The latest two publications from our work on groundwater treat taxonomic questions on Niphargus and Haplotaxis. In a first study published in Zoologischer Anzeiger, we used molecular methods to review the taxonomic status of the Niphargus ruffoi clade, including the species N. ruffoi and Niphargus arolaensis, across the Alpine arc. In another study published in Zoosymposia, we questioned the supposedly sub-cosmopolitan species status of Haplotaxis gordioides, with our results suggesting that the species is a complex of at least 6 cryptic species in Switzerland.
Through close cooperation with local waterproviders in the Töss catchment area, we were able to detect a diverse groundwater fauna. The corresponding publication has just been published in Molecular Ecology (https://doi.org/10.1111/mec.16955). In contrast to earlier studies, we did not have to use nets and actually catch the organisms, but were able to detect them on the basis of DNA traces in water samples. We were able to show that the diversity of groundwater fauna differs depending on whether the samples were taken from agricultural or forested sites. However, it is not yet possible to make a statement about the cause or to do a water quality assessment. Eawag has published a news article on the publication. Many thanks also to the FOEN, the SVGW and Eawag for their financial support of the research project.
Being a field biologist by training, I always wanted to study my beloved amphipods under laboratory conditions. Turns out it is not as straightforward. Our recent publication in Science of The Total Environment highlights some of the things we learned over the last few years. While some amphipod species such as Hyalella azteca are easy to breed in captivity, the freshwater genus Gammarus from Central Europe is notoriously hard to keep and maintain in the lab. Hence, most experiments rely on wild-caught animals. From an scientific point of view, having lab-bred individuals available is the preferred option. To improve survival and reproduction in lab cultures of Gammarus fossarum, we caught thousands of G. fossarum and ran several experiments in our laboratory facilities, tweaking around with food supply, day-length, water temperature, cage size etc. We supplemented the diet of G. fossarum with protein-rich food and provided additional shelter. Both these measures increased survival rate of laboratory-based populations significantly, especially the feed enrichment. We also manipulated the day length (fixed vs. variable). We did not observe a significant effect of day length on the abundance and reproductive activity of G. fossarum. Apart from these main findings, we provide several detailed husbandry protocols in the paper (https://doi.org/10.1016/j.scitotenv.2022.158730). They are intended as starting point for future experiments in environmental sciences and ecotoxicology that rely on lab-bred G. fossarum. I want to thank everyone involved in improving our lab cultures of G. fossarum, especially Sarah Bollina, Eva Cereghetti, Morris Galli, Samuel Hürlemann, Silvana Kaeser, Chelsea Little, Manja Schleich and I want to acknowledge financial support by Eawag, University of Zurich, and BAFU.
In our recently published study in Molecular Ecology, Emanuel A. Fronhofer, Florian Altermatt, and me analyzed empirically observed genetic diversity of Gammarus fossarum metapopulations across the Rhine drainage area within Switzerland. We used microsatellite data and stochastic simulations to study the role of dispersal behaviour on observed genetic diversity. Allelic richness and observed heterozygosity were higher in more central nodes, unlike expected heterozygosity. Stochastic simulations suggest upstream movement probability and dispersal rate to be key factors explaining this finding. The study is open access. A huge thank you to Anja Westram and Jukka Jokela for support early on during analysis and providing data.