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Dragonflies and Damselflies disperse in the heat

By Dave Armstrong - 29 Feb 2012 0:31:0 GMT
Dragonflies and Damselflies disperse in the heat

A dragonfly considers his options. Disperse or stay in his river? - Credit: © Christian Hof

Christian Hof and his co-authors have looked at how water habitats affect the dispersal ability of animals. In the Royal Society Journal, Biology Letters, "Habitat stability affects dispersal and the ability to track climate change," he and his international group of researchers studied every European member of the ancient Odonata order of insects (dragonflies and damselflies). A stream or flowing water habitat tends to last longer in the landscape than a lake or still water habitat, which fills in over time. The hypothesis to be tested here is whether dragonflies and damselflies have been able to adapt more quickly to recent climate change where the water is still or lentic.

Lotic species (in running water) would then be less able to disperse to new habitats because there have more time to equilibrate with their longer-term home ground. Still water species have a larger range than the lotic species and lower genetic diversity, while the recolonisation of Europe by still water species after the last glaciation was faster than for running water spp.

A bioclimatic envelope model (BEM) projects a potential range based on an animal's present distribution. It was used here to infer a species' climatic equilibrium. The dragonfly adult and larval distributions for 1988 and 2006 were first added to a European grid along with temperature and rainfall data. A potential distribution for 2006, based on the 1988 figures gave one of the most interesting gambles - would they agree with reality? In fact, many cases produced evidence of lotic over-predictions.

Lentic dragonflies indicated that they are closer to equilibrium with their climates in most of the results. Low stability of habitats selects animals with dispersal ability. But the availability of a habitat obviously affects whether a species can spread, such as when no freshwater is available. Pollution, land-cover change and predators could equally affect outcomes for dispersal. The authors in this study assume that both lotic and lentic habitats would be equally - affected.

Running water species cannot spread as efficiently as still water species because the still water species have to track environmental change more often and more carefully. The nature of lakes is that they last for a short time in evolutionary terms. What the multifarious dragonflies do show is that within their Odonata group, different dispersal abilities occurred within different habitat types. That means that all animal and plant groups might have varying abilities to survive global warming, meaning more detailed results, ideally on species and genera, would be useful.

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Topics: Insects