Comparing the dynamics of agonistic interactions between the native crayfish Faxonius erichsonianus Faxon, 1898 and the invasive F. virilis Hagen, 1870 (Decapoda: Astacidea: Cambaridae)

Abstract

Abstract Alabama is a hotspot for aquatic biodiversity in North America, but that biodiversity is currently jeopardized by anthropogenic influence and invasive species. Alabama holds nearly a quarter of North America’s crayfish species, but recent introduction of invasive crayfishes poses a threat to crayfish biodiversity in the region. Previous studies suggest higher basal aggression in invasive species allows them to outcompete native species by more efficiently seizing and holding resources. Faxonius virilis (Hagen, 1870) is an invasive crayfish currently spreading throughout Alabama. Our aim was to determine if differences in basal aggression exist between an Alabama native, Faxonius erichsonianus (Faxon, 1898), and the invasive F. virilis. Individuals were used in size-matched dyadic fight trials housed in a specialized arena. Three treatment groups were used to compare basal aggression differences: native versus native, invasive versus invasive, and interspecific. Videos of fight trials were reviewed, and duration and intensity of fights were recorded using a previously established ethogram. Contest duration between individuals was compared using Kruskal-Wallis tests with a Wilcoxon post-hoc. Analyses showed the invasive control treatment was significantly (P = 0.041) shorter than both the native control and interspecific treatments; however, interspecific trials had higher intensity contests than either control treatment. These results did not show that the invasive F. virilis are more aggressive than F. erichsonianus, suggesting that a closer look is necessary to determine the factors affecting the invasion success of F. virilis. The F. virilis invasion may be attributed to other factors like fecundity or growth.