XVI International Botanical Congess

The Solanum nigrum complex is widely distributed in Taiwan and in many other parts of the world. Plants of this complex are phenotypically variable and exhibit complex polyploidy. This study concerns two species of the complex, i.e. S. nigrum and S. alatum, which differ mainly on fruit and flower characters. We used morphological and cytological analyses to study these taxa throughout their ranges in Taiwan, in conjunction with RAPD analysis. Solanum alatum is more common in Taiwan, growing mainly in waste places at lower elevations. Solanum nigrum is much less common. RAPD data show considerable differences between the species, with low similarity between them in cluster analysis. The data also reveal considerable variation within S. alatum, some of which is reflected in morphological, cytological, or physiological differences among populations. These data suggest that S. alatum is undergoing rapid evolution as it expands into different environmental conditions. Solanum nigrum is the polyploid derived from its diploid ancestor of the species complex.