Distribution and habitat segregation on different spatial scales among diploid, tetraploid and hexaploid cytotypes of Senecio carniolicus (Asteraceae) in the Eastern Alps

Abstract

Background and AimsThe spatial distribution of cytotypes can provide valuable insights into evolutionary patterns of polyploid complexes. In a previous study the macro-scale distribution of the three main cytotypes in Senecio carniolicus (Asteraceae) within the Eastern Alps was characterized. Employing a roughly 12-fold extended sampling, the present study focuses on unravelling patterns of cytotype distribution on the meso- and microscale and on correlating those with ecological properties of the growing sites.MethodsDAPI flow cytometry of dried samples was used to determine DNA ploidy level in 5033 individuals from 100 populations spread over the entire Eastern Alpine distribution area of S. carniolicus. Descriptors of microhabitats as well as spatial data were recorded in the field, and analysed with a mixed-effects ANOVA.Key ResultsExtensive variation in DNA ploidy levels (2x, 3x, 4x, 5x, 6x, 7x, 8x, 9x) was detected. Of the main cytotypes, diploids and hexaploids were widespread and had strongly overlapping distributions resulting in the frequent occurrence of cytotype mixtures (half of the investigated populations), whereas tetraploids were disjunctly distributed and occurred in the south-west and the east of the species' distribution area. In spite of the frequent co-occurrence of cytotypes, only 1 % of the samples belonged to secondary cytotypes (3x, 5x, 7x, 8x, 9x). Diploids, tetraploids and hexaploids were altitudinally segregated, but with broad overlap. Similarly, highly significant differences in vegetation and rock cover as well as microhabitat exposure were found between the main cytotypes.ConclusionsSenecio carniolicus shows a remarkable diversity of cytotypes. The distribution of the three main cytotypes (2x, 4x, 6x) has been shaped by Pleistocene glaciations to different extents. Whereas tetraploids are nearly entirely restricted to refugia, hexaploids colonized areas that were extensively glaciated. Diploid and hexaploid individuals often co-occur in mixed populations, where they are spatially and ecologically segregated at both the meso-scale (altitudinal differentiation, exposure of the growing site) and the micro-scale (cover of vegetation and bare rock). With regard to the ecological parameters investigated, the tetraploid cytotype occupies an intermediate position. The rareness of secondary cytotypes suggests the presence of strong pre- or post-zygotic mating barriers.

The effects of rapid desiccation on estimates of plant genome size

“…This has included geographic surveys (e.g., Šmarda and Stančík 2006;Whittemore and Olsen 2011), phylogeographic studies (Eidesen et al 2007;Schönswetter et al 2007;Suda et al 2007;Popp et al 2008), and studies of the evolution of polyploid complexes (Harbaugh 2008;Balao et al 2009;Hersch-Green and Cronn 2009;Dušková et al 2010;Sonnleitner et al 2010). At the same time, the practical advantages of the method have led researchers to extend its use beyond ploidy analysis into reports of absolute genome size (e.g., Little et al 2007;Cires et al 2009;Whittemore and Olsen 2011) and fine-scale comparisons among populations or species of the same ploidy Popp et al 2008;Hersch-Green and Cronn 2009;Balao et al 2009;Dušková et al 2010).…”

No evidence for a role of competitive capabilities of adults in causing habitat segregation of diploid and hexaploid Senecio carniolicus (Asteracaeae)

“…(Reisigl and Pitschmann 1958). Within the Eastern Alps, S. carniolicus comprises three main cytotypes (2 x , 4 x , 6 x ; Suda et al 2007; Sonnleitner et al 2010). The most frequent cytotypes are diploids and hexaploids and they frequently co-occur in mixed populations within narrow contact zones (Sonnleitner et al 2010; Suda et al 2007).…”

“…Within the Eastern Alps, S. carniolicus comprises three main cytotypes (2 x , 4 x , 6 x ; Suda et al 2007; Sonnleitner et al 2010). The most frequent cytotypes are diploids and hexaploids and they frequently co-occur in mixed populations within narrow contact zones (Sonnleitner et al 2010; Suda et al 2007). Previous studies found cytotypes of S. carniolicus segregating along an ecological gradient with diploids occurring mainly in open vegetation on rocky micro-sites, whilst the hexaploids were more abundant on sites with high vegetation cover (Hülber et al 2009; Schönswetter et al 2007; Sonnleitner et al 2010).…”

Phylogenetic relationships and evolution of high mountain buttercups (Ranunculus) in North America and Central Asia

“…Polyploidy may have further enhanced differentiation and partitioning of habitats among cytotypes (Soltis et al, 2004). A pronounced habitat differentiation was also observed in other North American polyploid complexes (e.g., Tolmiea menziesii, Soltis and Soltis, 1989; Antennaria rosea complex, Bayer et al, 1991) and was observed in European alpine polyploid plants as well (Sonnleitner et al, 2010). Since clade I has about the same age as the Himalayan clade II, we suppose that also in North America Quaternary climatic oscillations and consequently secondary contact hybridization was the major driver of polyploidization.…”

“…However, present distribution patterns and case studies suggest that also sympatric speciation has to be considered for alpine plant evolution (Baack, 2004;Kadereit et al, 2008;Sonnleitner et al, 2010Sonnleitner et al, , 2013. In sympatry, species can evolve either via ecological differentiation or via postzygotic isolation, the latter being often a result of chromosomal rearrangements or of polyploidy (Coyne and Orr, 2004).…”