Carlson, Jane , Holsinger, Kent E. , Prunier, Rachel .
Plant responses to climate in the Cape Floristic Region of South Africa: evidence for plasticity and adaptive differentiation in the Proteaceae.
The cape region of South Africa is a global hotspot of plant endemism and diversity. The rapid generation of species within the region has been attributed in part to local adaptation along strong gradients in rainfall, temperature and soil fertility. Although such gradients clearly exist, it is unclear whether speciation was fueled by environmental selective pressures, rather than by genetic drift following isolation. To address this, we determine the degree to which climate data predicts functional traits within and among species in a monophyletic clade in the Proteaceae. If natural selection has shaped functional traits, we expect climate-trait relationships to exist across populations grown in common gardens, and if plasticity is minimal, in wild populations as well. We tested climate-trait relationships across 34 populations of 6 species in the genus Protea (section Exsertae). First, we compared functional traits of wild plants to three key climate variables from GIS climate layers: the severity of drought, cold, and rainfall seasonality. Second, we compared these climate variables to traits of offspring from each population, grown in two common gardens: one at 141m elevation, and the other at 945m. Results from the wild and the gardens suggest adaptive differentiation in some, but not all functional plant traits. Some traits were not correlated with the same climate variables in the gardens as in the wild, and phenotypes differed between gardens. Even so, climate-trait relationships existed for a suite of interrelated garden-plant traits, including specific leaf area, leaf length:width ratio, growth rate, and maximum photosynthetic rate. We conclude that plasticity is prevalent among measured traits, but adaptation to varying climates is also likely to have occurred. Our findings begin to clarify the extent to which the environment shapes and has shaped populations and species in this linage.
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Evolutionary radiations in South African Proteaceae
1 - University of Connecticut, Ecology and Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, CT, 06268, USA
2 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
3 - University of Connecticut, Ecology and Evolutionary Biology, 75 N. Eagleville Rd., U-3043, Storrs, CT, 06269, USA
Cape Floristic Region
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Wasatch B/Cliff Lodge - Level C
Date: Monday, July 27th, 2009
Time: 1:45 PM