Polyploids with odd-ploidy levels may play an important evolutionary role as they enable backcrosses with their parental cytotypes. We chose the ploidy-variable Senecio carniolicus species group to address the overarching question if pentaploid individuals, which occur at high frequencies in immediate contact zones of parental tetraploids and hexaploids, mediate effective interploidy gene flow. We employed a set of approaches including relative genome size (RGS) determination and viability tests of pollen, RGS of the embryo, viability tests and germination experiments of seeds, and RGS and survival experiments of seedlings to tackle the following specific questions. Is pollen of pentaploid individuals viable suggesting regular meiosis in spite of the odd-ploidy level? Are the five sets of chromosomes split into 2.5 compliments, or rather into two and three compliments? Do crossings between pentaploid individuals produce viable seeds and seedlings, suggesting that pentaploids are an independent evolutionary unit? We found that pollen stainability is not strongly reduced in pentaploids and that the five chromosome complements are most often split into 2.5 complements. Seeds originating from homoploid crossings of pentaploids show a very low viability whereas backcrosses with tetraploids or hexaploids were more successful. No significant difference in seedling survival was observed among the different crossings but seedlings emerging from 5x5x crosses were significantly smaller than both, seedlings from backcrosses and from homoploid parental crosses. Altogether, our results indicate that pentaploids may play an important evolutionary role as mediators of gene flow but that they rather do not form an independent evolutionary unit.

Silbernagl L. & Schönswetter P. (2019) Genetically divergent cytotypes of Vaccinium uliginosum co-occurring in the central Eastern Alps can be distinguished based on the morphology of their flowers.-Preslia 91: 143-159. The cloudberries (Vaccinium uliginosum s. lat.) are among the most frequent constituents of dwarf shrub communities in the Alps. Recently, we have shown that (i) both diploid and tetraploid cytotypes are widespread in the Eastern Alps and sometimes occur in mixed "populations" and that (ii) these two cytotypes correspond to two non-overlapping AFLP groups, which are in almost perfect congruence with two plastid lineages. Further (iii), we revealed that diploids and tetraploids show some degree of niche separation, but co-occur in low-alpine heath vegetation. Finally, (iv), in spite of the clear separation of diploids and tetraploids in the molecular data sets, we failed to detect consistent morphological differences. Here, we focused on patterns of genetic, ecological and morphological divergence between cytotypes at mixed-ploidy sites as well as on the underlying processes. Our study is based on a sampling of a hundred individuals each at three sites with previously determined co-occurrence of diploids and tetraploids in the Central Alps of Tirol, Austria. We employed an integrative approach combining flow cytometry, plastid DNA sequencing, AFLP fingerprinting, morphometry of leaf and flower characters as well as a characterization of ecological niches based on the vegetation surrounding the individual Vaccinium plants, in order to address the following questions. What is the small-scale distribution of diploid and tetraploid V. uliginosum s. lat. at the three sites investigated? Are the molecular genetic (AFLP and plastid DNA) relationships reflecting the previously detected divergence governed by differences in ploidy level or is there evidence of across-cytotype gene flow in areas of immediate co-occurrence of diploid and tetraploid V. uliginosum s. lat.? Is there evidence for ecological or morphological separation between cytotypes? More specifically, do flower characters allow for a better discrimination between cytotypes than the previously used leaf characters? We show that mixed-ploidy sites are clearly secondary contact zones as based on AFLP markers individuals cluster by cytotype and not by locality. We found no evidence for recent hybridization across the ploidy boundary but the intersection of biparentally inherited recombining AFLPs with maternally inherited plastid DNA sequences provided strong evidence for past inter-ploidy gene flow as one fifth of the tetraploids exhibited a haplotype otherwise restricted to diploids. Further, small-scale ecological segregation between cytotypes was weak, but statistically significant. Leaf characters indicated little differentiation between the cytotypes, whereas flower characters had relatively strong discriminative power. Overall, from a taxonomic point of view, we suggest that clear genome-wide differentiation combined with consistent morpho...

The goal of this study was to tackle two questions related to the systematics of small-flowering Euphrasia species from the Eastern Alps. Our first aim was to test the hypothesis of a wider distribution of diploid E. inopinata, considered endemic to the uppermost Ötztal valley in Austria based on ploidy screening of ca. 70 populations along a latitudinal transect. We failed to find new populations of E. inopinata but during the sampling campaign, a diploid population was detected in the eastern Ortler/Ortles mountain range (Italy), which could neither be assigned to E. inopinata nor to E. minima. Thus, our second aim was to clarify, based on a comprehensive sampling of individuals and the use of Amplified Fragment Length Polymorphisms (AFLPs) and/ or morphometric data, if this diploid population is morphologically and genetically consistently divergent from both, tetraploid widespread E. minima and E. inopinata. As this was confirmed, we established the relationships of the new entity based on Internal Transcribed Spacer sequences, which uncovered a close relationship with E. minima and describe it here as a new diploid species, E. ultima, which, based on current knowledge, is locally endemic even if a bigger distribution area appears likely.