Adaptation to climate in Juglans nigra: exploring how home climate shapes growth patterns of natural populations
Open Access
- Author:
- Onofrio, Lauren
- Graduate Program:
- Ecology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 25, 2020
- Committee Members:
- Laura P Leites, Thesis Advisor/Co-Advisor
Kim C Steiner, Committee Member
John Edward Carlson, Committee Member
Jason Philip Kaye, Program Head/Chair
Margot Wilkinson Kaye, Committee Member - Keywords:
- black walnut
Juglans nigra
tree populations
local adaptation
climate
climate change
spatial climate variability
temporal climate variability
early growth patterns
growth rates
natural selection
genetic differentiation
provenance test
dendrochronology
phenotypic plasticity
common garden - Abstract:
- Many autochthonous tree species are distributed across extensive geographic ranges. To survive, tree populations must adapt to both spatial and temporal climate heterogeneity through evolutionary processes, such as natural selection, which act on genetic variation. Most tree species combine adaptation to the local climate (i.e. specialization) with phenotypic plasticity. Adaptation to local climate is common in wide ranging tree species and fitness clines driven by climate have been documented for many tree species. This thesis focuses on adaptation to climate in black walnut (Juglans nigra L.) and explores how home climate shapes growth patterns of natural populations. Chapter 1 evaluates population differentiation in adaptation to spatial and temporal climate variability using average annual scaled growth, annual ring width increment, and the coefficient of variation in average annual scaled growth. We found evidence of specialization, and thus adaptation to spatial climate variability, in populations’ average scaled radial growth as a function of climate transfer distance. We also found that temporal variability of populations’ home climate was linked to phenotypic plasticity and populations from more temporally variable climates exhibited less interannual growth variability. Chapter 2 evaluates height growth up to age 10 from planting of black walnut populations to elucidate differences in early growth patterns. We found that populations from warmer climates had the highest cumulative growth and reached maximum absolute growth earlier in time. Populations from colder climates had a smaller size (cumulative growth), reached maximum absolute growth later in time, and had higher relative grow rates at any given age within our study’s age range. The results from this thesis highlight the role natural selection and temporal/spatial climate variability may play in driving growth patterns among black walnut populations.