Frequent shifts in pollination strategy are decoupled from diversification in the terrestrial orchids

Jamie B Thompson , Eric Robert Hagen, Elizabeth Anne Forward, Oscar Alejandro Pérez-Escobar, James W Clark, Nicholas Kiefer Priest

Pollinator attraction strategies are central to orchid reproductive biology and have long been hypothesised to accelerate speciation rates, particularly through specialised coevolutionary interactions. However, most macroevolutionary evidence comes from studies of individual genera or tribes, leaving broad-scale patterns unresolved. Here, we reconstruct the evolution of pollination strategy in the terrestrial orchid subfamily Orchidoideae and test for associations with speciation rate. We identify multiple transitions among reward-based, deception-based, and autonomous pollination, but via an evolutionarily constrained pathway in which some transitions do not occur. We find no significant impact of any pollination strategy on speciation rates, nor degree of specialisation or pollinator identity. Despite shaping ecological interactions and reproductive isolation, pollination strategies do not strongly impact diversification in orchids. Our findings support a growing view that plant radiations are shaped by complex interactions between traits, ecological opportunity, and environmental context, rather than by any single force alone.