Abstract
The plasticity of performance traits is expected to promote the successful invasion of species. Therefore, the comparison of reaction norms of invasive species with native competitors should enhance predictions of alien species establishment. Yet, most studies focus on a reduced set of traits, rarely in combination, or do not include trait variability to make predictions of establishment success. Here, we acclimated individuals to a cold, medium or warm temperature regime and measured critical thermal limits, life-history traits, and starvation resistance of the globally invasive Harmonia axyridis and its native counterpart Cheilomenes lunata. The native C. lunata had higher thermal plasticity of starvation resistance and higher upper thermal tolerance than H. axyridis. By contrast, H. axyridis outperformed C. lunata in most life-history traits. We combined trait responses, transport duration and propagule pressure to simulate the final number of beetles established in the introduced site in cold, medium and warm scenarios, where beetles also experienced a heatwave once established. Although C. lunata initially outcompeted the invasive species during transport, more H. axyridis survived in all environments because of higher life-history trait responses, in particular, higher fecundity. Despite increased starvation mortality in the warm scenario, H. axyridis established successfully given sufficient propagule size. By contrast, in the event of a heatwave, H. axyridis numbers plummeted and higher numbers of the native species established in the cold scenario. This study underscores the importance of considering a combination of traits and respective cascading effects when estimating the establishment potential of species and responses to climate warming.
Environmental determinants of population divergence in life-history traits for an invasive species: climate, seasonality and natural enemies
