Limited role of aquatic habitat complexity in mitigating the ecological impact of invasive bullfrogs on native amphibians

Le résumé fourni par la source

Spatial overlap in habitat use and structural habitat complexity can shape the ecological impact of biological invasions. Environmental conditions that mitigate these impacts can be exploited in nature-based conservation strategies aimed at damage reduction when complete eradication is no longer feasible. In this study, we investigated how site-level habitat characteristics shape the ecological impact of non-native American bullfrogs ( Lithobates catesbeianus ) on native amphibian communities. We surveyed 134 standing water bodies in Belgium using environmental DNA (eDNA) quantitative barcoding and metabarcoding to assess bullfrog density and native amphibian community structure, respectively, and recorded 25 habitat characteristics. We investigated ( i ) environmental niche overlap between native amphibians and bullfrogs, ( ii ) species-habitat associations, and ( iii ) the interactive effect of aquatic habitat complexity, based on aquatic macrophyte coverage, and bullfrog density on native amphibians. Our findings show that the environmental niche of native amphibians was substantially smaller than and nested within that of bullfrogs, potentially limiting opportunities for impact mitigation through niche differentiation. Native species with smaller niches and stronger habitat associations were generally more affected by bullfrogs than less habitat-specific species. Although structurally complex aquatic habitats generally benefited most native amphibians, these positive effects were often outweighed by the negative impacts of increasing bullfrog densities. The ability of aquatic habitat complexity provided by aquatic macrophytes to reduce the impact of non-native bullfrogs depended on the native amphibian species involved and the specific conservation objectives being pursued—whether oriented toward maintaining amphibian species richness or ensuring the persistence of focal species. Increasing aquatic habitat complexity alone is thus insufficient as a stand-alone management strategy to protect native amphibians from non-native bullfrogs.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.