Monitoring Ecological Change with Northern Beetles

Entomology Today April 28, 2015 Leave a Comment

A northern beetle: Carabus vietinghoffi. Photo by Henri Goulet.

By Chris Buddle

Beetles are among the most adored of all insects. They exemplify diversity, perform virtually all ecological functions, and they are beautiful. They capture our imagination and wonder. Beetles are also found across the continent, including the far northern tundra in Canada. Some people find this surprising, but beetles — and other arthropods, from tiny mites to big, hairy wolf spiders — do occur far above the tree line. Despite a frozen landscape for much of the year, the tundra is alive with insects in the short summer.

Chris Buddle

Dr. Crystal Ernst and I just recently published a paper about these northern beetles. We were part of a massive project that spanned much of northern Canada, from Labrador to the Yukon, and from James Bay to the top of Ellesmere Island at 81°N latitude. In this work, we wanted to understand what beetle species were found where, and whether their ecological roles also varied across this large part of Canada. For two summers, we collected beetles at 12 different sites: four sites were in the northern boreal forest, four in the sub-Arctic region (a biome that essentially runs from the treeline to the harsher high Arctic biome), and four sites on the Arctic islands.

A map showing the collection sites and the major ecoclimatic zones of Canada. We sampled in the northern Boreal, sub-Arctic, and Arctic over a two-year period.

Beetles, along with other ground-dwelling insects and spiders, were collected using pitfall traps and pan traps. These are essentially “bowls” stuck into the tundra, and when insects happen upon them, they fall in and get killed by a preservative in the bottom of the traps, as you can see in the following video:

After countless hours in the lab sorting and doing identifications, and after much consulting with other taxonomic experts, Crystal tallied up more than 9,000 beetles represented by almost 500 species and 18 different functional groups. As we expected, fewer beetles species were found at our most northern sites, and the most species were collected from sites in the north-boreal region. The species richness followed the rather well-known pattern of decreased species richness towards the poles. Our work contributed significantly to what we know about beetles from the top half of North America. Our database is online and accessible so others can see what species are found where, and our work documented new records for Canadian territories and provinces. We recorded 15 species in some of these vast regions for the very first time.

Crystal Ernst installing pitfall traps on the tundra.

The diversity of functions performed by beetles also varied along our latitudinal gradient. Although quite a number of functions were found in the south, our more northern sites had a very high proportion of carnivores. This is curious and somewhat unexpected. Why would so many predatory beetles live on the Arctic islands, and what about the other functions? Some of this may be related to other aspects of the system. If there is lower plant diversity in the north, this may explain why there are fewer herbivores, or perhaps predators are just better adapted to harsher conditions in the north.

A selection of Arctic beetles. Photos by Henri Goulet.

We discovered that temperature was one of the main environmental factors that helped explain our patterns in species richness and functional diversity. Insects are highly sensitive to temperature, so perhaps it’s not surprising that this factor is important. However, this does lead to the question of climate change. If temperatures become more variable or higher in the North, it may have a big effect on the tundra-dwelling beetles. This in turn could have implications for how these northern systems work. If beetles end up emerging at a different time of year because of climate change, their effects on prey populations could also change, and this potential “de-coupling” within an ecosystem is worrisome.

To best understand climate change and its effect on ecosystems, we need solid ecological monitoring programs that include critters like beetles. These insects can really help inform us about the effects of environmental change. They are sensitive to their environments and certainly have rapid life cycles and respond quickly to change. However, to detect change we need robust and quantitative data from a range of sites, across a suite of different ecosystems, and this is what we see as a key deliverable from our research. Future studies can build upon what we have done at the same sites in future years to better understand whether communities of beetles are changing. Tracking change requires key benchmarks, and our six-legged friends can help us with this.

Chris Buddle is an associate professor at McGill University, where he teaches about environmental biology and has a research program focused on northern insects and spiders. You can follow Chris on Twitter at @CMBuddle and visit his blog at www.arthropodecology.com.

Crystal Ernst is a postdoctoral research scholar at the Earth to Oceans Research Group, Simon Fraser University in British Columbia, Canada. You can follow her on Twitter at @GeekInQuestion and visit her website at www.crystalernst.com.