Among families of flowering plants, the grass family (Poaceae) is one of the most conspicuous elements of world vegetation, and economically the most important. The grass family is classified taxonomically into six morphologically distinct subfamilies, among them the Pooideae, which includes the majority of grasses of the world's cool temperate regions. Phylogenetic or evolutionary relationships remain obscure among the 650 or so genera of the Poaceae, including the 150 or so of subfamily Pooideae, in part because of the reduced and streamlined nature of grass vegetative and reproductive parts. Dr. Jerrold Davis of Cornell University is studying the phylogenetic relationships of selected members of the Pooideae with specific attention to two of its major subgroupings, the tribe Poeae (including fescues, bluegrasses, and wheats) and the tribe Aveneae (including oats). Both morphological and molecular data are being collected, the latter from intensive analyses of nucleotide mutations in the chloroplast DNA of representative grass samples. Comparisons between morphological and molecular patterns of diversification are being made, and congruent patterns are being used to clarify evolutionary trends within the grass family and determine pathways of migration and geographical distribution.
