Behavioural, morphological, and life history shifts during invasive spread.
Invasive species are common around the world, but we still do not know which traits are most important for successfully establishing in new environments. Different stages of the invasion process, including transport, introduction, establishment, and spread, can act as selective filters for different combinations of phenotypic traits. Theoretical and empirical studies predict that invasive populations should have suites of behaviours that improve dispersal and spread, including higher boldness, dispersal propensity, and activity levels than native populations. In this study, we tested these predictions by comparing the morphology, life history, and behaviour of an invasive population of redback spiders, Latrodectus hasselti, from Japan to a population of native spiders from Australia, with additional comparisons of another invasive population from New Zealand. We found that both a longer-established invasive New Zealand population and the more recently-established invasive population from Japan were more dispersive than the native population from Australia. The invasive population from Japan showed elevated levels of sibling cannibalism relative to the native population, which may increase total reproductive success of females under food limitation. Spiders from Japan were also less bold in response to a simulated predator threat compared to native spiders from Australia. In contrast to the prediction that invasive populations would show uniformly fast life history traits, the invasive population from Japan was more fecund, yet took longer to develop than the native population under laboratory conditions. Overall, our results show that invasive populations are phenotypically distinct from native populations, with some behavioural, life history, and morphological traits that would increase spread (dispersal tendency, high fecundity) and persistence (sibling cannibalism) in new habitats.