Species distribution models for natural enemies of monarch butterfly (Danaus plexippus) larvae and pupae: distribution patterns and implications for conservation

Abstract

Prey populations can be strongly influenced by predators and parasitoids, and migratory prey whose distributions vary geographically throughout their breeding seasons encounter different combinations of predators and parasitoids throughout their range. North American monarch butterflies (Danaus plexippus) are susceptible to a wide variety of natural enemies, but the distribution of these natural enemies has not been quantified. We developed ecological niche models using environmental data to identify areas with suitable abiotic conditions for eight known natural enemies of monarchs, including six predators: Arilus cristatus, Harmonia axyridis, Monomorium minimum, Podisus maculiventris, Polistes spp., and Solenopsis geminata; and two parasitoids: Lespesia archippivora and Pteromalus cassotis. We combined correlated suitable areas for individual predators and parasitoids to identify regions with the most predator and parasitoid species potential. The Gulf Coast, West Coast, Florida, and parts of the eastern United States are predicted to have the most natural enemy species. We suggest that future research should assess monarch mortality rates in these areas, and that monarch conservation strategies consider pressure from natural enemies.