Loss of branches due to winter storms could favor deciduousness in oaks

Abstract

Premise: Ecologists have an incomplete understanding of the factors that select for deciduous, evergreen, and marcescent leaf habits. Evergreens have more opportunities for photosynthesis but may experience costs when abiotic conditions are unfavorable such as during ice and windstorms. Methods: We documented branch loss for species of oaks (Quercus spp.) in a common garden in California during an unusual windstorm. Results: Branches of marcescent trees were more likely to break during the storm, and this pattern had a negligible phylogenetic signature. Branches of evergreen and marcescent species were mostly alive before breaking, which likely accrued a fitness cost, while those of deciduous species were mostly already dead. One explanation for the overrepresentation of broken branches from marcescent species is that their petioles are inflexible and have greater wind loading compared to the flexible petioles of evergreen leaves and the leafless condition of deciduous branches. Conclusions: These results suggest that branch loss during unusual winter storms may be an important cost of a marcescent leaf habit.