Exploring the Genetic Basis of Branching Variation in a Wild Mustard Boechera stricta

Grazing herbivores can significantly reduce plant fitness by causing apical meristem damage and completely removing reproductive structures. Compensation is a type of tolerance to grazing herbivores by which plants replace the removed reproductive structures. However compensation is possibly costly because of resource allocation to new reproductive structures, which can cause a tradeoff in survival probability overwinter in perennial plants. We show that variation in compensation is heritable and correlated with the environment from which the accessions originated in B. stricta. Specifically, length of lateral branches produced upon apical meristem damage when flowering was associated with climatic variables that change along an elevation gradient. Genotypes originating from low elevations— where the temperature is warmer and growing seasons are longer — produce longer lateral branches. Genotypes from high elevation sites — where the temperature is cooler and growing seasons are shorter — produce shorter lateral branches. This study suggests that compensation in the form of lateral branch length is affected by natural selection, which is potentially the result of tradeoffs between survival and reproduction.