Life history evolution of sea lamprey is predicted to reduce the effectiveness of pesticide control

Abstract

Pesticide resistance can evolve in pest populations as a strategy to increase reproduction and survival in the face of strong selective pressures imposed by chemical control. Invasive sea lamprey (Petromyzon marinus) in the Great Lakes have not evolved physiological resistance after 62 years of control with a chemical pesticide, 3-trifluoromethyl-4-nitrophenol (TFM), which is applied to tributaries to target the larval stage of the life cycle. However, it is unknown whether sea lamprey life histories could evolve in response to TFM. Sea lamprey larvae undergo metamorphosis within tributaries, transforming from filter feeders into parasites that emigrate to the lake where they prey on other fishes. We developed an eco-genetic model to evaluate if TFM treatment, which has an estimated mortality rate on larvae >90%, can cause evolution of the ages and lengths at metamorphosis and maturation. Our model predicts a rapid decrease in the size threshold at metamorphosis, resulting in an earlier age at outmigration from tributaries, and reducing the probability of larvae dying from pesticide treatment. The evolutionary response in metamorphosis increased with the number of tributaries treated each year. Conversely, there was little evolution of the size threshold at maturation. Importantly, we identify a cost of evolution to sea lamprey control whereby TFM-induced evolution of metamorphosis causes an increase in parasite abundance, which is the life stage destructive to fish populations. Mitigation measures are prudent to recognize and address the potential for reduced efficacy of TFM control and the resultant threat posed to fisheries resources in the Great Lakes.