Much of extant biodiversity may have arisen from a small
number of adaptive radiations occurring on large spatiotemporal
scales [1–3]. Under the niche-filling model of adaptive radiation,
ecological opportunities arise from key innovations, the extinction
of competitors, or geographic dispersal [1,4,5]. These cause rapid
evolutionary rates in ecologically relevant traits, as diverging
lineages exploit distinct resources. Rates of trait evolution then
decelerate as niches become saturated, a pattern that has been
formalised as the ‘‘early burst’’ model (e.g., [6,7]).