Workers aggression on male aggregations in a Brazilian stingless bee
Isabella Rodrigues Francatti, Isabella Rodrigues Francatti , Sheina Koffler , Maria Cristina Arias , Isabel Alves dos Santos
Departamento de Biologia, Universidade de São Paulo, Ribeirão Preto, Brasil; Departamento de Biologia, Universidade de São Paulo, Ribeirão Preto, Brazil ; Departamento de Ecologia, Universidade de São Paulo, São Paulo, Brazil ; Departamento de Genética e Biologia Evolutiva, Universidade de São Paulo, São Paulo, Brazil ; Departamento de Ecologia, Universidade de São Paulo, São Paulo, Brazil
Inbreeding is a form of non-random mating in which individuals are more likely to mate with relatives than with nonrelatives. Negative effects of inbreeding, as reduced ability to adapt to environmental changes, are especially deleterious for the haplodiploid Hymenoptera, in which homozigosity on the sex determiner locus may result in the production of diploid male offspring. In stingless bees, queens are singly mated and male aggregations were suggested to act as inbreeding avoidance mechanisms. Observations of male aggregations of Scaptotrigona aff. depilis revealed workers performing aggressive behavior towards males, a behavior not yet reported in the literature. Our aim was to test if the aggressive behavior exhibited by the workers could be a mechanism of inbreeding avoidance, restricting the access of a virgin queen to related males. The premise that workers belonged to the colony in which the aggregation occurred was tested. Three male aggregations were observed and 12 to 15 aggressive workers were collected with their corresponding attacked male and a nearby non-attacked male. Males and workers were genotyped using up to eight microsatellite markers and relatedness coefficient was estimated with ML-Relate software. The aggressive behavior varied from simple threat to biting and wrestling, sometimes leading to death of the targeted male. Most aggressive workers (74%) belonged to the colony where the aggregation took place. However, attacked males were not more related to workers than the non-attacked ones. These results suggest that aggression by workers does not act as an inbreeding avoidance mechanism, and future studies should focus on other potential roles of this intriguing behavior.