Forrestel, Elisabeth , Ackerly, David D. , Emery, Nancy C. .
Niche evolution and functional trait convergence in vernal pool endemics of the genus Lasthenia .
The relatively recent radiation of the genus Lasthenia (Asteraceae) in California has resulted in multiple independent transitions of Lasthenia species into vernal pool habitat. The vernal pools of California are semi-aquatic habitats characterized by prolonged submergence in the winter followed by a hot, dry spring and summer. These unique habitats are home to a community of primarily endemic, annual wildflower species. Within pools, species occupy predictable elevational ranges caused primarily by gradients in inundation time. This novel environment and tight habitat association of some Lasthenia species render this taxon suitable for studying niche evolution and functional convergence. Field surveys were conducted in the springs of 2007 through 2009 to quantify the microelevational niche of Lasthenia species within vernal pools across California. We found that species associated with the vernal pool habitat have a highly conserved microelevational niche among surveyed pools. A subsequent common garden greenhouse experiment including eighteen Lasthenia species was conducted and a range of functional traits, hypothesized to be associated with adaptation to a semi-aquatic environment, were measured. These traits included specific leaf area, leaf laminar perimeter to area ratio, percent cross sectional aerenchyma, mean airspace size, number of airspaces, leaf cross sectional area to perimeter ratio, mean stomatal length, stomatal density, stomatal pore index, and leaf heterophylly. A Bayesian molecular phylogeny of the Lasthenia genus was constructed and used for the phylogenetic comparative analyses. Phylogenetic independent contrasts were used to detect correlations between leaf traits and microeleveational niche optima for each species. Preliminary results indicate a significant correlation between stomatal length, percent aerenchyma in juvenile leaves, leaf heterophylly and elevational position in the pool, suggesting that these traits have converged in species adapted to vernal pools. Specific leaf area and stomatal density were not correlated with pool depth. These traits could be exaptations which initially enabled Lasthenia species to invade vernal pools or unimportant in the species ability to persist in vernal pool habitat.
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1 - Yale University, Ecology and Evolutionary Biology, Environmental Science Center, 21 Sachem St, New Haven, CT, 06520-8105, USA
2 - University of California, Berkeley, Department of Integrative Biology, 3060 Valley Life Sciences Bldg #3140, Berkeley, California, 94720, USA
3 - Purdue University, Department of Biological Sciences, 915 West State Street, West Lafayette , IN, 47907-2054, USA
phylogenetic independent contrasts
Presentation Type: Oral Paper:Papers for Sections
Location: 552A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 4:30 PM