Diversification of inflorescence development in the PCK Clade (Poaceae: Panicoideae: Paniceae).
REINHEIMER RENATA; ZULOAGA FERNANDO; VEGETTI ABELARDO C.; RAÚL POZNER
AMERICAN JOURNAL OF BOTANY
Año: 2009 vol. 96 p. 549 - 564
In grasses, infl orescence diversifi cation and its correlation with species evolution are intriguing and not well understood. Part of this problem lies in our lack of comprehension about the infl orescence morphological complexity of grasses. We focused our study on the PCK clade (named for phosphoenol pyruvate carboxykinase), a well-supported monophyletic group for which the relationships among its taxa are not well resolved. Interestingly, the PCK clade has an extensive diversity of adult infl orescence forms. A comparative developmental approach can help us to understand the basis of such morphological differences as well as provide characters that can be used in phylogenetic studies of the group. Using SEM studies, we demonstrate that infl orescence morphology in this clade is even more complex than what is typically observed in adult forms. We describe a number of new characters, and some classical features previously used for taxonomic purposes are redefi ned on the basis of development. We also defi ne four morphological groups combining adult infl orescence form and development, and we discuss some of the evolutionary aspects of infl orescence diversifi cation in the PCK clade. Taxonomic delimitation among genera in the PCK clade remains confusing and unclear where molecular and morphological studies support different classifi cations.