Fossil leaf economics quantified: calibration, Eocene case study, and implications

By D. Royer, L. Sack, P. Wilf, C. Lusk, Gregory J. Jordan, U. Niinemets, I. Wright, M. Westoby, Bárbara Cariglino, P. D. Coley and 6 more. Paleobiology, 2007

135 citations recorded by the source corpus.

Abstract 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.

Subfields: Ecology, Evolution, Behavior and Systematics, Nature and Landscape Conservation

View Paper: https://www.semanticscholar.org/paper/5d05708e9d43788f4d587cc32501dc751e05a00f

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In Ecology, Evolution, Behavior and Systematics

1. Peter B. Reich
2. C. Violle
3. A. Moles
4. David D. Ackerly
5. M. Westoby
6. S. Lavorel
7. Eric Garnier
8. I. Wright

In Nature and Landscape Conservation

1. Peter B. Reich
2. M. Westoby
3. C. Violle
4. A. Moles
5. I. Wright
6. S. Lavorel
7. Eric Garnier
8. David D. Ackerly

Citations in the corpus

• Viewing leaf structure and evolution from a hydraulic perspective (2010, background): “the general positive correlation of photosynthetic rates per mass with nitrogen per mass, with both negatively correlated with leaf mass per area and leaf lifespan (Wright et al. 2004; Royer et al. 2007).”
• Fossil insect folivory tracks paleotemperature for six million years (2010, methodology): “The insect herbivore damage studied here records terrestrial ecosystem response to both temperature and pCO2, which are coupled in natural systems over long timescales (Siegenthaler et al. 2005, Royer et al. 2007a).”
• The Fossil Record of Plant-Insect Dynamics (2013, background): “…fungi (Vega & Blackwell 2004, Janson et al. 2008), physical and chemical defenses of plants to ward off insect herbivores (Krings et al. 2002, Royer et al. 2007, Futuyma & Agrawal 2009, Pott et al. 2012), and various types of deceptive camouflage and other categories of mimicry between…”
• Rapid determination of comparative drought tolerance traits: using an osmometer to predict turgor loss point (2012, methodology): “For the bestfit models, we calculated the 95% confidence intervals and 95% pre- diction intervals assuming sample sizes of 3, 6, or 10 leaves per species (Sokal &Rohlf 1995; Royer et al. 2007).”
• TRY – a global database of plant traits (2011, background): “…trait evolution (Moles et al., 2005a), phylogeny reconstruction (Lens et al., 2007), metabolic scaling theory (Enquist et al., 2007), palaeobiology (Royer et al., 2007), biogeochemistry (Garnier et al., 2004; Cornwell et al., 2008), disturbance ecology (Wirth, 2005; Paula & Pausas, 2008), plant…”