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The Role of Geographic Origin and Life History Stages in Invasion Ecology - a Comparative Assessment of Northern European, Ponto-Caspian and North American Species

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The Role of Geographic Origin and Life History Stages in Invasion Ecology - a Comparative Assessment of Northern European, Ponto-Caspian and North American Species The role of geographic origin and life history stages in invasion ecology - a comparative assessment of Northern European, Ponto-Caspian and North American species Dissertation in fulfillment of the requirements of the degree “Dr. rer. nat.” of the Faculty of Mathematics and Natural Sciences at Kiel University Submitted by Filipa Paiva Kiel, 2020 The role of geographic origin and life history stages in invasion ecology - a comparative assessment of Northern European, Ponto-Caspian and North American species Dissertation in fulfillment of the requirements of the degree “Dr. rer. nat.” of the Faculty of Mathematics and Natural Sciences at Kiel University Submitted by Filipa Paiva Kiel, 2020 Cover Illustration - From left to right: Gammarus salinus (native to Northern Europe); Pontogammarus maeoticus (native to the Ponto-Caspian region); and Gammarus tigrinus (native to North America). First referee: PD Dr. Elizabeta Briski Second referee: Prof. Dr. Martin Wahl Date of oral examination: 14.12.2020 Valeu a pena? Tudo vale a pena Se a alma não é pequena. Fernando Pessoa – Mar Português Table of contents Summary ......................................................................................................................................... i Zusammenfassung........................................................................................................................ iii Chapter 1 ....................................................................................................................................... 1 Global change ............................................................................................................................. 3 Invasion ecology ......................................................................................................................... 3 The Ponto-Caspian, Northern European and North American Regions ..................................... 6 Salinity and life history stages .................................................................................................... 9 Aquatic enclosed experiments .................................................................................................. 10 Thesis objectives ....................................................................................................................... 12 Chapter 2 ..................................................................................................................................... 13 Abstract ..................................................................................................................................... 16 Introduction ............................................................................................................................... 17 Materials and methods .............................................................................................................. 20 Results ....................................................................................................................................... 25 Discussion ................................................................................................................................. 33 References ................................................................................................................................. 39 Appendix ................................................................................................................................... 47 Chapter 3 ..................................................................................................................................... 69 Abstract ..................................................................................................................................... 72 Introduction ............................................................................................................................... 73 Materials and methods .............................................................................................................. 77 Results ....................................................................................................................................... 82 Discussion ................................................................................................................................. 93 References ................................................................................................................................. 99 Chapter 4 ................................................................................................................................... 107 Abstract ................................................................................................................................... 110 Introduction ............................................................................................................................. 111 Methods................................................................................................................................... 114 Results ..................................................................................................................................... 119 Discussion ............................................................................................................................... 122 References ............................................................................................................................... 127 Chapter 5 ................................................................................................................................... 133 Geographic origin and invasion success ................................................................................. 135 Life history stages ................................................................................................................... 137 The case of North American species ...................................................................................... 138 Mesocosm and laboratory experiments - the importance of community ................................ 139 Conclusion and future directions ............................................................................................ 140 References for Chapters 1 and 5.............................................................................................. 143 Acknowledgements ................................................................................................................... 153 Contribution of authors ............................................................................................................ 155 Declaration................................................................................................................................. 157 Summary The biological composition of most of the earth’s major ecosystems is being dramatically changed by human activities. The breakdown of natural barriers, as a consequence of an increasingly connected world, has contributed to a rise in biological invasions worldwide with thousands of non-indigenous species established in freshwater, brackish, and marine ecosystems. Identifying traits correlated with invasion success is a central goal in invasion ecology to predict and prevent future invasions. This dissertation is divided into five chapters. Chapter 1 gives a general introduction to the main topic of the thesis, including invasion ecology and possible determinant factors that might influence invasion success such as geographic origin and life history stages. Furthermore, it also explores the influence of experimental design on results in ecology. In Chapter 2, I question the role of geographic origin on invasion success, specifically, whether Ponto-Caspian species are better able to acclimatize to and colonize habitats across a range of salinities than taxa from Northern European and North American regions. The experiments, using eight gammarid species native to those three regions, demonstrated that although species from all three tested regions indicated high tolerance to a wide range of salinities, significant differences in the direction of salinity tolerance were observed among the regions, with Northern European species having a better survival in higher salinities, and Ponto-Caspian species in lower salinities. Therefore, it is important to consider geographic origin as a predictor of invasion success because it might foresee pre-adaptation of certain species due to its evolutionary history. Following these findings, in Chapter 3, I further compare the salinity tolerance of adults and juveniles of three gammarid species originating from Northern European, the Ponto-Caspian and North American regions to determine whether juveniles tolerate salinity changes equally well as adults. During the invasion process, individuals must overcome several challenges and be able to survive and i reproduce to establish a successful population. Thus, the role of life history stages in the context of invasion ecology is important to consider. While experimental results determined that both adults and juveniles of all three species endured wide ranges of salinity, juveniles tolerated a narrower salinity range than their parents. The evidence from this study emphasizes the importance of testing several life history stages when constructing models to predict future invasions. In Chapter 4, bearing in mind that the approaches used to test scientific questions may differ not only in spatial scale but also in ecological complexity,
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