RESUMO

Culicivora caudacuta occurs in the Cerrado, Pampa and Chaco grasslands of Bolivia, Brazil, Paraguay, Argentina and Uruguay. Its breeding biology is poorly known. Here, I present a summary of the published information and new data gathered between 2003 and 2009 in southeast Brazil at Tapira, Minas Gerais. Breeding occurred during the rainy season (October to March), clutch size being three eggs. Juveniles and immatures show a different plumage from the adults, mostly brownish orange. All nests studied at Tapira showed evidence of cooperative breeding, with one helper engaged in incubation and provisioning the young. This is the first observations of this behavior for the species. The species has a wider range than currently understood and its presence in protected areas is similarly more common.(AU)

Assuntos

RESUMO

Abstract Culicivora caudacuta occurs in the Cerrado, Pampa and Chaco grasslands of Bolivia, Brazil, Paraguay, Argentina and Uruguay. Its breeding biology is poorly known. Here, I present a summary of the published information and new data gathered between 2003 and 2009 in southeast Brazil at Tapira, Minas Gerais. Breeding occurred during the rainy season (October to March), clutch size being three eggs. Juveniles and immatures show a different plumage from the adults, mostly brownish orange. All nests studied at Tapira showed evidence of cooperative breeding, with one helper engaged in incubation and provisioning the young. This is the first observations of this behavior for the species. The species has a wider range than currently understood and its presence in protected areas is similarly more common.

RESUMO

Abstract Culicivora caudacuta occurs in the Cerrado, Pampa and Chaco grasslands of Bolivia, Brazil, Paraguay, Argentina and Uruguay. Its breeding biology is poorly known. Here, I present a summary of the published information and new data gathered between 2003 and 2009 in southeast Brazil at Tapira, Minas Gerais. Breeding occurred during the rainy season (October to March), clutch size being three eggs. Juveniles and immatures show a different plumage from the adults, mostly brownish orange. All nests studied at Tapira showed evidence of cooperative breeding, with one helper engaged in incubation and provisioning the young. This is the first observations of this behavior for the species. The species has a wider range than currently understood and its presence in protected areas is similarly more common.

RESUMO

Previous research has found that the presence of grandparents, particularly grandmothers, is often positively associated with child survival. Little research has explored the potential mechanisms driving these associations. We use data from rural Guatemala to test whether contact with and direct investment (advice and financial) from grandparents is associated with child health, proxied by height. Our results demonstrate the complexity of family relationships and their influence on child health, suggesting that both cooperative and competitive relationships exist within the family. The clearest evidence we find for grandparental influence is that having a living paternal grandmother tends to be negatively associated with child height. By contrast, contact with maternal kin appears broadly to be beneficial for child height, although these relationships are weaker. These patterns are mirrored in maternal body mass index, suggesting grandparental influence acts partly through maternal health. These findings support the hypotheses that, under conditions of limited resources, family relationships may be competitive within the family lineage which shares the same resource base, but cooperative when there are few costs to cooperation. Finally, financial assistance from maternal grandfathers is positively correlated with infant length but negatively with the height of older children, perhaps because the receipt of financial support is an indication of need. The provision of advice shows no associations with child height.

RESUMO

Partible paternity refers to the conception belief that children can have multiple fathers ("co-fathers") and is common to indigenous cultures of lowland South America. The nature of social relationships observed between co-fathers reveals information about the reproductive strategies underlying partible paternity. Here we analyze clan, genealogical, and social relationships between co-fathers for the Suruí, an indigenous horticultural population in Brazil. We show that co-fathers roughly assort into two separate categories. In the affiliative category, co-father relationships are amicable when they are between close kin, namely brothers and father-son. In the competitive category, relationships are more likely of avoidance or open hostility when between more distant kin such as cousins or unrelated men of different clans. Results therefore imply multiple types of relationships, including both cooperative and competitive contexts, under the rubric of partible paternity. These complexities of partible paternity institutions add to our knowledge of the full range of cross-cultural variation in human mating/marriage arrangements and speak to the debate on whether or not humans should be classified as cooperative breeders.

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Cooperatively breeding animals live in social groups in which some individuals help to raise the offspring of others, often at the expense of their own reproduction. Kin selection--when individuals increase their inclusive fitness by aiding genetic relatives--is a powerful explanation for the evolution of cooperative breeding, particularly because most groups consist of family members. However, recent molecular studies have revealed that many cooperative groups also contain unrelated immigrants, and the processes responsible for the formation and maintenance of non-kin coalitions are receiving increasing attention. Here, I provide the first systematic review of group structure for all 213 species of cooperatively breeding birds for which data are available. Although the majority of species (55%) nest in nuclear family groups, cooperative breeding by unrelated individuals is more common than previously recognized: 30% nest in mixed groups of relatives and non-relatives, and 15% nest primarily with non-relatives. Obligate cooperative breeders are far more likely to breed with non-kin than are facultative cooperators, indicating that when constraints on independent breeding are sufficiently severe, the direct benefits of group membership can substitute for potential kin-selected benefits. I review three patterns of dispersal that give rise to social groups with low genetic relatedness, and I discuss the selective pressures that favour the formation of such groups. Although kin selection has undoubtedly been crucial to the origin of most avian social systems, direct benefits have subsequently come to play a predominant role in some societies, allowing cooperation to persist despite low genetic relatedness.

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RESUMO

In social insects, the typical mode of colony foundation occurs when a single queen is inseminated by a male and establishes a new colony, although we can find interspecific and intraspecific variations in queen number and queen-mating frequencies in a single colony. This study aimed to verify the queen number in Pachycondyla striata (Smith) colonies and to evaluate the level of aggressiveness among workers. We collected 14 colonies of P. striata. The behaviors of individuals from five multiple-queen colonies maintained in laboratory were studied by the method of scan sampling. In order to evaluate aggressiveness, dyadic encounters among heterocolonial and homocolonial workers were performed. The results showed that colonies of P. striata can have two or more mated queens (polygynous colonies) besides to monogynous ones (colony containing one queen). Because in polygynous colonies the number of workers was relatively low, such colonies could represent colonies in the foundation phase that characterize a pleometrosis state. In fact, ovarian development analysis from queens showed that the number of queens in the colonies seemed to be unstable. Despite a few cases of oophagy (egg cannibalism), social hierarchy among queens is unclear in comparison to other Pachycondyla species. In addition, aggressiveness increased with distance among nests. Nearby colonies (less than 1 m apart) showed a low level of aggressiveness, suggesting the presence of polydomy, that is, a unique colony can occupy multiple nests. Polygyny associated to polydomy in founding colonies may confer benefits on growth and dispersion of colonies in the studied environments.

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