The genus Melipona is subdivided into four subgenera based on morphological characteristics, and two groups based on cytogenetic patterns. The cytogenetic information on this genus is still scarce, therefore, the goal of this study was to characterize Melipona paraensis, Melipona puncticollis, and Melipona seminigra pernigra using the following techniques: C-banding, DAPI/CMA3 fluorochromes, and FISH with an 18S rDNA probe. Melipona paraensis (2n=18) and M. seminigra pernigra (2n=22) were classified as high heterochromatin content species (Group II). Their euchromatin is restricted to the ends of the chromosomes and is CMA3 +; the 18S rDNA probe marked chromosome pair number 4. Melipona puncticollis (2n=18) is a low heterochromatin content species (Group I) with chromosome pair number 1 marked with CMA3 and 18S rDNA. Low heterochromatin content is a putative ancestral karyotype in this genus and high content is not a monophyletic trait (Melikerria presents species with both patterns). Differences concerning the karyotypic characteristics can be observed among Melipona species, revealing cytogenetic rearrangements that occurred during the evolution of this genus. Studies in other species will allow us to better understand the processes that shaped the chromatin evolution in Melipona.

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Astyanax taeniatus occurs in coastal areas of southeastern Brazil, and it is very abundant in the Upper Doce River Basin. Our objective was to study C-, argyrophilic nucleolar organizer region (Ag-NOR) and fluorescent in situ hybridization (FISH) banding patterns using 5S, 18S, CA(15), and GA(15) repetitive DNA probes on a population of A. taeniatus present in the Piranga River, in the Doce Basin. Two syntopic cytotypes were found, both with 2n = 50: cytotype A (14m + 12sm + 16st + 8t) and cytotype B (10m + 14sm + 18st + 8t). In both cytotypes, heterochromatic blocks occurred in all the chromosomes; Ag-NOR sites were multiple, ranging from four to eight. The 5S rDNA probe marked eight chromosomes in both cytotypes, a unique condition within Astyanax, suggesting a recent divergence between these cytotypes. The 18S rDNA probe differed between the cytotypes, marking 10 and 8 chromosomes in cytotypes A and B, respectively. CA(15) and GA(15) FISH patterns were mainly subtelomeric, but CA(15) showed centromeric markings that were diagnostic for each cytotype. Although overall cytogenetic evidence suggests that these cytotypes are closely related, morphological and molecular data in progress will provide further hypothesis test on their phylogenetic relationship.

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The bee diversity (Apidae) estimative ranges from 18,000 to 20,000 species worldwide. Together, they show an impressive diversity in morphological, ecological, and behavioral traits, and there is still much to be understood about their taxonomy and systematics. Their chromosome count variability and genome biology are also astonishing. To date, around 200 bee species have already been karyotyped, with chromosome numbers varying from n = 3 to n = 28, and nuclear haploid genome sizes are available for approximately 70 species with a variation of 1C = 0.19 pg to 1C = 1.38 pg. The Bee Chromosome database was created (www.bees.ufop.br) to summarize the Apidae cytogenetic knowledge by assembling all the cytogenetic information published on bees. Considering the importance of cytogenetic studies for taxonomy, phylogeny, genetics, systematics, conservation, and evolution, the main goal of this database is to outline the advances in the field of bee cytogenetics over the last century.chromosomal evolution / chromosome number / cytogenetics / karyotypic formula / nuclear genome size

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Genome changes, evidenced through karyotype or nuclear genome size data, can result in reproductive isolation, diversification and speciation. The aim of this study was to understand how changes in the karyotype such as chromosome number and nuclear genome size accompanied the evolution of neotropical stingless bees, and to discuss these data in a phylogenetic context focusing on the karyotype evolution of this clade. We sampled 38 species representing the three Neotropical Meliponini groups; 35 for karyotype analyses and 16 for 1C value measurement. The chromosome number varied from 2n = 16 to 2n = 34, with distinct karyotypic formulae and the presence of a few polymorphisms, such as B chromosomes in one species and arm size differences between homologous chromosomes in two species. The mean 1C value varied from 0.31 pg to 0.92 pg. We associated empirical data on chromosome number and mean 1C value to highlight the importance of Robertsonian fusion rearrangements, leading to a decrease in chromosome number during the Neotropical Meliponini evolution. These data also allowed us to infer the independent heterochromatin amplification in several genera. Although less frequent, Melipona species with 2n = 22 represent evidence of Robertsonian fissions. We also pointed out the importance of chromosomal rearrangements that did not alter chromosome number, such as inversions and heterochromatin amplification.

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