Theoretical expectations for the fitness responses of the study species at three temperatures. The invasive species H. axyridis (solid circles) follows one of three patterns a Jack-of-all-trades: H. axyridis is able to maintain fitness in all environmental conditions, including sub-optimal or stressful ones (cold and warm). The native C. lunata (empty circles) may outperform the invasive in some conditions b Master-of-some: H. axyridis is better able to increase fitness in favourable conditions and, typically, more so than the native c Jack-and-master: H. axyridis is able to maintain fitness and perform better than its native counterpart. The medium regime is assumed to be the most favourable environment for both species but given the lack of literature for the native species, optimal temperatures for fitness could correspond to the medium or the warm regime since information about its thermal optimum is limited (see text). Diverse lines of reaction norms within species means that multiple trajectories are possible.