Sulman, Joshua , Sytsma, Kenneth J. .
Evolution of Emergent, Floating and Submerged-Leaved Habits in Sparganium.
Sparganium (bur-reed, Typhaceae) is an aquatic and wetland genus of 14 species widely distributed across north temperate regions. A molecular phylogeny was estimated from two chloroplast (trnL-F, psbJ-petA) and two nuclear (ITS, Phy C) regions, using parsimony, likelihood and Bayesian approaches – all generating results largely in agreement. The genus is divided into two highly-supported subclades that do not correspond with previous subgeneric classifications. The S. eurycarpum-S. erectum clade is recognized by the presence (usually) of distigmatic flowers. The remaining 12 species form a unistigmatic, ‘core’ clade. The species are specialized in growth habit (emergent, floating, or submerged leaves). The character evolution of the growth habit in the Sparganium phylogeny was analyzed in parsimony and Bayesian frameworks. The results suggest that the floating and submerged habits arose independently from emergent ancestors. The relationship between growth habit and water electrical conductivity (EC) was analyzed for 7 North American species. Results indicated that floating (S. angustifolium, S. fluctuans) and submerged species (S. natans) are largely restricted to low EC water. Some emergent species were widely distributed over moderate to high EC (S. eurycarpum, S. emersum), though others (S. americanum, S. androcladum) apparently are restricted to low EC waters. The narrow EC range occupied by the floating and submerged-leaved species reflects a specialization to a low-nutrient environment. The loss of rigid structural tissues in leaves may confer an advantage in oligotrophic habitats, allowing the plant to devote more resources to photosynthetic tissues.
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1 - University of Wisconsin, Botany, 430 Lincoln Drive, Madison, WI, 53706, USA
2 - University of Wisconsin Madison, Department of Botany, Birge Hall, 430 Lincoln Drive, Madison, Wisconsin, 53706-1381, USA
phylogenetics of monocotyledons
Presentation Type: Oral Paper:Papers for Sections
Location: 555A/Convention Center
Date: Monday, August 2nd, 2010
Time: 11:15 AM