Testing a personality‑dispersal hypothesis: behavioural comparisons along a round goby invasion gradient

Behaviour is thought to drive dispersal of invasive species and populations, with bold, exploratory and active individuals pushing expansion range. We tested this hypothesis in the round goby (Neogobius melanostomus) along an invasion gradient in Ontario, Canada. We collected fish from a core population established two decades ago, and from an edge population representing a six-month-old invasion front, and we compared the personality traits of a sub-set of size-matched males from these core and edge populations. Four behaviours assessed showed significant repeatability (after a one-week interval) and they were correlated together in a behavioural syndrome. Based on these correlated traits, we calculated a proactivity score (based on boldness and activity) for each fish. In contrast to expectations, the core and edge fish did not differ in their proactivity levels. We did uncover a strong correlation between body size and behaviour, in which the smallest fish were the most proactive. Our results show that after controlling for sex and size there was no clear influence of personality facilitating dispersal along the investigated round goby invasion gradient. Our results challenge the idea that personality always drives range expansion, warranting further exploration into the strength of this association.