When taxonomy makes the news, it’s usually because somebody’s just described a new species. But there’s more to taxonomic research than just discovering and describing new species. A new paper from our lab that’s been published on-line in early view is a nice example of some of the other aspects of taxonomy. In this paper, former Lyman student Christine Barrie and I revised the North American species of the genus Dicraeus, in the fly family Chloropidae. The last taxonomist to work on this genus in North America was chloropid fly expert Curt Sabrosky who published a paper on the North American Dicraeus in 1950. Now, while some people may think “1950? That’s ages ago! That’s before we had DNA figured out!”, it’s actually not THAT long ago for a taxonomic revision. Because there are so many more insects than there are insect taxonomists, we’re still trying to get by with identification keys written long before 1950 in many groups. But, even so, there have been enough changes in what we know about North American Dicraeus flies that it seemed like a good time for an update.
Dicraeus is a fairly distinctive genus of chloropid flies. Acalyptrate flies, the bigger group of families that includes Chloropidae, has a well-deserved reputation of being a huge pile of species that are cryptic and hard to identify, so “distinctive” in this group usually mean “slightly more easily recognizable than usual, based on looking at a couple of obvious characters that you may not actually need a key for once you get to know them”. There are Dicraeus species on most major continents and the larvae are herbivores, feeding on seeds of grasses. Because some of the grasses they like to eat are also cereal crops that humans like to eat, this makes Dicraeus an occasional pest. Don’t hold it against them; they were eating those grass seeds long before we were. Dicraeus is widespread in North America, especially in grassy prairies and meadows.
New species from North America
We described a new species from the western United States (Oregon, Idaho and Nevada). We named it Dicraeus curtisi, in honour of Curt Sabrosky. But that was only one of the taxonomic contributions in the paper. So in this post, I won’t describe the exciting expedition that led to the capture and discovery of this new species (because, well, all the specimens of the new species had been sitting in the insect collection at the Smithsonian Institution since the 1950s–1970s). Instead, I want to talk about some of the other contributions taxonomic papers make to documenting and organizing the diversity of life on earth, beyond the headline-friendly new species.
Old species in new places
We had a species from California, and a few sites in the Appalachian mountains, that we originally thought might be a second new species, but it was also very similar to a known European species. In the end, and after one of the reviewers of the manuscript commented on the similarity to the European species, we went back to our specimens, and to some more European specimens in museums, and decided the differences we’d seen weren’t big enough to justify a new species. Instead, we concluded this was the first North American record of a European species called Dicraeus vagans. So, not something new, but something old in a new and distant place.
In 1950, Sabrosky described an unusual species of Dicraeus from New Mexico that he called Dicraeus aberrans. It had a few obvious characters that clearly set it apart from other species in the genus (hence the species name). Christine thought it probably belonged somewhere else and, having worked on Central American chloropid flies for the past few years, I had an idea where it did belong. The traits that make aberrans aberrant for Dicraeus, are, as it turns out, the defining characters for the genus Notaulacella, which was previously known only from Central and South America. Transferring the species from Dicraeus to Notaulacella updates the classification, puts aberrans in the same group as its likely close relatives, and now means that Notaulacella occurs in North America as well as Central and South America. (I suspect Sabrosky would have reached this same conclusion eventually if he’d gone back to look at “Dicraeus aberrans” in later years, because one of the last papers he published included the description of several new species of Notaulacella from Panama)
New identification tools
The taxonomic changes I’ve outlined above mean that the last identification key to Dicraeus species is out of date. Sabrosky’s key didn’t include Dicraeus curtisi or Dicraeus vagans. It also didn’t include Dicraeus fennicus, another European species that we first recorded in North America a few years ago. On the other hand, his key did include Dicraeus aberrans in this genus. That means that anybody using the 1950 key to put a name on North American Dicraeus specimens might well get it wrong. So Christine spent time with all the North American species of Dicraeus on our updated list and produced a new and accurate key to the species.
Taxonomy under the radar
We rarely see headlines like “Scientists move species from one genus to another!” or “This simple key will change the way you identify flies!” But the reality is that it’s as much a part of the day-to-day work of taxonomy as the new species with the memorable names that grab media attention.
Barrie, C.L. & T.A. Wheeler. 2016. Revision of the Nearctic species of Dicraeus Loew (Diptera: Chloropidae). Canadian Entomologist doi: 10.4039/tce.2015.74