Gevaert, Scott , Donovan, Lisa .
Spatial and temporal variation in drought induced mortality for the rock outcrop annual sunflower, Helianthus porteri.
Plant communities which occur in depressions on granite outcrops in the southeastern United States have been used to demonstrate the role of drought stress in shaping community structure by driving species zonation. Here we ask whether drought may additionally be an agent of selection driving adaptive differentiation for geographically isolated populations. We focused on an endemic annual species that has to persist through hot, dry summer conditions in order to reproduce in the fall, Helianthus porteri. We followed plant performance (height and survival to flowering) and water status of H. porteri plants in three populations (CMR, PM, HR) that spanned its range in GA, and in relatively wet and dry habitats within each population. The three year study encompassed a regional drought year (2008), a relatively wet year (2009) and a year with approximately average precipitation (2010). Population differences in plant growth and survival depended on year, with the fewest differences apparent during the wettest year, and the greatest differences in the drought year when all plants at HR died before flowering. There was also variation within populations, with sites initially identified as relatively dry having lower growth and survival whenever habitats differed. Survival to flowering was correlated with soil water availability estimated by plant predawn water potentials. The range of predawn water potentiatls for H. porteri was similar to those reported for other mesic plants, suggesting that it is not drought tolerant. However, the spatial variation in plant performance of H. porteri related to water availability could drive adaptive differentiation in drought avoidance traits among the isolated populations. Common garden comparisons are being conducted to assess genetic differentiation among populations for traits that might be related to drought avoidance.
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1 - University of Georgia, Plant Biology, 2502 Miller Plant Sciences, Athens, GA, 30602, United States
2 - University Of Georgia, PLANT BIOLOGY DEPT, 2052 MILLER PLANT SCIENCES, Athens, GA, 30602-7271, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Forsyth Room/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 4:35 PM