Do Opposites Attack? Resource Interactions Between an Alien and Native Crayfish from the Lake Eyre Basin

Context Investigating resource competition between introduced and native species is important to understand the impacts of invasive species, not only on native species, but also with respect to the wider ecosystem. Within the Lake Eyre Basin, there is concern that feral populations of the tropical Cherax quadricarinatus are outcompeting the basins’ native crayfish species, the temperate–subtropical Cherax destructor. Aims This study sought to observe the behavioural and inter-specific food competition between juvenile C. quadricarinatus and C. destructor under experimental conditions to inform whether C. quadricarinatus has the potential to outcompete native C. destructor populations. Methods Interactions were quantified by establishing a behavioural intensity score, dominance score and recording the total time in possession of the food resource in a range of interspecific and intraspecific experimental pairings at 26°C. Key results Cherax quadricarinatus had a significantly higher dominance (z = −2.276, P = 0.023) and behavioural intensity score (t = 4.723, P < 0.001) than did C. destructor, but there was no difference between the two species for time in possession of the food resource (z = −1.334, P = 0.182). Conclusions and implications These results have significant ecological implications because the capacity of C. quadricarinatus to displace C. destructor, a keystone species, has the potential to irreversibly alter ecosystem function in invaded habitats.