Abstract
Ecological immunology is an interdisciplinary field that helps elucidate interactions between the environment and immune response. The host species individuals experience have profound effects on immune response in many species of insects. However, this conclusion comes from studies of herbivorous insects even though species of mycophagous insects also inhabit many different host species. The goal of this study was to determine if fungal host species as well as individual, sex, body size, and host patch predict one aspect of immune function, phenoloxidase activity (PO). We sampled a metapopulation of Bolitotherus cornutus, a mycophagous beetle in southwestern Virginia. B. cornutus live on three species of fungus that differ in nutritional quality, social environment, and density. A filter paper phenoloxidase assay was used to quantify phenoloxidase activity. Overall, PO activity was significantly repeatable among individuals (0.57) in adult B. cornutus. While there was significant variance among individuals in PO activity, there were surprisingly no significant differences in PO activity among subpopulations, beetles living on different host species, or between the sexes; there was also no effect of body size. Our results suggest that other factors such as age, genotype, disease prevalence, or natal environment may be generating variance among individuals in PO activity.
Highlights
The goal of ecological immunology is to understand the evolutionary processes and ecological factors that affect immune function and infection in the wild [1, 2]
The goal of this study was to determine if individuals, sex, body size, patch, and host species predict one aspect of immune function, phenoloxidase activity, across a metapopulation of adult B. cornutus
We found no correlation between darkness of hemolymph in buffer and darkness of hemolymph in the phenoloxidase immunoassay (F1, 28 = 1.08, P = 0.31; Fig 1) suggesting that the differences in darkness among samples was due to the reaction between phenoloxidase activity (PO) activity and the L-DOPA and not due to darkening quinones in the defensive secretion
Summary
The goal of ecological immunology is to understand the evolutionary processes and ecological factors that affect immune function and infection in the wild [1, 2]. Sex, body size, geographic location, social environment, and even micro-environmental differences among populations are all ecological factors shown to influence immune response in insects [3,4,5,6,7,8]. The species and quality of the host plants of herbivorous insect can affect several components of immune response [9,10,11]. Ecological factors that are influenced by the host, such as density of the population, nutritional quality, or risk of predation have been shown to affect immune function in insects [12,13,14]. Emerging work on the effects of host species on immune response is largely centered on herbivorous insects [4, 7, 9, 15, 16]. Many families of mycophagous insects such as PLOS ONE | DOI:10.1371/journal.pone.0141167 October 29, 2015
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