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Abstract

Paspalum simplex is a grass distributed throughout the phytogeographic Chaco region in South America from which sexual diploid and apomictic tetraploid races have been reported. We analysed native populations to determine their homogeneity of ploidy level, and the relationship between geographic distribution, ploidy levels, and reproductive systems. The ploidy level was established for 379 plants from 32 wild populations. Tetraploidy and apomixis constitute the most common combination for this species all over the Chaco region. Apomictic hexaploid plants were found associated with 4x populations. Diploids were confined to a small sector of the region. One sexual triploid plant arose from seed harvested in a pure 2x population, and one apomictic 3x plant was found in a mixed 2x-4x population. The results suggest that P. simplex is a core agamic complex characteristic of the Chaco region from which other apomictic polyploid species of the subgenus Anachyris could have evolved.

Chromosome numbers and ploidy levels of Paspalum species from subtropical South America (Poaceae)

“…The most frequent ploidy level among these collections was tetraploidy, and all counts agree with previous reports (Davidse and Pohl 1972, 1974, 1978Honfi et al 1990;Norrmann et al 1994a;Hunziker et al 1998;Pagliarini et al 2001;Urbani et al 2002;Adamowski et al 2005;Morrone et al 2006;Souza-Chies et al 2006;Essi and Souza-Chies 2007;Pozzobon et al 2000Pozzobon et al , 2008 and references therein) (Figs. 1j-l, 2m-n).…”

Diversity in Diploid, Tetraploid, and Mixed Diploid–Tetraploid Populations of Paspalum simplex

“…Paspalum simplex is a good representative species of the genus since it contains 2x, 3x, 4x and 6x cytotypes, and apomixis always appears linked to polyploidy (Urbani et al, 2002). However, the sources of the observed diversity are not well defined for most species.…”

“…Two of these populations were previously characterized as diploid (2n = 2x = 20) while the other four were characterized as tetraploid (2n = 4x = 40) (Urbani et al, 2002). The fluorescence intensity of 4',6-diamidino-2-phenylindole (DAPI)-stained nuclei was analyzed with a Partec PA II flow cytometer.…”

“…The ploidy level determination for morphological characterizations was previously performed by Urbani et al (2002). Approximately 200 seeds from each population Partec).…”

“…Paspalum simplex is an interesting species to study because it is also a multiploid species, and sympatric, mixed diploid and polyploid, and pure diploid and tetraploid populations have been reported (Urbani et al, 2002). The species grows naturally in northern Argentina, Paraguay, northeastern Uruguay, and eastern Bolivia.…”