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Fossil leaf economics quantified: calibration, Eocene case study, and implications
- Dana L. Royer, Lawren Sack, Peter Wilf, Bárbara Cariglino, Christopher H. Lusk, Ian J. Wright, Mark Westoby, Gregory J. Jordan, Ülo Niinemets, Phyllis D. Coley, Asher D. Cutter, Conrad C. Labandeira, Matthew B. Palmer, Kirk R. Johnson, Angela T. Moles, Fernando Valladares
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- Journal:
- Paleobiology / Volume 33 / Issue 4 / Fall 2007
- Published online by Cambridge University Press:
- 08 April 2016, pp. 574-589
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- Article
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Leaf mass per area (MA) is a central ecological trait that is intercorrelated with leaf life span, photosynthetic rate, nutrient concentration, and palatability to herbivores. These coordinated variables form a globally convergent leaf economics spectrum, which represents a general continuum running from rapid resource acquisition to maximized resource retention. Leaf economics are little studied in ancient ecosystems because they cannot be directly measured from leaf fossils. Here we use a large extant data set (65 sites; 667 species-site pairs) to develop a new, easily measured scaling relationship between petiole width and leaf mass, normalized for leaf area; this enables MA estimation for fossil leaves from petiole width and leaf area, two variables that are commonly measurable in leaf compression floras. The calibration data are restricted to woody angiosperms exclusive of monocots, but a preliminary data set (25 species) suggests that broad-leaved gymnosperms exhibit a similar scaling. Application to two well-studied, classic Eocene floras demonstrates that MA can be quantified in fossil assemblages. First, our results are consistent with predictions from paleobotanical and paleoclimatic studies of these floras. We found exclusively low-MA species from Republic (Washington, U.S.A., 49 Ma), a humid, warm-temperate flora with a strong deciduous component among the angiosperms, and a wide MA range in a seasonally dry, warm-temperate flora from the Green River Formation at Bonanza (Utah, U.S.A., 47 Ma), presumed to comprise a mix of short and long leaf life spans. Second, reconstructed MA in the fossil species is negatively correlated with levels of insect herbivory, whether measured as the proportion of leaves with insect damage, the proportion of leaf area removed by herbivores, or the diversity of insect-damage morphotypes. These correlations are consistent with herbivory observations in extant floras and they reflect fundamental trade-offs in plant-herbivore associations. Our results indicate that several key aspects of plant and plant-animal ecology can now be quantified in the fossil record and demonstrate that herbivory has helped shape the evolution of leaf structure for millions of years.
Chapter 10 - The seedling as part of a plant's life history strategy
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- By Angela T. Moles, University of New South Wales, School of Biological, Earth, and Environmental Sciences, Sydney, Australia, Michelle R. Leishman, Macquarie University, Department of Biological Sciences, Sydney, Australia
- Edited by Mary Allessio Leck, Rider University, New Jersey, V. Thomas Parker, San Francisco State University, Robert L. Simpson, University of Michigan, Dearborn
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- Book:
- Seedling Ecology and Evolution
- Published online:
- 05 June 2012
- Print publication:
- 18 September 2008, pp 217-238
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- Chapter
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Summary
Introduction
In this chapter, we will describe the intricate links between seedling ecology and life history traits such as seed mass, time to maturity, adult size, and reproductive life span. We will pay particular attention to seed mass, as this is the trait most closely linked to seedling ecology. Seed mass affects the initial size of the seedlings, the amount of reserves seedlings have for establishment, the sites to which seeds are dispersed, and the time seeds spend in the soil before germinating.
Much of our understanding of seed and seedling ecology has been based on the idea that plants face a trade-off between producing a few large seeds, each with high rates of survival as seedlings, versus producing many small seeds, each with lower rates of survival as seedlings. We, therefore, begin by reviewing the evidence for this trade-off. Our review shows that a full understanding of seed and seedling ecology requires consideration of life history variables such as plant height, reproductive life span, and the length of the juvenile period. Then we present a new framework for understanding seed and seedling traits as part of an overall life history strategy. Next we outline relationships between seed and seedling traits and other aspects of plant ecological strategy, such as seed dispersal syndrome, the capability to form soil seed banks, tissue density, and adult plant traits.