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Occurrence of multiple nucleolus organizer regions and intraspecific karyotype variation in Scaptotrigona xanthotricha Moure (Hymenoptera, Meliponini)

Author(s): O.M.P. Duarte1, C.C.C. Martins1, A.M. Waldschmidt2 and M.A. Costa1

Scaptotrigona xanthotricha has a wide geographic distribution in the Brazilian Atlantic rainforest. One population from southeast and two from northeast Brazil were analyzed and were found to have chromosome polymorphisms. Although the chromo­some number 2n = 34 is conserved in this species, karyotypic analy­sis revealed clear differences between the three populations. Congru­ent and ubiquitous multiple nucleolus organizer regions, heterochro­matin and CMA3-positive blocks were found. The variations suggest that this species is in a process of genetic differentiation. This dif­ferentiation process might have been enhanced by restricted nesting preferences, combined with recent extensive fragmentation of the Atlantic rainforest, which limits gene flow between populations. Scaptotrigona xanthotricha has a wide geographic distribution in the Brazilian Atlantic rainforest. One population from southeast and two from northeast Brazil were analyzed and were found to have chromosome polymorphisms. Although the chromo­some number 2n = 34 is conserved in this species, karyotypic analy­sis revealed clear differences between the three populations. Congru­ent and ubiquitous multiple nucleolus organizer regions, heterochro­matin and CMA3-positive blocks were found. The variations suggest that this species is in a process of genetic differentiation. This dif­ferentiation process might have been enhanced by restricted nesting preferences, combined with recent extensive fragmentation of the Atlantic rainforest, which limits gene flow between populations.