PHYLOGENY OF AGAVACEAE BASED ON ITS RDNA SEQUENCE VARIATION

Several systems of classification have been proposed for the family Ag avaceae. A distinctive bimodal karyotype and similarities of fruits an d seeds strongly support close relationships among Yucca, Hesperaloe B eschorneria, Furcraea, Agave, Manfreda, Polianthes, Prochnyanthes, and perhaps Hosta. However, Dasylirion, Beaucarnea, Nolina, Calibanus, Dr acaena, and Sansevieria differ in so many cytological and morphologica l features that many have concluded they should be excluded from Agava ceae and separated into two families, Nolinaceae and Dracaenaceae. Chl oroplast DNA restriction site data support these separations and indic ate that Nolinaceae and Dracaenaceae are very close to Convallariaceae (Maianthemum, Convallaria, Aspidistra, Liriope, etc.). In this paper we report the results of an ITS rDNA sequencing study of 40 taxa in Ag avaceae sensu late and related groups in the order Asparagales. Sequen ce alignments were optimized using the Consistency Index, Retention In dex, and Rescaled Consistency Index to find the alignment that exhibit ed the least amount of homoplasy. The results of our study are congrue nt with the conclusions drawn from cytological, immunological, cpDNA, and rbcL studies, which support a narrow interpretation of Agavaceae a nd a close relationship among Convallariaceae, Dracaenaceae, and Nolin aceae. In addition, the ITS sequence data provide evidence for some in teresting relationships within these families.