Figure 1.
Morphological diversity within the order of Amphipoda.
Three (of the in total 29) different species/species complexes known from Switzerland are shown: A) Gammarus fossarum complex, B) Gammarus roeseli and C) Dikerogammarus villosus. G. fossarum is native to Switzerland, G. roeseli is a non-native species that arrived in Switzerland around 1850, and D. villosus is a non-native species that arrived in Switzerland in the late 1990s. The scale bar is equivalent to 1 cm and gives approximate size differences between the species. The diverse color patterns visible in these pictures of living animals are completely lost in specimens preserved in alcohol. All pictures by Florian Altermatt.
Table 1.
Overview of the hitherto published diversity of Amphipoda in Switzerland, neighboring countries of Switzerland (Austria, Germany, Italy, France) as well as Slovenia.
Figure 2.
Sampling locations and diversity pattern of amphipods in Switzerland.
A) Map of Switzerland showing all sampling sites included in our study (crosses). The four drainage basins (Rhine, Rhone, Inn/Danube and Ticino/Po) are given in different colors, and the major river and lakes are given in blue. The grid of the 20×20 km squares was used to calculate diversity patterns in panel B. B) Diversity of amphipods in 20×20 km squares covering all of Switzerland. Local species richness in each square is given as color gradient and a number. C) Interpolated fits of local amphipod species richness using a thin plate spline surface to irregularly spaced data.
Table 2.
Checklist of all amphipods (class Crustacea, order Amphipoda) hitherto known from Switzerland, as well as tentative year of arrival for the non-native species.
Figure 3.
Distribution maps of all 29 amphipod species of Switzerland.
Each panel gives the distribution of a species within Switzerland, in alphabetic order (see also Table 2). For G. fossarum, a map is given for the complex and the individual cryptic species respectively. Symbols show where the individuals were sampled: in lakes (circle), rivers and streams (square), or in the groundwater (diamond).
Figure 4.
Occurrence of native and non-native amphipods relative to elevation and drainage basin.
A) Occurrence of native and non-native amphipods relative to elevation. Probability density distributions are given for these two groups separately. The peaks of non-native amphipod occurrence at three elevations is linked to high sampling intensity at lakes in Ticino and River Rhine in Basel (elevation around 250 m), river Aare (elevation around 350 m) and Lake Constance (elevation 395 m). The dashed line gives the species richness at 50 m altitudinal bins. Note that the x-axis is on a log10-scale. B) Occurrence of native and non-native amphipod species across the four drainage basins in Switzerland.
Figure 5.
Venn diagram of amphipod co-occurrences.
The Venn diagram is showing the number of co-occurring amphipod species across the four different drainage basins in Switzerland. The colors of the drainage basins follow Fig. 2.
Figure 6.
Bayesian phylogenetic tree of Niphargus.
Samples from this study are in red, species occurring in Switzerland, but not sequenced within this project, are in blue. Numbers above nodes indicate posterior probabilities. Asterisk denotes specimens in which sequencing of 28S gene failed.