Ice age, current climate, habitat availability, and the diversity of European dragonflies and damselflies

Several studies show that species richness patterns are determined by current climate and Pleistocene climatic oscillations. Additionally, habitat availability is an important driver of current species diversity, especially in aquatic ecosystems where lentic (standing water) and lotic (running water) habitats play distinct roles in species composition and richness. Odonates, an order of aquatic insects, exhibit distinct adaptive traits in response to climate and to lentic and lotic habitats. In this work, we study the species richness patterns of European odonates and the influence of past climate, current climate, and habitat availability. The study covers 124 species distributed across Europe (excluding Russia and all European islands except Great Britain and Ireland), divided into three groups: Odonata, lentic species, and lotic species. We analyzed their diversity in Northern and Southern Europe, divided according to the 0ºC Isotherm of the Last Glacial Maximum (21,000 years ago), using data on current and Last Glacial Maximum climate (temperature and precipitation), as well as on habitat data from land cover and hydrology GIS maps. Our results suggest that the species richness patterns of dragonflies and damselflies are largely determined by the water-energy balance, with temperature influencing the decline in richness towards the south and precipitation determining the decline towards the north. Past climate oscillations affect species richness in southern and northern Europe. Habitat availability also influences odonate diversity, though to a lesser extent, with a positive correlation between lotic habitat availability and lotic species richness. In contrast, lentic species show a negative correlation with the availability of lentic habitats.