PHYLOGENETIC-RELATIONSHIPS OF THE MONOGENOMIC SPECIES OF THE WHEAT TRIBE, TRITICEAE (POACEAE), INFERRED FROM NUCLEAR RDNA (INTERNAL TRANSCRIBED SPACER) SEQUENCES

Phylogenetic relationships of 30 diploid species of Triticeae (Poaceae ) representing 19 genomes were estimated from the sequences of the int ernal transcribed spacer (ITS) region of nuclear ribosomal DNA. The IT S sequence phylogeny indicated that: (i) each genome group of species is monophyletic, concordant with cytogenetic evidence; (ii) Hordeum (I ) and Critesion (H) are basal; (iii) Australopyrum (W) is closely rela ted to Agropyron (P); (iv) Peridictyon (G), Heteranthelium (Q), and Da sypyrum (V) are closely related to Pseudoraegneria (S); (v) most of th e annuals, Triticum s.l. (A, B, D), Crithopsis (K), Taeniatherum (T), Eremopyrum (F), Henrardia (O), Secale (R), and two perennials, Thinopy rum (J) and Lophopyrum (E), all of Mediterranean origin, are a monophy letic group. However, phylogenetic trees based on morphology group the se Mediteranean species with various perennial lineages of the Arctic- temperate region. The molecular data and biogeography of the tribe sug gest that the Mediterranean lineage is derived from the Arctic-tempera te lineage and that the two lineages have evolved in parallel. Extensi ve morphological parallelism apparently obscures the true genealogical history of the tribe when only morphology is considered.