1Universidade Federal de Juiz de Fora, Laboratório de Ecologia Comportamental e Bioacústica, Departamento de Zoologia. Campus Universitário, Juiz de Fora, Minas Gerais, Brazil, CEP 36036-900 2Universidade Federal de Viçosa, Departamento de Entomologia. Avenida Peter Henry Rolfs s/n, Viçosa, Minas Gerais, Brazil, CEP 36571-000 3Universidade Estadual Paulista Julio de Mesquita Filho, Centro de Estudos Ambientais, Avenida 24A, 1515, Rio Claro, São Paulo, Brazil, CEP 13506-900 *Corresponding author; E-mail: fabio.prezoto@ufjf.edu.br 556 2015 — Florida Entomologist — Volume 98, No. 2 Foundress association in the paper wasp Polistes simillimus (Hymenoptera: Vespidae) Fábio Prezoto1,*, Mariana Monteiro de Castro1, André Rodrigues de Souza2, and Nivar Gobbi3 Abstract In many animal species, females are faced with at least 2 reproductive options: independent or cooperative breeding. Some individuals in cooperative groups choose to help in rearing the broods of conspecific females. Through observations of how females of Polistes simillimus Zikán, 1951 (Hymenoptera: Vespidae) started new nests in the field, we investigated whether ecological constraints and the geographic varia- tions explain group formation in this species. The founding of nests was studied between 1996 and 2000 in various localities of 2 states of southeastern Brazil. Weekly observations were carried out on 109 pre-worker nests. We kept track of 40 colonies in Minas Gerais State and 69 in São Paulo State, each started either by a single female or by an association of females. There was a chance that worker production would become numerically similar in both solitary and associative colonies in both states. An increased number of foundresses did not improve the chance of colony success in Minas Gerais State, but it improved this chance in São Paulo State, so that colonies each with 3 or more found- ressess were always successful. In colonies in both states, nest cell productivity was higher with a greater number of associated females per nest. Females were able to start building nests alone, being the only reproductive, or 2 or more females could cooperate to found a nest, thus increasing worker production. However, the type of environment chosen to establish the nest (anthropogenic or natural) seemed to influence strongly the choice of the founding strategy. Key Words: ecological constraints; foundress number; group augmentation; helping; Polistinae Resumen En muchos animales, las hembras se enfrentan con por lo menos 2 opciones de reproducción: la reproducción independiente o coo- perativa, asi como, el cuidado de los progenies. A pesar de ser potencialmente capaz de reproducción directa, algunos individuos en grupos cooperativos optan por ayudar en criar los progenie de hembras conspecificas. ¿Por qué se asuma el papel de ayudar? Esta pregunta es de interés general, como se observa cría cooperativa en muchas especies de aves, mamíferos e insectos. Basado en las observaciones de campo de la forma en que las hembras de la avispa papel Polistes simillimus Zikán, 1951 (Hymenoptera: Vespidae) fundaron nuevos nidos durante 4 años consecutivos, se discuten algunas hipótesis que pueden explicar la cría cooperativa en esta especie. Una hembra de P. simillimus puede empezar un nido por sí misma y ser la única reproductiva. Por otra parte, varias hembras pueden cooperar para fundar un nido, y de ese modo mejorar la probabilidad de que la cría llegue a la etapa de la producción de los trabajadores. A pesar de informes anteriores que mostraron asimetrías inmediatos o un sesgo reproductivo entre las hembras que cooperan, los ayudantes pueden mejorar su aptitud indirectamente al criar los que no son descendientes de ellas, o incluso mejor su aptitud directamente por esperar de una oportunidad para aparearse. Palabras Clave: restricciones ecológicas; aumento del grupo; Polistinae; seguro de sobrevivencia Females of Polistes Latreille, 1802 (Hymenoptera: Vespidae) paper wasps have the options of independent or cooperative breeding, and usurpation in a few species in temperate climates (Reeve 1991). In the latter, individuals potentially capable of direct reproduction choose to assist in the rearing of broods of conspecific females. Why they ac- cept a helping role is a question central to sociobiology. The choice of cooperative breeding is thought to be affected by several factors. For example, ecological constraints on solitary reproduction can be important, as single-foundress nests (i) are less likely to be rebuilt af- ter a predation event (Strassmann et al. 1988), (ii) tend to be usurped more often (Gamboa 1978; Klahn 