Earlier flowering explains only a small part of experimental drought's effects on a wildflower's population growth

Flowering times are shifting with climate change, but whether these changes will affect population dynamics of long-lived plants remains largely unknown. We combined eight years of demographic censuses and a four-year phenological survey to examine the effects of experimental drought and irrigation on flowering phenology and population growth in a perennial wildflower using integral projection models. Drought advanced flowering and earlier-flowering plants produced more seeds regardless of treatment. However, when decomposing rainfall treatment effects on population growth rates into effects of phenology and direct, non-phenological effects, direct effects on both growth and reproduction were much larger than phenology-driven changes in seed production for either treatment. Our results highlight how phenological shifts may only marginally impact population dynamics in perennial plants and demonstrate that assessing flowering phenologys consequences for persistence under climate change must also account for direct demographic effects of the climate driver itself.