Poliploidy and area in the genus Tarasa (Malvaceae)

Abstract

In the genus Tarasa we can find a clear relation between the chromosome number and the geographical distribution. The diploid species (2n = 10) are almost always endemics and they form a belt bordering the Andes between 10° and 40° of southern latitud. The tetraploid species (2n = 20) live inside this belt, have invaded the andinean high plateau, they grow at higher altitudes an ocupy bigger areas. The tetraploid species show a number of morfological reduction: mericarp?s awns are shorter, corollas are smaller an they have lower number of anthers than the diploid species. A new species, Tarasa umbellata, from Curicó, Chile, is described, belonging to the new section Umbellatae.