Department Fish Ecology and Evolution

Die einzigartige Fischvielfalt in Fliessgewässer-Ökosystemen in und um die Schweiz
Aufgrund der geografischen Lage in vier der wichtigsten Wassereinzugsgebieten Europas und der grossen Vielfalt an Lebensräumen weisen die aquatischen Ökosysteme der Schweiz eine aussergewöhnlich hohe Fischvielfalt auf. Diese Vielfalt ist hauptsächlich durch zwei verschiedene Prozesse entstanden, einerseits durch die Zusammenführung bereits vorhandener Vielfalt, und andererseits durch postglaziale Evolutionsprozesse. Der letztgenannte Prozess hat zu einem hohen Grad an Endemismus vor allem in den grösseren Seen des Alpenraums geführt. Diese einzigartige Vielfalt ist auf vielen verschiedenen Ebenen zu finden. Neben der Artenvielfalt beherbergen die verschiedenen Flüsse und Bäche auch eine Vielfalt an diversen Fischgemeinschaften, wobei sowohl die Unterschiede in der Artenzahl als auch in der Artenzusammensetzung zu unterschiedlichen Nahrungsnetzen und Ökosystemprozessen zwischen den Flüssen führen. Viele Fischarten weisen auch ein hohes Mass an intraspezifischer Vielfalt auf, z. B. in Bezug auf Morphologie, Physiologie, Ökologie, Lebensgeschichte und Genom. Diese intraspezifische Vielfalt ist insofern von Bedeutung, dass verschiedene Populationen möglicherweise an unterschiedliche Lebensräume angepasst sind und eine hohe genetische Vielfalt aufweisen. Letzteres ermöglicht es den einzelnen Individuen innerhalb einer Population, verschiedene Nischen zu besetzen, und es ermöglicht den Populationen, sich besser an veränderte Umweltbedingungen anzupassen. [...]

The unique fish diversity in riverine ecosystems in and around Switzerland
As a consequence of its geographic location within four of Europe’s major watersheds and a large amount of habitat diversity, aquatic ecosystems in Switzerland harbor an exceptionally high amount of fish diversity. This diversity has mainly been formed by two different processes, i.e. assembly of previously existing diversity and postglacial evolutionary processes. The latter of these processes has led to a high degree of endemism in especially the larger lakes in the Alpine region. The unique diversity can be found on many different levels. Besides the diversity of species, the different rivers and streams also harbor a diversity of fish communities, where both the variation in the number of species and the composition of species result in different food webs and ecosystem processes between rivers. Many of the fish species also show a high degree of intraspecific diversity in e.g. morphology, physiology, ecology, life history and in their genome. This intraspecific diversity is important in terms of different populations potentially being adapted to different habitats and in terms of populations harboring a high genetic diversity. The latter makes the individual fish within a population able to occupy different niches and makes the populations better able to adapt to changing environmental conditions. [...]

While ecological monitoring and biodiversity assessment programs are widely implemented and relatively well developed to survey and monitor the structure and dynamics of populations and communities in many ecosystems, quantitative assessment and monitoring of genetic and phenotypic diversity that is important to understand evolutionary dynamics is only rarely integrated. As a consequence, monitoring programs often fail to detect changes in these key components of biodiversity until after major loss of diversity has occurred. The extensive efforts in ecological monitoring have generated large data sets of unique value to macro-scale and long-term ecological research, but the insights gained from such data sets could be multiplied by the inclusion of evolutionary biological approaches. We argue that the lack of process-based evolutionary thinking in ecological monitoring means a significant loss of opportunity for research and conservation. Assessment of genetic and phenotypic variation within and between species needs to be fully integrated to safeguard biodiversity and the ecological and evolutionary dynamics in natural ecosystems. We illustrate our case with examples from fishes and conclude with examples of ongoing monitoring programs and provide suggestions on how to improve future quantitative diversity surveys.

The concept of the niche has long been a central pillar in ecological theory, with a traditional focus on quantifying niches at the species or population level. However, the importance of individual-level niche variation is increasingly being recognised, with a strong focus on individual specialisation. While examples illustrating the contribution of the individual niche to whole population niche structure are accumulating rapidly, surprisingly little is known about the conditions that shape the differences between these two potentially divergent components. Though theory predicts that stability should influence the extent of such intra-specific specialisation, we know of no previous study that has investigated its role in individual specialisation, and the differentiation between individual- and population niches. Here, we studied the diet of individuals from multiple populations of an aquatic top-predator, Salmo trutta, inhabiting contrasting stable, groundwater fed and unstable, surface water fed pre-alpine streams. Based on stomach content analysis, we found that individuals living in stable environments displayed a higher degree of specialisation than those in unstable environments, with the between individual component of niche width being approximately twice as high in the former. We subsequently validated these results by evidence gained from stable isotope analysis of muscle tissue. As such, we reveal that environmental stability can signifi cantly infl uence individual niches within populations, leading to increased specialisation.