INVESTIGADORES
URTUBEY estrella
artículos
Título:
Chromosome numbers and kariotypes of additional South American species and populations of Hypochaeris
Autor/es:
WEISS-SCHNEEWEISS, H; T. F. STUESSY; K. TREMETSBERGER; E. URTUBEY; H. A. VELDEBENITO; S. G. BECK; C. M. BAEZA
Revista:
BOTANICAL JOURNAL OF THE LINNEAN SOCIETY
Editorial:
Blackwell Publishing
Referencias:
Lugar: Londres; Año: 2007 vol. 153 p. 49 - 60
ISSN:
0024-4074
Resumen:
One hundred and thirty-seven new chromosome counts are reported from 104 populations of 26 native South American taxa of Hypochaeris (Asteraceae, Lactuceae), and two invasive Mediterranean species: H. glabra and H. radicata. First reports are provided for seven taxa (H. alba, H. cf. eremophila, H. caespitosa, H. hookeri, H. parodii, H. patagonica, H. pinnatifida) and one new ploidy level (diploid for H. incana, so far reported as tetraploid). Including results of the present study 39 of c. 50 Hypochaeris species known from the New World are counted chromosomally. Most species are diploid with 2n = 2x = 8 and have bimodal, asymmetric karyotypes. Tetraploidy (2n = 4x = 16) is reported here for the first time in H. caespitosa. Infraspecific polyploidy (probably autopolyploidy) is reported in both H. incana and H. taraxacoides, both cases including infrapopulational cytotype mixtures (2x and 4x). Polyploidy is now known from eight South American Hypochaeris species (c. 16%). Basic karyotype analyses allow the placement of the newly counted taxa into previously proposed, but slightly modified groupings, with some modifications, and provide the framework for further molecular cytogenetic analyses. The reported findings suggest that chromosomal change in South American Hypochaeris, in contrast to Old World species, has not involved aneuploidy, but polyploidy and/or more subtle changes in chromosome length, perhaps via satellite DNA amplification/deletion or activity of retroelements, and rDNA reorganization. ADDITIONAL KEYWORDS: Asteraceae — chromosome numbers — Hypochaeris — karyotype — polyploidy — South America — speciation.