Limited net poleward movement amongst Australian reef species over a decade of climate extremes.

Warming seas are expected to drive marine life poleward. However, few systematic observations can confirm movement among entire communities at both warm and cool range edges. We analysed two continent-scale reef monitoring datasets to quantify changes in latitudinal range edges of 662 Australian shallow-water reef fishes and invertebrates over a decade punctuated by climate extremes. Temperate and tropical species both showed little net movement overall, with retreat often balancing expansion across the continent. Within regions, however, range edges shifted ~100 km per decade, on average, in the poleward or equatorward directions expected from warming or cooling seas following climate extremes. While some species responded rapidly to temperature change, we found little evidence for mass poleward drift. Previous studies based on extreme observations, rather than tracking all species through time, may have over-estimated the prevalence, magnitude and longevity of range shifts amongst marine taxa.