Morphological identification of genomic genera in the Triticeae

Abstract

Our goal was to determine whether the genomic groups of perennial species Triticeae having solitary spikelets could be identified morphologically and, if so, to construct identification keys that could be used for this purpose. If so, it would strengthen the argument for recognizing such groups as genera. We conducted Discriminant and Random Forest® analyses of 61 characters scored on 218 herbarium specimens representing 13 genomic groups. In addition, we closely examined some additional characters that came to our attention, evaluating our findings on specimens not scored for the two kinds of analysis. Random Forest® analysis was almost always more successful in distinguishing the genomic groups, whether separating all 13 groups or a subset of the 13. The results suggest that it is usually possible to identify the genomic group to which a specimen of perennial Triticeae with solitary spikelets belongs on the basis of its morphology but that doing so will require examination of characters that have not been considered particularly important in the past. Among these are the length of the middle inflorescence internodes, the width of the palea tip, and the morphology of the glumes. Generic descriptions and keys have been posted to the web (see http://herbarium.usu.edu/ triticeae). They include all the genera that we recognize in the tribe, not just those included in the analyses, and will be improved as additional information becomes available.