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Université de Fribourg

Contrasting spatio-temporal climatic niche dynamics during the eastern and western invasions of spotted knapweed in North America

Broennimann, Olivier ; Mráz, Patrik ; Petitpierre, Blaise ; Guisan, Antoine ; Müller-Schärer, Heinz

In: Journal of Biogeography, 2013///n/a–n/a

Aim: The spotted knapweed (Centaurea stoebe), a plant native to south-east and central Europe, is highly invasive in North America. We investigated the spatio-temporal climatic niche dynamics of the spotted knapweed in North America along two putative eastern and western invasion routes. We then considered the patterns observed in the light of historical, ecological and evolutionary...

Université de Fribourg

Ploidy level and genome size variation in the homosporous ferns Botrychium

Dauphin, Benjamin ; Grant, Jason ; Mráz, Patrik

In: Plant Systematics and Evolution, 2016, vol. 302, no. 5, p. 575–584

Recent cytological and molecular studies have investigated genome size variation and evolution in the homosporous ferns, but representatives of the Ophioglossaceae were largely overlooked, despite their evolutionary singularity. Flow cytometry analysis was performed on 41 individuals of eight species of the genera Botrychium (B.), Botrypus, and Sceptridium to estimate their ploidy level...

Université de Fribourg

Evidence for a combination of pre-adapted traits and rapid adaptive change in the invasive plant Centaurea stoebe

Henery, Martin L. ; Bowman, Gillianne ; Mráz, Patrik ; Treier, Urs A. ; Gex-Fabry, Emilie ; Schaffner, Urs ; Müller-Schärer, Heinz

In: Joural of Ecology, 2010, vol. 98, no. 4, p. 800–813

1. Introduced plants have the potential to rapidly evolve traits of ecological importance that may add to their innate potential to become invasive. During invasions, selection may favour genotypes that are already pre-adapted to conditions in the new habitat and, over time, alter the characteristics of subsequent generations. 2. Spotted knapweed (Centaurea stoebe) occurs in two predominantly...

Université de Fribourg

Geographical parthenogenesis, genome size variation and pollen production in the arctic-alpine species Hieracium alpinum

Mráz, Patrik ; Chrtek, Jindřich ; Šingliarová, Barbora

In: Botanica Helvetica, 2009, vol. 119, no. 1, p. 41-51

Hieracium alpinum L. (Asteraceae) is an arctic-alpine species distributed throughout Europe with both diploid and triploid cytotypes. We determined the ploidy levels of plants from 23 populations from Austria, Bosnia and Herzegovina, Finland, Italy, Norway, Romania, Slovakia, Switzerland and Ukraine. Data showed a non- overlapping pattern of cytotype distribution: sexually reproducing diploids...

Université de Fribourg

Interspecific hybridization in the genus Hieracium s. str. : evidence for bidirectional gene flow and spontaneous allopolyploidization

Mráz, Patrik ; Chrtek, Jindřich ; Fehrer, Judith

In: Plant Systematics and Evolution, 2011, vol. 293, p. 237-245

Although reticulation has indisputably played an important role in the evolutionary history of the genus Hieracium s. str. (Asteraceae), convincingly documented cases of recent interspecific hybridization are very rare. Here we report combined evidence on recent hybridization between two diploid species, Hieracium alpinum and H. transsilvanicum. The hybrid origin...

Université de Fribourg

Polyploidy in phenotypic space and invasion context: a morphometric study of Centraurea stoebe s.l.

Mráz, Patrik ; Bourchier, Robert S. ; Treier, Urs A. ; Schaffner, Urs ; Müller-Schärer, Heinz

In: International Journal of Plant Sciences, 2011, vol. 172, no. 3, p. 386-402

The taxonomy of the Centaurea stoebe complex is controversial. Diploid and tetraploid plants occur in its native European range, but to date only tetraploids have been recorded from its introduced range in North America. We examined morphological differentiation of C. stoebe using multivariate and univariate approaches to clarify the taxonomic status of the known cytotypes. We measured more...

Université de Fribourg

Allopolyploid origin of highly invasive Centaurea stoebe s.l. (Asteraceae)

Mráz, Patrik ; Garcia-Jacas, Núria ; Gex-Fabry, Emilie ; Susanna, Alfonso ; Barres, Laia ; Müller-Schärer, Heinz

In: Molecular Phylogenetics and Evolution, 2012, vol. 62, no. 2, p. 612–623

Spotted knapweed (Centaurea stoebe) occurs from Western Asia to Western Europe both as diploid and tetraploid cytotypes, predominantly in single-cytotype populations with higher frequency of diploid populations. Interestingly, only tetraploids have been recorded so far from its introduced range in North America where they became highly invasive. We performed phylogenetic and network analyses of...