Temperature drives asymmetric competition between alien and indigenous freshwater snail species, Physa acuta and Physa fontinalis

Abstract

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.

Physidae (Mollusca: Gastropoda) of western and central European range - morphological diversification and ecological features

“…In habitats that have a higher water temperature, P. acuta bene ts compared to other Physids such as, e.g. P. fontinalis, which according to the results of the study of Früh et al [35] is the evidence that the environmental context in uences species interactions and impacts of alien species. Our previous study showed that this species can occur in waters with high pH values [36] .…”

The introduction of Physa acuta (Gastropoda: Physidae) on Ilha Grande, Southeast Brazil, from initial stages to an established population

“…The effect of P. acuta over the other molluscs was not evaluated in this study, but a negative effect of the invasive M. tuberculata over P. punctiferum was previously observed on the same stream (Braga et al, 2014). There were reported negative effects of P. acuta over native species (Zukowski and Walker, 2009;Früh et al, 2017), and it can be of concern on Ilha Grande, especially if the species spread to more preserved streams of the island.…”

“…This wide distribution raised attention to how this snail was interacting with the new habitat and native species. The population of P. acuta in a new habitat can attain high densities, possibly causing impacts on native fauna (Cope and Winterbourn, 2004;Albrecht et al, 2009;Zukowski and Walker, 2009;Núñez, 2010;Vinarski, 2017;Früh et al, 2017). Furthermore, introduced freshwater snails were also linked to the dispersion of parasites (e.g., Font, 2003;Paula-Andrade et al, 2012;Mitchell and Leung, 2016;Ebbs et al 2018).…”

Biotic interactions are more important at species’ warm vs. cool range-edges: a synthesis

“…BIOCLIM, Maxent) use climate as their major predictor (Phillips et al 2006, Booth et al 2014). However, climate-based distribution models can significantly mispredict species' ranges (Bayly and Angert 2019), and species often fail to occupy regions with seemingly suitable climates (Früh et al 2017) and occupy different abiotic niches on islands vs. mainland ecosystems (e.g. MacArthur 1984, Velasco et al 2016.…”