In the recently published open-access article in Ecosphere we studied the influence of fluvial network topology on different measures of amphipod diversity. The scientific novelty is the distinction between native and non-native species within a single taxonomic group in a large and natural system. The study covers the 27,882-km2 drainage basin of the river Rhine in Switzerland and is based on a graph theory approach.
Patterns of native and non-native species in fluvial networks
As hypothesized, species richness increased along the network from headwaters to the outlet nodes. But native and non-native amphipod showed different patterns, with headwaters being refugia for native species and more downstream nodes being hotspots of biological invasions. Additionally, results from species turnover indicated a much lower dispersal limitation for non-native species. The amphipod community structure closely mirrored the topological modularity of the network.
Implications for conservation ecology
Our results highlight that connectivity plays an important role in community formation, also on a larger scale. Rivers and streams are essential in explaining biological invasions.
Our most recent paper in Systematics and Biodiversity reveals three new and endemic species of Niphargus in Switzerland. We describe them from the Hölloch cave system in central Switzerland, with no further findings known so far. The paper updates the current knowledge of amphipoda in Switzerland, specifically for the genus of Niphargus.
A fruitful collaboration
Thanks to the collaboration with the caving society of the Hölloch we could retrieve the exciting samples. It was also them who provided the names given to the new species. Without their knowledge about the gigantic cave system we would not have been able to publish these results.
In our most recent paper, Florian Altermatt, Cene Fišer, and me describe a new amphipod species that is endemic to the Alps. What has been considered to belong to the circumboreal Gammarus lacustris species complex turned out to be a highly diverged lineage. It represents an own species within the Alps. Given its natural but restricted distribution, we name the endemic amphipod species Gammarus alpinussp. nov.
The species is commonly found in high alpine lakes of Central Europe. Although its wide distribution, invasive species and increasing anthropogenic pressure in its natural habitat impose challenges to the newly described species. Assigning a name to this biological entity hopefully facilitates the conservation efforts. Our study is published in the Zoological Journal of the Linnean Society. It highlights the importance of combining different methods to resolve cryptic diversity. Furthermore I would hereby like to acknowledge all the people and institutions that helped to conduct this study.
Our study on chironomids of high elevation and non-glacial streams is available online via Schweizerbart. We found highly diverse and spatially-structured communities of these ecologically important macroinvertebrates. Rarity was prevalent and highlighted the local differences between sites. Regional patterns reflected distributions of the more common taxa. Hence, projections of chironomid assemblages under climate warming are difficult and conservation of these diverse habitats is therefore important.
Work that initially started as a small semester project in 2011, thought to provide a better understanding of amphipod communities in streams around Lake Constance, now got published in BMC Ecology. I’m really happy that Florian Altermatt suggested this project when I started my Master’s studies and that his research group continued to work on the study system. The project introduced me to the world of amphipods and this is how I eventually became an amphipodologist.
In the paper, we report replicated patterns of community composition and spatial distributions in smaller tributary streams of Lake Constance. However, invading species had no clear effect on the genetic diversity of native amphipods on this small spatial scale. This suggests that large scale observations of invasion biology may not be directly reflected on a smaller scale.