Experimental shifts in exotic flowering phenology produce strong indirect effects on native plant reproductive success

By causing phenological shifts that vary among species, climate change is altering time envelopes for species interactions, often with unexpected demographic consequences. Indirect interactions, like apparent competition and apparent facilitation, are especially likely to change in duration because they involve multiple interactors, increasing the likelihood of asynchronous phenological shifts by at least one interactor. Thus, we might observe ecological surprises if intermediaries of indirectly interacting species change their mediating behavior.
We explored this possibility in a plant-pollinator community that is likely to experience asynchronous phenological shifts. We advanced and delayed the flowering phenology of two ubiquitous exotic plants of western Washington prairies, Hypochaeris radicata and Cytisus scoparius, relative to seven native perennial forb species whose phenologies remained unmanipulated. These species interact indirectly through shared pollinators, whose fora...