Department Fish Ecology and Evolution

In the "Projet Lac" research project, 35 lakes in the Alpine region were systematically examined for their fish populations for the first time: In Switzerland alone, 106 fish species were detected. With almost 20 percent of all known fish species in Europe, Switzerland is one of the hotspots for fish species diversity. The results are now the basis for measures for sustainable fishing and the protection of this still preserved diversity.

Researchers from 90 scientific institutions worldwide have stated that freshwater biodiversity research and conservation lag far behind the efforts carried out in terrestrial and marine environments. In a new publication in Ecology Letters, they propose a research agenda with 15 priorities aimed at improving research on biodiversity in lakes, rivers, ponds and wetlands. This is urgently needed, as biodiversity loss is taking place much faster in inland waters than on land or in the oceans.

Luiz Jardim de Queiroz and Naomi Heller won the eight edition of the CEEB poster competition! The Center of Competence for Ecology, Evolution and Biogeochemistry (CEEB) in Kastanienbaum is organising this annual event in order to provide a unique opportunity for young researchers to demonstrate their scientific activity as well as their creativity and quality of work.

Researchers Christoph Vorburger and Florian Altermatt talk about the importance and state of aquatic biodiversity in Switzerland and Eawag’s commitment to conserving natural biodiversity.

Rising temperatures, invasive species and other factors have changed the composition of species in Lake Constance over the last century. Researchers are trying to understand how this could have happened and what it means for the lake.

Europe has relatively low biodiversity compared to most other continents because many species became extinct during the ice ages. In subterranean ecosystems, however, which were shielded from climatic turbulences, a great diversity of ancient species were able to survive. This is the conclusion of a study on the amphipod genus Niphargus.

Evolution plays a crucial role in ecosystem tipping points, as shown in two recently published studies by Eawag researchers. If this influence is taken into account, ecosystem collapses can be better predicted in the future. At the same time, the studies reveal how the risk of ecosystem collapse can be reduced and the chances of recovery increased.

Open Science is an important development in science - open access to the results of research. Eawag supports these and makes a growing part of its research data, including descriptions, images and even software, available publicly and free of charge on the Eawag platform ERIC or, in special cases, on discipline-specific, international databases. ERIC complements the long-standing platform DORA for scientific publications.

Adaptive radiations are bursts of evolutionary species diversification that have contributed to much of the species diversity on Earth. An exception is modern Europe, where descendants of ancient adaptive radiations went extinct, and extant adaptive radiations are small, recent and narrowly confined.

Science journalist Ashley Yeager has written a beautiful article in The Scientist about the paradigm shift in our understanding of the role that interspecific hybridisation plays in the evolution of biodiversity. Among other things, she describes the work of Ole Seehausen in connection with hybridisation in Lake Victoria cichlids.

The motto of today’s World Water Day is “Valuing water – What means water to you?”. With this motto, the United Nations wants to raise awareness of the vital importance of water and call on people to think about the value of water. In an interview, Eawag Director Janet Hering explains the importance of water for the aquatic research institute Eawag and also her personally.

In Lake Constance, sticklebacks are occupying increasingly varied habitat types – in recent years even including the open and deep waters of the lake. In an Eawag review undertaken as part of the “SeeWandel” project, these uniquely diverse ecological adaptations are explained in terms of renewed contact between three stickleback lineages – including one originating from the Baltic region, whose genetic material is as yet rarely observed in other Swiss lakes.

Europe still has barely any downstream passage facilities that guide fish past the turbines of run-of-river power stations unharmed. Now, an interdisciplinary team of engineers from ETH Zurich and fish biologists from Eawag have developed a rack that uses pressure and flow differences to guide fish out of the main flow and into the safe fish passage. Laboratory tests have shown that the system, which works by influencing fish behaviour, is particularly effective for cyprinid fish and salmon parr.

A factsheet from the Swiss Academy of Sciences (SCNAT) shows: Too much nitrogen and phosphorus is released into the Swiss environment. There they damage biodiversity, forests and water bodies, exacerbate climate change and affect human health. Actually the causes are known.

