Cytotaxonomy and karyotype evolution in Neotropical Meliponini (Hymenoptera: Apidae) inferred by chromosomal mapping of 18S rDNA and five microsatellites

Abstract

The Neotropical Meliponini bees, commonly known as stingless bees, are phylogenetically subdivided into three clades in which the chromosome numbers vary from n = 8 to n = 17. The goal of this study was to identify the major chromosomal rearrangements that occurred during the Neotropical Meliponini (Apidae) karyotypic evolution. In this way, we mapped 18S rDNA and five microsatellites in 33 stingless bee species collected from different Brazilian regions. The species belonged to 15 genera and showed six different chromosome numbers: n = 8, n = 9, n = 11, n = 14, n = 15, and n = 17. The 18S rDNA probe showed a variation from 2 to 12 marked chromosomes in different positions (terminal, subterminal, or centromeric), including 2 B chromosomes out of the 7 B found in Tetragonisca fiebrigi. The microsatellite (GA)₁₅, (GAG)₁₀, (CAA)₁₀, and (TCAGG)₆ probes formed clusters on the euchromatic regions of the chromosomes and were useful in the identification of putative Robertsonian fusion events that led to the decrease in the chromosome number during the evolution of the Neotropical Meliponini clade. (TTAGG)₆ constituted the telomeric sequence of the analyzed species. The ancestral state of the three Neotropical Meliponini clades is difficult to infer, although, the putative ancestral karyotype probably had a single pair of 18S rDNA cistrons, and the decrease in chromosome number and increase in the 18S rDNA sites occurred independently between genera.

Keywords:

• 18S rDNA
• chromosome evolution
• cytotaxonomy
• microsatellites
• molecular cytogenetics
• stingless bees

Acknowledgments

This work was developed as part of the Ph.D. thesis of the first author Marina Souza Cunha (Cunha, 2021a). The authors wish to thank Maurício Adu Schwade, Gil Viana de Oliveira, Clovis Sales Silva, and Terezinha Lins Rangel for logistical support during field work done in the Amazonas, Brazil.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Financial support is acknowledged from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG).