Climate-driven redistribution of Cheilinus wrasses and Acanthaster planci

Anthropogenic carbon emissions are a major driver of ocean warming, with increasing consequences for marine species distributions and potential ecological interactions. This study investigates the cascading impacts of emission-driven climate change on the distributions and interspecific spatial relationships of ecologically important Cheilinus wrasses across the Indo-Pacific convergence zone. Using species distribution modelling (MaxEnt) under multiple future emission scenarios (RCP2.6-8.5 for the 2050s and 2100 s), we project a marked divergence in habitat suitability responses. Narrow-range species, such as C. quinquecinctus, retained core habitats while expanding at their margins, resulting in a projected net habitat gain of up to 52.82%. In contrast, the wide-ranging and functionally important humphead wrasse (C. undulatus) showed persistent internal erosion within its current range, with a projected net habitat loss of up to 8.53%. These warming-associated redistributions, primarily constrained by changes in mean salinity, were accompanied by a reorganization of the potential spatial-overlap network among congeners. The potential spatial overlap between C. undulatus and the crown-of-thorns starfish (Acanthaster planci) was projected to decline modestly under future climate scenarios. Their current high range overlap (Schoener's D = 0.864) declined to 0.828 under the 2050s RCP2.6 scenario and 0.826 under the 2100 s RCP8.5 scenario. This projected reduction in potential spatial overlap may indicate a possible climate-driven predator-prey spatial mismatch, which could reduce spatial opportunities for interaction between C. undulatus and A. planci and warrants further empirical validation. Overall, our findings indicate that carbon emission pathways may reshape the broad-scale potential distribution patterns and spatial relationships of reef-associated fishes. The projected stable suitable areas, vulnerable reef regions, and potential reduced-overlap zones provide scenario-based spatial information for future conservation assessment and field validation, rather than direct spatial prioritization or policy recommendations.