@article{BoliusWiednerWeithoff2017,
  author    = {Bolius, Sarah and Wiedner, Claudia and Weithoff, Guntram},
  title     = {High local trait variability in a globally invasive cyanobacterium},
  series = {Freshwater biology},
  volume    = {62},
  journal   = {Freshwater biology},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0046-5070},
  doi       = {10.1111/fwb.13028},
  pages     = {1879 -- 1890},
  year      = {2017},
  abstract  = {1. During the last couple of decades, invasive species have become a worldwide problem in many freshwater systems. Besides higher plants and animals, microbes, in particular the potentially toxic cyanobacterium Cylindrospermopsis raciborskii, has attracted increasing attention, due to its spread towards temperate zones of the northern and southern hemisphere. A number of advantageous functional traits and a high intraspecific plasticity have been suggested to explain its invasion success. 2. The aim of this study was to examine intraspecific functional trait variability in 12 different isolates of C.raciborskii originating from different lakes in an invaded region in Northeast Germany. We measured growth rate, C:N:P ratios, chlorophyll-a content and the abundance of heterocysts under nutrient-replete and phosphorus-limited conditions. Moreover, the isolate-specific morphology and grazing losses by an herbivorous rotifer, as a top-down force, were studied. 3. DNA fingerprinting revealed that all isolates were genetically different. C.raciborskii exhibited a large variability in all measured traits among isolates. The C:P, N:P and Chl-a:C ratios differed by a factor of two or more. The trait variability among isolates was higher under nutrient-replete conditions, except for the C:P ratio, which varied most during phosphorus limitation. The susceptibility to grazing, calculated as maximum ingestion rates of the rotifer Brachionus calyciflorus on C.raciborskii, varied most among isolates, but was not related to any of the measured physiological or morphological traits, i.e. no trade-off was found. 4. Ecological and genetic clustering did not match, indicating that the genetic relationship based on DNA fingerprinting did not cover ecological differences. 5. Our results show a high trait variability within locally occurring and partly co-occurring C.raciborskii isolates. No overall trade-offs between the measured functional traits were found. This demonstrates the ecological relevance of linking multiple traits, e.g. competitive and consumptive. Furthermore, this study emphasises the importance of analysing more than one strain of a species, as different strains show different trait values potentially relevant for their invasibility and the field of general trait-based ecology.},
  language  = {en}
}
@phdthesis{Bolius2018,
  author    = {Bolius, Sarah},
  title     = {Microbial invasions in aquatic systems - strain identity, genetic diversity and timing},
  school      = {Universit{\"a}t Potsdam},
  pages     = {154},
  year      = {2018},
  abstract  = {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 <i>Cylindrospermopsis raciborskii</i> 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 <i>C. raciborskii</i> 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 <i>C. raciborskii</i>, 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 <i>C. raciborskii</i> is not found in all lakes of a region.},
  language  = {en}
}