TY - GEN A1 - Bolius, Sarah A1 - Morling, Karoline A1 - Wiedner, Claudia A1 - Weithoff, Guntram T1 - Genetic Identity and Herbivory Drive the Invasion of a Common Aquatic Microbial Invader T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Despite the increasing number of species invasions, the factors driving invasiveness are still under debate. This is particularly the case for “invisible” invasions by aquatic microbial species. Since in many cases only a few individuals or propagules enter a new habitat, their genetic variation is low and might limit their invasion success, known as the genetic bottleneck. Thus, a key question is, how genetic identity and diversity of invading species influences their invasion success and, subsequently, affect the resident community. We conducted invader-addition experiments using genetically different strains of the globally invasive, aquatic cyanobacterium Raphidiopsis raciborskii (formerly: Cylindrospermopsis raciborskii) to determine the role of invader identity and genetic diversity (strain richness) at four levels of herbivory. We tested the invasion success of solitary single strain invasions against the invader genetic diversity, which was experimentally increased up to ten strains (multi-strain populations). By using amplicon sequencing we determined the strain-specific invasion success in the multi-strain treatments and compared those with the success of these strains in the single-strain treatments. Furthermore, we tested for the invasion success under different herbivore pressures. We showed that high grazing pressure by a generalist herbivore prevented invasion, whereas a specialist herbivore enabled coexistence of consumer and invader. We found a weak effect of diversity on invasion success only under highly competitive conditions. When invasions were successful, the magnitude of this success was strain-specific and consistent among invasions performed with single-strain or multi-strain populations. A strain-specific effect was also observed on the resident phytoplankton community composition, highlighting the strong role of invader genetic identity. Our results point to a strong effect of the genetic identity on the invasion success under low predation pressure. The genetic diversity of the invader population, however, had little effect on invasion success in our study, in contrast to most previous findings. Instead, it is the interaction between the consumer abundance and type together with the strain identity of the invader that defined invasion success. This study underlines the importance of strain choice in invasion research and in ecological studies in general. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 971 KW - alien species KW - genotype KW - invasibility KW - cyanobacteria KW - consumptive resistance KW - phytoplankton KW - Raphidiopsis KW - genetic diversity Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-474333 SN - 1866-8372 IS - 971 ER - TY - JOUR A1 - Bolius, Sarah A1 - Karoline Morling, A1 - Wiedner, Claudia A1 - Weithoff, Guntram T1 - Genetic Identity and Herbivory Drive the Invasion of a Common Aquatic Microbial Invader JF - Frontiers in Microbiology N2 - Despite the increasing number of species invasions, the factors driving invasiveness are still under debate. This is particularly the case for “invisible” invasions by aquatic microbial species. Since in many cases only a few individuals or propagules enter a new habitat, their genetic variation is low and might limit their invasion success, known as the genetic bottleneck. Thus, a key question is, how genetic identity and diversity of invading species influences their invasion success and, subsequently, affect the resident community. We conducted invader-addition experiments using genetically different strains of the globally invasive, aquatic cyanobacterium Raphidiopsis raciborskii (formerly: Cylindrospermopsis raciborskii) to determine the role of invader identity and genetic diversity (strain richness) at four levels of herbivory. We tested the invasion success of solitary single strain invasions against the invader genetic diversity, which was experimentally increased up to ten strains (multi-strain populations). By using amplicon sequencing we determined the strain-specific invasion success in the multi-strain treatments and compared those with the success of these strains in the single-strain treatments. Furthermore, we tested for the invasion success under different herbivore pressures. We showed that high grazing pressure by a generalist herbivore prevented invasion, whereas a specialist herbivore enabled coexistence of consumer and invader. We found a weak effect of diversity on invasion success only under highly competitive conditions. When invasions were successful, the magnitude of this success was strain-specific and consistent among invasions performed with single-strain or multi-strain populations. A strain-specific effect was also observed on the resident phytoplankton community composition, highlighting the strong role of invader genetic identity. Our results point to a strong effect of the genetic identity on the invasion success under low predation pressure. The genetic diversity of the invader population, however, had little effect on invasion success in our study, in contrast to most previous findings. Instead, it is the interaction between the consumer abundance and type together with the strain identity of the invader that defined invasion success. This study underlines the importance of strain choice in invasion research and in ecological studies in general. KW - alien species KW - genotype KW - invasibility KW - cyanobacteria KW - consumptive resistance KW - phytoplankton KW - Raphidiopsis KW - genetic diversity Y1 - 2019 U6 - https://doi.org/10.3389/fmicb.2020.01598 SN - 1664-302X VL - 11 PB - Frontiers Media CY - Lausanne ER - TY - THES A1 - Bolius, Sarah T1 - Microbial invasions in aquatic systems – strain identity, genetic diversity and timing N2 - Biological invasions are the dispersal and following establishment of species outside their native habitat. Due to globalisation, connectivity of regions and climate changes the number of invasive species and their successful establishment is rising. The impact of these species is mostly negative, can induce community and habitat