Peat meadows as amphibious systems: composition, functionality and cross interactions of insect communities across water and land habitat

Abstract

Dutch peat meadows combine aquatic and terrestrial environments, but these are typically studied separately, missing whole-system perspectives and potential cross-habitat interactions. To address this, I conducted a study to compare insect communities in both environments within the same peat meadow systems. Additionally, I explored species movements between aquatic and terrestrial areas. Samples for the terrestrial communities were collected in June 2022 and in June 2023 for aquatic communities, considering a gradient of groundwater levels (GWL) and ditch morphologies. Results reveal that aquatic environments display more distinct community compositions than terrestrial environments, with no discernible correlation between community composition, diversity, or functional diversity across these habitats. Aquatic communities exhibit higher functional richness relative to species richness compared to terrestrial communities, which are influenced by a broader range of environmental factors. Functionally, while dispersal traits are crucial in both environments, terrestrial environments show greater diversity in effect traits, contrasted by a higher diversity of life-history traits in aquatic environments. Additionally, direct cross-habitat interactions constitute 5-10% of all possible habitat interactions; with aquatic-to-terrestrial movements, driven by yearly GWL variation, significantly enhancing terrestrial richness, while terrestrial-to-aquatic movements, driven by species-specific behaviors, have negligible effects on aquatic diversity. Overall, this study's results point towards differentiated filtering processes for aquatic and terrestrial habitats, with the aquatic communities being molded by biotic interactions, and the terrestrial communities being more influenced by environmental filtering. Furthermore, this study provides interesting results on the effects of water and land cross-habitat interactions on the ecological diversity of each community.