Genetic Evidence of Multiple and Diverse Range Expansion Events From an Outbreak of the Crown‐of‐Thorns Seastar, <i>Acanthaster</i> Cf. <i>Solaris</i> on a Subtropical Reef

Understanding the dynamics of range expanding species, particularly those that have effects on recipient reefs, is vital to inform management and conservation strategies. A rare outbreak of the tropical Crown of Thorns seastar (<i>Acanthaster</i> cf. <i>solaris</i>) (COTS) on a subtropical coral reef and a subsequent control program, presented the opportunity to determine the likely origins and number of recruitment events that may have generated this outbreak. The presence of both cosmopolitan and regional mitochondrial haplotypes in this outbreak population indicated larval connectivity via the poleward flowing East Australian Current (EAC) from the Great Barrier Reef (GBR) and Coral Sea. High genetic connectivity with the GBR, based on mitochondrial COI variation, where multiple COTS outbreak events have occurred through time, suggests a high risk of future outbreaks in subtropical eastern Australia. Additionally, levels of COI genetic diversity in the subtropical outbreak population are consistent with either ongoing recruitment or multiple source populations, rather than a new founder population from a single dispersal event. Outbreaks of COTS are likely to become a more frequent occurrence under future climate change scenarios as the poleward-flowing EAC strengthens and brings warmer waters to subtropical reefs. Agencies that manage subtropical reefs should prepare and plan for future outbreak events and develop policy and management strategies for this range extending species.