While visiting Alaska last week, I had the pleasure of meeting Niels M. Schmidt.  He is a community ecologist (from Aarhus University, Denmark), who studies Arctic sytems and he is one of the key people behind the Zackenberg Research Station in Greenland.   He told me about one of his recently published papers (authored by Nicolai V. Meyling, Niels M. Schmidt, and Jørgen Eilenberg) titled “Occurrence and diversity of fungal entomopathogens in soils of low and high Arctic Greenland” (published in Polar Biology).

An ecological black box: the tundra

By definition (from Wikipedia) entomopathogenic fungi act as parasites of insects – these fungi can kill, or seriously disable insects.  I was amazed at this paper because I have never given much thought to fungal entomopathogens in the Arctic (despite knowing their prevalence in other ecosystems).    Could these fungi be ecologically important in Arctic?  I think Arctic community ecology has been seriously understudied, and we know little about what drives the relative abundance of species.  From an arthropod perspective, we know that some birds depend  on Arthropods for food (e.g. see Holmes 1966), and that flies are important nuisance pests to large mammals (e.g., Witter et al. 2012), but I would argue that most ecological interactions in the Arctic involving arthropods (and their relative importance) remain a mystery.   I could not even speculate on the role of fungal entomopathogens in the Arctic.  This is one of those feared ‘black boxes in ecology’:  probably there, possibly important, likely complex, but knowledge is seriously lacking. 

So along comes this paper: Meyling et al.  took soil samples from locations in the high and low Arctic (i.e., including Zackenberg, at about 74.5 degrees N), and they returned the samples to their laboratory in Denmark.   In their lab, the authors allowed live insects (using Lepidoptera [Pyralidae)] and Coleoptera [Tenebrionidae]) to be exposed to their samples, and they checked regularly for mortality: “...cadavers were rinsed in water, incubated in moist containers and monitored for the emergence of fungi“.  Any fungi that emerged from the (dead) host were identified.

The results: they identified five species of fungal entomopathogens (all in the division Ascomycota).  As the authors state in the start of their discussion “This study is the first to document fungal entomopathogens in soils from Greenland at both low and high Arctic sites. Furthermore, the use of in vivo isolation with living insect baits explicitly documented pathogenicity to these insects.”

Could this Arctic Weevil die from a fungal infection?

The black box has been opened:  indeed, fungal entomopathogens are in the high and low Arctic of Greenland, and are therefore likely in the high and low Arctic around the globe.  These fungi probably play a role in arthropod mortality in these systems, but this remains completely understudied.  As the authors point out, given the tight relationship between fungi and temperature, what effect could a changing climate have on these fungal entomopathogens?   This is potentially very important, as increased mortality of insects by fungi could trickle all the way up the food web…  I think we need to get more mycologists into the Arctic, and we must work to properly articulate high Arctic food webs with all the black boxes opened wide. 

References:

Holmes, R. (1966). Feeding Ecology of the Red-Backed Sandpiper (Calidris Alpina) in Arctic Alaska Ecology, 47 (1) DOI: 10.2307/1935742

Meyling, N., Schmidt, N., & Eilenberg, J. (2012). Occurrence and diversity of fungal entomopathogens in soils of low and high Arctic Greenland Polar Biology DOI: 10.1007/s00300-012-1183-6

Witter, L., Johnson, C., Croft, B., Gunn, A., & Gillingham, M. (2012). Behavioural trade-offs in response to external stimuli: time allocation of an Arctic ungulate during varying intensities of harassment by parasitic flies Journal of Animal Ecology, 81 (1), 284-295 DOI: 10.1111/j.1365-2656.2011.01905.x