Key innovation or adaptive change? A test of leaf traits using Triodiinae in Australia

摘要: The evolution of novel traits (“key innovations”) allows some lineages to move into new environments or adapt changing climates, whereas other may track suitable habitat go extinct. We test whether, and how, trait shifts are linked environmental change using Triodiinae, C4 grasses that form the dominant understory over about 30% Australia. Using phylogenetic relaxed molecular clock estimates, we assess Australian biogeographic origins Triodiinae reconstruct stomatal vascular bundle positioning. diversified from mid-Miocene, coincident with aridification Subsequent niche have been mostly Eremaean biome savannah, expansion latter. Biome correlated changes in leaf anatomy radiations within largely regional. Symplectrodia Monodia nested Triodia. Rather than enabling shifts, convergent probably occurred after taxa moved savannah biome—they likely subsequent adaptions rather key innovations. Our study highlights importance testing timing origin assumed be phenotypic innovations enabled ecological shifts.