Category Archives: Lab Work

What’s in a name? A previously unrecognized species of North American black fly from Baffin Island

Biting flies are a scourge at northern latitudes. Nearly every early explorer made reference to the tenacity and voracity of these tiny insects. Not surprisingly, biting flies reach their peak abundances in northern environments, with mosquito densities reaching a staggering 12.5 million individuals per hectare in the Hudson Bay Lowlands. Similarly, black fly larvae can reach densities of 1.2 million per square meter of stream substrate under optimal conditions. Given their abundances, and economic importance (through blood feeding and transmission of parasitic diseases), it is not surprising that biting flies are among the best known insects in North America.

Black flies are an especially well known as they were the subject of a monumental revision of the North American simuliid fauna by Adler et al. (2004).  In fact, no new North American species have been described since that book was published 9 years ago. Consequently, I was amazed to discover a hitherto unknown species near Iqaluit, NU on southern Baffin Island (Figure 1). It is a member of the circumpolar genus Stegopterna (Enderlein 1930) which includes 8 North American species.  However, only one species — St. emergens (Stone 1952) — is known to be distributed widely at northern latitudes.

This previously unknown species was overlooked during initial sorting and counting. However, subsequent DNA barcoding, revealed >10% sequence divergence between this species and Stegopterna emergens, the species it was initially mistaken for. This prompted a closer examination of the morphology of the Iqaluit population, which differed from St. emergens in 2 important ways. The first relates to the length of the pupal gill trunk (Figure 2). Pupal gills are often used for species level identification of black flies, and this difference was consistent in all specimens examined. However, a more striking and ecologically significant difference is that the Iqaluit species has mouthparts adapted for blood feeding. Distributional records reveal that, of the 9 black fly species previously recorded from the Canadian Arctic Archipelago, only 2 had biting mouthparts. The other species were arctic-adapted (i.e., non-bloodsucking) species that use nutrients from their larval stages to develop their eggs. Interestingly, the two biting species were both found only on southernmost Baffin Island.

The discovery of this previously unknown species of bloodsucking black fly raises important ecological and evolutionary questions. Historical records suggest that St. emergens was present on southern Baffin Island during the 1950s; however, contemporary collections yielded only this previously unrecognized one. Were historically collected specimens simply mistaken for this undescribed species, or was St. emergens supplanted by this new one on southern Baffin Island? Reexamination of historically collected material in the Canadian National Collection of Insects is needed to select from these alternative hypotheses. DNA barcoding may again prove useful should the diagnostic life stages (i.e., adult females, pupae) prove unavailable for study.

Another important question is why southern Baffin Island was the only region in the Canadian Arctic Archipelago to historically support bloodsucking black flies. The recent discovery of yet another blood feeding species on the Island (Schaefer 2011) further reinforces the suitability of conditions for this feeding habit. A more favorable climatic regime seems a likely explanation; however, further analyses are required.

Finally, this undescribed species was not present at any other Arctic or Boreal site sampled by the NBP. This raises the question of how widely distributed this species is. There have been no records of morphological or chromosomal differences between mainland and continental island populations, nor have any continental island endemic black flies have ever been found in North America. This makes it extremely unlikely that this new species is restricted to Baffin Island and suggests its distribution likely extends southward into northern Quebec or westward across Nunavut (albeit in potentially low numbers).

The process of assigning a name to this previously unrecognized species is not particularly straightforward. While it’s possible that the southern Baffin Island Stegopterna is an undescribed (i.e., is a new to science) species, we can’t rule out the possibility that it’s actually a Holarctic species that already carries a valid scientific name.  Unfortunately, Stegopterna species are notoriously difficult to identify morphologically, and there are at least 7 candidate names to consider from the northern Palearctic Region (all members of the St. trigonium species complex). We must now begin the process of poring over species descriptions to determine whether any of the available names could reasonably be applied to the southern Baffin Island population. But however this exercise turns out, it’s gratifying to know that there are still new and exciting discoveries to be made in northern Canada.

