Many people see the arctic as a pretty barren place, with not much biological diversity. In fact, one of the most well-known patterns in ecology — the latitudinal diversity gradient — incorporates that idea. As you leave the tropics and head north, species diversity drops. Apparently, the flies didn’t get the memo. There are lots of flies in the north. Lots. In fact, some groups of flies are so successful at living in the north that they defy the latitudinal diversity gradient and are much more diverse in the far north than in warm temperate or tropical regions. Lyman M.Sc. student Sabrina Rochefort and I have just published a new paper on one of those families, the skipper flies, or Piophilidae.
In our research with the Northern Biodiversity Program, we collected arthropods at 12 sites across northern Canada from treeline to the northern tip of Ellesmere Island. And flies were the most abundant group of arthropods at those sites, especially in the north. So far we’ve processed more than 100,000 flies representing a few hundred species of flies from our sites. And early on in the project, Sabrina, who was an undergrad student at the time, adopted the little family Piophilidae. Nobody had really worked on the family in North America since Frank McAlpine, another Canadian fly worker, published a taxonomic overview of the family in the 1970s, so they were ripe for some new attention.
Sabrina’s first task was to identify the species we had from our northern collections. Fortunately, most of the specimens that McAlpine had studied, including northern material collected a half-century ago by the Northern Insect Survey, were two hours up the road at the Canadian National Collection of Insects in Ottawa. Sabrina sorted out the material, putting names on the known species, and flagging the weird things for a closer look. As often happens in taxonomy, that closer look turned up some new discoveries.
The first discovery was a fly that Sabrina recognized early on as a new species. The first specimens she recognized were collected at Kugluktuk, Nunavut, a small hamlet near the mouth of the Coppermine River, where NBP grad student Crystal Ernst spent the summer collecting in 2010. Soon, we started finding more specimens of this new species from our other northern sites, and in some older museum samples from the Rocky Mountains in Alberta and British Columbia, and even a few specimens from northern Sweden that former Lyman grad student Jade Savage collected more than a decade ago. We now know this new species is widespread in northern Canada and also in Sweden, but the first locality was special enough that Sabrina decided to call the new species Parapiophila kugluktuk.
But a species doesn’t have to be new to be a surprise. Sabrina also identified a couple of new North American records of species that were previously known only from Europe, or from Europe and Greenland. This is a fairly common occurrence in arctic insects, as well as other arctic species, where the same species is found in both North America and Eurasia. On the other hand, two of the previously known species looked a little too similar, so we looked at as many specimens as we could, extracted and sequenced DNA barcodes, and concluded that, even though they are known under two names, we couldn’t justify treating them as distinct species, so we combined the two under a single name. One new species added, one old species synonymized – a taxonomic trade-off that happens a lot in this sort of work.
We also looked at the distribution of the species from south to north. There was a little surprise here too. Very few species or specimens were collected at boreal forest sites near treeline (in these sites many other fly families were still very diverse in our samples). On the other hand, 16 of the 17 piophilid species identified were collected at low arctic tundra sites on the Canadian mainland. Even on the far northern arctic islands, we collected only five species, but hundreds of specimens. Piophilids seem to thrive on the tundra. They’re tough little flies.
Shiny little survivors.