Complex Geographical Distribution of Ploidy Levels inPolylepis australis(Rosaceae), an Endemic Tree Line Species in Argentina

Abstract

Premise of research. The geographical distribution of ploidy levels provides insights into evolutionary pathways. For the subtropical tree line species Polylepis australis (Rosaceae), we tested the hypotheses that (1a) incidence of polyploidy is higher in the northern parts than in the southern parts of the species range due to the presence of related species that might favor hybridization (allopolyploidy), (1b) incidence of polyploidy is higher in the southern part of the range because the species here presumably reaches the limit of its environmental tolerance (autopolyploidy), and (2) ploidy levels increase with elevation, as polyploids are believed to perform better in stressful environments.Methodology. We used flow cytometry to assess the ploidy levels of 361 individuals from 27 populations across most of the distribution range of the species in two disjunct Argentinean high mountain regions.Pivotal results. The northern stands had lower ploidy levels (diploid) than the southern populations, in whic...