Researchers Juliane Hollender, Ole Seehausen, Bernhard Truffer and Urs von Gunten from the aquatic research institute Eawag are among the "highly cited researchers 2020".

In the journal ZooKeys, a group of scientists from Eawag and Bern University have described seven whitefish species endemic to the Bernese Oberland lakes – including four not previously described scientifically, two of which have only been identified as distinct species in the last few years. In Switzerland, the whitefish diversity of Lakes Thun and Brienz is possibly matched only by that found in Lake Lucerne; and in deep lakes of this kind further surprises cannot be ruled out.

Exploration and utilisation of resources from the world’s oceans is not equally distributed across the globe. Although many of these resources originate in the Global South, they are mostly being researched by just a few countries from the North. Accordingly, this is also where most of the benefits and profits are flowing to, despite the Convention on Biological Diversity. This was the finding of an analysis of literature from the last 50 years.

Using genomic analyses of 100 cichlid species, scientists from Eawag and the University Bern, together with co-workers in Australia, the UK, Tanzania, Uganda and the US, have investigated the striking variation observed in cichlid fish speciation rates. Their findings show that exchanges of genetic variants between existing species dramatically accelerate the development of new species – given favourable ecological conditions.

Biodiversity and thus the state of river ecosystems can now be predicted. To achieve this, researchers from the University of Zurich and Eawag (Aquatic Science and Technology) are combining environmental DNA with hydrological methods. Using the river Thur as an example, the approach allows identifying target areas for conservation and initiating protective measures.

Interspecific hybrids can have transgressive phenotypes that may allow them to explore novel ecological niches.

Around 500 different cichlid species are found in Lake Victoria. According to a study by scientists at Eawag and Bern University, whether closely related species can persist within the same area depends on the effect sizes of individual genes underlying key mate-choice traits.

126 Swiss researchers, including 6 from Eawag, want to draw the attention their Swiss compatriots to the scientific evidence showing the link between the emergence of pandemics and human disturbance of the natural environment.

Drawing insights from multiple disciplines is essential for finding integrative solutions that are required to tackle complex environmental problems. Human activities are causing unprecedented influence on global ecosystems, culminating in the loss of species and fundamental changes in the selective environments of organisms across the tree of life.

To understand how specific organisms evolve, adapt to new environments, and form new species it is important to be able to compare the DNA sequences of different individuals and organisms. The best way of doing this is to have species-specific genetic resources, such as a genome assembly, for the species of interest which allow us to find genetic similarities and differences between individuals. 

ABCD: All continents, balanced gender, low carbon transport and diverse backgrounds. These criteria should shape the scientific conferences of the future.

ABCD: All continents, balanced gender, low carbon transport and diverse backgrounds. These criteria should shape the scientific conferences of the future. 

Parasites may have strong eco-evolutionary interactions with their hosts. Consequently, they may contribute to host diversification. The radiation of cichlid fish in Lake Victoria provides a good model to study the role of parasites in the early stages of speciation. We investigated patterns of macroparasite infection in a community of 17 sympatric cichlids from a recent radiation and 2 older species from 2 nonradiating lineages, to explore the opportunity for parasite-mediated speciation.

One hallmark of the East African cichlid radiations is the rapid evolution of reproductive isolation that is robust to full sympatry of many closely related species. Theory predicts that species persistence and speciation in sympatry with gene flow are facilitated if loci of large effect or physical linkage (or pleiotropy) underlie traits involved in reproductive isolation. 

Seasonal spatio-temporal variation in habitat quality and abiotic conditions leads to animals migrating between different environments around the world. Whereas mean population timing of migration is often fairly well understood, explanations for variation in migratory timing within populations are often lacking.

The lakes of East Africa are home to a surprising number of different cichlid species. This level of biodiversity has developed partly due to hybrids that managed to take over new ecological niches in their habitats, according to recent research carried out by scientists at the Swiss Federal Institute of Aquatic Science and Technology, Eawag, and the University of Bern.

