Data from: No apparent cost of evolved immune response in Drosophila melanogaster

Maintenance and deployment of the immune system are costly and are hence
predicted to trade-off with other resource demanding traits, such as
reproduction. We subjected this long standing idea to test using
laboratory experimental evolution approach. In the present study,
replicate populations of Drosophila melanogaster were subjected to three
selection regimes – I (Infection with Pseudomonas entomophila), S
(Sham-infection with MgSO4) and U (Unhandled Control). After 30
generations of selection flies from the I-regime had evolved better
survivorship upon infection with P. entomophila compared to flies from U
and S regimes. However, contrary to expectations and previous reports, we
did not find any evidence of trade-offs between immunity and other
life-history related traits, such as longevity, fecundity, egg
hatchability or development time. After 45 generations of selection, the
selection was relaxed for a set of populations. Even after 15 generations,
the post-infection survivorship of populations under relaxed selection
regime did not decline. We speculate that either there is a negligible
cost to the evolved immune response or that trade-offs occur on traits
like reproductive behaviour or other immune mechanisms that we have not
investigated in this study. Our research suggests that at least under
certain conditions, life-history trade-offs might play little role in
maintaining variation in immunity.