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Functional–phylogenetic diversity in European and African freshwater systems

Human population growth and climate change severely threaten the integrity of freshwater systems globally, reducing their ability to provide ecosystem services and to support biodiversity. Freshwater systems contain the highest concentrations of biodiversity on Earth - they occupy less than 1% of the Earth's surface but harbour approximately 10% of all described species, of which at least 60% are aquatic insects. Yet almost nothing is known about the processes that led to this remarkable diversity and shaped the contemporary distributions of freshwater species. We previously found that thermal adaptations and differences in the ecology of species adapted to standing or running waters have shaped the distribution of insect species in temperate regions, but their broad-scale distribution is unknown and whether these traits are also important for the diversification of freshwater insects remains unclear. In our proposed project, we will use African and European dragonflies (Odonata) as a model system to understand the association of several potential thermal adaptations and proxies of dispersal ability with the diversification history and contemporary distribution of freshwater insects. Our framework combines a near-complete phylogeny of the dragonflies of the world with data on the distribution as well as functional and phylogenetic differences of approximately 900 African and European dragonfly species - the diversity of an entire insect order across a complete latitudinal gradient. This will allow us to address (1) whether the association of temperature with the variation in body colour (lightness) and body size of dragonfly species is of general (mechanistic) importance for their distribution, (2) the importance of adaptations in wing morphology that are associated with the stability of the species habitats for the diversification of and range size variation among Odonata lineages, and (3) whether the majority of Odonata lineages have retained their initial, tropical niche (phylogenetic niche conservatism). Our approach combines a wide spectrum of state-of-the-art methods, including computer-assisted digital image analysis, Anchored Hybrid Enrichment sequencing, structural equation models and null models of functional-phylogenetic diversity. These methods will allow unprecedented insights into the fundamental ecological and evolutionary processes that shaped the distributions of dragonflies and other freshwater organisms. With the results of this research we will be able to assess the sensitivity of dragonfly species to climate changes and their ability to disperse accordingly.