Playing it safe at early life stages: Balancing energy allocations to
maximize fitness under seasonal pathogen dynamics
Abstract
Infections carry inherent tradeoffs in growing hosts due to the changing
demands for resource allocation among key processes (i.e., growth and
immunity). We implemented dynamic state variable models to determine
which changes in energy allocation maximize fitness in amphibians with
enzootic infections. By accounting for seasonality in our mechanistic
models, we identified critical windows that maximize individual growth
while limiting mortality under increased pathogen burden. The model
predicted that seasonality in pathogen exposure and foraging success
exacerbate growth-defense tradeoffs, resulting in delayed maturity and
lower survival when frogs hatched under sub-optimal environmental
conditions. Our simulations support well-known field patterns showing
that increased frog reproduction coincides with high resource
availability and low pathogen risk. Our models can be further
parameterized to understand the effect of emerging diseases under
predicted climate change across taxa, and to evaluate the best timing
for species re-introductions that would reduce fitness tradeoffs in the
population.