1988), (iii) have less survival chances (Metcalf & Whitt 1977; Gibo 1978; Pfenning & Klahn 1985; Queller & Strassmann; 1988), and (iv) are less productive than multiple-found- ress nests (West-Eberhard 1969; Tibbetts & Reeve 2003). Additionally, indirect fitness benefits of cooperative breeding also can be involved, as helpers can rear non-descendant kin (Hamilton 1964; Foster et al. 2006). According to Tibbetts & Reeve (2003), numerous models have been developed to predict the circumstances that favor association (Reeve 1991; Reeve & Ratnieks 1993; Reeve & Emlen 2000). In general, these studies used correlational data to show that multiple-foundress Polistes colonies were more successful than single-foundress colonies, because Prezoto et al.: Foundress association in Polistes simillimus 557 they were usurped less often (Gamboa 1978; Klahn 1988), survived better (Metcalf & Whitt 1977; Gibo 1978), and were more productive than single-foundress colonies (West-Eberhard 1969; Gamboa 1980). Reeve (1991) presented a model in which the ecological constraints explain the optimal nesting strategy. In agreement with the model, the joining of females occurs more frequently in species with lower solitary-foundress success probabilities. Makino (1985), for example, showed that solitary-foundress success rates of Japanese species in- dicated relatively weak ecological constraints on solitary nesting. Mul- tiple-foundress associations were rare in those species, with solitary founding and usurpation occurring as the principal founding strategies. Despite all previous studies (see Tibbetts & Reeve 2003), the pos- sible role of geographic variation in a species has not been addressed. The study of this subject will help to improve the understanding of the relationship between the founding strategy and the influence of geographical variation of the species. In the Neotropical eusocial paper wasp Polistes simillimus Zikán, 1951, both solitary and cooperative breeding are common reproduc- tive tactics exhibited by females (Prezoto 2001). When females coop- erate to found a nest, a reproductive division of work established by aggressive interactions occurs. The dominant female spends the most time in the colony laying eggs and is the predominant participant in direct reproduction, whereas subordinate females assume the role of workers, foraging for food (Grazinoli et al. 2010). By studying the nest founding period in P. simillimus over a 4 yr period, we investigated whether ecological constraints and the geographic variation explain group formation in this species. Materials and Methods The founding of P. simillimus nests was studied between 1996 and 2000 in various localities of Minas Gerais and São Paulo States of Brazil (Table 1). To verify how females begin new nests, weekly observations were carried out on 109 pre-worker nests, immediately after dark (be- tween 6 and 8 PM). In each observation, the number of associated females in each nest was registered. Solitary nest founding occurred when a single female was registered during all observations in a given nest, and associative nest founding occurred when a particular nest was inhabited simultaneously by more than 1 female. We located most nests at a very early pre-emergent phase (number of nest cells when a colony was registered for the first time averaged 6 ± 6 (range: 1–24); however, we located some colonies late in the pre-emergent phase. As a result, the process of observing foundress association was not always the same for each colony. Nests were observed until they reached the worker production phase, characterized by the presence of cells with vestiges of cocoons and the presence of newly-emerged adults. Addi- tionally, the number of cells in each nest was registered at the end of the pre-worker period. Statistical analysis was performed with GraphPad InStat 3.0®. The significance level was fixed at 5%. Results We kept track of 40 colonies of P. simillimus in Minas Gerais State. In this state, nests were started either by a single female (50%) or by an association of 2 to 15 females (50%). The chances of reaching the worker production phase were similar (2-sided Fisher’s exact test: P = 0.6262) in both solitary (40%) and associative (40%) colonies. Further, an increase in the number of foundressess did not improve the chance of colony success (Spearman’s correlation test: r = 0.6513, P = 0.1612). An increase of the number of associated females per nest resulted in higher nest cell productivity at the end of the pre-worker phase (r = 0.8295, P = 0.0411). In São Paulo State, 69 colonies of P. simillimus were studied. In