Sistemática y evolución del género Yucca (Agavaceae): evidencias de análisis nunfológicos y moleculares

Abstract

Yucca L. (the Desert Soaptree, Agavaceae) consists of 45 perennial species distributed primarily in the deserts of Mexico and the United States. Although several taxonomic treatments of yuccas exist; the-phylogeny of the group is poorly known. It is unclear which taxa retain primitive characters and how characters have evolved. In addition, relationships of taxa within the genus are uncertain. We compare our phylogeny based upon reproductive characters with a chloroplast phylogeny (Hanson and Rieseberg, 1991 ; Hanson, 1993) and with data from the ITS region of the nuclear genome (Bogler, this volume). The molecular analyses of the chloroplast genome by Hanson and Rieseberg (1991) led to a phylogeny only partially congruent with the traditional morphology-based phylogeny (McKelvey, 1938, 1947) because the cpDNA analysis indicated that chloroplast capture among distantly related, sympatric/parapatric species has been a factor in the evolution of the group. Our results indicate that Yucca in the traditional sense is paraphyletic, that sect. Chaenocarpa is more basal than sect. Yucca ( =Sarcocarpa), and that Yucca (=Hesperoyucca) whipplei falls outside of Yucca.