Summary: | The presented Ph.D. thesis contains an introduction and four chapters concerning herbivory of Cirsium arvense in its native and invasive range. The chapters include two peer- reviewed papers and two manuscripts prepared for submission. The first chapter focuses on the effect of insect herbivory on plant growth and reproduction in field conditions. C. arvense in four populations in the Czech Republic were measured in 2005 and 2006 (chapter 1). Observational studies in C. arvense were done in the Czech Republic (Europe) and Nebraska (USA), native and invasive ranges, in 2006 and 2007. I tested whether plants suffer less damage than plants from populations in the native range, as the enemy release hypothesis (Keane, Crawley 2002) states (chapter 2). Afterwards I tested for direct and indirect effects of non-overlapping herbivore insects on plant growth and reproduction (chapter 3) and compared this effect between plants from the native (Spain and the Czech Republic, Europe) and invasive range (Nebraska and Illinois, North America). In a common garden experiment herbivore insects were added alone and in combinations to C. arvense which were planted in the Czech Republic in March 2008 and grew from seeds for two growing seasons (chapter 3). One underground insect (Cleonis pigra) and 3 aboveground insect...
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