Dynamics and Structure of a Native Pieris Population in the Presence of a Non-Native, Toxic Larval Host Plant

ABSTRACT. There have been reports of butterflies that oviposit on non-native plants that do not support the development of the larvae, and the fitness cost of this behavior has been estimated in one such case. However, the long-term consequences of this fitness cost for the population dynamics of such butterflies have not been studied. Here we report changes over 40 years in a population of Pieris macdunnoughii (Lepidoptera, Pieridae; formerly Pieris napi macdunnoughii Remington), which oviposits on a lethal, non-native plant, Thlaspi arvense (Brassicaceae), as well as on suitable native hosts. Mark-release-recapture (MRR) studies conducted at four intervals over 40 years showed no significant trends across years in population structure or dynamics, including estimated population density and temporal changes in the number of newly emerged individuals within a year. The estimated daily residence rate differed between the sexes. However, male estimated daily residence rate showed no significant change acros...