Article

Biodiversity & Conservation

, Volume 14, Issue 12, pp 2901-2911

First online:

Green Frogs Show Reduced Foraging Success in Habitats Invaded by Japanese knotweed

  • John C. MaerzAffiliated withEcology and Management of Invasive Plants Program, Department of Natural Resources, Cornell University Email author 
  • , Bernd BlosseyAffiliated withEcology and Management of Invasive Plants Program, Department of Natural Resources, Cornell University
  • , Victoria NuzzoAffiliated withNatural Area Consultants

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Abstract

Habitat loss is causing amphibian population declines worldwide, so there is increased attention to forces that degrade remaining habitats. Terrestrial habitats surrounding wetlands are critical foraging areas for temperate anurans. We investigated plant community changes in two old fields invaded by Japanese knotweed (Fallopia japonica) and the foraging success of Green frogs (Rana clamitans) in invaded and non-invaded portions of those fields. Within each field, vegetation data were recorded in quadrats located along two transects bisecting the invasion fronts. We placed frogs in ‘foraging buckets’ along transects and measured their change in mass over a 38 h period. There were significant changes in vegetation structure and composition associated with Japanese knotweed invasion. Diverse assemblages of native plants that covered non-invaded plots were absent from areas invaded by Japanese knotweed. There was also a significant change in vegetation architecture between invaded and non-invaded habitats. Change in frog mass declined significantly along transects, with most frogs in non-invaded plots gaining mass and no frogs in invaded plots gaining mass. Most frogs from non-invaded plots but only two from invaded plots defecated shortly after removal from foraging buckets (verification of recent feeding). We hypothesize that Japanese knotweed invasions degrade terrestrial habitat quality for frogs by indirectly reducing arthropod abundance. Nonnative plant invasions may be another factor contributing to amphibian population declines.

Keywords

Fallopia japonica Invasive plants Landscape complementation Rana clamitans