The drivers of algal invasion success: adaptation and co-evolution of resistance towards foulers?
Biological invasions have become one of the most prominent elements of global change and are occurring with increasing frequency both in terrestrial and aquatic ecosystems. Spread of macroalgae beyond their native habitat has become an increasing ecological and economical problem. The interactions between introduced species and their enemies have been often proposed as key processes that determine invasion success. and three main hypotheses have been postulated. A species introduced to an exotic area may leave behind many of its enemies (e.g. herbivores, foulers, pathogens), but it may also encounter a new set of potential enemies in the invaded area. When the new potential enemies fail to recognize the introduced species as a suitable host the invader may experience a decrease in regulation by herbivores and other natural enemies (e.g. foulers, pathogens) compared both to the native range and to competitors from the new range, which may then result in a rapid increase in distribution and abundance (Enemy Release Hypothesis (ERH)). On the other hand, when the new enemies are able to attack the newly arrived un-adapted non-native species, they have the potential to prevent the successful establishment and spread of the introduced species (Biotic Resistance Hypothesis). But even when the enemies in the new area recognize the introduced species as potential prey, the latter may possess defensive mechanisms which the enemies do (not yet) tolerate (Novel Weapon Hypothesis, NWH). Thus, well defended individuals or populations are more likely to be able to establish themselves and spread in a new environment even when intense pressure from its major enemies i.e. herbivores, pathogens and foulers exists. To date, quite a few studies have been able to demonstrate that certain invasive algal species have invested in increased defense (towards herbivores) when compared to their native range. Even though both herbivores and foulers can exert selective pressures and regulate the establishment and spread of exotic seaweeds, no attempt has been made yet to understand whether exotic seaweeds might also regulate their antifouling chemical defense to cope with the native foulers existing in the new habitat. Goal of this proposal is to determine how the antifouling defense capacity of invasive algal species (using the East Asian invasive red alga (Gracilaria vermiculophylla)) has evolved during the invasion process?
