Publikation: Cladoceran trait dynamics during oligotrophication of Lake Constance
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Understanding the responses of zooplankton populations to environmental changes and predator pressures is crucial for predicting ecosystem dynamics in lakes. In this study, we investigate the defensive adaptations of two key zooplankton genera, Daphnia and Bosmina, in response to predation threats, focusing on both macrodefenses and microdefenses. Additionally, we assess the long-term trends in species turnover and trait dynamics in a Bosmina assemblage in Lake Constance in order to study the role of species turnover for Bosmina trait dynamics.
Chapter II delves into the defensive mechanisms of Daphnia, revealing species-specific responses to predation pressure. While D. cucullata and D. galeata exhibited macrodefenses, D. longispina lacked such defenses, possibly due to its diel vertical migration behavior and the absence of certain predators like Chaoborus in Lake Constance. Interestingly, neonates but not adults of D. cucullata displayed microdefenses, indicating predator-specific adaptations and the modular nature of defense strategies.
In Chapter III, our investigation extends to two Bosmina species, B. coregoni and B. longirostris, unveiling the role of invertebrate predators, particularly Bythotrephes, in shaping Bosmina morphology. In contrast to daphnids, we did not detect different defensive strategies between the two Bosmina species, which included elongation of antennule and mucro in response to predators, and additionally an increase of eye diameter by predators. Transgenerational maternal effects on Bosmina traits were also observed, emphasizing the nuanced strategies employed across different developmental stages in response to predation pressures.
Chapter IV presents an analysis of the long-term trends in three Bosmina populations (B. coregoni, B. longispina, and B. longirostris) of Lake Constance, highlighting significant shifts in species composition and trait dynamics over three decades of environmental change. While stability was observed in species composition and traits during the initial two decades of nutrient decline, the final decade saw rapid turnover and trait changes at both the genus and species levels likely caused by direct and indirect effects of increased fish predation. Trait changes seen at the genus level were accompanied by species – level alterations that only partly matched genus-level changes. For instance, the intra-specific antennule size of all three species increased during the last study years, where at the genus level there was pronounced interannual heterogeneity of antennule size due to species replacements. This indicates diverse selection pressures driving species fluctuations and intraspecific morphological shifts. Within – species trait dynamics suggests a significant influence of invertebrate predators, presumably of Bythotrephes longimanus, in shaping Bosmina species turnover and trait dynamics. These observed fluctuations suggest complex interactions between environmental factors, predator pressures, and Bosmina assemblages.
In this thesis, I was able to study experimentally antipredator defenses at the community level and showed that two predatory cladocerans, Bythotrephes longimanus and Leptodora kindtii did induce antipredator responses in five different herbivorous cladoceran species (three Daphnia species and two Bosmina species). As these defenses presumably will differ in their costs and the species will differ in their vulnerabilities to predation, these two predators will likely shift the relative abundances of these species in lakes in complex and difficult ways to predict. Investigating shifting trait dynamics of the species during environmental changes might contribute to shed light on the role of invertebrate predators on food web dynamics within a lake. The analyses of the Bosmina assemblage trait dynamics in Lake Constance during three decades of environmental changes indeed provided insights in the role of environmental pressures for population dynamics and into the adaptive responses of organisms to shifting ecological conditions.
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BALUDO, Marjohn, 2024. Cladoceran trait dynamics during oligotrophication of Lake Constance [Dissertation]. Konstanz: Universität KonstanzBibTex
@phdthesis{Baludo2024-06-19Clado-70167, year={2024}, title={Cladoceran trait dynamics during oligotrophication of Lake Constance}, author={Baludo, Marjohn}, address={Konstanz}, school={Universität Konstanz} }
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In this study, we investigate the defensive adaptations of two key zooplankton genera, Daphnia and Bosmina, in response to predation threats, focusing on both macrodefenses and microdefenses. Additionally, we assess the long-term trends in species turnover and trait dynamics in a Bosmina assemblage in Lake Constance in order to study the role of species turnover for Bosmina trait dynamics. Chapter II delves into the defensive mechanisms of Daphnia, revealing species-specific responses to predation pressure. While D. cucullata and D. galeata exhibited macrodefenses, D. longispina lacked such defenses, possibly due to its diel vertical migration behavior and the absence of certain predators like Chaoborus in Lake Constance. Interestingly, neonates but not adults of D. cucullata displayed microdefenses, indicating predator-specific adaptations and the modular nature of defense strategies. In Chapter III, our investigation extends to two Bosmina species, B. coregoni and B. longirostris, unveiling the role of invertebrate predators, particularly Bythotrephes, in shaping Bosmina morphology. In contrast to daphnids, we did not detect different defensive strategies between the two Bosmina species, which included elongation of antennule and mucro in response to predators, and additionally an increase of eye diameter by predators. Transgenerational maternal effects on Bosmina traits were also observed, emphasizing the nuanced strategies employed across different developmental stages in response to predation pressures. Chapter IV presents an analysis of the long-term trends in three Bosmina populations (B. coregoni, B. longispina, and B. longirostris) of Lake Constance, highlighting significant shifts in species composition and trait dynamics over three decades of environmental change. While stability was observed in species composition and traits during the initial two decades of nutrient decline, the final decade saw rapid turnover and trait changes at both the genus and species levels likely caused by direct and indirect effects of increased fish predation. Trait changes seen at the genus level were accompanied by species – level alterations that only partly matched genus-level changes. For instance, the intra-specific antennule size of all three species increased during the last study years, where at the genus level there was pronounced interannual heterogeneity of antennule size due to species replacements. This indicates diverse selection pressures driving species fluctuations and intraspecific morphological shifts. Within – species trait dynamics suggests a significant influence of invertebrate predators, presumably of Bythotrephes longimanus, in shaping Bosmina species turnover and trait dynamics. These observed fluctuations suggest complex interactions between environmental factors, predator pressures, and Bosmina assemblages. In this thesis, I was able to study experimentally antipredator defenses at the community level and showed that two predatory cladocerans, Bythotrephes longimanus and Leptodora kindtii did induce antipredator responses in five different herbivorous cladoceran species (three Daphnia species and two Bosmina species). As these defenses presumably will differ in their costs and the species will differ in their vulnerabilities to predation, these two predators will likely shift the relative abundances of these species in lakes in complex and difficult ways to predict. Investigating shifting trait dynamics of the species during environmental changes might contribute to shed light on the role of invertebrate predators on food web dynamics within a lake. The analyses of the Bosmina assemblage trait dynamics in Lake Constance during three decades of environmental changes indeed provided insights in the role of environmental pressures for population dynamics and into the adaptive responses of organisms to shifting ecological conditions.</dcterms:abstract> </rdf:Description> </rdf:RDF>