Data from: Natural selection on gall size: variable contributions of individual host plants to population-wide patterns

Studies that provide estimates of the form and magnitude of selection on
herbivore traits at the level of individual plants in natural populations
represent a vital step in understanding the interaction of selection and
gene flow among host-affiliated insect populations when individual plants
equate to differing selective regimes. We analyzed phenotypic selection on
the trait gall size for a host-specific gall former at both the individual
host plant and population level (across host plants) in each of two years.
Linear and nonlinear selection and the fitness function relating gall size
to the probability of survivorship in the absence of natural enemies were
estimated for each level and year. Selection imposed by the host plant was
observed in 19 of the 22 subpopulations monitored. At the population
level, linear and nonlinear selection were evident each year. However,
population-level estimates masked the significant heterogeneity in the
form and direction of selection evident among plants each year.
Heterogeneity among gall-former subpopulations is emphasized by our
findings that selection varied from directional to stabilizing among
plants and the majority of selection gradients estimated for individual
plants did not fall within the 95% CIs of the population-level estimates.