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Revista Chilena de Historia Natural 85 (3): 245-266, 2012
Evolution of sociality in Hymenoptera: Behavioural traits linked to social levels and precursors of sociality in solitary species
The levels of sociality in Hymenoptera have been associated with key behavioural traits, such as nesting and agonistic behaviour, and intraspecific recognition capacity. Nestmate recognition is a widespread condition among eusocial species, and can be inferred from the outcome of the interaction between females from the same or different nests; females are more tolerant towards nestmate than towards non-nestmate females. By contrast, in most solitary species females are aggressive towards conspecific females. In eusocial species, food for immature brood is directly provided by the mother or by workers; thus, the frequent contact of the brood with nursing adults may help our understanding of social recognition behaviours. At the other extreme, females in solitary species construct nests that do not allow physical interaction between adult and immature individuals. Despite this, recent studies suggest that self-referencing may contribute to overcoming the lack of stimulation with conspecific cues, and perhaps corresponds to the starting point in the development and evolution of sociality. The Xylocopinae (Apidae) subfamily has emerged as a valuable model to study the transitions in social evolution because it contains species ranging from solitary to eusocial. The tribe Manueliini represents an interesting taxon in the study of the evolution of sociality in Xylocopinae because it has been hypothesized as the sister group of all other Xylocopinae. It is a relictual taxon retaining several ancestral morphological features and contains only largely solitary species (although nestmate and kin recognition has been recently demonstrated in one of these species), and some species exhibit behavioural traits that have been proposed as prerequisite for the evolution to social life. In this work, the degrees of sociality associated with behavioural traits are reviewed in Hymenoptera, the hypothetical evolutionary routes, origins and losses of highly social behaviour are discussed, and information about taxonomic groups that have emerged as valuable models to study the evolution of sociality is reported. Additionally, features proposed as precursors of sociality are compared within the subfamily Xylocopinae, evidence demonstrating nestmate recognition in a Manueliini species, a phenomenon first demonstrated in a largely solitary species, is discussed, and the evolution of sociality associated with behavioural traits is analyzed, on the basis of a new phylogenetic hypothesis for the Xylocopinae.
Key words:
evolutionary routes, nesting, recognition, sociality.

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