A mammalian herbivore selects local and cooler provenance trees in a restoration common garden experiment: implications for community‐assisted migration efforts

Abstract

Rapid changes in climate have the potential to alter habitats faster than evolution may respond, leading to maladapted tree populations. Assisted migration may help foundation tree species persist in future climates by identifying populations and genotypes that are robust to expected climate change‐induced alterations. Importantly, community‐assisted migration accounts for impacts of those populations and genotypes on the broader community, including herbivores, often adapted to local plants. These impacts have been examined in arthropod communities, but few studies have assessed mammals, and fewer still have leveraged an experimental design to disentangle genetic contributions to herbivore selection among genotypes and populations. We tested whether North American porcupine (Erethizon dorsatum) browsing on Fremont cottonwood (Populus fremontii) is under genetic control in a common garden to uncouple genetic and environmental contributions on browse selection. Porcupines selected trees from climatically similar and cooler areas, where trees from cooler climates suffered greater than 2× more herbivory than trees from warmer areas. Plant genotype was a significant factor for selection, with the most heavily browsed genotype having greater than 10× more herbivory than the least browsed. Broad‐sense heritability of porcupine tree selection was H2B = 0.27 among genotypes, indicating a genetic component to tree defenses against porcupine herbivory that can be predicted by source population climate. Our results have important implications for future mammalian herbivore populations, should climate change render local tree genotypes maladaptive. We recommend assisted migration efforts plant stock from areas up to 3°C warmer and climatically similar areas to maintain productivity and mammalian herbivore browsing.