DIFFERENTIATION OF DROSOPHILA-SERIDO (ISOFEMALE LINE A95F3) AND D-KOEPFERAE (ISOFEMALE LINE B20D2) - REPRODUCTIVE ISOLATION, DEVELOPMENT TIME AND POLYTENE CHROMOSOME-BANDING PATTERNS

Drosophila serido is considered to be a superspecies consisting of two species: D. serido, from Brazil and D. koepferae from Argentina and Bolivia. However this probably does not express the entire evolutionary complexity of its populations. Isofemale lines A95F3 (from Brazil) and B20D2 (from Argentina), at present representing, respectively, the first and second species, were analyzed for fertility and fecundity in pair-mating intracrosses and intercrosses, as well as for development time, banding patterns and asynapsis of polytene chromosomes in the isofemale lines and their hybrids.Although variations in experimental conditions resulted in some variability in the results, in general A95F3 fertility and fecundity were lower than in B20D2. Intercrosses of A95F3 females and B20D2 males showed lower fertility and fecundity than the reciprocal crosses, following more closely characteristics of the mother strains. This is in contrast to the results obtained by Fontdevilla et al. (An. Entomol. Soc. Amer. 81: 380-385, 1988) and may be due to the different geographic origin of D. serido strains they used in crosses to B20D2. This difference and others cited in the literature relative to aedeagus morphology, karyotype characteristics, inversion polymorphisms and reproductive isolation strongly indicate that A95F3 and D. serido from the State of Bahia, Brazil are not a single evolutionary entity, reinforcing the idea of greater complexity of the superspecies D. serido than is known today.The reproductive isolation mechanisms found operating between A95F3 and B20D2 were prezygotic and postzygotic, the latter included mortality at the larvae stage in both directions of crosses and sterility of male hybrids in intercrosses involving B20D2 females and A95F3 males. The two isofemale lines differed in egg-adult development time, which was also differently affected by culture medium composition.A95F3 and B20D2 also showed differences in the banding patterns of proximal regions of polytene chromosomes 2, 3 and X, a fixed inversion in chromosome 3 (here named 3t), apparently not described previously, and a high degree of asynapsis in hybrids.These observations, especially those related to reproductive isolation and chromosomal differentiation (including the karyotype, previously described, and the differentiation of banding patterns, described in this paper), as well as the extensive asynapsis observed in hybrids reinforces the distinct species status of A95F3 and B20D2 isofemale lines.

Chromosome polymorphism and cytotype establishment in Bidens pilosa (Asteraceae)

Chromosome evolution, in the Bidens genus, was by polyploidy mechanisms. The basic number to the genus is X = 12 chromosomes, as all the Fitchinae subtribe. The association of chromosome number and environment in these plants was made some time ago, concerning the cytotypes of the species. In this paper, the chromosome number of nine Bidens pilosa populations was studied. The chromosome numbers found were 2n = 48, 70 and 72. In six of the nine populations analysed the most frequent number was 2n = 72. The Ibiuna population had 2n = 70 chromosomes and two had the lowest chromosome number (2n = 48). Observations of the B. pilosa population suggests that ploidy levels were related to a geographical gradient establishing the environmental altitudes. The data showed that lower ploidy levels, that is 2n = 48, were found at lower altitudes, while the populations higher ploidy levels were found in several environments, over a wide distribution.

Chromosome reduction in Eleocharis maculosa (Cyperaceae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chromosome analysis in Pseudopaludicola (Anura, Leiuperidae), with description of sex chromosomes XX/XY in P-saltica

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chromosome analysis of two species of sugar cane pests of the genus Mahanarva (Homoptera, Cercopidae)

Studies on the cytogenetics of Homoptera are scarce. Some references in the literature have reported a chromosome number for the genus ranging from n=5 to 19 and 2n=10 to 2n=39 chromosomes. The genus Mahanarva includes two species of agricultural importance as pests of sugar cane culture in Brazil. We report here the first data concerning the chromosome number and morphology of the species Mahanarva fimbriolata and M. posticata. The chromosome number observed for the two species was 2n=19 for males and 2n=20 for females. The sex determining mechanism of these species was of the XX/X0 type (for males and females, respectively), with chromosome X being the smallest in the complement.