this state, nests were started by a single female (61%) or by associations of 2 to 6 females (39%). The chances of nests reaching the worker pro- duction phase were similar (2-sided Fisher’s exact test: P = 0.0975) in both associative (36%) and solitary females (42%). An increase in the number of foundressess improved the chance of nest success (Spear- man’s correlation test: r = 0.8450, P = 0.0342 ), so that colonies with 3 or more foundressess were always successful. Finally, an increase in the number of associated females per nest resulted in a higher nest cell productivity at the end of the pre-worker phase (r = 0.9976, P < 0.0001). Discussion Associative nest founding was a more successful reproductive strat- egy than the solitary nest founding. However, increased colony ben- efits in multiple-foundress associations were not necessarily benefits to all individuals that had been selected for cooperation. If individual P. simillimus females, like many other Polistes species, can successfully found colonies by themselves and each female can be the only repro- ductive in the colony, why do they form groups in which an aggressive female performs all or most of the direct reproduction, whereas the less aggressive females play a subordinate role as a helper with a low fraction of direct reproduction (Grazinoli et al. 2010)? In colonies with up to 4 females, the greater the number of associated foundresses, the greater the probability of colony success. This suggests that survival insurance benefits may be important in small group formation. Thus, in a solitary nest, the single female must perform all colony tasks, but in a foundress-associative colony, subordinate females perform the riskier Table 1. Location, number of Polistes simillimus nests studied, and type of environment sampled in the states of São Paulo and Minas Gerais, southeastern Brazil. State City Coordinates Colonies studied (n) Environment São Paulo Ferraz 22°23’28.59”S, 47°34’07.31”W altitude 627 m 18 Anthropogenic Piracicaba 22°44’02.50”S, 47°38’52.94”W altitude 534 m 33 Anthropogenic Rio Claro 22°24’49.28”S, 47°33’52.35”W altitude 619 m 18 Natural Minas Gerais Ibitipoca 21°42’13.37”S, 43°53’08.02”W altitude 1453 m 25 Natural Juiz de Fora 21°45’44.35”S, 43°20’36.24”W altitude 678 m 2 Anthropogenic Lima Duarte 21°50’22.50”S, 43°47’31.24”W altitude 742 m 13 Anthropogenic 558 2015 — Florida Entomologist — Volume 98, No. 2 tasks such as foraging, whereas the dominant female focuses on direct reproduction (Grazinoli et al. 2010). As a result, the dominant female in foundress associations would have increased survival probability compared with solitary females. Because P. simillimus foundresses are closely related (Simikomaki & Del Lama 2000), subordinate females would still gain in indirect fitness. In Polistes dominula (Christ, 1791), foundresses in cooperative nests may benefit from increased survivorship in relation to single foundresses, but unlike what we observed for P. simillimus, these ben- efits are not directly correlated with the number of foundresses in the group (Zanette & Field 2011). This suggests that the relevance of sur- vival insurance may be higher for P. simillimus than for P. dominula. However, because groups of 4 or more P. simillimus females have the same probability of success, survival insurance alone does not explain large group formation, and therefore other factors may be involved. Alternatively, it is possible that long-term survival and reproduction benefit from helpers being present, as has been observed in many co- operatively-breeding vertebrates (Hatchwell et al. 2004; Hodge 2005; Russel et al. 2007; Sparkman et al. 2011; Brouwer et al. 2012). There- fore the long-term survival and reproduction benefits from helpers may play an important role in promoting large group formation in P. simil- limus. In this sense, such direct benefits may play a role in group forma- tion (Field et al. 2006; Field & Cant 2007; Sumner et al. 2010). Shreeves & Field (2002) showed a strong positive correlation between group size and breeder productivity in the hover wasp Liostenogaster flavolineata Cameron. In a similar way, in P. simillimus as in many other paper wasps (West-Eberhard 1969; Tibbetts & Reeve 2003; Tindo et al. 2008), a cor- relation between nest cell productivity and group size was observed. Thus, if a female helped to rear the current breeder’s offspring, she acquired more helpers for herself if later she inherited the breeding position. Thus, the importance of group augmentation benefits must depend on the chance that the helper later inherits the breeder posi- tion. Inheritance