The Challenge of a Siberian Bluegrass (Poa) Phylogeny

In Siberia, the bluegrass genus (Poa) comprises 43 species and 61 subspecies in 12 sections. Diverse modes of speciation, including polyploidy and hybridization, have led to reticulate evolution and adaptive radiation. Cladistic methods that ignore hybridization and reticulate evolution may not be appropriate for morphological data. The number of morphological characters suitable for bluegrass analysis is limited, a majority does not have clear adaptive significance, and the character states cannot be readily polarized, rendering phylogenetic reconstruction very difficult in this group. Other methods of estimating phylogenetic relationships should be used to test hypotheses about relationships and hybridization. Biochemical and molecular data, as well as karyological, phytogeographical, and other lines of evidence should be combined to establish an explicit and testable hypothesis of the sequence of character state changes acquired during biotic differentiation.