Behavioural modification of range-extending coral reef fishes in temperate ecosystems

1. Coral-reef fishes are shifting their distributions poleward in response to human-mediated ocean warming, yet the consequences for recipient temperate fish communities remain poorly understood. Behavioural modification is often the first response of species to environmental change, but we know little about how this might shape the ongoing colonisation by tropical fishes of temperate-latitude ecosystems under climate change. 2. In a global hotspot of ocean warming (southeast Australia), we quantified 14 behavioural traits of invading tropical and local co-occurring temperate fishes at 10 sites across a 730 km latitudinal gradient as a proxy of species behavioural niche space in different climate ranges (subtropical, warm-temperate, cold-temperate). 3. We found that tropical fishes (4 species) modified their behavioural niches as well as increased their overall behavioural niche breadth in their novel temperate ranges where temperate species predominate, but maintained a moderat...