From 'magic traits' to diversification mechanisms

Species richness is markedly uneven across the tree of life, and traits have long been invoked to explain this pattern. Expanding phylogenetic and trait datasets enable broader comparisons, but trait-diversity associations alone do not reveal how differences in richness arose. We argue that such associations should be reframed as process hypotheses about three non-exclusive processes: lineage origin, access to ecological or geographic opportunity, and persistence. Mixed trait-diversity associations are expected when the same trait influences multiple processes whose relative contributions vary across contexts. This process-based framework makes alternative diversification histories explicit and specifies contrasting temporal predictions that can be evaluated with complementary evidence. It clarifies what findings would weaken each hypothesis and when available data leave alternative histories unresolved.