Comparative impacts of long-term trends in snowmelt and species interactions on plant population dynamics

Climate change can impact plant fitness and population persistence directly through changing abiotic conditions and indirectly through its effects on species interactions. Pollination and seed predation are important biotic interactions that can impact plant fitness, but their impact on population growth rates relative to the role of direct climatic effects is unknown.
We combined 13 years of experiments on pollen limitation of seed set and pre-dispersal seed predation in Ipomopsis aggregata, a subalpine wildflower, with a long-term demographic study that has documented declining population growth with earlier spring snowmelt date. We determined how pollen limitation and seed predation changed with snowmelt date over 21 years and incorporated those effects into an integral projection model to assess relative impacts of biotic factors on population growth.
Both pollen limitation and the difference in stigma pollen load between pollen-supplemented and control plants declined over years. N...