Combining bottom-up and top-down analyses to test fundamental concepts in invasion biology
Final Report Abstract
Many concepts and hypotheses in invasion biology have not yet been tested rigorously and have been highly debated. A better understanding of them is crucial for at least two reasons: First, these concepts and hypotheses are highly interlinked with concepts and hypotheses in other ecological and biological disciplines, e.g. community ecology or evolutionary biology, so better understanding them also improves ecological and biological knowledge in general. Second, effective management of biological invasions depends on understanding them. This project thus aimed to test fundamental concepts and hypotheses in invasion biology. My collaborators and I developed a novel approach to analyze the usefulness of ecological hypotheses. This hierarchy-of-hypotheses approach captures the complexity of fundamental hypotheses by hierarchically structuring them into smaller sub-hypotheses. We developed this approach for invasion biology, but it can be easily applied to other disciplines as well. Researchers empirically testing a major fundamental hypothesis do not usually test it in all of its complexity. Most major hypotheses are not even empirically testable as such, as they are too broad and unspecific. As a result, researchers typically test a certain sub-hypothesis of the major hypothesis, although they are rarely explicit about this restriction. The hierarchy-of-hypotheses approach reflects this observation by formulating hypotheses in a way that makes them better testable, and by further dividing them into testable subhypotheses, as far as necessary. We applied the hierarchy-of-hypotheses approach to test the following six fundamental concepts and hypotheses in invasion biology: biotic resistance, island susceptibility, invasional meltdown, novel weapons, enemy release, and the tens rule. Previously, these hypotheses have not been comparatively evaluated based on a standard approach. We found that those hypotheses that consider interactions of alien species with their environment (invasional meltdown, novel weapons, enemy release) are better supported by empirical evidence than hypotheses that either only consider the ecosystems where alien species were introduced (biotic resistance, island susceptibility) or only the alien species themselves (tens rule). More detailed analyses, particularly of the enemy release hypothesis, showed that some sub-hypotheses are much stronger empirically supported than others. We also found significant differences in empirical support among taxonomic groups and habitats, both at the level of the major hypotheses and more specific sub-hypotheses. At the same time, we found taxonomic biases in research on the six major hypotheses, and we show that invasion biology lacks cross-taxonomic studies compared to other ecological disciplines. This lack of cross-taxonomic studies and taxonomic biases in invasion biology are crucial, as our results clearly show that different hypotheses and sub-hypotheses show different levels of empirical support for different taxonomic groups. We also show that over time, empirical support for the six major invasion hypotheses analyzed have declined over time. Overall, our results provide evidence that some of invasion biology’s fundamental concepts and hypotheses are empirically not well supported. The hierarchy-of-hypotheses approach not only forms the basis of these results but can additionally give guidance as to how existing hypotheses can be revised or specified so that they are more reliable and useful. We also applied other approaches to address fundamental concepts and hypotheses in invasion biology: the propagule pressure hypothesis was addressed with a modeling approach, and the plasticity hypothesis was addressed with an approach combining theory with empirical work. Furthermore, we connected fundamental hypotheses using an eco-evolutionary framework, and we combined invasion biology’s enemy release hypothesis with a classic concept in evolutionary biology, the Red Queen hypothesis, to a new hypothesis that we compared against empirical data. We also prepared overviews of (i) existing concepts and knowledge about biological invasions in Europe; and (ii) knowledge about biological invasions that is useful for managers and decision makers. Additionally, we analyzed the pathways and impacts of over 300 invasive species worldwide, showing important taxonomic differences, and we found that vertebrates adapting well to captivity are also good at coping with translocation to areas beyond their native range. Another important project result is a framework that allows comparing different types of novel organisms (i.e. invasive species, range-expanding species, genetically modified organisms (GMOs), synthetic organisms, and emerging pathogens), and to compare concepts and hypotheses about different novel organisms. The framework provides a common terminology for novel organisms, which may improve communication among researchers, managers, and policy makers working on novel organisms. Also, it helps detect research gaps and can give guidance as to how these gaps might be filled with appropriate concepts on other types of novel organisms. In a nutshell, the project has developed various methods and tools that help address and test fundamental concepts and hypotheses about invasive species and other novel organisms. The project has also provided insights into the usefulness of several fundamental hypotheses in invasion biology, and it has developed guidance as to how such hypotheses can be revised to become more useful. The project results have been featured in public media, particularly in the radio and online news.
Publications
-
2013. Conceptual frameworks and methods for advancing invasion ecology. AMBIO 42, 527-540
Heger, T.; Pahl, A.T.; Botta-Dukat, Z.; Gherardi, F.; Hoppe, C.; Hoste, I.; Jax, K.; Lindström, L.; Boets, P.; Haider, S.; Kollmann, J.; Wittmann, M.J.; Jeschke, J.M.
-
2011. Integrating biological invasions, climate change, and phenotypic plasticity. Communicative & Integrative Biology 4, 247-250
Engel, K.; Tollrian, R.; Jeschke, J.M.
-
2011. Invasive species in Europe: ecology, status, and policy. Environmental Sciences Europe 23, 23
Keller, R.P.; Geist, J.; Jeschke, J.M.; Kühn, I.
-
2012. Support for major hypotheses in invasion biology is uneven and declining. NeoBiota 14, 1-20
Jeschke, J.M.; Gómez Aparicio, L.; Haider, S.; Heger, T.; Lortie, C.J.; Pyšek, P.; Strayer, D.L.
-
2012. Taxonomic bias and lack of cross-taxonomic studies in invasion biology. Frontiers in Ecology and the Environment 10, 349-350
Jeschke, J.M.; Gómez Aparicio, L.; Haider, S.; Heger, T.; Lortie, C.J.; Pyšek, P.; Strayer, D.L.
-
2013. Can Daphnia lumholtzi invade European lakes? NeoBiota 16, 39-57
Wittmann, M.J.; Gabriel, W.; Harz, E.-M.; Laforsch, C.; Jeschke, J.M.
-
2013. Decision tools for managing biological invasions: existing biases and future needs. Oryx
Dana, E.D.; Jeschke, J.M.; García-de-Lomas, J.
-
2013. Novel organisms: comparing invasive species, GMOs, and emerging pathogens. AMBIO 42, 541-548
Jeschke, J.M.; Keesing, F.; Ostfeld, R.S.
-
2013. Plastic animals in cages: behavioural flexibility and responses to captivity. Animal Behaviour 85, 1113-1126
Mason, G.; Burn, C.C.; Dallaire, J.A.; Kroshko, J.; McDonald Kinkaid, H.; Jeschke, J.M.
-
2013. The role of eco-evolutionary experience in invasion success. NeoBiota 17, 57-74
Saul, W.-C.; Jeschke, J.M.; Heger, T.