may be an important component of helpers’ fitness in both hover wasps and P. simillimus because the brood rearing period extends year round (Prezoto 2001; Shreeves & Field 2002), so the time available to queue for breeding positions is not strongly constrained by the arrival of winter. Finally, P. simillimus colonies are among the larg- est formed by Polistes spp. Prezoto (2001) reported some P. simillimus nests with more than 1,000 cells (1,065–1,325), with productivity rang- ing between 759 to 1,355 individuals. Large colonies of this species are probably polygynous (Gobbi et al. 1993), illustrating another way by which helpers could achieve direct reproduction. Regarding geographic variation, there was no significant difference between the data for nests started by a single female or by an associa- tion of females in the states of São Paulo and Minas Gerais. Therefore in this study, geographic variation did not have significant influence on the founding strategy of P. smillimus. Nevertheless, for São Paulo State, increases in the number of foundressess improved the chances of nest success. This may be explained by the fact that a higher number of foundings registered in this locality were by single females, usually in anthropogenic environments. This data suggests that, in this type of environment, ecological constraints to solitary founding are much reduced. This allows the species to invest in the founding of more nests (through more isolated foundings) rather than joining associations of females. According to Prezoto et al. (2007), anthropogenic environments, such as urban areas, present various characteristics that favor the es- tablishment and success of wasp nests. Among these characteristics, we can mention: (i) a great offering of nesting places, (ii) protection against harsh weather conditions, (iii) reduced predation pressure, and (iv) reduced competition for resources. Our results agree with the theory proposed by Reeve (1991), in which variation in ecological con- straints either may or may not favor the occurrence of isolated found- ings or of associative foundings. In the particular case of P. simillimus in our study, the results attained for São Paulo State show the founding behavior to be closer to P. biglumis in Japan (Makino 1985), whose predominant founding strategy is by individual females, because eco- logical constraints in the São Paulo environment are small. In conclusion, each individual P. simillimus female can start the nest by herself and be the only reproductive individual in the nest. Alternatively, P. simillimus females can cooperate to found a nest, and thereby improve the chance of reaching the worker production phase. Despite the immediate asymmetries concerning the reproductive skew of cooperative females (Grazinoli et al. 2010), helpers may gain indirect fitness by rearing non-descendent kin or even direct fitness by waiting for a breeding opportunity. However, the type of environment (anthro- pogenic or natural) chosen to establish a nest seems to exert a strong influence on the choice of the founding strategy. Acknowledgments The authors are thankful to S. Sumner for the valuable insights during preparation of early versions of the manuscript. We are deeply grateful to Mateus Detoni for helping with translations. Also, we are deeply grateful to the Conselho Nacional de Desenvolvimento Cientí- fico e Tecnológico – CNPq (307264/2010-6 and 310713/2013-7 under Grant 143246/2011-9) for financial support. References Cited Brouwer L, Richardson DS, Komdeur J. 2012 Helpers at the nest improve late-life offspring performance: evidence from a long-term study and a cross-foster experiment. PLoS One 7(4): 1-9. Field J, Cant MA. 2007. Direct fitness, reciprocity and helping: a perspective from primitively eusocial wasps. Behavioural Processes 76(2): 160-162. Field J, Cronin AL, Bridge C. 2006. Future fitness and helping in social queues. Nature 441: 214-217. Foster KR, Wenseleers T, Ratnieks FLW. 2006. Kin selection is the key to altruism. Trends in Ecology and Evolution 21(2): 57-60. Gamboa GJ. 1978. Intraspecific defense: advantage of social cooperation among paper wasp foundresses. Science 199: 1463-1465. Gamboa GJ, 1980. Comparative timing of brood development between mul- tiple- and single-foundress colonies of the paper wasp, Polistes metricus. Ecological Entomology 5: 221-225. Gibo DL. 1978. The selective advantage of foundress associations in Polistes fuscatus (Hymenoptera: Vespidae): a field study of the effects of predators on productivity. Canadian Entomologist 110(5): 519-540. Gobbi N, Fowler HG, Netto JC, Nazareth SL. 