rights reserved.

Comparative analysis of morphological, structural and morphometric patterns of Polistes versicolor (Olivier) (Hymenoptera: Vespidae) hypopharyngeal glands

O presente estudo descreve, por meio de técnicas de histologia e ultramorfologia, os padrões morfológico e estrutural das glândulas hipofaríngeas de Polistes versicolor (Olivier), comparando-os aos de outros grupos de Hymenoptera. Além disso, analisa a presença de variações intraespecíficas dessas glândulas por meio de análises morfométricas das células secretoras de vespas em diferentes idades. Na espécie estudada foi constatada a presença de glândulas com características primitivas, possuindo células secretoras que desembocam individualmente na placa hipofaríngea. O padrão morfológico encontrado nas glândulas hipofaríngeas foi basicamente o mesmo para todas as vespas estudadas, entretanto o comprimento das células glandulares apresentou variações significativas entre indivíduos. Aparentemente essas variações não estão relacionadas com a idade.

Ultrastructural features of the hypopharyngeal glands in the social wasp Polistes versicolor (Hymenoptera : Vespidae)

The wasps of the genus Polistes have been considered the key to understanding the evolution of social behavior in Hymenoptera. Several studies have shown that the development of organized insect societies was accompanied by the evolution of structures like exocrine glands, which became specialized to perform specific functions. This article investigates the ultrastructural and cytochemical features of the hypopharyngeal glands of Polistes versicolor. These glands have been studied in depth in social bees, where they occur only in nurses and produce the royal jelly. Our results revealed that these glands basically did not vary among individuals or between sexes. They are constituted by spherical cells, each with a large nucleus and well-developed rough endoplasmic reticulum. Secretion vesicles are abundant, but lipid droplets were not observed, indicating that these glands may not have a role in pheromone synthesis. Acid phosphatase was detected in lysosomes, and also free in the cytosol, but did not seem to be related with cell death. Thus, our results suggest that the hypopharyngeal glands of P. versicolor may not have a specialized social role, but could produce digestive enzymes.

Produtividade em colônias de Polistes (Ap hanilopterus) vers icolor Olivier, 1791 (Hymenoptera: Vespidae, Polis tinae)

From August 2000 to December 2003, 185 colonies of Polistes versicolor were observed at the Bioterio of the Instituto de Biociencias, UNESP, Campus de Rio Claro, SP. In 144 colonies (77,84%) didn't emerge wasps, and of others 41 (22,16%), in 16 it was not possible to obtain the number of meconia, because they were attacked in several degrees of injury by natural enemies such as, ants, birds and parasitic wasps. The colonies productivity was measured through the meconia count in the cells of 25 colonies, which ranged from 1 to 6 meconia by cell.

Divisão de trabalho em colônias da vespa social neotropical Polistes canadensis canadensis Linnaeus (Hymenoptera, Vespidae)

Foram realizadas 100 horas de observação usando o método scanning sample para a qualificação e quantificação dos atos comportamentais de rainhas e operárias de quinze colônias de Polistes canadensis canadensis. Foi descrito um repertório comportamental com 28 atos, no qual rainhas executam 19 atos na colônia, enquanto operárias 26, ocorrendo 17 atos em comum entre as duas castas. Dentre esses atos, dois foram exclusivos do repertório de rainhas e nove de operárias. O resultado do teste do qui-quadrado apontou diferenças significativas entre os repertórios das duas castas, sendo que rainhas permanecem mais tempo no ninho e executam com maior freqüência atividades intra-nidais, ligadas à reprodução, enquanto que as operárias executam mais freqüentemente atividades relacionadas à manutenção das colônias, como a atividade de forrageamento que demanda um maior risco e alto custo energético.