Background: It has been proposed that animals and plants of the same species vary in their shape and size depending on where they live. Individuals living close to the cooler, northern range boundary might possess traits that increase their ability to deal with cooler temperatures, for example. However, under climate change the places where animals can live are expected to move as warmer temperatures expand the areas where climate is suitable for different species.
What we did: This study was part of my doctoral research and compared populations of three species between their range core and their range margins. The three species varied in the degree to which they were expanding their ranges under climate change: Pyrrhosoma nymphula (the large red damselfly) is not expanding in the UK and is found all the way to the northern coast of Scotland, Erythromma najas (the red-eyed damselfly) is found as far north as Cheshire and is not expanding its range margin, and Calopteryx splendens (the banded demoiselle) is found as far north as Northumbria and is expanding rapidly. The results showed that there was greater variation between the core and range margins in C. splendens, the species which was expanding, less difference in E. najas which is barely expanding, and almost no difference in P. nymphula, which has expanded its range as far as it can.
Importance: In order to respond to climate change, species will likely need to shift their geographical ranges. This involves being able to colonise new habitats which are currently outside of their range. The detection of variation in morphology such as in this study suggests that there might be traits that would facilitate this colonisation at range margins. If it could be demonstrated that the variation in morphology was evolutionary and not the result of phenotypic plasticity, then this would provide important evidence of adaptation to coping with climate change.
This is part of a series of short lay summaries that describe the technical publications I have authored. This paper, entitled “Variation in morphology between core and marginal populations of three British damselflies”, was published in the journal Aquatic Insects in 2009. You can find this paper online at the publisher, or on Figshare.
Image credit: Jean-Daniel Echenard, CC BY-ND 2.0, http://bit.ly/1AHimY5