High degree of philopatry is required for mobile insects used as local indicators in biodiversity studies

Local changes in land use and climatic conditions provoke transformations of habitats and therefore, distribution changes of species in the landscape. Different insect groups are repeatedly used as indicators of local ecological conditions in biodiversity research. Here we suggest that only highly philopatric groups can be relevant indicators pointing to differences in ecological conditions among spatially close habitats. For our study in open agriculture landscape, we chose aculeate Hymenoptera and hoverflies as two insect, mostly pollinator groups differing in their degree of philopatry within the registered pool of our survey where hoverflies were represented by common generalist species showing high mobility. We tested if these groups appeared in significantly different species numbers in two most contrasting habitats typical for the European open agriculture landscape: patches of flower-rich, semi-natural habitats around fields with a variety of nesting sites and wheat fields in proximity that represented a non-viable agricultural habitat with no nesting and foraging opportunities. For this purpose, comparison of results from attractant based (pan traps) and observational (transect walks) methods were used. Philopatric species were detected in significantly different species numbers in the two habitat types using both methods. In contrast, highly mobile non-philopatric species showed a mixed pattern. We assume that these species can be attracted at any place if containing a suitable attractant (flowers or pan traps in this case) what may not indicate their actual living in the habitat.