Lagged effects of early-season herbivores on valley oak fecundity
The seasonal match between folivore and leaf phenology affects the annual success of arboreal folivore populations because many folivores exploit developing leaves, which are an ephemeral resource. One strategy for folivores to exploit early-season leaves is to anticipate their emergence. The consequence of this behavior for trees is that individuals that set leaves earlier may experience greater rates of folivore damage, with potential negative fitness consequences. To test this hypothesis, we surveyed the early-season phenology, insect folivore damage, and acorn crop of a population of valley oaks (Quercus lobata) over a 3-year period. We found that trees that set leaves earlier experienced greater rates of folivore damage than trees that set leaves later in the season. In addition, we observed a lagged effect of folivore damage on acorn production, whereby trees with greater leaf damage produced fewer acorns in the subsequent year. These results indicate potential negative fitness consequences of earlier leaf phenology. Our study suggests that folivore pressure may be one factor that affects the optimal timing of leaf set in oaks.
KeywordsHerbivory Leaf set Phenology Quercus Chionodes
We thank Vince Voegeli and the University of California’s Hastings Reservation for support while conducting this study. We thank Brian Barringer and Eric Walters for help collecting data on folivore damage and oak phenology, John DeBenedictis for help in moth identification, and David Zayaand Marshall McMunn for statistical advice. This study was supported by the National Science Foundation (Grant DEB-0816691) and the University of California Integrated Hardwood Range Management Program. Data supporting this article are archived with Dryad (doi: 10.5061/dryad.63rv4).
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