Conservation strategies for threatened species frequently include habitat restoration, but the success of such recovery efforts has been mixed. When the target is an insect herbivore, restoration efforts have traditionally attempted to increase the abundance of its host plant, but this actions' impact on host plant quality has largely been ignored. Here, we test the impact of two forms of habitat restoration, tree removal and stream damming, on the physical and chemical properties of a wetland sedge and on the adult traits of its larval consumer, a wetland butterfly. Tree removal altered plant physical and chemical traits in a manner largely consistent with reduced host plant quality. Females emerging from these plots had fewer mature oocytes in their ovaries upon emergence, suggesting that tree removal has a negative effect on butterfly potential fecundity. Stream damming did not affect plant traits but forewing length increased more steeply with body mass for females from these plots, indicating that small females from dammed plots have a relatively higher wing loading ratio that likely increases the energetic cost of flight. This idea was supported by results from our subsequent capture–mark–recapture study, where both female and male butterflies were less likely to emigrate from dammed plots. Male dispersal was also affected by restoration, but individual body mass rather than wing allometry mediated this effect. Our results highlight the need to consider restoration's impact on host plant quality, in addition to other aspects of habitat quality, when undertaking habitat restoration for threatened herbivores.
