Abstract

URDAMPILLETA, Juan D.; AMAT, Aníbal G.  and  BIDAU, Claudio J.. Karyotypic studies and morphological analysis of some reproductive features in five species of Conyza (Astereae: Asteraceae) from Northeastern Argentina. Bol. Soc. Argent. Bot. [online]. 2005, vol.40, n.1-2, pp.91-99. ISSN 1851-2372.

The cosmopolitan genus Conyza Less. comprises about 100 species, 22 of which occur in Argentina. Current taxonomic treatments, largely based on exomorphological characters, are insufficient to characterize and circumscribe some of their polymorphic species. Interspecific variations in inflorescences typology and capitula structure, as well as karyotypic aspects, were studied in five species of Conyza that naturally occur in Misiones Province (Argentina): C. blakei (Cabrera) Cabrera, C. bonariensis (L.) Cronquist var. bonariensis, C. glandulitecta Cabrera, C. primulaefolia (Lam.) Cuatrec. & Lourteig, C. sumatrensis (Retz.) E. Walker var. sumatrensis and C. sumatrensis (Retz.) E. Walker var. floribunda (Kunth) J. B. Marshall. Chromosome numbers for C. bonariensis, C. sumatrensis var. sumatrensis and C. sumatrensis var. floribunda, all with 2n= 54 and C. primulaefolia (2n= 72), were confirmed; two new counts are reported: C. blakei (2n= 54) and C. glandulitecta (2n= 54). All karyotypes were compared, and related with the variation both in flower number per capitula as well as typology of the inflorescence. The results obtained considering the different sources of evidence, demonstrated a close relationship between C. sumatrensis var. sumatrensis and C. sumatrensis var. floribunda, that exhibit characteristics that may be considered primitive for the genus; C. primulaefolia shows the most advanced ones while C. blakei, C. bonariensis and C. glandulitecta occupy an intermediate position.

Keywords : Asteraceae; Astereae; Chromosomes; Conyza; Inflorescence; Interspecific variation; Karyotype.

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