alterations, and is one main cause for biodiversity loss. This impact is particularly high and less researched in aquatic systems and microbial organisms and despite the high impact, the knowledge about overall mechanisms and specific factors affecting invasions are not fully understood. In general, the characteristics of the habitat, native community and invader determine the invasiveness. In this thesis, I aimed to provide a better understanding of aquatic invasions focusing on the invader and its traits and identity. This thesis used a set of 12 strains of the invasive cyanobacterium Cylindrospermopsis raciborskii to examine the effect and impact of the invaders’ identity and genetic diversity. Further, the effect of timing on the invasion potential and success was determined, because aquatic systems in particular undergo seasonal fluctuations. Most studies revealed a higher invasion success with increasing genetic diversity. Here, the increase of the genetic diversity, by either strain richness or phylogenetic dissimilarity, is not firstly driving the invasion, but the strain-identity. The high variability among the strains in traits important for invasions led to the highly varying strain-specific invasion success. This success was most dependent on nitrogen uptake and efficient resource use. The lower invasion success into communities comprising further N-fixing species indicates C. raciborskii can use this advantage only without the presence of competitive species. The relief of grazing pressure, which is suggested to be more important in aquatic invasions, was only promoting the invasion when unselective and larger consumers were present. High abundances of unselective consumers hampered the invasion success. This indicates a more complex and temporal interplay of competitive and consumptive resistance mechanisms during the invasion process. Further, the fluctuation abundance and presence of competitors (= primary producers) and consumers (= zooplankton) in lakes can open certain ‘invasion windows’. Remarkably, the composition of the resident community was also strain-specific affected and altered, independent of a high or low invasion success. Prior, this was only documented on the species level. Further, investigations on the population of invasive strains can reveal more about the invasion patterns and how multiple strain invasions change resident communities. The present dissertation emphasises the importance of invader-addition experiments with a community context and the importance of the strain-level for microbial invasions and in general, e.g. for community assemblies and the outcome of experiments. The strain-specific community changes, also after days, may explain some sudden changes in communities, which have not been explained yet. This and further knowledge may also facilitate earlier and less cost-intensive management to step in, because these species are rarely tracked until they reach a high abundance or bloom, because of their small size. Concluded for C. raciborskii, it shows that this species is no ‘generalistic’ invader and its invasion success depends more on the competitor presence than grazing pressure. This may explain its, still unknown, invasion pattern, as C. raciborskii is not found in all lakes of a region. N2 - Biologische Invasionen beschreiben die Ausbreitung und Etablierung von Arten außerhalb ihres natürlichen Verbreitungsgebiets. Das Eindringen dieser invasiven Arten in ein neues Ökosystem hat meist negative Auswirkungen. Beispiele sind unter anderem veränderte Ökosystemprozesse, Lebensräume und Zusammensetzungen der einheimischen Arten, die zu einem Verlust der biologischen Vielfalt führen. Durch die fortschreitende Globalisierung und den Klimawandel steigt die Anzahl invasiver Arten weltweit. Um dies möglichst zu verhindern, müssen die zugrundeliegenden Mechanismen und Faktoren verstanden sein. Besonders bei aquatischen Mikroorganismen ist die Wissenslücke dabei groß und umso drängender, da diese Arten ein hohes Invasionspotential und potentiell stärkere negative Auswirkungen haben. Die vorliegende Dissertation untersuchte anhand der invasiven Cyanobakterie Cylindrospermopsis raciborskii, den anfänglichen Invasionsprozess, unter besonderer Berücksichtigung der Stamm-Identität, der genetischen Diversität und des Zeitpunkts der Invasion. Die meisten Studien zu Invasionen zeigen einen positiven Effekt der genetischen Diversität auf Invasionen. Diese Arbeit konnte zeigen, dass der Invasionserfolg auf bestimmte Stamm-spezifische Eigenschaften zurückzuführen ist. Für C. raciborskii war dies eine erhöhte Aufnahme von Stickstoff und eine effizientere Nutzung von Ressourcen. Wie einige andere aquatischen Arten hat C. raciborskii die Fähigkeit über differenzierte Zellen Stickstoff aus der Luft zu fixieren. Des Weiteren fördern bestimmte Umweltbedingungen, wie eine niedrige Nährstoffkonzentration, das Wachstum von C. raciborskii. Fraßdruck wirkte sich nur negativ aus, wenn unselektive Prädatoren anwesend waren. Zudem zeigten weitere Versuche, dass ihr Konkurrenzvorteil nur in Gemeinschaften ohne weitere Stickstoff-Fixierer und in Stickstoff-reduzierten Habitaten die Etablierung positiv beeinflusst. Diese Erkenntnisse lassen darauf schließen, dass diverse Eigenschaften und eine zeitliche Abfolge dieser, den Invasionserfolg beeinflussen. Dieser kann einerseits durch den Widerstand der heimischen Arten-Gemeinschaft und zum anderem durch die herrschenden abiotischen Bedingungen verhindert werden. Gerade aquatische Systeme unterlaufen saisonalen Schwankungen und diese erlauben somit bestimmte, temporäre Invasionsmöglichkeiten. Zusätzlich führte die Stamm-Identität zu Änderungen in der einheimischen Artenzusammensetzung, unabhängig vom Erfolg der Invasion - dies wurde bis jetzt nur Art-spezifisch gezeigt. Damit betont die vorliegende Arbeit die Bedeutung von Stamm-Identitäten auf Invasionen und deren Auswirkungen auf ökologische Prozesse und den Ausgang von Experimenten. Zusammengefasst für C. raciborskii zeigt die Arbeit, dass diese Art keine ‚generell‘ erfolgreiche invasive Art ist und dass der Invasionserfolg eher von den vorhanden konkurrierenden Arten abhängt. Dies könnte das noch unklare Ausbreitungs-Muster erklären. KW - invasion KW - cyanobacteria KW - population KW - Cylindrospermopsis raciborskii Y1 - 2018 ER -