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/CMA3 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.
Highlights
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
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, 1997, 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, 1997, 2005; Tosta et al, 2004)
Brito et al (1997) distinguished two morphological types of B chromosomes occurring in P. helleri in southeastern Brazil
Summary
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, 1997, 2005; Tosta et al, 2004). We report a new type of B chromosome in populations from the northern limits of the distribution of P. helleri in the state of Bahia, Brazil.
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