How many generations does it take for phytophages to colonize invasive plants? Mathematical modeling predictions

Abstract

Native phytophagous insects are often not adapted to novel chemistry of invasive plants, but over time they begin to adapt and feed on them. We simulated the spread of a mutant allele that enables phytophages to feed on invasive plant as efectively as on native plant. Tis simulation involved two insect populations associated with native and invasive plant species, with gene fow between them. Fitness was assigned using the Ricker function, which incorporated plant abundance, insect feeding efciency, and competition between genotypes. For the mutation to become fxed in fewer than one hundred generations, invasive plant must be at least as abundant as native one. Te efect of invasive plant relative abundance is larger than that of ftness diferences in feeding efciency of wild type phytophages between plants. Te spread of this allele under natural selection is faster if it has come from standing genetic variation, rather than newly arisen mutation, or, in the latter case, if there is assortative mating.

Keywords

• mathematical model
• population dynamics
• biological invasions
• insect phytophages