Comparative study on the physical mapping of ribosomal genes and repetitive sequences in Friesella schrottkyi (Friese 1900) (Hymenoptera: Apidae, Meliponini)

Abstract

Over the past several decades, stingless bee cytogenetic studies have focused on chromosome number and morphology of specific samples, with little emphasis on population variations. More recently, molecular techniques have facilitated analyses of the fine chromosomal structure, allowing the identification of interspecific variations and increasing our knowledge of the karyotype structure. Thus, the present study aimed to analyse the distribution of ribosomal genes and repetitive sequences in the genome of Friesella schrottkyi (Friese 1900), providing relevant information about its genomic organization. Two samples were obtained from Minas Gerais state (Rio Paranaíba and Viçosa) and one from Cunha/São Paulo state, Brazil, all of which showed 2n = 34 chromosomes, 2K: 10m + 12sm + 12st. Heterochromatin (C-banding) was detected mainly in the centromeric/pericentromeric region, but some specific patterns were verified in individuals from each location. An intense spreading of the microsatellite (GA)15 was observed, most commonly in the euchromatic areas of the chromosomes. The CMA3+ bands were found in two chromosomes in the samples from Cunha and Viçosa, while the sample from Rio Paranaíba contained three CMA3+ bands. There were also differences in the number and locations of the 18S rDNA clusters among the different samples. Although we found no differences between samples from the same location, the many intraspecific variations founded clearly demonstrate the potential of utilising molecular cytogenetics as a method of improving our understanding of the genetic variability in the Meliponini tribe.