By Terry Wheeler (originally posted at http://lymanmuseum.wordpress.com/2013/06/08/mastering-northern-flies-another-student-crosses-the-finish-line/)
I’ve written previously about our work on the flies from the Northern Biodiversity Program (the joys of collecting them, and the challenge of processing them). Three years, tons of travel, a mind-boggling number of hours in the lab, and more than a hundred thousand specimens into the project, we are starting to see the first wave of student projects wrapped up. And it’s a great feeling.
I’m delighted to report that my M.Sc. student Meagan Blair has joined the list of NBP grad students who have finished their thesis. Meagan’s thesis on spatial patterns and long-term change in northern scathophagid flies has been awarded a Pass. So, huge congratulations to Meagan for successfully steering an ambitious project on a large and difficult group of flies through to completion. Meagan was part of the first wave of students who joined the NBP in the first year of sampling in 2010 and she was one of the few students who was in the field from start to finish in both the 2010 and 2011 field seasons. That’s a lot of northern time! Meagan was also one of the stalwarts in the NBP “sorting room” in the Lyman Museum, cleaning, sorting and processing vast amounts of material before she could start in on the long hours of microscope time needed to identify her flies.
Scathophagids, also known by the unflattering common name of “dung flies” are probably most familiar to many people through the big fuzzy yellow dung fly Scathophaga stercoraria, which seems to be fond of sitting on fresh piles of cow manure (hence the name). They don’t eat the manure though; they eat the insects that feed on the manure. But that yellow dung fly is only one member of this morphologically and ecologically diverse family of flies, a family that has some very sleek, colourful and, yes, very attractive species. Many scathophagids are predators, others are scavengers and many feed on live plants. They are also interesting from the perspective of our NBP project because they are one of the few families of flies (and indeed one of the few families of insects) that becomes more diverse as you move north into the arctic.
Meagan found high species richness and high abundance of scathophagids at our NBP sampling sites from the northern edge of the boreal forest right up to the high arctic islands. And there is a significant change in the species found from site to site. Our late colleague Dick Vockeroth had a great interest in northern Scathophagidae and in 1958 Dick proposed what some of us informally call “Vockeroth’s Rule”. Dick hypothesized that tree line is a strong filter for scathophagid distributions, with species found either north of, or south of, tree line, but not both. Meagan’s work added several species to Vockeroth’s initial data set from his 1958 paper and in most cases confirmed that strong split at tree line (although what it is about tree line that actually limits the distribution of generalist scavengers and predators is another question).
Meagan’s work on documenting the current patterns of distribution of northern scathophagids will provide a valuable starting point for tracking change in distributions in the future as climate change causes the north to warm up. Will these flies track tree line north, or will a more complex set of interactions drive future patterns? Will the species that are dominant now remain dominant at the same sites into the future?
Meagan also reached back into time to compare our NBP specimens to specimens of the same species collected at the same sites in the early 1950′s. Her question was simple: “have northern flies themselves changed over the past half-century?”. The answer was “yes”, and in an interesting way. It’s not just the composition of the insect communities that are being affected by a changing north, there are evolutionary changes in the species themselves.
I won’t give away any more details of Meagan’s results here. A finished thesis is a very satisfying milestone along the academic journey, but it’s the published papers that matter most — those are the products that are read by the broader scientific community. We’re working on those now and you’ll be hearing more about Meagan’s results in the future.