Genetic variables, population features and reproductive success of Gymnocalycium monvillei (Cactaceae) along an altitudinal gradient

Abstract

Altitudinal gradients in mountain environments impose selection pressures that could result in marked heterogeneity in genetic characteristics, population features and reproductive success. Most Cactaceae occur in arid and semi-arid areas of the American continent, from sea level to 4500 m a.s.l., and some species have wide altitudinal ranges. The aim of this work was to analyse how cytogenetic features (mitotic chromosomes analysed using molecular cytogenetic techniques, DNA content estimated by flow cytometry), amplified fragment length polymorphism genetic diversity, population features (population density and individual size) and reproductive success (seeds per plant and fruit production) are related to an altitudinal gradient in five sites of Gymnocalycium monvillei located between 878 and 2230 m a.s.l. Our results showed that the sites at three intermediate altitude have optimal conditions as greatest genetic diversity, highest population density and highest seed production, whereas extreme sites are characterized by greatest reproductive isolation and highest DNA content and seed mass. The results indicate that the species has various mechanisms to survive along altitudinal gradients.