The invasive Procambarus clarkii and the distribution of amphibians on Western Lombardy

Procambarus clarkii is a crayfish native of North America, and it is currently invasive all around the world. Invasive populations of P. clarkii can cause the decline of native amphibians, yet studies on the relationships between this crayfish and amphibians remain scarce in Italy. We analysed the relationship between amphibian communities and P. clarkii in 114 wetlands in Lombardy, Northern Italy; P. clarkii has been introduced only recently in this area. We detected nine amphibians: Salamandra salamandra, Triturus carnifex, Lissotriton vulgaris, Bufo bufo, Hyla intermedia, Rana dalmatina, R. latastei, R. temporaria and Pelophylax klepton esculentus. Amphibian communities were significantly different in wetlands with and without P. clarkii; newts and salamanders were lacking in wetlands with P. clarkii. Brown frogs sometimes bred in wetlands with P. clarkii. However, we rarely detected brown frog tadpoles in these wetlands later in the season, suggesting high mortality. Procambarus clarkii is a clear threat to amphibians in areas where it is invasive; the complexity of the management of P. clarkii is a further challenge to amphibian conservation.