Tracking the evolution of sex chromosome systems in Melanoplinae grasshoppers through chromosomal mapping of repetitive DNA sequences

Background: The accumulation of repetitive DNA during sex chromosome differentiation is a common feature of many eukaryotes and becomes more evident after recombination has been restricted or abolished. The accumulated repetitive sequences include multigene families, microsatellites, satellite DNAs and mobile elements, all of which are important for the structural remodeling of heterochromatin. In grasshoppers, derived sex chromosome systems, such as neo-XY♂/XX♀ and neo-X1X2Y♂/X 1X1X2X2♀, are frequently observed in the Melanoplinae subfamily. However, no studies concerning the evolution of sex chromosomes in Melanoplinae have addressed the role of the repetitive DNA sequences. To further investigate the evolution of sex chromosomes in grasshoppers, we used classical cytogenetic and FISH analyses to examine the repetitive DNA sequences in six phylogenetically related Melanoplinae species with X0♂/XX♀, neo-XY♂/XX♀ and neo-X1X2Y♂/X1X1X 2X2♀ sex chromosome systems. Results: Our data indicate a non-spreading of heterochromatic blocks and pool of repetitive DNAs (C 0 t-1 DNA) in the sex chromosomes; however, the spreading of multigene families among the neo-sex chromosomes of Eurotettix and Dichromatos was remarkable, particularly for 5S rDNA. In autosomes, FISH mapping of multigene families revealed distinct patterns of chromosomal organization at the intra- and intergenomic levels. Conclusions: These results suggest a common origin and subsequent differential accumulation of repetitive DNAs in the sex chromosomes of Dichromatos and an independent origin of the sex chromosomes of the neo-XY and neo-X1X2Y systems. Our data indicate a possible role for repetitive DNAs in the diversification of sex chromosome systems in grasshoppers. © 2013Palacios-Gimenez et al.; licensee BioMed Central Ltd.

Avaliação do emprego de um novo método de triagem molecular da síndrome do cromossomo X frágil em indivíduos brasileiros

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Interploidy hybridization in sympatric zones: the formation of Epidendrum fulgens x E. puniceoluteum hybrids (Epidendroideae, Orchidaceae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chromosome Evolution in Dendropsophini (Amphibia, Anura, Hylinae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comparative Chromosome Mapping of U2 snRNA and 5S rRNA Genes in Gymnotus Species (Gymnotiformes, Gymnotidae): Evolutionary Dynamics and Sex Chromosome Linkage in G. pantanal

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A new species of Endecous Saussure, 1878 (Orthoptera, Gryllidae) from northeast Brazil with the first X(1)X(2)0 chromosomal sex system in Gryllidae

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Construction and preliminary characterization of a river buffalo bacterial artificial chromosome library

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Distribution of constitutive heterochromatin in species of triatomines with fragmentation of sex chromosomes X

Cytogenetic analyses of triatomines are considered to be important taxonomic tools. Thus, we analyzed the pattern of constitutive heterochromatin in 7 species of triatomine with fragmentation of the sex chromosome X, focusing on the cytotaxonomy of these triatomines. The species analyzed included Triatoma vitticeps, Triatoma melanocephala, Triatoma tibiamaculata, Triatoma protracta, Meccus pallidipennis, Panstrongylus megistus, and Panstrongylus lignarius. The seminiferous tubules of the adult males were subjected to C-banding. P. megistus and P. lignarius showed differences in chromosome number and disposition of constitutive heterochromatin, as only P. lignarius showed C-blocks in autosomes. C-banding can differentiate these species, since one of the sex chromosome (X) is heterochromatic in T. vitticeps. T. protracta showed C-blocks in both ends of all autosomes, T. tibiamaculata showed terminal C-dots in some autosomal pairs and M. pallidipennis did not show constitutive heterochromatin in autosomes. Thus, we confirmed the heterochromatic pattern of 7 species of insects and emphasized the importance of cytogenetic techniques for C-banding for taxonomy studies of the triatomines, which are important vectors of Chagas disease.

Chromosomal evolution in Pleurothallidinae (Orchidaceae: Epidendroideae) with an emphasis on the genus Acianthera: chromosome numbers and heterochromatin

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chromosome evolution in lycosoid spiders (Araneomorphae): a scenario based on analysis of seven species of the families Lycosidae, Senoculidae and Trechaleidae

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)