The Interplay Between Phenotypic Plasticity and Long‐Term Evolution in Shaping Life History Strategy in the Seed Beetle

ABSTRACT Phenotypic plasticity, the capacity of organisms to adjust to varying environments, could play various roles in the evolution of phenotype development. Host shift in phytophagous insects is a perfect setting for studying the interplay between plasticity of life history traits and the evolution of life history strategies on novel plant hosts. Utilizing the benefits of a long‐term laboratory evolution experiment, we used populations of seed beetle [ Acanthoscelides obtectus Say (Coleoptera: Chrysomelidae)] reared on three plant hosts [common bean ( Phaseolus vulgaris L.), chickpea ( Cicer arietinum L.) and mung bean ( Vigna radiata (L.) R Wilczek), all Fabaceae] for more than 150 generations. Reciprocal transplant experiments on inbred lines derived from these populations enabled the assessment of both long‐term changes in beetles' life history strategies and the alterations in their plastic capacity to adjust on diverse hosts. Our results demonstrate that seed beetle populations evolved distinct life history strategies, as well as different environmental sensitivity of life history traits. Beetles evolved on common beans showed stable pre‐adult development within seeds of all three plant hosts but high variation in their reproductive output. On the other hand, populations adapted to chickpeas became specialized for development on chickpeas and constantly allocated more resources to reproduction. Populations evolved on mung beans were associated with high plasticity and variance in both larval survival and fecundity on all plant hosts, indicating the ongoing process of adaptation. This work is discussed in the context of how phenotypic plasticity induced by host shift can shape life history strategies, providing insights into the evolutionary and ecological dynamics of adaptation.