Do floral and niche shifts favour the establishment and persistence of newly arisen polyploids? A case study in an Alpine primrose

Abstract

Background and Aims Polyploidization plays a key role in plant evolution. Despite the generally accepted 'minority-cytotype exclusion' theory, the specific mechanisms leading to successful establishment and persistence of new polyploids remain controversial. The majority of newly formed polyploids do not become established, because they are less common, have fewer potential mates or may not be able to compete successfully with co-occurring progenitors at lower ploidy levels. Changes in floral traits and ecological niches have been proposed as important mechanisms to overcome this initial frequency-dependent disadvantage. The aim of this study was to determine whether dodecaploids of the heterostylous P. marginata differ from their hexaploid progenitors in P. marginata and P. allionii for selected floral traits and ecological preferences that might be involved in establishment and persistence, providing a possible explanation for the origin of polyploidized populations.Methods Floral morphological traits and ecological niche preferences among dodecaploids and their hexaploid progenitors in P. marginata and P. allionii, all restricted to the south-western Alps, were quantified and compared Key Results Differences in floral traits were detected between dodecaploids and their closest relatives, but such differences might be too weak to counter the strength of minority cytotype disadvantage and are unlikely to enable the coexistence of different cytotypes. Furthermore, the results suggest the preservation of full distyly and no transition to selfing in dodecaploids. Finally, dodecaploids occur almost exclusively in environments that are predicted to be suitable also for their closest hexaploid relatives.Conclusions In light of the results, P. marginata dodecaploids have probably been able to establish and persist by occupying geographical areas not yet filled by their closest relatives without significant evolution in their climatic and pollination niches. Dispersal limitation and minority-cytotype exclusion probably maintain their current range disjunct from those of its close relatives.

Different Patterns of Ecological Divergence Between Two Tetraploids and Their Diploid Counterpart in a Parapatric Linear Coastal Distribution Polyploid Complex

“…sabularia at south). Spatial segregation between cytotypes has been observed in several other polyploid complexes (e.g., Husband and Schemske, 1998;Balao et al, 2009;Kolář et al, 2009;Sonnleitner et al, 2010;Castro et al, 2012Castro et al, , 2018Casazza et al, 2016;Wefferling et al, 2017). Spatial segregation reduces inter-cytotype interactions and constitutes a physical barrier that prevents gene flow between cytotypes (Segraves and Thompson, 1999;Husband and Schemske, 2000;Baack, 2005;Nuismer and Cunningham, 2005) and weakens frequency-dependent selection on minority cytotypes (Levin, 1975).…”

Pure polyploidy: Closing the gaps in autopolyploid research

“…Most studies address the common hypothesis that polyploids will evolve to occupy wider or more extreme ranges than their diploid progenitors (Husband et al, 2013). Numerous studies of niche differentiation in autopolyploid complexes have supported this hypothesis (e.g., Baack & Stanton, 2005;Thompson et al, 2014;Arnold et al, 2015;H€ ulber et al, 2015;Liu et al, 2015;Visger et al, 2016), but many others have found little to no abiotic niche differentiation between cytotypes (e.g., Godsoe et al, 2013;Casazza et al, 2016;Duchoslav et al, 2016), including studies that compared different cytotypes in multiple species (Glennon et al, 2014). Similarly, allopolyploids also show variable amounts of climatic niche divergence-and often broad niche overlap-when compared to their diploid progenitors (Marchant et al, 2016).…”

Autopolyploid lineage shows climatic niche expansion but not divergence in Arabidopsis arenosa

“…Most of the reported examples about ecological consequences of polyploidization, which use niche‐modeling approaches, come from studies focused on allopolyploids. Although several studies show niche divergence between allopolyploids and at least one of their progenitors (Glennon et al., , ; Theodoridis et al., ; Harbert et al., ; Han et al., ; López‐Alvarez et al., ; Marchant et al., ), other studies show allopolyploid lineages have intermediate or non‐divergent ecological niches (Oberprieler et al., ; Glennon et al., ; Harbert et al., ; Boucher et al., ; Marchant et al., ; Casazza et al., ). For autopolyploids, some studies have found significant ecological segregation between polyploids and their ancestors (Schönswetter et al., ; Stahlberg, ; Thompson et al., ; Hülber et al., ; Zozomová‐Lihová et al., ; Lazaroff et al., ; Mandák et al., ; Mered'a et al., ; Sonnleitner et al., ; Visger et al., ), and yet other studies find no ecological divergence between cytotypes (Godsoe et al., ; Hanzl et al., ).…”