Four arthropod datasets of different taxonomic detail were compared on their discriminatory power for various environmental characteristics in a lowland floodplain area along the river Rhine. The arthropod datasets comprised ground-dwelling arthropods at class-order level (n = 10), beetle families (n = 32), ground beetle genera (n = 30) and ground beetle species (n = 68). Environmental characteristics included vegetation characteristics, hydro-topographic setting, physical-chemical soil properties and soil contamination levels. Relations between arthropod assemblages and environmental factors were assessed with variance partitioning: a multivariate statistical approach that attributes variation in community composition to specific explaining variables. The variance partitioning showed comparable results for the four datasets. A substantial part of the variation (31-38%) could be ascribed to vegetation characteristics. Variance could further be attributed to physical-chemical soil properties (7-10%), hydro-topographic setting (3-7%) and soil metal contamination (2-4%). Thus, in strongly heterogeneous landscapes like lowland river floodplains, relatively coarse taxonomic data can already provide a valuable indication of the relative importance of different environmental factors for structuring arthropod communities. However, the ground beetles showed a higher specificity for different vegetation types and a more distinct relation to soil contamination levels than the other arthropod datasets. Hence, a higher degree of taxonomic detail will be beneficial for investigating the consequences of for example environmental pollution or vegetation characteristics in terms of taxonomic diversity or community composition.

The regular fluctuation of resources across the Globe guides movements of migratory animals. To ensure sufficient reproductive output and maintain viable population sizes, migratory animals should match arrival at breeding areas with local peaks in resource availability. It is generally assumed that breeding phenology dictates the timing of the annual cycle, but this is poorly studied. Here, we use light-level geolocator tracking data to compare the annual spatiotemporal migration patterns of a longdistance migratory songbird, the red-backed shrike, Lanius collurio, breeding at widely different latitudes within Europe. We find that populations use remarkably similar migration routes and are highly synchronized in time. Additional tracks from populations breeding at the edges of the European range support these similar migration patterns. When comparing timing of breeding and vegetation phenology, as a measure of resource availability across populations, we find that arrival and timing of breeding corresponds to the peak in vegetation greenness at northern latitudes. At lower latitudes birds arrive simultaneously with the more northerly breeding populations, but after the local greenness peak, suggesting that breeding area phenology does not determine the migratory schedule. Rather, timing of migration in red-backed shrikes may be constrained by events in other parts of the annual cycle.

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