Numerical chromosome polymorphism in Mikania cordifolia Willd. (Asteraceae)

Abstract

Cytogenetical analysis of Mikania cordifolia, from southeastern Brazil, using the conventional Feulgen method, showed a chromosome number of 2n = 36. Previous karyotypic descriptions for this species showed a numerical chromosome variation of 2n = 34 to 38. There was a secondary constriction in every metaphase in the first chromosome pair, which constitutes a cytological marker. Small extranumerary chromosomes with numerical variation in the same plant were found in the tenth chromosome pair.<br>As análises citogenéticas mitóticas realizadas através de coloração convencional (Feulgen) em Mikania cordifolia, nativa da região de Campinas (SP), revelaram um número cromossômico de 2n = 36 cromossomos. Descrições cariotípicas anteriores para essa espécie mostraram um número cromossômico variando de 2n = 34 a 2n = 38. Em todas as metáfases foi encontrada uma constrição secundária no primeiro par cromossômico (já descrito anteriormente como um marcador citológico). Foi descrito, pela primeira vez nesta espécie, um satélite no 10º par cromossômico. Foram encontrados também cromossomos extranumerários pequenos com variação numérica na mesma planta

Chromosome studies in the genus Mikania (Asteraceae)

“…In a study of ten species of Mikania Ruas (1989) and Ruas and Aguiar-Perecin (1997) proposed a correlation between morphological and chromosomal evolution, while an analysis of 12 cytotypes of Mikania micrantha by Maffei (1996) showed that the same evolutionary mechanisms that occur among species also occur at intraspecific level, results also seen in a study of two populations of M. cordifolia by Maffei et al (1999a).…”

“…Chromosome studies show a regular aneuploid series with x = 17, 18, 19, 20 and 21 in the genus Mikania (King et al, 1976;Robinson and King, 1977;King and Robinson, 1987;Ruas and Ruas, 1987;Ruas, 1989;Ruas and AguiarPerecin, 1997;Maffei et al, 1998Maffei et al, , 1999a, with aneuploidy seeming to be an important component of chromosomal evolution in this genus.…”

“…Thirty-two taxa of Mikania have so far been examined, including 16 different species (Ruas and Ruas, 1987;Ruas, 1989;Ruas and Aguiar-Perecin, 1997), 14 populations of M. micrantha (Ruas and Ruas, 1987;Maffei, 1996;Maffei et al, 1998Maffei et al, , 1999b and two populations of M. cordifolia (Ruas and Ruas, 1987;Maffei et al, 1999a). All the karyotypes were characterized by the presence of a secondary constriction in the long arm of chromosome 1, and Ruas and Ruas (1987), in the analysis of six species, proposed that this secondary constriction should be considered a cytological marker for the genus.…”

“…Ruas (1989) and Ruas and Aguiar-Perecin (1997) reported a hexaploid species, M. sessilifolia with 2n = 6x = 108; the karyotype of this species showed 18 subsets of chromosomes, each of them having three pairs of morphologically similar chromosomes, suggesting autopolyploid origin. M. micrantha has populations with 2n = 34, 36, 38, 40, 42, and 72 chromosomes (Powell and King, 1969;King et al, 1976;Turner, 1977;Strother, 1983;Waisman et al, 1984;Ruas and Ruas, 1987;Maffei, 1996;Maffei et al, 1998Maffei et al, , 1999b while M. cordifolia has aneuploid cytotypes with n = 17, 18, and 19 (Gaiser, 1954;Powell and King, 1969;Ruas and Ruas, 1987;Robinson et al, 1989;Maffei et al, 1999a). M. cordata and M. capricorni have counts of n = 17 and 18 (Coleman, 1968) and M. pachyphylla has counts of n = 17, 18, and 20 (Nevlin, 1969).…”

Análises químicas qualitativas e quantitativas de duas espécies de 'Mikania: Mikania glomerata' Sprengel e 'Mikania laevigata' Schultz Bip

“…Este gênero possui aproximadamente 415 espécies (KING & ROBINSON, 1987) com distribuição tropical (MAFFEI et al, 1999). Está melhor representado na América do Sul, sendo amplamente distribuído no Brasil, onde aproximadamente 200 espécies têm sido descritas (RUAS & AGUIAR-PERECIN, 1997).…”