Project Report

The goal of this research was to develop a proxy by which life history attributes can be inferred by simple measurements of a fossil leaf. It is known from the leaf economics spectrum that leaf mass per area (LMA) positively covaries with leaf life span. Leaf mass (LM) positively covaries with petiole width (PW). When LM and PW are area-normalized, petiole width measurements may be used to predict LMA, which in turn correlates with leaf life span, an important life history attribute. Earlier work has shown that petiole width per area is correlated with LMA in living woody and herbaceous non-monocot angiosperms (dicots) and gymnosperms (Royer et al., 2007). It has also been shown that fossil leaves inferred to have low LMA also have other features indicating a short leaf life span, such as high herbivory (Royer et al., 2007). The principle of calibrating a structural relationship between area-normalized LM and PW to predict the life history attributes of fossils was applied to extant ferns. Results show that fern fronds show a strong positive correlation (r2 = .4061) between LM and PW when the plants were modeled as end-loaded cantilever beams, while fern pinnae show no correlation within any model. Due to the herbaceous nature of ferns, the remainder of the data may be explained by a hydraulic model, though one has not been developed. The untapered cantilever beam model was most strongly exhibited by terrestrial ferns, as may be expected from their self-supporting growth habit. Cenozoic ferns (Polypodiales) showed highest correlation, and this is assumed due to the high number of species studied that have recently evolved. The model is promising for fossil applications, but more analyses are needed within the more ancient fern families.

National Science Foundation (NSF)
Office of International and Integrative Activities (IIA)
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Carter Kimsey
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Lemons Casee R
United States
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