Effects of climate on reproductive investment in a masting species: assessment of climatic predictors and underlying mechanisms

1. Mechanisms by which climatic factors drive reproductive investment and phenology in masting species are not completely understood. Climatic conditions may act as a proximate cue, stimulating the onset of reproduction and indirectly increasing fitness through benefits associated with synchronous reproduction among individuals. Alternatively, climatic conditions may directly influence individual level allocation to reproduction and reproductive success through effects occurring independently of synchronous reproduction. We previously showed that masting in a ponderosa pine (Pinus ponderosa) population was strongly influenced by spring mean temperature two years before seed cone maturation (Ti-2). However, recent work shows that the difference in temperature between previous growing seasons (ΔT) is more predictive of reproductive investment in long-lived tree species. 2. Here we compared four candidate models that predict seed cone production in P. ponderosa based upon different climati...