1993. Comparative colony produc- tivity of Polistes simillimus and Polistes versicolor (Hymenoptera: Vespidae) and the evolution of paragyny in the Polistinae. Zoologische Jahrbücher 97: 239-243. Grazinoli DJ, De Souza AR, Prezoto F. 2010. Dominance hierarchy and division of work in colonies of Polistes simillimus (Hymenoptera, Vespidae). Sociobiol- ogy 56(2): 507-514. Hamilton WD. 1964. The genetical evolution of social behaviour. Journal of Theoretical Biology 7: 1-16. Hatchwell BJ, Russell AF, MacColl ADC, Ross DJ, Fowlie MK, McGowan A. 2004. Helpers increase long-term but not short-term productivity in cooperatively breeding long-tailed tits. Behavioral Ecology 15(1): 1-10. Hodge SJ. 2005. Helpers benefit offspring in both the short and long-term in the cooperatively breeding banded mongoose. Proceedings of the Royal Society of London Series B 272(1580): 2479-2484. Klahn J. 1988. Intraspecific comb usurpation in the social wasp Polistes fuscatus. Behavior, Ecology and Sociobiology 23(1): 1-8. Makino S. 1985. Foundress-replacement on nests of the monogynic paper wasp Polistes biglumis in Japan (Hymenoptera, Vespidae). Kontyû 53: 143-149. Metcalf RA, Whitt GS. 1977. Relative inclusive fitness in the social wasp Polistes metricus. Behavior, Ecology and Sociobiology 2(4): 353-360. Pfenning DW, Klahn JE. 1985. Dominance as a predictor of cofoundress disap- pearance order in social wasps (Polistes fuscatus). Zeitschrift fürTierpsycho- lologie 67(1-4): 198-203. Prezoto et al.: Foundress association in Polistes simillimus 559 Prezoto F. 2001. Estudos biológicos e etológicos de Polistes (Aphanilopterus) simillimus Zikán, 1951. Thesis. Universidade Estadual Paulista Julio de Mes- quita Filho, Brazil. Prezoto F, Ribeiro-Júnior C, Oliveira-Cortes SA, Elisei T. 2007. Manejo de vespas e marimbondos em ambiente urbano, pp. 123-126 In Pinto AS, Rossi MM, Salmeron E [eds.], Manejo de Pragas Urbanas. Editora CP2, Piracicaba, Bra- zil. Queller DC, Strassmann JE. 1988. Reproductive success and group nesting in the paper wasp, Polistes annularis, pp. 76-96 In Clutton-Brock TH [ed.], Re- productive Success: Studies in Selection, Adaptation, and Demography in Contrasting Systems. University of Chicago Press, Chicago, Illinois, USA. Reeve HK. 1991. Polistes, pp. 99-148 In Ross KG, Matthews RW [eds.], The Social Biology of Wasps. Cornell University Press, Ithaca, New York, USA. Reeve HK, Emlen ST. 2000. Reproductive skew and group size: an N-person stay- ing incentive model. Behavioral Ecology 11: 640-647. Reeve HK, Ratnieks FLW. 1993. Queen-queen conflicts in polygynous societies: mutual tolerance and reproductive skew, pp 45-85 In Keller L [ed], Queen Number and Sociality in Insects. Oxford University Press, Oxford, United Kingdom. Russell AF, Young AJ, Spong G, Jordan NR, Clutton-Brock TH. 2007. Helpers in- crease the reproductive potential of offspring in cooperative meerkats. Pro- ceedings of the Royal Society of London Series B 274(1609): 513-520. Shreeves G, Field J. 2002. Group size and direct fitness in social queues. The American Naturalist 159(1): 81-95. Simokomaki K, Del Lama MA. 2000. Genetic relatedness in colonies of Polistes simillimus (Hymenoptera: Vespidae) estimated through enzyme electropho- resis. Naturalia 25: 281-286. Sparkman AM, Adams J, Beyer A, Steury TD, Waits L, Murray DL. 2011. Help- er effects on pup lifetime fitness in the cooperatively breeding red wolf (Canis rufus). Proceedings of the Royal Society B Biological Sciences 278: 1381-1389. Strassmann JE, Queller DC, Hughes CR. 1988. Predation and the evolution of sociality in the paper wasp Polistes bellicosus. Ecology 69: 1497-1505. Sumner S, Kelstrup H, Fanelli D. 2010. Reproductive constraints, direct fitness and indirect fitness benefits explain helping behaviour in the primitively eu- social wasp, Polistes canadensis wasp. Proceedings of the Royal Society B Biological Sciences 277(1688): 1721-1728. Tibbetts EA, Reeve HK. 2003. Benefits of foundress associations in the paper wasp Polistes dominulus: increased productivity and survival, but no assur- ance of fitness returns. Behavioral Ecology 14(4): 510-514. Tindo M, Kenne M, Dejean A. 2008. Advantages of multiple foundress colonies in Belonogaster juncea juncea L.: greater survival and increased productiv- ity. Ecological Entomology 33(2): 293-297. West-Eberhard MJ. 1969. The social biology of Polistinae wasps. Miscellaneous Publications of the Museum of Zoology of the University of Michigan 140: 1-101. Zanette LRS, Field J. 2011. Founders versus joiners: group formation in the paper wasp Polistes dominulus. Behavior, Ecology and Sociobiology 82: 699-705.