Kai C. Paijmans and Marian Y.L. Wong
Contests are a method by which animals resolve conflict over access to resources such as food, shelter and mates. Contest theory is a complex set of models which explain the mechanisms, dynamics and outcomes of animal contests. Because competition for limiting resources is an established mechanism by which species coexist and biodiversity is maintained, contest theory has potentially important applications in understanding species coexistence and biodiversity maintenance within ecosystems.
We applied contest theory to investigate the link between contest dynamics and species coexistence using two intertidal rockpool fishes – Bathygobius cocosensis (the cocos frill goby) and Lepidoblennius haplodactylus (the eastern jumping blenny). Firstly, we assessed the abundance and distribution of the two species on intertidal rocky shores of South East Australia. Secondly, we conducted interspecific contest experiments between pairs of B. cocosensis and L. haplodactylus to assess the competitive dominance of the species. Then finally, to relate these results to community structure, we quantified the rockpool fidelity (the amount of time fish spend in a “home” pool) of each species on the rocky shore.
We found that B. cocosensis and L. haplodactylus appeared to avoid each other in the field and that B. cocosensis displayed higher rockpool fidelity than L. haplodactylus. Contest experiments revealed that B. cocosensis was competitively superior and highly aggressive relative to L. haplodactylus. Furthermore, the microhabitat preference of L. haplodactylus changed in the presence of B. cocosensis. In light of these findings we propose that, B. cocosensis is the superior competitor, but coexistence of both species is facilitated by low-cost contest resolution strategies, plasticity in microhabitat preference and interspecific variation in home range sizes.
Overall, this study highlights the applicability of contest theory for investigations of community scale ecology, community dynamics and biodiversity maintenance across a wide range of ecological systems.
Photo Caption: field work on an intertidal rocky shore in SE Australia (Photo Credit – Matt Rees).