Data from: Experimental evolution of external immune defenses in the red flour beetle

The red flour beetle, Tribolium castaneum, secretes quinones that control
the microbial flora in the surrounding environment. These secretions act
as an external immune defence that provides protection against pathogens.
At high concentrations, however, these secretions are harmful to the host
itself, and selection may thus have optimized the level of expression
under natural conditions. Here, we show that the expression of external
immunity responded to selection during experimental evolution within a few
generations. At the same time, one component of internal immune defence
(phenoloxidase activity) was compromised in beetles selected for either
high or low external defences. Intriguingly, offspring protection against
a natural pathogen was reduced in flour obtained from beetle lines
selected for low amounts of secretions. Altogether, this suggests that
external and internal immune defences work together efficiently under
natural conditions, whereas every manipulation on the side of external
immune defence comes with costs to the internal immune defence.