Predators with ontogenetic niche shifts: Interactive effects of adult and larval predation by dragonflies on pond community structure

Many organisms have complex life-cycles where they shift habitats through their ontogeny. For example, in aquatic communities, many species of insects and amphibians utilize both terrestrial and aquatic habitats at different points of their lives. When these species have strong interactions in either the aquatic, the terrestrial, or both habitats, these effects can cascade across ecosystems. Dragonflies are predatory in both their larval aquatic and terrestrial adult stages, and many species of their prey also have complex life cycles in aquatic and terrestrial habitats (e.g., mosquitoes, damselflies). Thus, both adult and larval dragonflies have the potential to impact aquatic community structure. Our experiment examined the separate and interactive effects of adult and larval dragonfly presence on the invertebrate community in the aquatic habitat. To remove adult dragonflies, we constructed large mesh exclosures that permitted entrance of smaller (prey) insects, but precluded dragonfly entrance. We found adult dragonflies had a strong effect on aquatic community structure by reducing the abundance of several prey species that have adult life stages. This emphasizes the importance of considering both aquatic and terrestrial habitats when examining the structure of communities when species have complex life cycles.