What the heck are you doing up there anyway?
I have been posting photos and clips of some of our adventures up here in Churchill, but I haven’t yet discussed in any detail what we’re actually doing. Today is a foggy day with not much prospect for collecting, so it seems like an opportune time to fill in the blanks.
As many readers will know, the primary area of research in my lab is the evolution of genome size — that is, the amount of DNA (including genes and noncoding DNA together) in different species. In animals, this ranges about 7,000-fold and is unrelated to organism complexity. It is, however, correlated with cell size and cell division and, depending on the group, with body size, metabolism, development, and other features.
In some groups, there appears to be a latitudinal pattern as well, with species in northern regions having larger genomes than temperate relatives. We’re exploring this question in various invertebrates and in plants.
But why Churchill? Several reasons. First, Churchill has an excellent (and soon to be significantly updated) research station. Second, it includes a range of environments, including both freshwater and marine, boreal and tundra, and lakes, streams, and ponds. Third, Churchill is one of two sites that is the focus of a “barcoding biotas” initiative to generate DNA barcodes of the entire fauna of a specific place (the other is Moorea in French Polynesia). This means that there are many expert taxonomists involved with whom we can collaborate, and also that we can perform identifications on many species that otherwise would be very difficult to work with. Fourth, this is where the Arctic ecology field course is held, which means we have an army of students out collecting samples. Finally, Paul Hebert and I co-authored a grant as part of the international polar year that provided funding for work in this area.
The basic procedure is to go to various sites, collect everything of interest, bring it back to the station, and process it. This means cataloguing, photographing, labelling, and storing the specimens (mostly in liquid nitrogen cryoshippers). Once we get back to the lab, we will perform genome size estimates using a flow cytometer. For spiders, I am making slides here and will do the genome sizes using image analysis densitometry.
We have five people here from our lab, each working on a different group but all collecting and sharing material from the taxa we’re working with. This includes insects, molluscs, crustaceans, spiders, leeches, soil invertebrates, and for the first time, plants. Actually, the latter are being collected for us by expert botanists who are working with the DNA barcoding group.
So far we have about 500 samples collected, and we have roughly 2 weeks left to get more. The shippers can hold 1,200 vials, and this doesn’t include plants, spiders, and most of the molluscs, which are not being frozen. We are also experimenting with some new field preservation methods which we hope will enable future studies like this in other places.
Lots of people are interested in genome size (usually framed in terms of “why is there so much junk DNA?”). One approach, definitely the most common, is to sit around and speculate. Another is to focus on a few genome sequences and look for conserved and/or transcribed elements. Our preference is to look at hundreds of species and see how diversity of genome size is actually distributed. Sometimes that means collecting in the cold wind and being eaten alive by mosquitoes. Next, we really should study tropical species…
Click here for the Churchill fieldwork posts.