plant invasions; herbivory; polyploidy; biological control; biogeographic comparison; Centaurea; evolution
Hahn Min A, Müller-Schärer Heinz (2013), Cytotype differences modulate eco-geographical differentiation in the widespread plant Centaurea stoebe, in Ecology
, 94(5), 1005-1014.
Collins Alexandra R, Thalmann Daniela, Müller‐Schärer Heinz (2013), Cytotypes of Centaurea stoebe found to differ in root growth using growth pouches, in Weed Research
, 53(3), 159-163.
Sun Yan, Collins A. Robin, Schaffner Urs, Müller-Schärer Heinz (2013), Dissecting impact of plant invaders: do invaders behave differently in the new range?, in Ecology
, 98(10), 2124-2130.
Maron John L, Waller Lauren P, Hahn Min A, Diaconu Alecu, Pal Robert W, Müller‐Schärer Heinz, Klironomos John N, Callaway Ragan M (2013), Effects of soil fungi, disturbance and propagule pressure on exotic plant recruitment and establishment at home and abroad, in Journal of Ecology
, 101(4), 924-932.
Hahn Min A, Lanz Tabea, Fasel Dominique, Müller-Schärer Heinz (2013), Increased seed survival and seedling emergence in a polyploid plant invader, in American journal of botany
, 100(8), 1555-1561.
Mráz Patrik, Garcia-Jacas Núria, Gex-Fabry Emilie, Susanna Alfonso, Barres Laia, Müller-Schärer Heinz (2012), Allopolyploid origin of highly invasive Centaurea stoebe sl (Asteraceae), in Molecular Phylogenetics and Evolution
, 62(2), 612-623.
Mráz Patrik, Španiel Stanislav, Keller Andreas, Bowmann Gillianne, Farkas Alexandre, Šingliarová Barbora, Rohr Rudolf P, Broennimann Olivier, Müller-Schärer Heinz (2012), Anthropogenic disturbance as a driver of microspatial and microhabitat segregation of cytotypes of Centaurea stoebe and cytotype interactions in secondary contact zones, in Annals of botany
, 110(3), 615-627.
Hahn Min A, van Kleunen Mark, Müller-Schärer Heinz (2012), Increased phenotypic plasticity to climate may have boosted the invasion success of polyploid Centaurea stoebe, in PloS one
, 7(11), e50284-e50284.
Hahn Min A, Buckley Yvonne M, Müller‐Schärer Heinz (2012), Increased population growth rate in invasive polyploid Centaurea stoebe in a common garden, in Ecology letters
, 15(9), 947-954.
Collins Alexandra R, Müller-Schärer Heinz (2012), Influence of plant phenostage and ploidy level on oviposition and feeding of two specialist herbivores of spotted knapweed, Centaurea stoebe, in Biological Control
, 60(2), 148-153.
Collins Alexandra R, Naderi Ruhollah, Mueller-Schaerer Heinz (2011), Competition between cytotypes changes across a longitudinal gradient in Centaurea stoebe (Asteraceae), in American Journal of Botany
, 98(12), 1935-1942.
Callaway Ragan M, Waller Lauren P, Diaconu Alecu, Pal Robert, Collins Alexandra R, Müller-Schärer Heinz, Maron John L (2011), Escape from competition: neighbors reduce Centaurea stoebe performance at home but not away, in Ecology
, 92(12), 2208-2213.
Schaffner Urs, Ridenour Wendy M, Wolf Vera C, Bassett Thomas, Müller Caroline, Müller-Schärer Heinz, Sutherland Steve, Lortie Christopher J, Callaway Ragan M (2011), Plant invasions, generalist herbivores, and novel defense weapons, in Ecology
, 92(4), 829-835.
Thébault Aurélie, Gillet François, Müller-Schärer Heinz, Buttler Alexandre (2011), Polyploidy and invasion success: trait trade-offs in native and introduced cytotypes of two Asteraceae species, in Plant Ecology
, 212(2), 315-325.
Mráz Patrik, Bourchier Robert S, Treier Urs A, Schaffner Urs, Müller-Schärer Heinz (2011), Polyploidy in phenotypic space and invasion context: a morphometric study of Centaurea stoebe sl, in International Journal of Plant Sciences
, 172(3), 386-402.
