Rising temperatures and extreme climate events are driving tropical species into temperate marine ecosystems, but not all can persist. This study uses the heatwave-driven expatriation of tropical Black Rabbitfish (*Siganus fuscescens*) to Western Australia to assess their persistence mechanisms. Population genomic assays showed little genetic differentiation between tropical and temperate populations due to high migration rates, likely enhanced by the heatwave. DNA metabarcoding revealed a diverse diet including regional resources like kelp. Projected favorable climate conditions and diet versatility suggest self-recruitment and range expansion by 2100, potentially impacting kelp forests. Favorable climate, genetic connectivity, and diet versatility are key for tropical range-shifting fish establishment in temperate ecosystems.

Laura Gajdzik, Thomas M. DeCarlo, Adam Koziol, Mahsa Mousavi-Derazmahalleh, Megan Coghlan, Matthew W. Power, Michael Bunce, David V. Fairclough, Michael J. Travers, Glenn I. Moore, Joseph D. DiBattista