@phdthesis{Kiemel2023,
  author    = {Kiemel, Katrin},
  title     = {Zooplankton adaptations and community dynamics in space and time},
  school      = {Universit{\"a}t Potsdam},
  year      = {2023},
  abstract  = {In times of ongoing biodiversity loss, understanding how communities are structured and what mechanisms and local adaptations underlie the patterns we observe in nature is crucial for predicting how future ecological and anthropogenic changes might affect local and regional biodiversity. Aquatic zooplankton are a group of primary consumers that represent a critical link in the food chain, providing nutrients for the entire food web. Thus, understanding the adaptability and structure of zooplankton communities is essential. In this work, the genetic basis for the different temperature adaptations of two seasonally shifted (i.e., temperature-dependent) occurring freshwater rotifers of a formerly cryptic species complex (Brachionus calyciflorus) was investigated to understand the overall genetic diversity and evolutionary scenario for putative adaptations to different temperature regimes. Furthermore, this work aimed to clarify to what extent the different temperature adaptations may represent a niche partitioning process thus enabling co-existence. The findings were then embedded in a metacommunity context to understand how zooplankton communities assemble in a kettle hole metacommunity located in the northeastern German "Uckermark" and which underlying processes contribute to the biodiversity patterns we observe. Using a combined approach of newly generated mitochondrial resources (genomes/cds) and the analysis of a candidate gene (Heat Shock Protein 40kDa) for temperature adaptation, I showed that the global representatives of B. calyciflorus s.s.. are genetically more similar than B. fernandoi (average pairwise nucleotide diversity: 0.079 intraspecific vs. 0.257 interspecific) indicating that both species carry different standing genetic variation. In addition to differential expression in the thermotolerant B. calyciflorus s.s. and thermosensitive B. fernandoi, the HSP 40kDa also showed structural variation with eleven fixed and six positively selected sites, some of which are located in functional areas of the protein. The estimated divergence time of ~ 25-29 Myr combined with the fixed sites and a prevalence of ancestral amino acids in B. calyciflorus s.s. indicate that B. calyciflorus s.s. remained in the ancestral niche, while B. fernandoi partitioned into a new niche. The comparison of mitochondrial and nuclear markers (HPS 40kDa, ITS1, COI) revealed a hybridisation event between the two species. However, as hybridisation between the two species is rare, it can be concluded that the temporally isolated niches (i.e., seasonal-shifted occurrence) they inhabit based on their different temperature preferences most likely represent a pre-zygotic isolation mechanism that allows sympatric occurrence while maintaining species boundaries. To determine the processes underlying zooplankton community assembly, a zooplankton metacommunity comprising 24 kettle holes was sampled over a two-year period. Active (i.e., water samples) and dormant communities (i.e., dormant eggs hatched from sediment) were identified using a two-fragment DNA metabarcoding approach (COI and 18S). Species richness and diversity as well as community composition were analysed considering spatial, temporal and environmental parameters. The analysis revealed that environmental filtering based on parameters such as pH, size and location of the habitat patch (i.e., kettle hole) and surrounding field crops largely determined zooplankton community composition (explained variance: Bray-Curtis dissimilarities: 10.5\%; Jaccard dissimilarities: 12.9\%), indicating that adaptation to a particular habitat is a key feature of zooplankton species in this system. While the spatial configuration of the kettle holes played a minor role (explained variance: Bray-Curtis dissimilarities: 2.8\% and Jaccard dissimilarities: 5.5\%), the individual kettle hole sites had a significant influence on the community composition. This suggests monopolisation/priority effects (i.e., dormant communities) of certain species in individual kettle holes. As environmental filtering is the dominating process structuring zooplankton communities, this system could be significantly influenced by future land-use change, pollution and climate change.},
  language  = {en}
}
@article{KunyuJuangSchachneretal.2021,
  author    = {Kunyu, David Khisoni and Juang, Linda P. and Schachner, Maja Katharina and Schwarzenthal, Miriam},
  title     = {Discrimination among youth of immigrant descent in Germany},
  series = {Zeitschrift f{\"u}r Entwicklungspsychologie und p{\"a}dagogische Psychologie},
  volume    = {52},
  journal   = {Zeitschrift f{\"u}r Entwicklungspsychologie und p{\"a}dagogische Psychologie},
  number    = {3-4},
  publisher = {Hogrefe},
  address   = {G{\"o}ttingen},
  issn      = {0049-8637},
  doi       = {10.1026/0049-8637/a000231},
  pages     = {88 -- 102},
  year      = {2021},
  abstract  = {Ethnic discrimination has a negative impact on the socioemotional, behavioral, relational, and academic adjustment ofadolescents, while belonging with classmates, teachers, heritage, and national group may promote positive socioemotional and academicadjustment. We investigate (1) whether greater discrimination by peers and a lower sense of belonging with classmates, teachers, heritagegroup, and national group are associated with lower socioemotional and academic adjustment of adolescents of immigrant descent inGermany; and (2) whether a sense of belonging with these different sources acts as a protective factor lowering the negative effects ofdiscrimination on adjustment. Our sample included 439 7th-grade adolescents (51\% female,Mage= 12.4 years) of immigrant descent from15 Berlin secondary schools. Results showed that higher discrimination was related to greater physiological stress, depressive symptoms,and disruptive school behavior. Higher heritage (but not national) identity, a higher sense of belonging with classmates and with teacherswere associated with better socioemotional and academic adjustment. An examination of interaction effects between discrimination andforms of belonging on adjustment revealed that, while the association between discrimination and poorer adjustment weakened for thosewith higher heritage identity, the association between discrimination and physiological stress increased for those with higher teacherrelatedness. We conclude that heritage identity (but not national identity or sense of belonging with classmates) can indeed be a protectivefactor against the negative effects of discrimination for adolescents of immigrant descent in Germany. Even though belonging with teachersmay exacerbate discrimination effects, further investigation with longitudinal data is needed. The findings underline the important role ofheritage ties among adolescents of immigrant descent as a source of adjustment, especially in light of discrimination experiences.},
  language  = {en}
}