Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

CABI Book Chapter

Invasion biology: hypotheses and evidence.

Book cover for Invasion biology: hypotheses and evidence.

Description

This book, containing 18 chapters, combines the hierarchy-of-hypotheses (HoH) approach with hypothesis networks for invasion biology. This book aims to further develop the HoH approach by inviting critical comments (Part I), apply it to 12 major invasion hypotheses (Part II) and explore how it can be expanded to a hierarchically structured hypothesis network (Chapter 7 and Part III). It is importa...

Chapter 12 (Page no: 103)

Evolution of increased competitive ability and shifting defence hypotheses.

This chapter focuses on two of the various hypotheses that take into account the role of biotic interactions in invasion biology, namely the evolution of increased competitive ability (EICA) hypothesis and the shifting defence hypothesis (SDH). Both hypotheses mainly consider changes in concentrations of chemical defences in plant individuals from native vs exotic populations and are studied independently of the novelty of the chemical metabolite in the invasive range. The EICA hypothesis predicts that chemical defences should be lower in plants of invasive populations because enemy pressure is reduced in the exotic range. The SDH predicts a shift in chemical defences by discriminating between qualitative and quantitative defences. Qualitative defences (toxins) are cheaper to produce and expected to increase in invasive populations because they are needed as defence against generalists, whereas expensive quantitative defences (digestibility reducers) may be reduced in plants of the invasive range owing to the overall lower enemy pressure. Methodological issues are pointed out that should be considered when testing the differences in plant traits between native and invasive populations. A literature review on qualitative and quantitative defence traits, which were compared between plants of native and invasive origin grown under standardized common-garden conditions, revealed 37 studies, comprising 22 plant species. The results of the review infrequently support predictions for defence distributions of the EICA hypothesis, whereas predictions of the SDH are supported by somewhat more traits. The definition of qualitative vs quantitative defences has shortcomings, however. In particular, actual costs of these defences are difficult to estimate but should be investigated in future studies. Furthermore, instead of focusing on individual defences, multiple defences should be considered in plant species that are invasive to gain a more complete understanding of resource-allocation patterns.

Other chapters from this book

Chapter: 1 (Page no: 3) Invasion biology: searching for predictions and prevention, and avoiding lost causes. Author(s): Cassey, P., García-Díaz, P., Lockwood, J. L., Blackburn, T. M.
Chapter: 2 (Page no: 14) The hierarchy-of-hypotheses approach. Author(s): Heger, T., Jeschke, J. M.
Chapter: 3 (Page no: 19) Hierarchy of hypotheses or hierarchy of predictions? Clarifying key concepts in ecological research. Author(s): Farji-Brener, A. G., Amador-Vargas, S.
Chapter: 4 (Page no: 23) Mapping theoretical and evidential landscapes in ecological science: Levins' virtue trade-off and the hierarchy-of-hypotheses approach. Author(s): Griesemer, J.
Chapter: 5 (Page no: 30) A hierarchy of hypotheses or a network of models. Author(s): Scheiner, S. M., Fox, G. A.
Chapter: 6 (Page no: 38) The hierarchy-of-hypotheses approach updated - a toolbox for structuring and analysing theory, research and evidence. Author(s): Heger, T., Jeschke, J. M.
Chapter: 7 (Page no: 49) A network of invasion hypotheses. Author(s): Enders, M., Jeschke, J. M.
Chapter: 8 (Page no: 60) Biotic resistance and island susceptibility hypotheses. Author(s): Jeschke, J. M., Debille, S., Lortie, C. J.
Chapter: 9 (Page no: 71) Disturbance hypothesis. Author(s): Nordheimer, R., Jeschke, J. M.
Chapter: 10 (Page no: 79) Invasional meltdown hypothesis. Author(s): Braga, R. R., Gómez Aparicio, L., Heger, T., Vitule, J. R. S., Jeschke, J. M.
Chapter: 11 (Page no: 92) Enemy release hypothesis. Author(s): Heger, T., Jeschke, J. M.
Chapter: 13 (Page no: 124) Tens rule. Author(s): Jeschke, J. M., Pyšek, P.
Chapter: 14 (Page no: 133) Phenotypic plasticity hypothesis. Author(s): Torchyk, O., Jeschke, J. M.
Chapter: 15 (Page no: 140) Darwin's naturalization and limiting similarity hypotheses. Author(s): Jeschke, J. M., Erhard, F.
Chapter: 16 (Page no: 147) Propagule pressure hypothesis. Author(s): Jeschke, J. M., Starzer, J.
Chapter: 17 (Page no: 157) Synthesis. Author(s): Jeschke, J. M., Heger, T.
Chapter: 18 (Page no: 167) Conclusions and outlook. Author(s): Heger, T., Jeschke, J. M.