Phylogenetic relationships of the Decumbentes Group of Paspalum, Thrasya, and Thrasyopsis (Poaceae: Panicoideae: Paniceae).

DENHAM, S.S.; F.O. ZULOAGA

aliso

Rancho Santa Ana Botanic Garden

Lugar: Claremont, Estados Unidos; Año: 2007 vol. 23 p. 545 - 559

0065-6275

Paspalum (Poaceae: Panicoideae: Paniceae) includes 330 species mainly distributed in tropical and subtropical regions of America. Due to the large number of species and convergence in many characters, an adequate infrageneric classification is still needed. Studies on Paniceae based on molecular and morphological data suggested that Paspalum is paraphyletic, including the genus Thrasya, but none of these analyses included a representative sample of these two genera. In this study, phylogenetic relationships among the informal group Decumbentes of Paspalum, plus other subgenera and informal groups, and the genera Thrasya and Thrasyopsis were estimated. A cladistic analysis under parsimony was performed using a matrix of 50 taxa and 77 morphological and anatomical characters. Different analytical parameters were explored: equal and implied weights varying the concavity constant k from 1 to 12. Almost all analyses showed that species of the Decumbentes group and Thrasya form a natural group, supported by the presence of axillary peduncles in the upper foliar sheath, upper glume slightly shorter than the spikelet, margins of the lower lemma plicate on the upper anthecium, and upper anthecium without simple papillae. The position of Thrasyopsis is not clear because it varies among the different analyses. The most important clades are discussed as well as diagnostic characters usually used to distinguish the studied genera. (Poaceae: Panicoideae: Paniceae) includes 330 species mainly distributed in tropical and subtropical regions of America. Due to the large number of species and convergence in many characters, an adequate infrageneric classification is still needed. Studies on Paniceae based on molecular and morphological data suggested that Paspalum is paraphyletic, including the genus Thrasya, but none of these analyses included a representative sample of these two genera. In this study, phylogenetic relationships among the informal group Decumbentes of Paspalum, plus other subgenera and informal groups, and the genera Thrasya and Thrasyopsis were estimated. A cladistic analysis under parsimony was performed using a matrix of 50 taxa and 77 morphological and anatomical characters. Different analytical parameters were explored: equal and implied weights varying the concavity constant k from 1 to 12. Almost all analyses showed that species of the Decumbentes group and Thrasya form a natural group, supported by the presence of axillary peduncles in the upper foliar sheath, upper glume slightly shorter than the spikelet, margins of the lower lemma plicate on the upper anthecium, and upper anthecium without simple papillae. The position of Thrasyopsis is not clear because it varies among the different analyses. The most important clades are discussed as well as diagnostic characters usually used to distinguish the studied genera.