Serotiny, the retention of seeds in a canopy seed bank until high temperatures cause seeds to be released, is an important life history trait for many woody plants in fire-prone habitats. Serotiny provides a competitive advantage after fire but increases vulnerability to predispersal seed predation, due to the seeds being retained in clusters in predictable locations for extended periods. This creates opposing selection pressures. Serotiny is favored in areas of high fire frequency but is selected against by predispersal seed predators. However, predation also selects for cone traits associated with seed defense that could reduce predation on serotinous cones and thereby relax selection against serotiny. This helps explain the elevated defenses in highly serotinous species. However, whether such interactions drive variation in seed defenses within variably serotinous populations has been studied rarely. We investigated the effects of phenotypic selection exerted by red squirrel (Tamiasciurus hudsonicus) predation on Rocky Mountain lodgepole pine (Pinus contorta latifolia) seeds. Squirrels preferentially harvested cones with more and larger seeds, indicating a preference for a higher food reward. We found evidence for stronger selection on trees with serotinous cones, which presumably accounts for the elevated defenses of and lower predation on serotinous compared to non-serotinous cones. Lower levels of predation on serotinous cones in turn lessens selection against serotiny by squirrels. This has important implications because the frequency of serotiny in lodgepole pine has profound consequences for post-fire communities and ecosystems widespread in the Rocky Mountains.

The methods used to locate trees, measure their cone traits, and estimate the survival of first-year cones from just prior to maturation to after the cones open for trees with non-serotinous cones and the following May for trees with serotinous cones are described in the Methods section of the paper. 

The diameter at breast height for one tree is missing.