We soon have the summer of 2009 behind us, and for me and my co-workers it has been an intense field season with damselflies (as usual). In early July, postdoctoral researcher Shawn Kuchta (upper left) made a field and collection trip up to central Sweden and the famous biogeographic limit Limes Norrlandicus, which is traditionally defined by the river Dalälven (which is not completely correct, however).
Many animal and plant species do either not move north of this sharp biogeographic boundary, or they do not move south (in the case of species with northern distributions). This sharp biogeographic barrier is of course extremely interesting in terms of constraints on the evolution of range limits: why do species not simply adapt and evolve traits so that they can expand their current ranges?
According to a much-discussed population genetic model developed by the evolutionary geneticists Mark Kirkpatrick and Nick Barton, range limits of species are constrained by migration and maladaptive gene flow from populations in the centre of a species range, which will "swamp" local adaptation of populations at range limits.
To evaluate this and other explanations for the range limit of the banded demoiselle (Calopteryx splendens, territorial male with wings spread out), Shawn Kuchta and I collected specimens of this species from Central Sweden, with the aim to analyze population genetic parameters (effective population sizes, migration rates etc) of these populations at the range limit, and compare these populations with populations in the centre of the species range. Another postdoc, Maren Wellenreuther, is also involved in this project.
We are also interested in the specific phenotypic traits that might limit range expansion in C. splendens. One such trait, which might be important in terms of thermoregulation, are the size of the dark melanized wing patches which cover c. a. 50 % of the wing area in this species. Compared to its close congeneric relative (C. virgo, lowest figure), C. splendens does not have as much melanin on its wings, and this interspecific difference might explain which C. virgo has a range that extends much further north, up to northernmost Fennoscandia.
The situation might change in the future, though, as studies in the UK on how dragonflies and damselflies respond to ongoing climate change have revealed that both species are expanding their range distributions northwards. Maren Wellenreuther, me and a finnish colleague (K. Tynkkynen) recently investigated the potential future consequences of such range expansions in terms of sexual isolation between these species by experimentally moving C. splendens female in to the allopatric zone of C. virgo. The results? Well, the study has now been accepted for publication and the article will appear in a future issue of the journal Evolution, so keep your eyes open!
During our trip north, Shawn and I also visited CAnMove-leader Professor Susanne Åkesson and her husband Professor Anders Hedenström at their cosy cottage in Östhammar, Uppland. Susanne and Anders took us on a floristic trip, and on the picture in the upper right corner, you see what an enthusiastic plant photographer Susanne is in her spare time! Being a naturalist myself, I think this is very important, to get new idéas for research and teaching.
For those of you who are interested in hearing more about our damselfly research projects, they have been covered quite extensively by Swedish media the last week. I was interviewed by the regional news programme "Sydnytt" about these damselflies and how they might respond to climate change, and you can see this programme here. You can also listen to a 20-minute long radio interview in the programme "Vetandets Värld", and this you can find here. Dragonflies and damselflies thus rock, and they are also excellent research organisms!