Karyotype diversity of Polybia (gr. occidentalis) species complex (Hymenoptera: Vespidae): Taxonomic and evolutionary implications

Polybia is a common wasp genus found in most of South America. Polybia (gr. occidentalis) encompasses several species that are difficult to identify because of their similar morphologies. Our goal was to cytogenetically characterize three species belonging to Polybia (gr. occidentalis) and discuss the importance of cytogenetic data for integrative taxonomy. Polybia colonies were sampled from different regions of Brazil to perform classical and molecular cytogenetic analyses. Polybia paulista and Polybia sp. 1 showed 2n = 34 and 18S rDNA loci on two chromosomes, whereas Polybia sp. 2 showed 2n = 40 and 18S rDNA clusters on four chromosomes. The microsatellites GA₍₁₅₎, GAG₍₁₀₎, CAA₍₁₀₎, TTAGG₍₆₎, and TCAGG₍₆₎ showed similar distributions among the species, forming blocks in the euchromatic regions of the chromosomes, whereas CGG₍₁₀₎ did not yield any positive markings. In contrast, TAT₍₁₀₎ hybridized on the centromeric heterochromatin, showing differences in the number of marked chromosomes among the species. Therefore, it may potentially be a species-specific cytotaxonomic marker in this group of wasps, but this feature needs further investigation. Fluorochromes evidenced that AT-rich DAPI⁺ sequence distribution was coincident with heterochromatin, while the distribution of CG-rich CMA₃⁺ sequences was coincident with the 18S rDNA region. The present study revealed differences in diploid number, heterochromatin content, 18S rDNA sites, and microsatellite patterns between morphologically similar species, demonstrating the usefulness of cytotaxonomy in studying species complexes.