A phylogenetic analysis of the genus Paspalum (Poaceae) based on cpDNA and morphology

Abstract

With about 350 species, Paspalum is one of the richest genera within the Poaceae. Its species inhabit ecologically diverse areas along the Americas and they are largely responsible for the biodiversity of grassland ecosystems in South America. Despite its size and relevance, no phylogeny of the genus as a whole is currently available and infrageneric relationships remain uncertain. Many Paspalum species consist of sexual-diploid and apomicticpolyploid cytotypes, and several have arisen through hybridization. In this paper we explore the phylogenetic structure of Paspalum using sequence data of four noncoding cpDNA fragments from a wide array of species which were combined with morphological data for a subset of diploid taxa. Our results confirmed the general monophyly of Paspalum if P. inaequivalve is excluded and the small genus Thrasyopsis is included. Only one of the four currently recognized subgenera was monophyletic but nested within the remainder of the genus. Some informal morphological groups were found to be polyphyletic. The placement of known allopolyploid groups is generally congruent with previously stated hypotheses although some species with shared genomic formulae formed paraphyletic arrangements. Other species formed a basal grade including mostly umbrophilous or hygrophilous species. It is hypothesized that the genus may have diversified as a consequence of the expansion of C4 grass-dominated grasslands in South America.

Genetic variation in polyploid forage grass: Assessing the molecular genetic variability in the Paspalumgenus

“…Previous molecular phylogenetic studies [99] have suggested a greater genetic distance between the third main group compared to the Plicatula and Notata groups, which explains the lower frequency of microsatellite polymorphisms observed for species from the third group. However, there was a clear distinction between the species of this group.…”

“…notatum and P . subciliatum [99-101] (these species form a monophyletic clade). Moreover, whether P .…”

“…cromyorhizon and P . ionanthum should be included in the subgenus Paspalum remains uncertain, but evidence provided by cpDNA sequences [99] supports a close relationship between these two species. P .…”

El género Paspalum L. (Paspaleae, Poaceae) en la Península de Yucatán, México

“…Morfológicamente las plantas de Paspalum se caracterizan por presentar espiguillas biflosculares plano convexas, siendo ésta probablemente la única sinapomorfia del género (Rua et al, 2010). Además, las espiguillas generalmente carecen de la primera gluma y la lema fértil presenta los márgenes enrollados (Chase, 1929;Hitchcock, 1971).…”

“…Han sido numerosos los trabajos encaminados a esclarecer la clasificación infragenérica de Paspalum (Döll, 1877;Nash, 1912;Chase, 1929;Pilger, 1929;Zuloaga, 1974;Clayton y Renvoize, 1986;Cialdella et al, 1995;Denham et al, 2002;Morrone et al, 1995Morrone et al, , 1996Morrone et al, , 2000Morrone et al, , 2004Rodríguez, 1992Rodríguez, , 1998Zuloaga y Morrone, 2003, 2005Zuloaga et al, 2004;Denham, 2005;Denham et al, 2010). Sin embargo, no existe un esquema natural de clasificación dentro del mismo (Rua et al, 2010), ya que dichas propuestas se basan en macrocaracteres morfológicos que se presentan en grupos de especies aparentemente poco relacionadas (Zuloaga y Morrone, 2005). En el presente trabajo, acorde con los trabajos de Zuloaga et al (2004), Zuloaga y Morrone (2005), Denham (2005) y Denham et al (2010), basados en los estudios previos de Nash (1912) y Chase (1929), se reconocen cuatro subgéneros: subg.…”