Plasticity of a range-expanding Brassicaceae and impact on natural enemies

• Applicant: Professorin Dr. Caroline Müller
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 265141944

Biological plant invasions have been studied mainly in transoceanic range expanding species, whereas the range-expansion of plants within continents has been neglected. However, such intracontinental range-expansion may become increasingly important, for example, due to climate change. The intracontinental range-expanders may, in contrast to the transcontinental invasives, not be entirely released by natural enemies, but the enemy community may still differ in the native and non-native distribution areas of the species. Furthermore, invasive plant species may show high phenotypic plasticity and differ in chemical and morphological traits in dependence of the nitrate availability of the site. In this project, I aim to I. determine the genetic diversity of populations of a range-expanding plant species along the distribution range, II. investigate the effects of plant origin and nitrate fertilisation on root and shoot growth and defence traits, and III. evaluate the relevance of differences in plant phenotypes for interacting organisms (shoot-feeders, shoot-infesting fungi, root-feeders). As model system, I propose the Brassicaceae Bunias orientalis, which is spreading its range towards Western Europe and is particularly invading fertile and disturbed sites. To characterise the genetic variation and phenotypic plasticity of B. orientalis, plants of different populations from the native, exotic, and invasive range will be grown in a common garden under two nitrate fertilisation conditions. The genetic diversity within and among populations will be determined by amplified fragment length polymorphism. The constitutive defence and growth pattern of shoots as well as roots will be determined in a comprehensive approach, measuring various morphological and chemical parameters. The relevance of differences in plant defence and growth syndromes found within the species will be determined in two ways. In a field-experiment, the herbivore and pathogen community attacking the different plants will be observed over two consecutive years. In a laboratory study, the resistance of plants from different origin and grown under different fertilisation will be determined using a leaf-herbivore, a leaf-pathogen and a root-herbivore as potential antagonists. Relating the different parts of this project will enable me to determine which plant traits are most decisive for interactions with potential enemies. I hypothesise that highly diverse plant populations may be best defended against enemies and that this may be an important success strategy of plant invaders.

• DFG Programme: Research Grants