There may be hundreds of species of char living in Greenland’s lakes and rivers, according to a team from the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and the University of Bern, that has discovered the largest known diversity of char species in the catchment area of the Eqaluit River.

Vision plays a major role in the life of most teleosts, and is assumingly well adapted to each species ecology and behaviour.

In aquatic ecosystems, both mussels and macrophytes increase water clarity and generally help to prevent excessive algal growth. However, according to a study carried out at Eawag’s experimental pond facility, these stabilizing effects can be disrupted when the co‑occurrence of species gives rise to complex interactions.

Rapid changes in the genome of two closely interlinked species cannot be explained only by processes such as evolutionary pressure. Equally important is the role played by ecological processes, for example the dynamics of population size. This has been shown for the first time experimentally by an international team of researchers under the direction of Eawag and the University of Konstanz with an alga and a virus. The study will be published today in the magazine Science Advances.

New species can evolve rapidly after adapting to new niches, a process called ecological speciation. But mutations are rare, so how is such rapid ecological speciation possible? Recently evolved lake and stream ecotypes of stickleback from Lake Constance reveal an unexpected answer.

An insight into her molecular neurobiologist's work and about means of visual communication between fish.

When animals migrate into an ecosystem, the ecosystem turns into a temporary land of milk and honey for predators. But novel findings from a recent study on local fish migration patterns in northern Europe indicate that even when animals migrate out of an ecosystem, their absence has an effect on food webs.

Since the last ice age, stickleback have managed to emerge from the sea to colonise many freshwater waterbodies. Genetic analysis by Eawag researchers and colleagues from the University of Bern and the National Institute of Genetics in Shizuoka, Japan, now demonstrate that they achieved this thanks to additional copies of a metabolism gene.

Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered predator–prey interactions and effects on community structure, remain poorly understood. This is to a large extent due to the scarcity of naturally replicated migration systems with negative controls, that is, ecosystems without migration. In this study, we tested whether partial migration of certain species within the overall prey community affects foraging ecology of top predators and thereby alters energy pathways in food webs.

Vertebrate vision is accomplished through light-sensitive photopigments consisting of an opsin protein bound to a chromophore. In dim light, vertebrates generally rely on a single rod opsin [rhodopsin 1 (RH1)] for obtaining visual information. By inspecting 101 fish genomes, we found that three deep-sea teleost lineages have independently expanded their RH1 gene repertoires.

By systematically collecting samples from Switzerland’s rivers, “Progetto Fiumi” has documented more than forty species of fish. In addition, within the various species, the Eawag research group has found a rich diversity that had not been fully assessed before. The project thus provides a basis for the protection of this genetic and ecological diversity.

Speciation is often thought of as a slow process due to the waiting times for mutations that cause incompatibilities, and permit ecological differentiation or assortative mating. Cases of rapid speciation and particularly cases of rapid adaptive radiation into multiple sympatric species have remained somewhat mysterious.

The contemporary genomic diversity of viruses is a result of the continuous and dynamic interaction of past ecological and evolutionary processes. Thus, genome sequences of viruses can be a valuable source of information about these processes. In this review, we first describe the relevant processes shaping viral genomic variation, with a focus on the role of host–virus coevolution and its potential to give rise to eco-evolutionary feedback loops.

When ecosystems tip abruptly out of balance, this can be catastrophic for humans and for biodiversity. Astonishingly little is known about the role of evolution in such processes. A research team including Eawag scientists has now published approaches to investigating such complex questions in the journal “Nature Ecology & Evolution”.

Rishi De-Kayne and Philine Feulner are investigating the genetic basis of the spectacular whitefish radiation in Swiss lakes. To do this, new genetic tools are essential. One such tool is the new linkage map they have published in the journal G3.

This study provides a genomic analysis (based on 16,173 RAD loci) of alpine whitefish from Lake Walensee and Lake Zurich. Philine and Ole show that with so many markers it is possible to clearly distinguish sympatric whitefish species. This then enabled them to show that in both lakes, populations of different, but ecologically similar, whitefish species declined after a period of eutrophication.

