GENOMICALLY BASED GENERA IN THE PERENNIAL TRITICEAE OF NORTH AMERICA: IDENTIFICATION AND MEMBERSHIP

Dewey and Löve have suggested that generic limits in the Triticeae should be determined by the genomic data, taxa with different genomic constitutions being placed in different genera. According to this interpretation, nine genera of perennial Triticeae occur in North America. Five of these ( Critesion, Elymus, Leymus, Pascopyrum , and Pseudoroegneria ) include species native to North America; the other four ( Agropyron, Elytrigia, Psathyrostachys , and Thinopyrum ) are represented only by introduced species. Four hybrid genera of perennial Triticeae also occur in North America, × Elyleymus , × Pseudelymus , × Leytesion , and × Elytesion , the last being a new generic hybrid name necessitated by the treatment presented here. The number of naturally occurring intergeneric hybrids in North America is 18 according to this treatment whereas Bowden, using more traditional generic treatments, recognized 22 such hybrids in North America. For nonhybrid genera, an identification key and a brief description are provided, together with a table showing the taxa included in each genus. For hybrid genera, the species are merely listed. Several new combinations, mostly of hybrid taxa, are presented in order to accommodate the revised generic treatment.