Long-term shifts in the communities of Odonata: Effect of chance or climate change?

Global climate change has been causing growing concern among conservationists for its strong implications on biodiversity alteration and loss at different levels of organization. Dragonflies and damselflies (order Odonata) occur in habitats threatened by global warming, thus they represent an ideal model organism to study the correlation patterns of climate change with taxonomic composition and the ecological functioning of communities. We carried out climate and diachronic faunistic analyses of Odonata community changes in three countries (Tunisia, Mauritania, Sweden) to test if the patterns uncovered for single assemblages as a response to local climate change may resist to the generalization across regions and latitudes. Clear climate warming occurred in the analysed regions during the last five decades. We found three main patterns of diachronic shifts in Odonata assemblage species composition based on correlative evidence: i) Generalists are likely advantaged from warming processes that cause the loss of specific habitats (i.e. temporary wetlands, cool lentic waters) and the formation of new or altered habitats suitable for pioneer species (i.e. warm and intermittent pools), whereas specialists are more likely to go toward local extinctions; ii) In Tunisia and Sweden new colonizers expanded northward from their southern distributions; iii) The Odonata communities inhabiting lentic waters are more prone to show species turnover than communities from standing waters. Our results provide new insights on the possible impact of climate change on Odonata fauna from large areas (i.e. countries) at different latitudes and represent an attempt of a generalization of the effects of climate change on Odonata range shifts and expansions. Despite that Odonata global assessment of conservation status has been completed, insufficient information is available to robustly assess all the main threats affecting their status, and extensive new field surveys are required to test if major changes in fauna composition have occurred during the last decades.