In Lakes Thun and Brienz, evolutionary biologists from Eawag and Bern University have discovered a new whitefish species. The species, provisionally named “Balchen2”, is clearly differentiated – morphologically, ecologically and genetically – from the five Lake Thun whitefish species previously described. The only lake known to harbour a higher number of whitefish species is the 200 times larger Russian Lake Onega.

Climate warming is not the only cause of temperature changes in lakes, rivers and other bodies of water. The use of waterbodies for heating and cooling also leads to increases or decreases in water temperature. There has been little research to date, however, on how this affects aquatic ecosystems. This lack of understanding has been highlighted by a recent literature review carried out at Eawag and the University of Bern.

A long-term study of Switzerland’s major watercourses has been continuing for almost 45 years. An evaluation of the time series shows that as the climate is changing, so are geochemical processes. Most of the measuring stations show an increase in the concentrations of bicarbonate. The changes are caused by increases in temperatures, the presence of nutrients in the lakes and the acidity of the soil. On the other hand, following a peak in the late 1980s, nitrogen concentrations have been decreasing. The reasons for this are a reduced input of nitrogen in agriculture and improved elimination in wastewater treatment.

Cichlids belong to one of the largest fish families, with new species emerging all the time. These colourful, shimmering fish evolve so fast that Eawag researchers have now been able to practically observe them in the process of their evolution.

Genetic linkage maps are essential for comparative genomics. In this study, we identified and genotyped markers via restriction-site associated DNA (RAD) sequencing to create a genetic linkage map based on 1,597 SNP markers from an interspecific F2 cross of two closely related Lake Victoria cichlids (Pundamilia pundamilia and P. sp. 'red head').

How quickly can organisms adapt to a new habitat? To answer this question, Tom Reimchen from the University of Victoria, Canada, set up a selection experiment in 1993 and let three-spined sticklebacks from a large lake evolve in a small pond for 19 years.

Kay Lucek and colleagues have found that within the Aare catchment, populations from geographically distant lakes are more closely related to each other than to nearby river populations. This pattern is consistent with two distinct colonisation waves rather than parapatric ecological speciation after a single colonisation wave.

Biological systems consist of ecological and evolutionary processes that interact within and across hierarchical levels. Yet quantitative frameworks to explore the complex dynamics of biological systems when interdependencies among levels of the hierarchy occur are scarce.

Microorganisms that live in symbiosis can sabotage biological methods of pest control by protecting their host from attackers, and host organisms can even pass on these beneficial “passengers” to their offspring. This phenomenon is one which has been paid little attention to date, but thanks to new research findings measures can now be taken to counteract it.

Lake Victoria in East Africa is known for its vast biodiversity. But according to a report published recently by the International Union for Conservation of Nature (IUCN), to which Eawag also contributed, many species of fish, molluscs, crustaceans and aquatic plants are currently at risk.

Moritz Muschick and colleagues searched sediment cores from Lake Victoria for fossils in layers before and after the lake dried up to test the "priority effect" hypothesis.

When the unicellular alga Chloralla variablis and its deadly opponent, the chlorovirus, wrestle with each other, the same thing comes out again and again in various identical experiments: After repeated phases of collapse and recolonisation, most of the algae cells are resistant to the pathogen in each repeated experiment.

Joana Meier receives the Faculty Award 2017 of the University of Bern for the best dissertation in biology. The title of the dissertation is "The role of hybridization in adaptive radiation: Genomic insights from Lake Victoria cichlids".

Jacco van Rijssel, Florian Moser, David Frei and Ole Seehausen have published a new paper in Proceedings of the Royal Society B on the influence of disruptive selection on gene flow in the evolutionary process. They ask whether differences in current divergent ecological selection can explain differences in genetic divergence between sympatric species. They have investigated this by comparing seven species pairs at different stages of speciation.

This is a very interesting blog series by theoretical ecologist Hari Sridhar. He interviews authors of well-known publications in ecology and evolution to find out about the genesis of the publication, the impact of the publication on the author's career and research, and what the author thinks about the content of the publication today.