Zyled Rodriguez Maldonado,

Sponsor or Client: 

Title:

Genetic and Environmental Effects on Cottonwood Leaf Traits Along an Elevation Gradient

Abstract:

Climate change is a threat to our ecosystems, therefore it is of great importance to study how species can adjust and survive. In this study, we examined six populations of a single species of cottonwood tree (Populus fremontii) in order to determine how their geographic origin and current growing environment affect their leaf traits. We hypothesized that leaf morphology, chemical traits, and stomatal density are all dependent on both the climate where they have evolved and the climate that they are currently experiencing. In order to test this hypothesis, we used three common gardens in Yuma (hot), Agua Fria (middle), and Southern Utah (cold). Each common garden contained all populations, though some populations were lost due to their inability to persist in very different climates. We found that trees make thicker leaves when grown at hotter temperatures. Leaves growing in the cold garden had the highest lignin concentrations with high variability among populations. In contrast, tannin concentrations were higher in the hotter gardens and in mid-elevation populations. We also found that populations that originated from high elevation had much lower stomatal densities than other populations and that trees grown at the hot garden increased their stomatal density. Overall, our findings were consistent with our hypothesis because specific leaf area, stomatal density, and chemical traits were affected by both garden and population. These results can help to select the optimal genetic stock for riparian restoration projects.