Karyotypic studies in the Chilean genus Placea (Amaryllidaceae)

Resumo

Chromosome numbers and karyotypes of seven specific taxa of the Chilean endemic genus Placea were determined. Chromosome numbers of P. lutea, P. ornata, P. grandiflora, P. germainii and P. aff. davidii are described for the first time. All taxa are diploid with 2n=2x=16 and karyotypes are composed of four metacentric (4 m), ten submetacentric (10 sm), and two subtelocentric (2 st) chromosomes. The most symmetrical karyotype was observed in P. lutea (AI: 6.84) while the most asymmetrical karyotype was shown by P. arzae (AI: 9.72). The constancy in karyotype formulae and high similarity in asymmetry indexes suggest that some orthoselection mechanism might be involved in Placea's chromosomal evolution. In spite that no significant karyotypic differences were observed, the species may be differentiated by their chromosomal sizes. Moreover, the tribal position of Placea and its likely relationships with other hippeastroid genera are discussed.