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Chromosome evolution in the genus Mikania (Compositae)
Author(s) -
Ruas Claudete F.,
AguiarPerecin Margarida L. R.
Publication year - 1997
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.2307/2446157
Subject(s) - biology , genus , secondary constriction , tribe , chromosome , botany , ploidy , karyotype , mikania micrantha , feulgen stain , aneuploidy , zoology , genetics , staining , sociology , anthropology , weed , gene
Karyotypic analysis of ten species of the genus Mikania was carried out using Feulgen staining. Species belonging to the following sections were analyzed: Section Thyrsigerae containing M. additicia (2 n = 34), M. hemisphaerica, M. lanuginosa, and M. punctata (2 n = 36), and Mikania sericea (2 n = 42), which adds a new basic chromosome number ( x = 21) to the genus and to the tribe Eupatorieae; Section Corymbosae with M. hastato‐cordata (2 n = 34) and M. involucrata and M. microptera with 2 n = 36 chromosomes; Section Spicato‐Racemosae with M. sessilifolia, with 2 n = 108 chromosomes. One unidentified species with 2 n = 34 chromosomes was also analyzed. All the species studied show one large pair of chromosomes with a secondary constriction in the middle region of the long arm. The morphology of this chromosome suggests that it can be considered as a cytological marker for the genus. Because of the distinctive inflorescence types found in the genus Mikania and the high frequency of species with x = 18, a correlation between morphological and chromosomal evolution is discussed. The present study suggests that the basic original chromosome number for the genus is x = 18, from which the others ( x = 17, 19, 20, 21) have been derived by aneuploidy to form the observed aneuploid series.