AbstractBiological invasions impose severe threats to biodiversity, and the extent of this phenomenon is predicted to intensify under climate warming. Only a few investigators have examined how temperature interacts with other environmental variables to affect competition between native and invasive species. Physa acuta, an invasive freshwater snail in Europe, often outcompetes the indigenous congener Physa fontinalis. Both species are hosts of the oligochaete Chaetogaster limnaei limnaei (CL). We examined how the growth rates of the 2 competing physid species are co-affected by CL infestation (0, 10, 20 CL/snail) and temperature regime (15, 20, 25°C). Physa acuta grew faster than P. fontinalis. Warmer temperatures strongly favored growth rates of P. acuta, whereas P. fontinalis hardly profited from increased temperatures. CL infestation reduced the growth rates of both physids, but affected P. acuta more strongly than P. fontinalis. At the highest CL infestation level, the growth rates of both species we...