References

Adler, P.H., D.C. Currie and D.M. Wood. 2004. The Black Flies (Simuliidae) of North America. Cornell University Press. Ithaca, NY.

Schaefer, P. 2011. Update on the biting fly component (Diptera: Simuliidae, Culicidae and Tabanidae) of the Northern Biodiversity Program. Newsletter of the Biological Society of Canada 30: 41-49.

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Autumn Wrap-up!

From Chris Buddle:

Hard to believe that we are already into 2012!  Although there has been a distinct lack of blog entries, this does not indicate a lack of activity – quite the opposite!  After our return from successful field trip in August, we were busy all fall sorting specimens, working on identifications, and gearing up for conference season.

The project had very good representation at national and international conferences this past autumn. M.Sc. student Anna Solecki, post-doc Laura Timms, and Terry Wheeler attended the Entomological Society of America’s annual meeting, held this year in Reno, Nevada.  Congratulations to Anna – she won the President’s Prize in a poster competition in Systematics, Evolution and Biodiversity!

The NBP also had good representation at the Entomological Society of Canada’s annual meeting, held in Halifax, Nova Scotia.  Terry and Laura also attended that meeting, as did Katie Sim, Crystal Ernst, Sarah Loboda, Chris Buddle, and the Toronto crew – Patrick Schaefer, Ruben Cordero, and Doug Currie.   Everyone gave oral talks or posters, and it’s very exciting to see preliminary results from the project.   We are especially proud of Katie, as she won the poster competition – congratulations, Katie!  Here’s a photo of Katie with her poster.  Up next – we continue working on sorting, identifications, and some analyses and manuscripts are also being prepared.  Stay tuned…

Katie Sim with her first-place poster!

Back in the lab: sorting the samples

From Terry Wheeler, McGill University:

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Field work is the glamour event of projects like ours, but every good day of collecting generates a huge amount of work back at the lab. One of the lab rooms at McGill University’s Lyman Entomological Museum has been transformed into Sorting Headquarters for the NBP and that’s where most of our energy has been focused this fall. Almost every available inch of counter space in the room is lined with microscopes, lights, vials, sorting trays, and boxes of carefully arranged labels.

sorting tray

Tools of the trade

A study such as ours, with multiple collecting methods and sample sites, can collect enormous numbers of our target groups of insects and spiders, but those trap samples also come complete with many other insects, leaves, seeds, soil, dirt and more. That means that every one of the thousands of samples we brought back from the field must now be sorted at the microscope, to separate the spiders, flies, beetles, wasps and aquatic insects for our individual projects. Each sample is carefully divided up into separate vials for each of our target arthropod groups. It’s long and hard work – six weeks of field collecting means several months of sorting and processing samples – but this is our first chance to get a sense of how the patterns look across our sites. Even at this early stage we are starting to see differences between the Malaise traps from Moosonee (hundreds of horseflies), and pan traps from Kuglugtuk  (lots of specimens of an unidentified yellow fly that we don’t see in the eastern samples). The Lake Hazen samples are quick and easy to deal with (there’s not much diversity that far north), but a single Malaise trap from one of the boreal sites can take more than a full day for one of the students to sort through.

Tabanid tray

Horsefly soup: halfway through a sample

This sorting is just the first stage in processing our samples from Year 1. Once everything is sorted to order (spiders, flies, beetles and the rest), the second round begins. Each student will sort their own group of interest to finer levels of resolution – family, genus, species – as we move toward the species-level identifications necessary to see ecological patterns at fine scales. Many of the flies, beetles and wasps will be mounted on pins; the softer-bodied spiders and aquatic insects will stay in ethanol. Specimens preserved in ethanol will also be used for DNA barcoding, to unlock the genetic diversity of the northern arthropods.

Sarah at scope

Sarah tackles a sample

At our current pace, it looks like this first round of sorting will be wrapped up by the end of the fall term. Seeing that last bag of samples come out of the freezer will probably be a welcome Christmas gift for the Sorting Crew.