PS 90-155 - Linking ecologies of past and present: Fern leaf economics quantified

Friday, August 12, 2011
Exhibit Hall 3, Austin Convention Center
Casee R. Lemons1, Daniel J. Peppe1, Dana L. Royer2, Ian J. Wright3 and Christopher H. Lusk4, (1)Geology, Baylor University, Waco, TX, (2)Earth and Environmental Sciences, Wesleyan University, Middletown, CT, (3)Biological Sciences, Macquarie University, NSW 2109, Australia, (4)Department of Biological Sciences, University of Waikato, Hamilton, New Zealand

Ferns play a substantial role in comprising the flora fossil record; however, the habitats and ecophysiological development of ancient ferns are poorly understood. Understanding the ecology of ancient ferns begins with assessing extant ferns. One way of measuring this is by the analysis of leaf traits. Leaf traits which reflect tradeoffs essential to plant survival are known as the leaf economics spectrum. Plants fall along a resource use spectrum, with “fast-return” at one end and “slow-return” at the other. Fast-return species have a short leaf life span, low leaf mass per area (LMA), and high rate of nutrient uptake. Slow-return species have a long leaf life span, high LMA, and low rate of nutrient uptake.

To explore the potential for reconstructing LMA from fossil ferns, a proxy was established using extant fern leaf traits. Petiole width, leaf area, and LMA were measured in 111 fern genera from Texas, Australia, and New Zealand. It has been shown that PW is correlated to LMA, which is used to indicate leaf life span in gymnosperms and woody and herbaceous dicotyledonous angiosperms. This relationship has been used to develop a predictive model for LMA that has been applied to fossil angiosperm and gymnosperm taxa.


Data collection focused on measuring the leaf traits of extant ferns to create a modern fern calibration data set used to develop a predictive model for LMA that can be applied to extant and extinct ferns. We find that the scaling relationship between leaf area and petiole width, normalized the leaf mass, in ferns is relatively weak compared to gymnosperms and woody and herbaceous angiosperms. Further, the variance within ferns is larger than that of gymnosperms, woody dicots, and herbaceous angiosperms combined. This poor fit suggests that factors other than biomechanics, such as growth habit or phylogeny, may affect leaf economic traits in ferns.

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