European distribution for metacercariae of the North American digenean Posthodiplostomum cf. minimum centrarchi (Strigeiformes: Diplostomidae).
Biological invasion represents one of the major threats to global biodiversity as alien species often displace indigenous species. Knowledge of the mechanisms behind such displacements and the driving factors of the competitive superiority of the alien species remain limited. We combined analysis of field data and laboratory experiments examining species interactions to investigate the impact of temperature in the case of the alien freshwater snail Physa acuta and the indigenous snail Physa fontinalis. From field data, we identified higher temperature as the most important difference between sites populated by P. acuta and P. fontinalis. Results of the species interaction experiment conducted at 15, 20, and 25 °C revealed that the competitive superiority of P. acuta over P. fontinalis increases at warmer temperatures. In single species treatments, increasing temperature stimulated growth rates in both species. Coexistence treatments revealed an asymmetric competitive interaction between the two snail species. In both species, the density of conspecifics did not affect growth rates; however, density of heterospecifics did. This effect of heterospecifics varied with temperature. At 15 °C, the presence of heterospecifics stimulated the growth rates of both species, while at higher temperatures the presence of heterospecifics stimulated the growth rate in P. acuta only, but inhibited the growth rate in P. fontinalis. Our study shows that temperature can be a powerful driver of competitive outcomes between alien and indigenous species and highlight that the environmental context influences species interactions and impacts of alien species.