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Anthropogenic‐driven transformations of dragonfly (Insecta: Odonata) communities of low elevation mountain wetlands during the last century

Freshwater environments are experiencing high rates of species extinction due to human impacts, with aquatic insects thought to be strongly threatened by these changes; however, long‐term research on this topic is scant. Among aquatic insects, dragonflies are considered valuable indicators of human disturbance at multiple scales. This study addresses transformations of odonate communities of low elevation mountain wetlands in the Alps over the last century, comparing historical and present assemblages based on past records derived from scientific collections or literature and present data derived from site resurveys. About 32.6% of species have been extirpated or strongly declined in the area (mostly temporary lentic and lotic water specialists, or cold‐adapted species). Conversely, only 12.2% of species were new or considerably increased (mostly permanent lentic specialists and warm‐adapted species). Nearly half of historical populations have been lost. The great majority of species which disappeared from all the study sites also disappeared (or strongly declined) at the regional scale. Although gamma species richness was higher in the historical period compared with the present, mean alpha species richness does not significantly differ between the two, likely suggesting homogenisation of communities from historical to the present period. Present communities of dragonflies show a significantly higher community temperature index compared with historical ones. These patterns are putatively explained by the joint effects of land‐use change (drainage and reclamation), land‐use intensification or abandonment, environmental pollution, and anthropogenic‐driven climate warming.