Monandria e Poliandria como estratégia evolutiva no complexo de subespécies de Melipona seminigra Friese, 1903 (Apidae, Meliponini) na Amazônia

Abstract

The stingless bee Melipona seminigra (Apidae, Meliponini) is a polytypic species widespread in the Amazon basin. It has a key role in the pollination of native and cultivated plants as well as in seed dispersal. It is highly eusocial as well as other Meliponini and Apini, characterized for evolution of the caste system; division of reproductive labor; overlapping of generations, queen mother and workers in the same nest; cooperative care of the offspring; queen (fertile female) and workers (sterile females) morphologically differentiated. The mating system predicted to stingless bees is monandria, common to most solitary and social Hymenoptera. Our aim was to study paternity and relatedness in feral and managed colonies of M. seminigra by using DNA microsatellite, and to identify molecularly the different subspecies by using DNA barcoding. Moreover, we aimed to study sex determination mechanism through male and female segregation. We sampled six subspecies, four of them described (M. s. abunensis, M. s. merrillae, M. s. pernigra and M. s. seminigra) and two of them undescribed (M. s. ssp1 and M. s. ssp2). We genotyped 4-5 DNA microsatellite loci in 576 workers, sampled in 24 colonies, of three subspecies (M. s. abunensis, M. s. merrillae and M. s. seminigra). We amplified a fragment of 526 base pairs of COI gene in 31 workers of the six subspecies, sampled in different nests. We observed poliandry in the 24 colonies of M. seminigra studied. Paternity frequency ranged from 3 to 11 (in average 7.416 ± 2.5) and effective paternity ranging from 2 to 11.613(in average 6.324 ± 2.655). This level of polyandry produced a degree of relatedness of 0.298 to 0.5 (in average 0.346 ± 0.051). In the most studied colonies (21/24) skew (S) values were close to zero. In 3/24 colonies we observed a relative monopoly of the paternity for some males (S ˃ 0.5) and in 6/24 of them we observed negative skew interpreted as zero. The genetic distance inter subspecies was on average of 1.8 ± 0.47 % while the genetic distance inter species (same subgenus) was on average of 2.13 ± 0.5 %. We observed a 1:1 sex ratio in 3/31 of the colonies, which evidences diploid male production. Queens of M. seminigra are highly polyandrous and intracolonial relatedness is low; moreoever, the different subspecies are geographically isolated by a long time. We argue that polyandry in M. seminigra is an evolutionary strategy to minimize the harmful effects of diploid male production. The knowledge of M. seminigra mating system is essential as regards to the management and conservation of this species. However, the greater implication of our results refers to the evolution of polyandy in social Hymenoptera.