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

Abstract

Editor: Richard ReePremise 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 which we found mainly tetraploids intermixed with diploids, triploids, and a single hexaploid. We did not find any environmental correlates to the geographical distribution of ploidy levels.Conclusions. Polyploidy appears to have arisen in P. australis via autopolyploidy, either twice in different parts of the range or, more likely, once followed by long-distance dispersal. This is also supported by amplified fragment length polymorphism (AFLP) data from a previous study that confirmed higher numbers of AFLP fragments and private bands in the southern populations. The checkerboard distribution of ploidy levels in the southern Sierras de Có rdoba may represent a time capture of the spread of the polyploid condition. We propose that polyploidy represents a key factor to understanding the high morphological variation in P. australis and should be taken into account in ongoing reforestation activities.

Pleistocene climatic oscillations rather than recent human disturbance influence genetic diversity in one of the world's highest treeline species

“…In part, this decrease may be related to decreasing aridity because we also found a negative relationship between annual mean precipitation and genetic diversity in P. tarapacana , which explains variation in genetic diversity better than latitude. The pattern of decreasing genetic diversity toward the north is consistent with our previous study of P. australis , which has both higher genetic diversity (Hensen et al, 2011) and higher variability of ploidy levels (Kessler et al, 2014) in the southern extent of its range. The genetic pattern of Podocarpus parlatorei also revealed the long‐term persistence of cold‐tolerant elements in the northern Argentinean Andes adjacent to our Argentinean cluster (Quiroga and Premoli, 2007).…”

No effect of elevation and fragmentation on genetic diversity and structure in Polylepis australis trees from central Argentina

“…While the species is diploid in its northern range, we carried out our study in its southern range, where the species is mainly tetraploid, with some populations having individuals with polyploidy levels of 2, 3 and 6 at low frequencies (Kessler et al . ). It is likely that P. australis is primarily an outcrosser, as selfing could be hampered by protogyny (Seltmann et al .…”

Análisis Citogeográfico En Turnera Krapovickasii (Passifloraceae).

“…Los diferentes citotipos de los complejos poliploides muestran, frecuentemente, marcadas diferencias en su distribución geográfica (Favarger, 1967;Stebbins, 1971;Brunsberg, 1977;Lewis, 1980;Levin, 1983Levin, , 2002Soltis, 1984;van Dijk et al, 1992;Husband & Schemske, 1998;Kessler et al, 2014). En el género Turnera, las investigaciones llevadas a cabo en el complejo autopoliploide T. sidoides demostraron que el citotipo diploide posee una distribución más restringida, los tetraploides poseen una distribución amplia ocupando gran parte del área de las subespecies, los hexaploides generalmente están restringidos a regiones marginales, mientras que los octoploides y poliploides impares son raros (Solís Neffa & Fernández, 2001;Solís Neffa et al, 2004;.…”