Mechanisms to understand the basis of species invasiveness

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Biological invasions are a leading source of biodiversity change globally. Understanding the factors that contribute to invasion success at both the establishment-spread stage and impact stage are vital to reducing ecological, economic and health problems associated with introduction of nonindigenous species (NIS). Prior work has determined that some NIS that are introduced to and establish in a new ecosystem will have a greater ecological impact than do complementary native species at the same trophic level, possibly owing to prey naivety. It has proven very challenging to develop generalities to predict NIS impact, though recent work has focused on differences in functional responses - the feeding rate of an animal relative to food density. This work revealed generally higher feeding rates by invasive (i.e. high impact) NIS than their native analogues. However, the underlying basis for these feeding rate differences has not been addressed, nor has the generality of the pattern across different taxonomic groups. In this proposal I will conduct comparative feeding trials of NIS and native species from a broad array of environments - including terrestrial and aquatic environments - and trophic levels - predators versus herbivores - to test for differences in functional responses. Taxa selected will include broadly different taxonomic groups including beetles, mussels, fishes, ascidians and crabs, allowing us to examine the generality of feeding rate differences. Feeding trials of beetles will be videotaped, which will allow us to determine the species' behavioural repertoires (e.g. time budgets, attack rate). Functional responses are expressed through the interaction of an organism’s physiology with its environment. When active, genes produce mRNAs, and up-regulation or down-regulation of these genes produces more or fewer of these molecules. Translation of these molecules into proteins enacts the responses (ie. feeding rate). We will apply transcriptomics using a candidate gene approach, whereby specific genes hypothesized to play a role in the efficiency of predation/herbivory, will be targeted. If invasiveness has a molecular basis, we expect that basic digestive enzymes (e.g. a-amylases), metabolic genes (eg. ATPases), sensory genes (e.g. opsin genes), or muscle genes (e.g. tropomyosin) should be differentially expressed in invasive NIS versus native species. Our studies will also explore the importance of ambient temperature and life stages to these results.