Highly Conserved Ecosystems Facing Climate Change: Rapid Shifts in Odonata Assemblages of Central European Bogs

Freshwater diversity is declining at an alarming rate worldwide, and climate change is a key driver. However, attributing biological shifts solely to climate warming remains challenging because of confounding anthropogenic stressors. Peatbogs, being highly conserved, strictly protected, and minimally disturbed, offer a unique study system to isolate climate effects. We compared odonate assemblages in 27 Central European raised and transitional bogs between two sets of standardized surveys approximately 20 years apart (1998-2006 and 2020-2024). During this period, the mean annual air temperature has increased by 1.23°C. We tracked species richness, composition, taxonomic diversity, and functional traits (thermal tolerance, conservation value indicators, and selected morphological and life-history traits) and also examined phylogenetic patterns of species turnover. Although species richness remained stable, assemblage composition shifted markedly from cold-adapted, vulnerable bog specialists toward warm-adapted habitat generalists with lower conservation value. Notably, Ponto-Mediterranean species and those with a lower upper elevational limit increased their occupancy. Although the phylogenetic signal across the evolutionary tree of odonates was low, implying that the responses of the species to climate change were independent of their phylogenetic position, we revealed frequent genus-level replacements. These findings reinforce the position of odonates as a model group for detecting climate-driven changes in freshwater communities. Our study has revealed that climate warming alone can trigger profound reorganization of insect communities in inherently stable peatbog habitats. Specific traits linked to vulnerability (e.g., thermal index, red list status) and specialization proved to be promising predictors of future shifts in odonatofauna of temperate peatlands. The pronounced changes documented here may precede irreversible transformations of these unique ecosystems, highlighting the urgency of monitoring bog habitats and maintaining their stability under ongoing global change.