Habitat connectivity and resident shared predators determine the impact of invasive bullfrogs on native frogs in farm ponds

Abstract

Habitat connectivity is considered to have an important role on the persistence of populations in the face of habitat fragmentation, in particular, for species with conservation concern. However, it can also impose indirect negative effects on native species through the spread of invasive species. Here, we investigated direct and indirect effects of habitat connectivity on populations of invasive bullfrogs and native wrinkled frogs and how these effects are modified by the presence of common carp, a resident shared predator, in a farm pond system in Japan. The distribution pattern analysis using a hierarchical Bayesian modelling indicated that bullfrogs had negative effects on wrinkled frogs, and that these negative effects were enhanced with increasing habitat connectivity owing to the metapopulation structure of bullfrogs. The analysis also suggested that common carp mitigated these impacts, presumably owing to a top-down trophic cascade through preferential predation on bullfrog tadpoles. These presumed interspecific interactions were supported by evidence from laboratory experiments, i.e. predation by carp was more intense on bullfrog tadpoles than on wrinkled frog tadpoles owing to the difference in refuge use. Our results indicate that metacommunity perspectives could provide useful insights for establishing effective management strategies of invasive species living in patchy habitats.

Cold tolerance of invasive freshwater snails, Pomacea canaliculata, P. maculata, and their hybrids helps explain their different distributions

“…Pomacea maculata could expand its distribution to colder area by hybridisation with P. canaliculata , another invasive species. Ecological connectivity among invasive species has been identified as a factor leading to more severe impacts on native species than either invasive species may have alone (Grosholz, ; Johnson et al ., ) or mitigating the impacts of biological invasion (Atobe et al ., ). Our study has shown that the interactive effects among invasive species can promote colonisation by invasive species in their non‐native ranges.…”

Informing recovery in a human-transformed landscape: Drought-mediated coexistence alters population trends of an imperiled salamander and invasive predators

“…Fish are typically stronger predators than bullfrogs, but we did not have enough information to estimate their effects separately or to determine if the presence of both predators resulted in additive, antagonistic, or synergistic effects (e.g., Simberloff & Von Holle, 1999;Adams et al, 2003). If Sonoran Tiger Salamanders and other native aquatic species can coexist long-term with bullfrogs, there would likely be more management options because it is easier to eradicate and prevent fish from recolonizing isolated ponds than species that disperse terrestrially (Atobe et al, 2014;Knapp et al, 2007). The lack of data on temporal and spatial variation in drying of ponds, and thus our assumption of uniform drought conditions across the valley, also limits inferences about mechanisms and our ability to estimate the effect of drought on both native and invasive species.…”

Regional diversity reverses the negative impacts of an alien predator on local species‐poor communities

“…Here, possible confounding factors are differences in the nature of stressors (i.e., type and magnitude; Thompson and Shurin , Symons and Arnott ) or dispersal treatments, which may introduce novel predators (Atobe et al. ) or tolerant species with poor resource‐use efficiency (Matthiessen et al. , Eggers et al.…”