Much has been written about DNA barcoding, ranging from evangelically PRO to fundamentalist CON. I must confess that my early reactions were negative, not because of the inherent science involved, but because of some unfortunate marketing tactics in the early days of the movement. As a taxonomist, one gets a bit weary of being told we can all be replaced by an, as yet, non-existent tricorder that will identify any species instantly and accurately in the field. DNA barcoding is a tool – nothing more, nothing less – and a tool that I have recently added to my toolbox of Ways to Discover Biodiversity. And ironically, it has given me the opportunity to spend a lot of time on the microscope looking at specimens.
I am involved in a project, spearheaded by the Biodiversity Institute of Ontario and the Polar Barcode of Life, on barcoding the biota of a single subarctic site – Churchill, Manitoba, on the shore of Hudson Bay. My role, along with some of the other people in my lab (Stéphanie Boucher, Chris Borkent, Anna Solecki) and several colleagues in Canada and around the world, is to document the Diptera species diversity at the site by comparing the results of DNA barcode identifications with species limits based on morphology, as determined by taxonomic specialists.
I was very keen to take on the Chloropidae (in collaboration with Anna Solecki, as well as Jinjing Wang and Ding Yang from China) because initial results suggested very high species diversity at Churchill. In the end, there has been a pleasing agreement between DNA barcodes and morphology in the nearly 50 species of chloropids in the collections (more on the areas of disagreement, as well as several new species, in some coming publications).
I also agreed to make an effort, with no guarantee of completeness, to do some initial sorting in the other families of acalyptrate flies that had not been spoken for by other collaborators. We have taxonomic expertise and experience in the lab on some of these families, but others are more of a challenge, for a variety of reasons. Fortunately, our reference collection is a good one. A good insect collection provides verification and taxonomic resolution that time spent with keys alone simply can’t replace.
Some acalyptrate families are species-rich at Churchill (Sciomyzidae, Ephydridae, Sphaeroceridae, Agromyzidae, Piophilidae), while several others were represented by only one or a few species. As with the Chloropidae, there will be greater detail on the diversity in these families, the recognition of some new species, and the fit between DNA barcodes and morphology, in some publications now in preparation. Stay tuned . . .
Beyond the goal to help document our own Canadian Diptera diversity, our involvement in the Diptera of Churchill project has another significant benefit – our ongoing research in the Northern Biodiversity Program is yielding extremely rich collections of Diptera from across Canada’s north from treeline to the high arctic, and from Labrador to the Yukon. Having a reference library of barcoded arctic species, confirmed by Diptera specialists, will give us a valuable baseline from which to describe Diptera diversity across the north on a much larger spatial scale.
In the process of sorting these several hundred acalyptrate specimens, I have had a few assorted realizations:
1. I dislike sorting specimens in ethanol. I realize that some of my colleagues swear by fluid-preserved material, but I find it SO much more convenient to work from dried, mounted specimens (not to mention the long-term preservation issues). Time constraints have conspired against me in this instance – chemically drying, mounting and labelling several hundred specimens takes time, so I resolved to try it in ethanol. My conclusion – I still dislike sorting specimens in ethanol.
2. Our knowledge of our own Diptera diversity is fragmentary compared to regions such as western Europe. I am envious of my European colleagues who can, often, not only put names on many acalyptrate species, but access information on the occurrence of species X in region Y of country Z. Compare this to Canada, where we have estimated that well over half of our Diptera fauna remains undescribed or unrecorded, and our knowledge of their actual geographic distribution, phylogenetic relationships and natural history is, well, often abysmal.
3. The Manual of Nearctic Diptera, rightfully regarded as a model of how to write an identification manual, is great (mostly) in getting a fly to genus (although some of the chapters are now, more than 20 years on, in need of updates), but things can break down at the species level. In many cases, identification to species is virtually impossible because keys either have never been written, or date from the 1920s or earlier, or are incomplete. Admittedly, there are only so many of us to get the work done, and we are stretched very thin. I, myself, have spent more time in recent years documenting and describing the Central American chloropid fauna while our own species remain unknown and unidentifiable. It is a source of frustration (and embarrassment!) that I still cannot put names on some local common chloropid species. I obviously need to shift my priorities, and recruit more good students
Clearly, we, as a community, have much to do to make the Nearctic Diptera fauna identifiable and accessible. There are many tools we can use as we move forward and there has never been a better time for taxonomists and ecologists to take advantage of the power of this array of techniques – high resolution photography for morphological characters, efficient molecular techniques, new approaches in data management and publication, powerful mapping tools, web-based methods for collaboration – to get the job done.