Opportunistic predation on earthworms
Invasive predators can strongly shape soil invertebrate communities, yet their impacts depend on trophic breadth, prey accessibility, and environmental context. The South American terrestrial flatworm Obama nungara, now widespread in Europe, consumes a wide range of soil macrofauna, but its effects on earthworm assemblages have been insufficiently characterized. The gut contents of 254 O. nungara collected from several sites in France were studied with a focus on earthworm prey, after calibrating the DNA metabarcoding method using laboratory and field controls. Prey communities' data allowed to test for feeding behavior, potential diet preferences, and interactions with environmental variables. Thirty-four earthworm species covering all available ecological and functional categories were identified in the samples. The composition of the diet largely reflected the availability of field prey, indicating that predation was opportunistic and governed by encounter rates and local abundance. Surface available taxa were significantly overrepresented, which is consistent with increased accessibility and demonstrates a broadly flexible feeding strategy. This generalist and opportunistic feeding strategy, which reflects O. nungara's trophic flexibility across prey types and functional categories, likely facilitates its invasion success while exerting diffuse impacts on soil macrofaunal communities, particularly those accessible at the soil surface. The study provides a validated methodological framework for assessing predator-prey dynamics in soil ecosystems and highlights the importance of environmental context in shaping realized predation patterns.
Invasive predators can strongly shape soil invertebrate communities, yet their impacts depend on trophic breadth, prey accessibility, and environmental context. The South American terrestrial flatworm Obama nungara, now widespread in Europe, consumes a wide range of soil macrofauna, but its effects on earthworm assemblages have been insufficiently characterized. The gut contents of 254 O. nungara collected from several sites in France were studied with a focus on earthworm prey, after calibrating the DNA metabarcoding method using laboratory and field controls. Prey communities' data allowed to test for feeding behavior, potential diet preferences, and interactions with environmental variables. Thirty-four earthworm species covering all available ecological and functional categories were identified in the samples. The composition of the diet largely reflected the availability of field prey, indicating that predation was opportunistic and governed by encounter rates and local abundance. Surface available taxa were significantly overrepresented, which is consistent with increased accessibility and demonstrates a broadly flexible feeding strategy. This generalist and opportunistic feeding strategy, which reflects O. nungara's trophic flexibility across prey types and functional categories, likely facilitates its invasion success while exerting diffuse impacts on soil macrofaunal communities, particularly those accessible at the soil surface. The study provides a validated methodological framework for assessing predator-prey dynamics in soil ecosystems and highlights the importance of environmental context in shaping realized predation patterns.
Universite Paris Est Creteil