Natural hybridization between two south American diploid species of Andropogon (Gramineae)

FLORENCIA GALDEANO; NORRMANN, G.

Otra

Año: 2000 vol. 127 p. 101 - 106

0040-9618

In two mixed populations of ANdropogon selloanus (Hack.) Hack. and A. macrothrix Trin. from northeastern Argentina we found two individuals that were morphologically intermediate between these two taxa. The hypothesis that these individuals were natural hybrids was tested through comparisons with a controlled hybrid obtained from the cross A. selloanus X A. macrothrix. The results show that there are neither morphological, nor cytological, nor reproductive differences among intermediate individuals and the controlled hybrid; therefore they deserve to be regarded as products of natural hybridization. Meiotic chromosome behavior in the hybrids indicates that these two species share different forms of a basis genome (S), wich accounts for the complete sterility of the hybrids. Therefore, although hybrids are produced in natural populations, the two taxa apparently well isolated and gene flow between them looks highly improvable. The S genome is also known to be present in A. ternatus, a South American triploid with strong similarities to A. macrothrix