We study ecology, evolution and biodiversity of fishes and other aquatic organisms. We are interested in the mechanisms that drive the origins, the maintenance and the loss of species, genetic and functional diversity.
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. Read more
May 31, 2019
“Copying & pasting” a gene allows stickleback to live in freshwater habitats
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. Read more
Ecological Consequences of Animal Migration: Prey Partial Migration Affects Predator Ecology and Prey Communities
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. We carried out the study in independent replicated freshwater lake systems, four with and four without opportunity for prey migration. Specifically, we compared predator foraging mode in lakes where cyprinid prey fish perform seasonal partial migrations into connected streams with lakes lacking migratory opportunities for prey fish. We found clear seasonal bottom-up effects of prey migration on predators, including changes in size structure and total biomass of ingested prey, size-specific changes in littoral versus pelagic origin of diet, and a higher degree of feast-and-famine for predators in systems with migratory prey. Our analyses further showed that partially migratory prey species constitute a larger part of the prey community in systems that allow migration. Hence, prey migrations have important implications for predator foraging ecology and may cause seasonal shifts in the importance of their supporting energy pathways. We suggest that such bottom-up effects of partial migration may be a widespread phenomenon both in aquatic and in terrestrial ecosystems. Read more
March 17, 2019
Sinergia project "20'000 years of evolution" has started
Our new SNF Sinergia project entitled "20'000 years of evolution and ecosystem dynamics in the world's largest tropical lake reconstructed from sediment cores, fossils and ancient DNA" has started!
May 10, 2019
Vision using multiple distinct rod opsins in deep-sea fishes
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. Among these, the silver spinyfin (Diretmus argenteus) stands out as having the highest number of visual opsins in vertebrates (two cone opsins and 38 rod opsins). Spinyfins express up to 14 RH1s (including the most blueshifted rod photopigments known), which cover the range of the residual daylight as well as the bioluminescence spectrum present in the deep sea. Our findings present molecular and functional evidence for the recurrent evolution of multiple rod opsin–based vision in vertebrates.
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. Read more