Network-based analysis of the distribution of taxa between the locations of our biodiversity monitoring 2.0 in Munich (2018) and Leipzig (2019). In the network diagram, there are two kinds of “nodes” represented, sample-nodes (blue and violet) and species/taxa-nodes (grey). Sampling points are visualized blue for Munich and violet for Leipzig. Gray dots represent the different species / taxa. Network-based analysis is used to show and analyze how species or OTUs are divided between different sampling times. This is a powerful way to visually display large and highly complex data sets to highlight similarities and differences between samples. The visual output of this analysis is a grouping of samples according to their common species / taxa - samples that have more species in common are closer together.
The generated network is based on a likelihood-ratio test (p <0.001) in terms of location (Munich / Leipzig) and timepoints. Taxa / species (gray) and samples (colored: blue = Munich, violet = Leipzig) are defined as nodes and their connections as edges. There is a link between sample and species if there are sequences of this type in the respective sample. The size of the nodes reflects the number of sequences generated per sample and the thickness of the edges reflects the number of connections to each sample. Connections are shown in color if this type has occurred in both Munich (blue) and Leipzig (violet). Gray connections show that these species / taxa were only found in one of the two locations.
The analysis resulted in a total of 6503 connections (edges) and 2103 nodes (including 20 timepoints in Leipzig, 21 timepoints in Munich and 2062 taxa). The spatial separation of the blue (Munich) and violet (Leipzig) points shows at first glance that there are clear differences in the species composition between Munich and Leipzig. The distance between the two locations is usually greater than the distance between the same colored sampling times. Based on the distribution of the sampling times, you can also see a seasonal trend in the species composition. Due to the large amount of insects, some samples were separated into micro (S = Small) and macro fractions (L = Large).
In order to visualize a further level of the network-analysis, three taxa (originally shown in gray) were highlighted in orange and connections are shown in more detailed graphics below. The thickness of the connections represents how many sequences of this taxon were generated in the respective sample.
Example 1 - Tersilochinae spec. (BOLD: ABZ2979)
Species of this subfamily were detected both in Munich (blue) and in Leipzig (violet) at each of the 41 sampling times. Therefore, there are links to this taxon-point (highlighted in orange) at each of the sampling times (blue and violet points).
Example 2 - Camptogramma bilineata (BOLD: AAA8017)
This species was only detected in Leipzig 2019 (violet) - at six out of 20 sampling times.
Example 3 - Anoplius nigerrimus (BOLD: AAN3329)
This species was only detected in Munich 2018 (blue) - at eight of 21 sampling times.