Henery Martin L, Bowman Gillianne, Mraz Patrik, Treier Urs A, Gex‐Fabry Emilie, Schaffner Urs, Müller‐Schärer Heinz (2010), Evidence for a combination of pre‐adapted traits and rapid adaptive change in the invasive plant Centaurea stoebe, in Journal of Ecology
, 98(4), 800-813.
Broz Amanda K, Manter Daniel K, Bowman Gillianne, Müller-Schärer Heinz, Vivanco Jorge M (2009), Plant origin and ploidy influence gene expression and life cycle characteristics in an invasive weed, in BMC Plant Biology
, 9(1), 33-33.
Treier Urs A, Broennimann Olivier, Normand Signe, Guisan Antoine, Schaffner Urs, Steinger Thomas, Müller-Schärer Heinz (2009), Shift in cytotype frequency and niche space in the invasive plant Centaurea maculosa, in Ecology
, 90(5), 1366-1377.
Broennimann O Mráz P Petitpierre B Guisan A and Müller-Schärer H., Contrasting spatio-temporal climatic niche dynamics during the eastern and western invasions of spotted knapweed in North America, in Journal of Biogeography
Biological invasions are recognized as a major component of global change, with profound effects on ecosystem functioning, biodiversity, health and economics. Why human introductions of some species result in increased abundance and competitiveness has turned out to be one of the greatest challenges to ecologists and evolutionary biologists. Many hypotheses have been put forward to explain plant invasions, including the role of herbivore escape and polyploidy.The proposed project will be the first one that considers the importance of polyploidy and herbivores for invasions simultaneously. Our leading hypothesis is that herbivore pressure and assemblage will, at least partially, explain the predominance of specific cytotypes both in the native and introduced range.The Centaurea stoebe L. (syn. C. maculosa Lam.) (Asteraceae) system provides an excellent model system to study these interactions, and we take advantage of the large knowledge already available on this plant and its herbivores. Native to Europe (EU) where it occurs as a diploid (2x) and a tetraploid (4x) cytotype, the species is highly invasive in North America (NA), where nearly exclusively only 4x plants have been found. Several specialist insect herbivores have been introduced to NA for its biological control, with only partial success so far. In a first part, we will conduct a European-wide survey to explore whether the level of herbivory differs between native populations of the two cytotypes, as well as between experimental transplants of the two cytotypes, and if this leads to differential fitness impact. In a second part, we will conduct a series of experiments to analyse interactions between two selected specialist herbivores that have been introduced as biocontrol agents more than 20 years ago, and the three geocytotypes of C. stoebe (EU 2x, EU 4x and NA 4x). For this, we will grow a large set of populations from both the native and introduced range, with known genetic background and cytotype. We will study oviposition and feeding preference, insect performance and host impact, as well as the population dynamics of the geocytotypes in the presence and absence of these herbivores. Furthermore, we will test, whether these herbivores have undergone evolutionary changes in host selection and performance in the new range. In the third part, we will investigate into the role of generalist herbivores for plant invasions. Firstly, we will assess feeding preference of generalist herbivores on seedlings of the three geocytoypes of C. stoebe. Secondly, we will test, whether exotic species experience a generally reduced attack rate by native generalists as compared to native species, and polyploids as compared to diploids. We will select five groups of four taxonomically closely related species within the Asteraceae. Each group will contain a diploid and polyploidy species that is native, and a diploid and polyploidy species exotic to Europe. Conducting parallel experiments in Europe and North America and testing the same plant species as in Europe, but in different roles (as natives/exotics) will allow us to further test the hypothesis that evolutionarily naïve generalists do less well on a specific introduced exotic species than generalists that have evolved tolerance against the same plant species in their communities of origin.Plant invasions offer great natural experiments to investigate rapid ecological and evolutionary change and to gain insight into factors that regulate the distribution and abundance of organisms. The proposed studies should allow us to draw some generalizations on the relative importance of herbivores as a potential key driver or facilitators for the invasion success of polyploid plants. By looking at mechanisms underlying the invasion success of some of the most prominent plant invaders in Europe and North America, and by conducting studies in both ranges, we will also contribute to the further development of potential control measures, especially for biological control using insect herbivores.