Developmental and Structural Section
Mocko, Kerri , Jones, Cynthia S. .
A phylogenetic analysis of stomatal evolution and leaf shape in Pelargonium.
Pelargonium (Geraniaceae) comprises a monophyletic clade of ~280 species largely endemic to South Africa, ranging in growth form from stem succulents and geophytes to shrubs. The genus also displays tremendous variation in leaf shape, which unlike growth form, is highly variable across the phylogeny. Differences in growth form and leaf shape have functional consequences for plant water use but the association between leaf and stem structural components and water balance is complex. Stomata govern the exchange of water and carbon dioxide into and out of the leaf and may be used as a structural proxy for functional differences that could link adaptations for water balance at the leaf level with water use strategies across the phylogeny. In this study, we ask how do stomatal characters vary across clades and as a function of leaf shape in co-occurring Pelargonium species? Stomatal characters were analyzed in relation to leaf shape and size in 30+ Pelargonium species representing all major growth forms. We found statistically significant differences in stomatal density and stomatal pore index between the three major clades. Stomatal density is positively correlated with leaf traits (leaf area, length, fresh and dry mass) and negatively correlated with lamina perimeter as well as leaf shape measured by a leaf dissection index. Phylogenetic independent contrast (PIC) analyses show that correlations are even stronger when phylogeny is considered. While stomatal variation is usually examined with suites of physiological measurements, our study is unique in that we are taking a phylogenetic approach to look at the association between stomata, leaf shape and the evolutionary adaptive value of structural variation.
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1 - University of Connecticut, Department of Ecology and Evolutionary Biology, 75 N. Eagleville Road, Unit 3043, Storrs, CT, 06269-3043, USA
stomatal pore index
phylogenetic independent contrasts.
Presentation Type: Oral Paper:Papers for Sections
Location: 555B/Convention Center
Date: Wednesday, August 4th, 2010
Time: 10:45 AM