Iles David T.
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ArticleShifting vital rate correlations alter predicted population responses to increasingly variable environments(University of Chicago Press, 2019-01-07) Iles, David T. ; Rockwell, Robert F. ; Koons, David N.Time series of vital rates are often used to construct “environment-blind” stochastic population projections and calculate the elasticity of population growth to increased temporal variance in vital rates. Here, we show that the utility of this widely used demographic tool is greatly limited by shifts in vital rate correlations that occur as environmental drivers become increasingly variable. The direction and magnitude of these shifts are unpredictable without environmentally explicit models. Shifting vital rate correlations had the largest fitness effects on life histories with short to medium generation times, potentially hampering comparative analyses based on elasticities to vital rate variance for a wide range of species. Shifts in vital rate correlations are likely ubiquitous in increasingly variable environments, and further research should empirically evaluate the life histories for which detailed mechanistic relationships between vital rates and environmental drivers are required for making reliable predictions versus those for which summarized demographic data are sufficient.
ArticleEctoparasite burden influences the denning behavior of a small desert carnivore(Ecological Society of America, 2019-05-17) Kluever, Bryan M. ; Iles, David T. ; Gese, Eric M.Quantifying the impacts of parasitism on a host can be arduous and is generally understudied for ectoparasites, with known works being either laboratory‐focused, correlational‐based, or only focusing on a few species and spatial extents. Many mammalian species have evolved the modality of denning behavior, a lifestyle that can lead to higher ectoparasite burden, and it has been posited that animals may alter their denning behavior in an attempt to reduce exposure to ectoparasites. We conducted a test of the ectoparasite release hypothesis for kit foxes (Vulpes macrotis) and fleas in the Great Basin Desert of the western United States, a hypothesis that has remained relatively untested for over half a century. We experimentally administered a flea reduction treatment to a subset of kit foxes. We then measured and compared the number of unique den usages and residency time across treatment and control foxes (no flea reduction treatment) while accounting for other factors known to influence denning behavior. Foxes treated with the flea medication reduced the number of unique dens and increased their residency times at dens. All kit foxes continued to use multiple dens on the landscape, suggesting several factors in addition to flea burden influence denning behavior. Our results confirm the long‐dormant ectoparasite release hypothesis and suggest ectoparasites may shape the behavior of burrowing vertebrates to a greater extent than previously recognized.