Invasive species proliferate in novel environments that may be quite different from the native range. However, it is not clear how they are able to do this because it is difficult to test ecological and evolutionary hypotheses at large spatial scales (e.g. between continents). The global garlic mustard field survey (GGMFS) is a multi-national initiative to collect comprehensive field data and genetic resources to understand the ecological and genetic basis of range limits and plant performance in the context of global change. To do this, we focus on a single widespread invasive species – garlic mustard (Alliaria petiolata). Our large research network (>150 scientists) has already collected seeds from >5,000 plants and performance data from ~400 locations across North America and Europe.
We are now in the process of analyzing the field data for publication, and several additional projects have started within the last year:
Preliminary analyses show that, after accounting for climate and other environmental influences, there are many systematic differences between native and invasive populations. On average, populations in the introduced range (North America) are larger, denser and less infected by pathogenic leaf fungi, consistent with the enemy release hypothesis. Additionally, there is considerable among-population variation in plant and population performance within both ranges. We are currently analyzing how much variation in performance is among- vs. within- ranges, and the relative effects on performance of biotic effects (herbivory and pathogens), abiotic factors (climate, shade), human disturbance (control efforts, roads) and region of origin (native vs. introduced).
Common garden phenotyping and seed propagation
In spring 2014 we began cultivating plants from 350 sampled populations in a common garden at the University of Tübingen, with several maternal families per population. Of these, ~1,000 will be used to propagate inbred lines for future research. Together with the data from the field survey, these seeds will be made available to other GGMFS participants, and to the broader scientific community. Our hope is that this will promote an integrative approach to understanding the ecological and genetic factors responsible for the garlic mustard invasion in North America.
Alliaria petiolata is in the Brassicaceae - a genetically well-studied family of angiosperm that includes the model plant Arabidopsis thaliana and many economically important crops. Together with Loren Rieseberg (University of British Columbia, Vancouver) we are assembling a draft genome. We do not expect to have a fully sequenced and annotated genome for several years, but the contigs produced in the early assembly stages will be useful for identifying candidate genes, and linkage analysis of future SNP data.