The Functional Significance of Leaf Shape Variation - Towards a Consensus from Gene to Community
Jones, Cynthia S. , Schlichting, Carl , Nicotra, Adrienne B. , Bakker, Freek T. , Martinez Cabrera, Hugo .
A case history: leaf shape evolution and functional diversification in the South African genus Pelargonium (Geraniaceae).
The plant genus Pelargonium (Geraniaceae) comprises approximately 280 species, with approximately 80% endemic to southern Africa. The genus is notable for dramatic variation in leaf shape and size as well as variation in growth form that ranges from annuals to geophytes and shrubs. Sectional classification within the genus is consistent with variation in growth form whereas leaf shape varies within sections. Ancestral state reconstructions of leaf shape features show that different features of shape evolved at different rates. Leaf apex and overall outline are conserved throughout the genus, leaf venation shows an intermediate rate of evolution, and lamina dissection is highly labile. The evolutionary shift in venation is concordant with formation of major clades. At the leaf level, the evolution of pinnate venation increases the extent of secondary lobing, so that pinnately veined leaves may become much larger and more highly dissected than palmately veined leaves. When paired species from different sections are contrasted on leaf shape, more dissected leaves have higher photosynthetic rates on an area basis than less dissected leaves. This increase in photosynthesis is explained in part by differences in specific leaf area—dissected leaves have lower specific leaf areas, but strength of this correlation is clade specific. Clade-specific differences also persist in plastic responses to water availability and temperature. These results suggest shifts in leaf venation may have preceded subsequence diversification in growth form in the perennial subclades. Growth form diversification appears to have been followed by variation in the degree of dissection within lineages with similar growth form as well as shape dependent differences in photosynthesis and plasticity.
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1 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
2 - Australian National University, School of Botany and Zoology, Bld 116 Daley Rd, Canberra, ACT, 0200, Australia
3 - National Herbarium Nederland, Wageningen University branch, Generaal Foulkesweg 37, 6703 BL Wageningen, The Netherlands
4 - University of Connecticut, Ecology and Evolutionary Biology, 75 North Eagleville Rd, U-3043, Storrs, Connecticut, 062693043, USA
specific leaf area
leaf shape evolution
leaf shape and photosynthesis.
Presentation Type: Symposium or Colloquium Presentation
Location: Williford B/Hilton
Date: Monday, July 9th, 2007
Time: 11:15 AM