Pleistocene refugia and polytopic replacement of diploids by tetraploids in the Patagonian and Subantarctic plantHypochaeris incana(Asteraceae, Cichorieae)

Abstract

We report the phylogeographic pattern of the Patagonian and Subantarctic plant Hypochaeris incana endemic to southeastern South America. We applied amplified fragment length polymorphism (AFLP) and chloroplast DNA (cpDNA) analysis to 28 and 32 populations, respectively, throughout its distributional range and assessed ploidy levels using flow cytometry. While cpDNA data suggest repeated or simultaneous parallel colonization of Patagonia and Tierra del Fuego by several haplotypes and/or hybridization, AFLPs reveal three clusters corresponding to geographic regions. The central and northern Patagonian clusters (approximately 38-51 degrees S), which are closer to the outgroup, contain mainly tetraploid, isolated and highly differentiated populations with low genetic diversity. To the contrary, the southern Patagonian and Fuegian cluster (approximately 51-55 degrees S) contains mainly diploid populations with high genetic diversity and connected by high levels of gene flow. The data suggest that H. incana originated at the diploid level in central or northern Patagonia, from where it migrated south. All three areas, northern, central and southern, have similar levels of rare and private AFLP bands, suggesting that all three served as refugia for H. incana during glacial times. In southern Patagonia and Tierra del Fuego, the species seems to have expanded its populational system in postglacial times, when the climate became warmer and more humid. In central and northern Patagonia, the populations seem to have become restricted to favourable sites with increasing temperature and decreasing moisture and there was a parallel replacement of diploids by tetraploids in local populations.

High chloroplast haplotype diversity in the endemic legume Oxytropis chankaensis may result from independent polyploidization events

“…The high levels of genetic and genotypic diversity that we found in this species based on allozyme data implied that polyploidy might have resulted from recurrent crosses between genetically different plants. Polyploidy is believed to be a common mechanism in the evolution of plants, and multiple origins have been shown for both auto-and allopolyploid plants including Oxytropis species (Jorgensen et al 2003;Segraves et al 1999;Soltis and Soltis 2000;Soltis et al 2003Soltis et al , 2007Tremetsberger et al 2009). The polytopic and recurrent origin of many polyploids may account for the overall complexities that are observed in such taxa (Gauthier et al 1997;Parisod et al 2010;Soltis and Soltis 2009).…”

Phylogeography, genetic diversity and population structure in a Patagonian endemic plant

“…Recent reviews of the phylogeographical patterns within some specific areas in Patagonia provide valuable insight into the historical processes underlying diversification in this region (Domínguez et al 2006; Morando et al 2007; Jakob et al 2009, 2010; Tremetsberger et al 2009; Cosacov et al 2010; Albino 2011; Pardiñas et al 2011; Sérsic et al 2011; Sede et al 2012; Nicola et al 2014; Morello and Sede 2016). The phylogeographical approach may also offer a means of estimating the historical processes that have influenced the structure of the genetic variation now observed in a given species (Avise 2000).…”

Isolation and characterization of microsatellite markers for Hypochaeris incana (Asteraceae) and close relatives1

“…The ploidy level of all individuals of the Cerro La Buitrera population of H. incana and of a few other populations was determined by flow cytometry (C. König, unpublished data; see Appendix 1). The ploidy level of the remaining populations was retrieved from Weiss et al (2003), Weiss-Schneeweiss et al (2007), and Tremetsberger et al (2009) and/or inferred from microsatellite peak patterns. One diploid individual of the Cerro La Buitrera population of H. incana was sequenced on a GS FLX Titanium sequencer (454 Life Sciences, a Roche Company, Branford, Connecticut, USA) at LGC Genomics (Berlin, Germany).…”

“…F. Stuessy & C. M. Baeza 15812/2000 (CONC, WU) e Chile, Región IX, Volcán Lonquimay52 x j Hypochaeris tenuifolia T. F. Stuessy & C. M. Baeza 15823/2000 (CONC, WU) c,e Chile, Región IX, Volcán Llaima22 x j Note: N = number of individuals used.aHerbarium code according to Index Herbariorum.bUsed for NGS run.cTest individuals for screening of primer pairs.dTest populations for assessment of genetic diversity in H. incana .eTest populations for assessment of cross-amplification in related species.fWeiss et al (2003).gWeiss-Schneeweiss et al (2007).hTremetsberger et al (2009).iDetermined by flow cytometry (C. König, unpublished data).jInferred from microsatellite peak patterns.…”

“…Peculiarly, diploids occur in the southern part of its range and tetraploids in the northern part of its range, but H. incana seems to have originated in the north (Tremetsberger et al, 2009). Tremetsberger et al (2009) suggested that tetraploids may have repeatedly replaced their diploid progenitors in the northern part of the range. The factors involved in the establishment of polyploid cytotypes, however, are still poorly understood.…”