Data from: Interactions between host sex and age of exposure modify the virulence-transmission trade-off

The patterns of immunity conferred by host sex or age represent two
sources of host heterogeneity that can potentially shape the evolutionary
trajectory of disease. With each host sex or age encountered, a pathogen’s
optimal exploitative strategy may change, leading to considerable
variation in expression of pathogen transmission and virulence. To date,
these host characteristics have been studied in the context of host
fitness alone, overlooking the effects of host sex and age on the
fundamental virulence-transmission trade-off faced by pathogens. Here we
explicitly address the interaction of these characteristics and find that
host sex and age at exposure to a pathogen affect age-specific patterns of
mortality and the balance between pathogen transmission and virulence.
When infecting age-structured male and female Daphnia magna with different
genotypes of Pasteuria ramosa, we found that infection increased mortality
rates across all age classes for females, whereas mortality only increased
in the earliest age class for males. Female hosts allowed a variety of
trade-offs between transmission and virulence to arise with each age and
pathogen genotype. In contrast, this variation was dampened in males, with
pathogens exhibiting declines in both virulence and transmission with
increasing host age. Our results suggest that differences in exploitation
potential of males and females to a pathogen can interact with host age to
allow different virulence strategies to coexist, and illustrate the
potential for these widespread sources of host heterogeneity to direct the
evolution of disease in natural populations.