Chemical cues released by heterospecific competitors: behavioural responses of native and alien invasive aquatic gastropods

Abstract

Chemical cues released by organisms have the potential to impact the behaviour of species, particularly in aquatic environments. These interactions affect the dynamics of resource utilisation at a small scale. Chemical cues may also be significantly involved in heterospecific competition and in reducing biotic resistance thus facilitating invasion success. This occurs if one species causes another to vacate optimal niches. This study aimed to assess (1) the behavioural responses of native gastropods to chemical cues released by other native gastropod species with which they did not co-occur, and (2) whether native gastropods from different localities exhibit similar behavioural responses to chemical cues released by the alien invasive Tarebia granifera, irrespective of their prior exposure to the alien. Behavioural responses were measured using an experimental approach both in situ and in the laboratory. Principal Components Analyses were used to visualize the variation in the behavioural responses of gastropods which were measured in terms of displacement, number of steps and turning angles. Gastropod behaviour was similar for populations from different sites, irrespective of their prior exposure to T. granifera. The behaviour of native gastropods was only different when exposed to chemical cues naturally released by T. granifera. Additionally, native gastropods did not behave differently when exposed to the chemical cues of an alien physid, Aplexa marmorata. This suggests that a change in behaviour when exposed to chemical cues of T. granifera may not be the result of having different evolutionary histories, but rather that T. granifera has evolved a unique metabolite which acts a deterrent to potential competitive snails. The role of chemical cues in mediating interactions between native and invasive species needs further research, as they may be important factors influencing biotic resistance and facilitating invasion success.