Hemispheric asymmetry in predicted range shifts of anti-tropical fish under future climate change

Anti-tropically distributed species have long intrigued biogeographers. However, how they will respond to future climate change remains a key unresolved question, particularly for marine species given an expected hemispheric asymmetry in ocean warming. Here, using species distribution models for 172 anti-tropical marine fishes, we predict that northern hemispheric lineages will experience significantly higher range contractions, in agreement with the hemispheric asymmetry in ocean warming. Our predictions show that suitable habitat will be reduced at a similar rate both within and outside marine protected areas, leading protection efficacy (the proportion of the total suitable habitat protected) to remain at current levels, irrespective of the scenario and period considered, and the level of protection efficacy to remain significantly higher in the Southern Hemisphere. These results highlight the need for accounting for hemispheric asymmetry in ocean warming when designing future conservation strategies. As oceans warm unevenly between hemispheres, the future of anti-tropical fishes is unclear. Despite larger future range contractions for northern lineages, protected area efficacy remains unchanged and significantly higher for southern lineages.