Environmental filtering of aquatic insects in spring fens: patterns of species-specific responses related to specialist-generalist categorization

Environmental factors driving compositional changes of headwater aquatic assemblages have been widely studied as these habitats are among the most vulnerable environments and host diverse and species-rich assemblages. However, responses of individual species to multiple environmental gradients remain poorly known, despite such information being essential for understanding the differences in metacommunity structuring. This study aims to explore species-specific responses to the main environmental gradients in Central European spring fens and to assess the responses in relation to the specialist-generalist categorization of species. In total, the responses of 40 species were analysed by GLM, cluster analysis and PCA. Spring-fen specialists responded predominantly to water temperature and the proportion of fine particulate organic matter in the substratum, while generalists responded mainly to flow conditions and oxygenation in the combination with various substratum characteristics. Our results revealed that it is not easy to find general patterns in species responses to environmental gradients. However, we found a clear distinction between specialist and generalist species in how the local environment affects their successful colonization and establishment of viable population. This result emphasizes the need to consider species specialization in future ecological studies of aquatic spring biota.