SciELO - Scientific Electronic Library Online

 
 número118Revisión taxonómica de Salvia subgénero Calosphace sección Scorodoniae (Lamiaceae), endémica de MéxicoRelaciones genéticas basadas en marcadores ISTR entre formas silvestres, cultivadas e intermedias de frijol de guía colectado en Jalisco, México índice de autoresíndice de assuntospesquisa de artigos
Home Pagelista alfabética de periódicos  

Serviços Personalizados

Journal

Artigo

Indicadores

Links relacionados

  • Não possue artigos similaresSimilares em SciELO

Compartilhar


Acta botánica mexicana

versão On-line ISSN 2448-7589versão impressa ISSN 0187-7151

Resumo

CASTRO-CASTRO, Arturo et al. Chromosomic numbers for three species of Cosmos section Discopoda (Asteraceae, Coreopsideae), with cytogeographic notes. Act. Bot. Mex [online]. 2017, n.118, pp.41-51. ISSN 2448-7589.  http://dx.doi.org/10.21829/abm118.2017.1199.

Background and Aims:

Cosmos section Discopoda (Asteraceae, Coreopsideae) is a model for studying polyploidy and aneuploidy. This section is monophyletic, including 24 herbaceous perennials with some polyploid species and others aneuploids. However, the chromosome numbers of some species are still unknown and their cytogeography has not been studied. Here the chromosome counts for three species are revealed and the ancestral levels of ploidy as well as geographical distributions of the different ploidy levels are compared.

Methods:

Previously known chromosome counts were retrieved and chromosome counts were made from vegetative parts of three species. After designating a ploidy level to each of 810 registers, including all species and through the use of a geographic information system, their distributions were analyzed based on those ploidy levels. In addition, using a maximum likelihood model, a reconstruction of ancestral ploidy was made.

Key results:

Cosmos nitidus and C. ramirezianus are diploids (2n=2x=24) while C. pseudoperfoliatus is tetraploid (2n=4x=48). To date, chromosome counts for the 20 species of Cosmos section Discopoda are known, of which 12 are diploids (2n=2x), six are exclusively polyploids (2n=4x, 6x, 8x), four are diploids and polyploids and there are two independent events of aneuploidy. The reconstruction of ancestral ploidy levels revealed that x=12 is the basic number of chromosomes in this section of Cosmos.

Conclusions:

A correlation between the ploidy levels and geographical ranges of the species of Cosmos section Discopoda does not seem apparent. In contrast, there does seem to be an increase in ploidy levels from south to north, with a concentration of polyploids in the northern area of the Sierra Madre Occidental.

Palavras-chave : cytogeography; Heliantheae; Mexican Transition Zone; polyploidy; Sierra Madre Occidental.

        · resumo em Espanhol     · texto em Espanhol     · Espanhol ( pdf )