Genotypic diversity among pasture and roadside populations of the invasive buffelgrass (Pennisetum ciliare L. Link) in north-western Mexico

Buffelgrass (Pennisetum ciliare L Link) is an African agamospermous grass that has been widely introduced into arid regions of the world to improve rangelands for cattle production and as a result, it has invaded adjacent habitats. In this study, ISSR markers were employed to assess genotypic variation in populations of P ciliare from north-western Mexico. We sampled plants from pasture and from colonizing roadside populations in order to explore if invasion success is associated with greater levels of genotypic diversity. Three ISSRs primers produced 27 reproducible bands that were used to screen 480 plants from sixteen populations. Mean values of the proportion of distinguishable genotypes (GIN) were 0.29, Nei's genotypic diversity was 0.75 and multilocus evenness (E) was 0.50. Sixty-seven multilocus genotypes were detected among 480 plants, with 46 (69%) restricted to single populations and 21 (31%) found in two or more populations. Our results showed no significant differences in genotypic diversity between pasture and roadside populations, suggesting that in P ciliare invasion success is not directly associated with greater levels of genotypic variation. Probably, other factors such as phenotypic plasticity and propagule pressure could be major determinants of the invasion success of buffelgrass in this region of Mexico. (C) 2008 Elsevier Ltd. All rights reserved.