A recent tweet by a Carleton University PhD graduate, Dr. Jenn Provencher, said something to the effect that Indigenous people are willing to share traditional knowledge, if they think you are willing to learn. She was live tweeting at the Annual General Meeting of the Association of Canadian Universities for Northern Studies (ACUNS) and was sending to twitter a paraphrase of one of the keynote’s, Sen Murray Sinclair’s, inspirational points. So true! For our work on avian cholera in the Arctic, Inuit participation, guidance, and direction was of paramount importance. Collectively, it steered another Carleton PhD candidate, now Dr. Sam Iverson, to many eider duck breeding colonies on islands along the shores of Hudson Strait.
Parasites are aggregated, but how are contaminants distributed among the hosts? And why does it matter?
A recent paper by André Morrill, Jenn Provencher and myself recently asked and partially answered these questions. We reviewed the literature over 23 years to show that interest in the combined effects of contaminants and parasites on host health was increasing exponentially.
In actual fact, the studies were of three main types: one type was the extent to which parasites bio-magnify the contaminants of their hosts. This effect of such parasites on contaminant burdens in hosts may well have host health effects. Much to build on there! Why parasites (typically intestinal helminthes are studied) even do such a thing is fascinating?
There has been some intriguing research on the potential links between peanut allergies and antibiotic use early in life. Two labs in the United States appear foremost in this research area. One is at the University of Chicago and the other is at New York University. The work by Dr. Nagler and her team have shown that the removal of Clostridia bacteria might be responsible for sensitization to peanut allergen, in a mouse model. Mice models are useful because researchers can document clinical signs of allergy. But the interesting result was that the presence of the Clostridia bacteria appears responsible for gut inflammation that reduces the rate at which the peanut allergen is absorbed into the blood. Other research by Dr. Blaser (Missing microbes fame) at NYU is suggesting that missing microbes may be important in several health issues (rogue bacteria, food allergies). These are exciting directions for future research.
I was walking on the weekend when I came across this little amphibian. Many of you will have recognized this as a red eft the terrestrial stage of a salamander species common to this neck of the woods (or at least to ponds therein).
Note the following blog was written before I knew about the research highlighted in another blog: see "Did rats spread the black death?" Anyway, with that caveat, you can still read my wiki thoughts on the plague, starting now…
I recently saw a serial called Spiral on Netflicks (an engaging crime drama set in France) wherein one of the episodes a judge intoned something to the effect that the lesser of two evils was itself still quite an evil. Loosely translated the statement was “it’s cholera or it’s the plague”. It got me doing a sort of imagining what it must have been like to live during one of the outbreaks of bubonic plague in Europe, while at the same time tasking by queuing up the next episode of Spiral (this episode featuring a cop with a drug addiction). To help with the former, I turned to the digital milieu of Wikipedia.
I am going to go out on a limb and suggest that many, if not most, parasite species exploit several to many hosts species, for a given stage of their (i.e., the parasite’s) life cycle. The question of why such parasite species are catholic in their diet (I say diet because, really, the host is a source of food for the parasite’s growth, development and/or reproduction), remains largely an open question. One interesting nuance is that a given species of parasite often has differential fitness or success on different host species (here, we are controlling for time and location of collection of both the parasite and host species). A troubling issue is why the parasite has not evolved discrimination, another is why some host species are better hosts than others, a third is whether there are alleles coding for host species use that are in competition with one another. There are several other questions such as how important is host species relative frequency across space and time in determining whether it is a principal species exploited by the parasite and what, if any, trade-offs exist in using one species over another. We are just starting to get answers to these questions. Sometimes, nature pitches real oddities at you. Consider, two damselfly species where one is totally susceptible to a mite ectoparasite and the other is totally susceptible. If you want to getthe scoop, visit Julia Mlynarek’s blog: Julia was one of my PhD students here art Carleton University.
Recently, one of my former students, André Morrill, got a paper accepted in the Canadian Journal of Zoology as first author on explaining covariation between ectoparasitic mites and endoparasitic eugregarine protozoans of Lestes damselflies. Many previous researchers have addressed the extent to which either mites or gregarines are associated with reduction in fitness of their insect hosts. In these singular studies examining just one parasite taxa or species, there is the implicit assumption that any patterns discovered are attributable to the parasite under study, and not some other parasites species that has not been monitored or enumerated. André’s work shows that there are reasons to expect these parasites might covary. The link to the paper for those interested can be found here. André also has recently senior authored a paper in International Journal of Parasitology concerning how a Poisson distribution of random parasite encounter and a normal distribution of host condition can combine through a few simple rules of condition-linked immunity to produce the oft-seen and oft-cited negative binomial distribution of parasites on hosts. This research suggests that we need not invoke environmental heterogeneity in parasite infective stages to explain aggregated distributions on hosts; such occurrences, however, will make parasite distributions even more aggregated. Read the abstract of that paper here.
Recently, Sam Iverson got a lot of press on one of his PhD papers coming from the lab. In brief, polar bears are visiting seabird colonies and eating eggs more and more as sea ice is disappearing. The strength of Sam’s analysis lies in his expanding the geographical extent of what previously was thought to be anecdotal observations. For the full story, click here.
Wildlife agencies in Canada and the U.S face a predicament. Migratory Canada geese, which fly to arctic regions every summer to breed, require conservation protection. However, resident Canada geese, which breed in southern Canada and the U.S., often within city limits, are experiencing seemingly out of control population growth. These migratory and resident populations co-mingle during the non-breeding season. In Ontario, and across North America, hunting regulations have been modified by wildlife services to permit hunting before (early September) and after (late February) the traditional waterfowl hunting period. The idea has been that by allowing hunting during ‘special’ seasons, resident Canada geese would be targeted for harvest, whereas migrant Canada geese would be largely spared. In a recently published study in the Journal of Wildlife Management, Sam Iverson (a PhD student at Carleton) and his co-authors evaluated how effective this approach has been. We found that while survival rates of resident population breeding adults have been reduced in association with changes to hunting regulations, a disproportionate amount of the harvest is now falling on reproductively immature Canada geese and other geese unaffiliated with Ontario’s local breeding population. Total Canada goose harvest has more than doubled in the province since the 1990s; however, the increase in harvest has not kept pace with population growth. Most of the additional harvest is occurring during the special early season. Although early season hunting has proven to be a good strategy for minimizing impact on migrant Canada geese it has been less effective than desired for controlling resident Canada goose population growth because most of the harvest pressure has fallen on individuals of low reproductive value.
Paper: Iverson, S. A., Reed, E. T., Hughes, R. J. and Forbes, M. R. (2013), Age and breeding stage-related variation in the survival and harvest of temperate-breeding Canada geese in Ontario. The Journal of Wildlife Management. doi: 10.1002/jwmg.636
I would venture to guess many of us have witnessed a cat with a dying songbird. Nature’s red domestic. But have we stopped long enough to think about the extent to which our house pets are responsible for declines of songbird populations? What other human activities reduce populations of songbirds and other birds from our (sub)urban and natural landscapes and our agro-ecosystems? There are many such direct sources of mortality including pesticide ingestion, destruction of nest or nesting hens by farm and forestry machinery, hunting the birds themselves, collisions with automobiles, buildings and cell phone towers or windmills and slicking from oil spills. But what are their single and combined impacts? Paul Smith, a research scientist recently hired at the National Widlife Research Centre, has recently been a guest editor, along with Travis Longcore, of an important series of contributed papers on this theme, in the journal Avian Conservation and Ecology.
Professor & student