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Leaf Size in Conifers: Global Associations With Climate and Evolutionary History
Katya I Bandow1,2, Timothy J Brodribb1,2, Benjamin Halliwell1,2
1School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia.
Global Change Biology
|June 29, 2026
Summary
Conifer leaf size evolution is strongly linked to climate, driven by temperature and phylogenetic history. Leaf hydraulic architecture shapes adaptations to diverse climates and influences their response to climate change.
Area of Science:
- Evolutionary Biology
- Plant Ecology
- Climate Change Biology
Background:
- Global leaf size patterns are dominated by angiosperms, potentially obscuring drivers in older groups like conifers.
- Understanding conifer leaf size evolution is crucial for predicting climate change impacts.
Purpose of the Study:
- Investigate how climate influences leaf size evolution across conifers.
- Examine trait correlations at phylogenetic and independent levels using a novel modeling framework.
- Analyze leaf size variation in scale-leaved Cupressaceae, needle-leaved Pinus, and broad-leaved Podocarpus.
Main Methods:
- Employed a novel multi-response phylogenetic mixed models (MRPMM) framework.
- Analyzed trait correlations at both phylogenetic and phylogenetically independent levels.
- Focused on conifer leaf size and climate niche traits, including temperature and precipitation.
Main Results:
- Found moderate to strong phylogenetic signal in conifer leaf and climate niche traits.
- Phylogenetic relationships explained most of the association between leaf size and climate.
- Temperature was a stronger driver than dry season precipitation, indicating deep-time co-evolution.
- Leaf hydraulic architecture influences trade-offs between leaf form and survival under climatic extremes.
Conclusions:
- Conifer leaf size evolution is shaped by deep-time co-evolutionary associations with climate, particularly temperature.
- Phylogenetic niche conservatism, driven by leaf hydraulic architecture, constrains conifer bioclimatic distributions and climate change responses.
- Highlights the importance of phylogenetic impacts on functional trait evolution in conservative groups like conifers.
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