Karyotype diversity of stingless bees of the genus Frieseomelitta (Hymenoptera, Apidae, Meliponini)

Frieseomelitta (Ihering, 1912) is a genus of stingless bees, distributed in the Nearctic and Neotropical regions. Specimens can be found in forests, cerrado, caatinga and mountainous regions. This genus has 16 species, of which 13 are recorded in Brazil. Cytogenetics has contributed to evolutionary studies of some Hymenoptera groups and although many Frieseomelitta species have been described, few species have been studied cytogenetically. The present study aims to contribute to the knowledge of the karyotype diversity of this genus, seeking to understand the possible evolutionary mechanisms that occurred in the diversification of the karyotype of this genus. Frieseomelitta portoi and Frieseomelitta trichocerata and Frieseomelitta doederleini showed diploid karyotypes with 2n = 30 chromosomes, similarly to all the species previously analyzed in the genus. Unprecedentedly, Frieseomelitta longipes showed 2n = 34. These results confirm that the frequent diploid number of 30 chromosomes is typical of this genus. The finding of 2n = 34 chromosomes in F. longipes comprises the first record of a diploid chromosome number different from 2n=30 in this group, which suggests that it can be the result of a recent chromosome change event. An interspecific comparative analysis was developed involving present and previous studies, as well as a discussion on the mechanisms involved in the karyotypic evolution in the genus.