MOLECULAR SYSTEMATICS OF IRIDACEAE: A COMBINED ANALYSIS OF FOUR PLASTID DNA SEQUENCE MATRICES

Abstract

Iridaceae are one of the largest families of Lilianae and probably also among the best studied families of monocotyledons. To further evaluate generic, tribal and subfamilial relationships, we have produced four plastid DNA data sets for 57 genera of Iridaceae plus outgroups: rps4, rbcL (both protein coding genes), and the trnL intron snd the trnL-F inter-gene spacer. All four matrices produce highly congruent, although not identical trees, and we thus analysed them in a combined analysis, which produced a highly resolved and well supported topology. In each of the individual trees, some genera or groups of genera are misplaced relative to Goldblatt’s and Rudall’s morphological cladistic studies, but the combined analysis produced a pattern much more similar to these previous ideas of relationships. In the combined tree, all subfamilies were resolved as monophyletic clades, except Nivenioideae, which formed a grade in which Ixioideae were embedded. The achlorophyllous Geosiris (sometimes referred to Geosiridaceae or Burmanniaceae) fell within the nivenioid grade. Most of the tribes are monophyletic, except for Ixieae, Watsonieae and Sisyrinchieae, but the topology within Ixioideae is not strongly supported due to extremely low levels of sequence divergence. Isophysis is sister to the rest of the family, and Diplarrhena falls in a well supported position as sister to Irideae/Sisyrinchieae/Tigridieae/Mariceae; Bobartia of Sisyrinchieae is supported as a member of Irideae.