New occurrence of B chromosomes in Partamona helleri (Friese, 1900) (Hymenoptera, Meliponini)

Abstract

Cytogenetic analyses of the stingless bee Partamona helleri collected in the state of Bahia, Northeast Brazil revealed the chromosome numbers n = 18 in the haploid males and 2n = 35 in the diploid females. All karyotypes displayed one large acrocentric B chromosome, which differs from the minute B chromosomes previously described in the populations from southeastern Brazil. Giemsa staining, C-banding and DAPI/CMA 3 fluorochrome staining also revealed a remarkable interpopulational divergence regarding both the regular karyotype and the B chromosomes. The B chromosomes found in the samples from Jequié, Bahia, were entirely heterochromatic, while those found in Cravolândia, Bahia, displayed a euchromatic portion at the telomeric end of the long arm. CMA 3 labeling sites varied from seven to eight between the two localities in Bahia, due to the presence of an extra GC-rich block in the karyotype of the samples from Jequié. This is the first report of a large B chromosome in P. helleri and reveals the occurrence of a geographic differentiation within this species.Key words: stingless Bee, Partamona helleri, geographic variation, supernumerary chromosomes. Partamona is a Neotropical genus of stingless bees with an ample distribution in a wide variety of habitats going from southern Brazil to central Mexico. These habitats include rain forests, cerrado (Brazilian savanna), caatinga, and highlands. Given the existence of morphologically similar species, this group has a problematic taxonomy. Some species can only be recognized by their nesting behavior or nest entrance architecture (Pedro and Camargo, 2003).Of the 33 species currently recognized (Pedro and Camargo, 2003), only eight, P. pearsoni (Tarelho ZVS, 1973, MSc Dissertation, University of São Paulo), P. seridoensis (Brito-Ribon et al., 1999, 2005), P. aiylae, P. vicina, P. mulata, P. nhambiquara (Brito-Ribon et al., 1999), P. peckolti (Brito et al., 2003), and P. helleri (Costa et al., 1992;Brito et al., 1997Brito et al., , 2005, were cytogenetically studied. All these species showed the regular chromosome number 2n = 34, but P. helleri showed a diploid numeric variation ranging from 2n = 34 to 2n = 38, due to the occurrence of up to four minute B chromosomes per individual (Costa et al., 1992;Brito et al., 1997Brito et al., , 2005Tosta et al., 2004). B chromosomes are extra chromosomes to the regular complement and are characterized by their dispensability, independent evolution, and non-Mendelian patterns of inheritance (Beukeboom, 1994). Their origin is a matter of recurrent debate among cytologists. Some have proposed that the appearance of the B chromosomes suggests the involvement of rearrangements in the regular chromosomes, e.g., centric fragment formation through chromosome fusions (Camacho et al., 2000). An alternative hypothesis suggests an origin through interspecific hybridization as observed in the fish Poecilia formosa (Schartl et al., 1995) and in the wasp Nasonia vitripennis (McAllister and Werren, 1997). Brito et al. (1997) distinguis...

Cytogenetic data on six leafcutter ants of the genus Acromyrmex Mayr, 1865 (Hymenoptera, Formicidae, Myrmicinae): insights into chromosome evolution and taxonomic implications

“…also presented uniform chromosome number (Mariano et al 2003), as did the other members of the genera Pheidole Westwood, 1839, Lasius Fabricius, 1804 and Iridomyrmex Mayr, 1862 (reviewed in Lorite and Palomeque 2010). Other animal groups, such as most birds and different genera of insects of the order Lepidoptera also demonstrated conservatism in respect to the chromosome number (White 1973), as did some bee genera, such as Melipona Illiger, 1806 (reviewed in Rocha et al 2007) and Partamona Schwarz, 1939 (reviewed in Martins et al 2009). …”

Investigation of Partamona helleri (Apidae, Meliponini) B chromosome origin. An approach by microdissection and whole chromosome painting

“…The stingless bee Partamona helleri (Friese 1900) ranges from southern to northeastern Brazil and exhibits the regular chromosome number 2n=34 and a variable number of B chromosomes (Costa et al 1992;Brito et al 2005;Tosta et al 2004;Martins et al 2009). Although larger B chromosomes were recently registered in northeastern Brazil populations ), Brito et al (1997) described two diminute B chromosomes, a small submetacentric (B1 chromosome), and a small acrocentric (B2 chromosome) occurring in this species restricted to southeastern Brazil.…”

Karyotypic description of the stingless bee Melipona quinquefasciata Lepeletier, 1836 (Hymenoptera, Meliponini) with emphasis on the presence of B chromosomes

“…The presence of a unique autosome pair with a nucleolus organizer in M.quinquefasciata corroborated previous reports about the location of the rDNA clusters in other Melipona species, independent of the technique used (Ag-NOR impregnation, CMA 3 staining or FISH; Rocha et al 2002, Brito et al 2003, Lopes et al 2011, Cunha et al 2018, Piccoli et al 2018). This seemed to be the most frequent pattern found in other Meliponini genera (Brito-Ribon et al 1999, Rocha et al 2003, Krinski et al 2010), although the presence of multiple rDNA clusters has also been described (Rocha et al 2003, Brito et al 2005, Duarte et al 2009, Martins et al 2009, Godoy et al 2013). …”