January American Naturalist highlights

"What makes a host profitable" parasites balance host nutritive resources against immunity"
Pierre Bize (Glasgow University), Caroline Jeanneret (University of Lausanne), Aurélie Klopfenstein (University of Lausanne), and Alexandre Roulin (University of Lausanne)

Is host immunity enough to explain parasite success" Scientists based at the Universities of Glasgow, Scotland, and Lausanne, Switzerland, have shown that parasites balance host nutritive resources against immunity. Pierre Bize, Caroline Jeanneret, Aurélie Klopfenstein, and Alexandre Roulin conducted research in Switzerland in a free-living colonial bird whose nestlings are heavily infested by blood sucking ectoparasites. They observed that ectoparasites achieved highest survival on nestlings in intermediate condition. By manipulating nestling food resources and cutaneous immune responses, they then demonstrated that ectoparasite blood meal size, and in turn survival, is shaped positively by host nutritive resources and negatively by host immunity. “The important point of our study,” states Pierre Bize, the lead author, “is that although parasites have a poor survival when feeding on hosts in prime conditions, because these hosts can mount a potent immune response, the reverse is not true. Indeed, parasites also have a reduced survival when feeding on hosts in poor conditions and with a low immune response, which points out that immunity is not the only factor accounting for parasite fitness.” Alexandre Roulin adds, “The appraisal of what factors make a host profitable are vital for our understanding of host-parasite interactions, and in turn to the implement of well-designed parasite control programmes.”

"Linking traits to energetics and population dynamics to predict lizard ranges in changing environments"
Lauren B. Buckley (Santa Fe Institute)

Does biology matter when predicting how animals will respond to climate change"

Most predictions of how animals will move in changing climates rely on statistically relating an animal’s current location to environmental conditions. This approach ignores potentially important aspects of an animal’s biology including size, physiology, and behavior. Lauren Buckley, an ecologist at the Santa Fe Institute, has developed a bottom-up approach that predicts distributions directly from an animal’s traits and environmental conditions by modeling the energy use of individuals and populations. Research forthcoming in The American Naturalist applies the model to five populations of a widespread North American lizard, Sceloporus undulatus, to examine whether geographic variation in traits influences range predictions. Buckley finds that lizards from the five populations are suited to live in different areas and are predicted to respond differently to a climate warming of 3°C, contrasting the predictions of statistical models. While all populations are predicted to shift northward in response to climate warming, the extent of the predicted northward shift depends on the lizard’s traits.