Early assessment of the impact of alien species: differential consequences of an invasive crayfish on adult and larval amphibians

Abstract

Aim Early assessment of the impact of invasive alien species is crucial to set up timely management, but often the impact is evident when it is too late for action. We evaluated relationships between the alien crayfish, Procambarus clarkii, the distribution of native amphibians, and the abundance of their larvae. We assessed whether considering measures of reproductive success provide a more prompt measure of impact than considering just species distribution.Location One hundred and twenty-five wetlands in Northern Italy, in an area recently invaded by P. clarkii.Methods We surveyed wetlands to assess the presence of breeding activity of amphibians and the distribution of P. clarkii. We measured the abundance of amphibian larvae before metamorphosis through pipe sampling. We built models analysing the relationships between amphibian and crayfish distribution, while taking into account spatial autocorrelation and environmental features. Analyses were performed at both the species level (generalized linear models and spatial eigenvector mapping) and community level (constrained redundancy analysis). ResultsIn terms of breeding site distribution, only two amphibians (Lissotriton vulgaris and Hyla intermedia) were negatively associated with P. clarkii, while the relationships between other the species and P. clarkii were positive or not significant. However, larval abundance for all amphibian species was negatively associated with the alien crayfish. Analyses performed at community and single species levels yielded consistent results.Main conclusions Procambarus clarkii impacts amphibians through different processes. Newts probably avoid invaded wetlands for breeding. Other species attempt breeding in wetlands with crayfish, but suffer very low success. Considering distribution data alone would not provide a correct picture of the impact of this alien species; measures of reproductive success may allow a more accurate assessment of the impact.

Causes and consequences of crayfish extinction: Stream connectivity, habitat changes, alien species and ecosystem services

“…For instance, in the study area, the alien crayfish consumes freshwater macroinvertebrates and amphibian tadpoles, thus causing the decline of multiple native taxa (Ficetola, Siesa, De Bernardi, & Padoa-Schioppa, 2012;Ficetola et al, 2011b). Procambarus clarkii also increases erosion, which modifies benthic geomorphology through mechanical disturbance (foraging, burrowing and locomotor activities).…”

Effects of the non-native amphibian species Discoglossus pictus on the recipient amphibian community: niche overlap, competition and community organization

“…Habitat loss, pollution and invasive alien species have the largest impact on Mediterranean amphibian communities (Cox et al 2006). Mediterranean ecosystems have a long history of biological invasions (Di Castri 1990;Rebelo et al 2010) and their temporary wetlands are especially threatened due to invasions and habitat destruction (Geiger et al 2005;Ficetola et al 2011;Lillo et al 2011), which have an impact on amphibian populations.…”

Spatial autocorrelation and the analysis of invasion processes from distribution data: a study with the crayfish Procambarus clarkii

“…Procambarus clarkii can have multiple negative consequences on native species, ecosystems and human health. It is a polytrophic and opportunistic crayfish, feeding on vegetal detritus but also on molluscs, insects, amphibians, fish and macrophytes, and therefore causing complex changes in food webs and leading to the decline in the abundance and diversity of several native species (Gherardi 2006;Souty-Grosset et al 2006;Cruz et al 2008;Ficetola et al 2011). Furthermore, P. clarkii can spread the crayfish plague Aphanomyces astaci and outcompete native European crayfishes, thereby causing their decline (Souty-Grosset et al 2006;Gherardi and Panov 2009).…”