Local adaptation and phenotypic plasticity drive leaf trait variation in the California endemic toyon dataset

Premise of the study: To survive climate change and habitat loss plants
must rely on phenotypic changes to the environment, local adaptation, or
migration. Understanding the drivers of intraspecific variation is
critical to anticipate how plant species will respond to climate change
and inform conservation decisions. Here we explore the extent of local
adaptation and phenotypic plasticity in Heteromeles arbutifolia, toyon, a
species endemic to the California Floristic Province. Methods: We
collected leaves from 286 individuals across toyon’s range and used seeds
from 37 individuals to establish experimental gardens in the northern and
southern parts of toyon’s range. We measured leaf functional traits of the
wild collected leaves, and functional and fitness traits of the offspring
grown in the experimental gardens. We then investigated the relationships
between traits and source environment. Key results: Most traits we
investigated responded plastically to the environment, and some traits
measured in young seedlings were influenced by maternal effects. We found
strong evidence that variation in leaf margins is a result of local
adaptation to variation in temperature and temperature range. However, the
source environment was not related to fitness traits or survival in the
experimental gardens. Conclusions: Our findings reiterate the adaptive
role of toothed leaf margins in colder and more seasonally variable
environments. Additionally, we provide evidence that fitness of toyon is
not dependent on where they are sourced, and thus toyon can be sourced
across its range for restoration purposes.