Data from: Eco-evolutionary theory and insect outbreaks

Eco-evolutionary theory argues that population cycles in consumer-resource
interactions are partly driven by natural selection, such that changes in
densities and changes in trait values are mutually reinforcing. Evidence
that the theory explains cycles in nature, however, is almost nonexistent.
Experimental tests of model assumptions are logistically impractical for
most organisms, while for others, evidence that population cycles occur in
nature is lacking. For insect baculoviruses in contrast, tests of model
assumptions are straightforward, and there is strong evidence that
baculoviruses help drive population cycles in many insects, including the
gypsy moth that we study here. We therefore used field experiments with
the gypsy moth baculovirus to test two key assumptions of eco-evolutionary
models of host-pathogen population cycles: that reduced host infection
risk is heritable and that it is costly. Our experiments confirm both
assumptions, and inserting parameters estimated from our data into
eco-evolutionary insect-outbreak models gives cycles closely resembling
gypsy moth outbreak cycles in North America, whereas standard models
predict unrealistic stable equilibria. Our work shows that
eco-evolutionary models are useful for explaining outbreaks of forest
insect defoliators, while widespread observations of intense selection on
defoliators in nature and of heritable and costly resistance in
defoliators in the lab together suggest that eco-evolutionary dynamics may
play a general role in defoliator outbreaks.