Biogeography of Dragonflies and Damselflies across the World

Odonate (dragonflies and damselflies) constitute an ancient lineage of predatory insects whose contemporary distribution reflects interactions among geological history, climatic conditions, freshwater availability, habitat heterogeneity, dispersal capacity and evolutionary diversification. Approximately 6,400 extant species are distributed across all continents except Antarctica, with the greatest richness occurring in tropical regions. Nevertheless, odonate diversity does not follow a simple latitudinal pattern. Regional richness and endemism are influenced by water-energy availability, topography, river-basin history, forest cover, hydroperiod, elevation, island area and isolation, and the dispersal characteristics of individual lineages. The aquatic larval and terrestrial-aerial adult stages of odonates produce a distinctive dual-realm biogeography: successful colonization requires both suitable freshwater breeding habitats and terrestrial landscapes through which adults can forage, mature and disperse. Molecular phylogenies indicate that the principal odonate lineages originated deep in geological time, while many family-level radiations were shaped by the fragmentation of Pangaea and Gondwana, continental isolation and subsequent long-distance dispersal. Tropical regions such as the Neotropics, Afrotropics, Oriental Region, Sundaland, Wallacea and New Guinea contain high lineage diversity and numerous range-restricted species. Oceanic islands generally support fewer species than comparable continental areas but frequently harbour evolutionarily distinctive endemic radiations, including Megalagrion in Hawaii and Nesobasis and Melanesobasis in the Pacific. By contrast, highly dispersive dragonflies such as Pantala flavescens maintain almost cosmopolitan distributions through continental and transoceanic migration. Climate change, habitat modification, pollution, river regulation and deforestation are now reorganizing odonate distributions. Poleward and elevational range shifts are increasingly recorded, particularly in Europe, while tropical forest-stream and montane specialists may experience range contraction. This review synthesizes the historical, ecological and evolutionary processes underlying global odonate biogeography and identifies priorities for improving geographical databases, tropical inventories, phylogeographic sampling and conservation planning.