Canary grasses (Phalaris, Poaceae): Molecular phylogenetics, polyploidy and floret evolution

The 21 wild species of Phalaris L. (Poaceae) are distributed in temperate areas of both hemispheres and in the mountains of tropical Africa and South America. The genus contains annual and perennial diploids based on x = 6 and 7 and polyploids based on x = 7, with the x = 6 cytotypes displaying less species diversification. Phalaris presents a potentially valuable case study for speciation in conjunction with chromosomal evolution and biogeography in Poaceae due to its global distribution, notable variation in morphological traits, and the key role of polyploidy in its evolution. We reconstructed the first phylogenetic tree for the genus using nuclear ITS and plastid trnT-F sequences to assess species relationships and map trends in floret differentiation and patterns of polyploid evolution. The study demonstrated a single origin of the x = 6 chromosome number and revealed the sister relationship of this lineage to the monophyletic x = 7 lineage. The clades recovered in the analyses display geographic affiliations and demonstrate diploid-polyploid associations. A trend in sterile lemma reduction is evident, with members of the early diverging x = 6 lineage displaying relatively large and lanceolate sterile lemmas, followed by gradual reduction in size, culminating in almost obsolete sterile lemmas in one of the terminal x = 7 clades.