Every individual is unique, and differences among individuals in the use of resources ("niche variation") can have important ecological and evolutionary consequences. Travis has collaborated with the Bolnick Lab from the University of Texas at Austin, testing hypotheses about the causes and consequences of intraspecific diet specialization. We used in-lake enclosure experiments on Vancouver Island to demonstrate effects of interspecific competitors on the degree of diet variation in threespine stickleback (Gasterosteus aculeatus) populations (pdf), and to show that increased variation in an ecologically important phenotypic trait will not necessarily increase diet variation or modify top-down control (link to free pdf).

Our current Marsden-funded research is investigating niche variation within fish populations and how it responds to interspecific interactions. We have focused on how common bully (Gobiomorphus cotidianus) responds to introduced perch (Perca fluviatilis) in wetland ponds near Lake Waihola, just outside Dunedin. We have used mark-recapture studies, stable isotope analysis, and mesocosm experiments to measure individual niche variation in habitat and diet in the presence of different life stages of perch. We have also linked individual niche variation with variation in behaviour (personality traits) and life history (using otolith microchemistry).

The causes and consequences of individual niche variation