Meeting Abstract
Tradeoffs among energy allocation to growth, reproduction, and immune function can impact fitness. While both sexes allocate energy to reproduction and immune function, tradeoffs between these functions may be structured in a sex-specific fashion. Specifically, the energetic costs of immunity can differ temporally between the sexes due to behavioral and energetic differences, but this sex-biased energy allocation is not understood for most species. We studied the relationships between ectoparasite (mite) load, organ mass, fat body mass, and total body size in the Panamanian slender anole. We hypothesized that the quantity of mites should increase with the body size and that both sexes would allocate energy away from immune function towards energetic investment in reproductive tissues. We found that larger lizards did have more mites in both sexes. However, only males with greater fat body mass had higher ectoparasite loads. In contrast, the number of mites increases with the size of the ovaries, but not with the size of the testes. We suggest that the number of mites reflected the amount of endogenous fat storage in males, which implies that abundant energetic stores can be channeled in to the immune response to suppress mite infection. In contrast, females that had greater energy invested in reproductive tissues had correspondingly greater mite infections, which implies that investment into reproduction trades off with investment into immune function. Our results suggest that ectoparasites affect energy allocation in ways that are likely to generate sex-specific patterns of fitness in wild ectotherms.
