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- Title
Carbon isotope discrimination differences within and between contrasting populations of Encelia farinosa raised under common-environment conditions.
- Authors
Sandquist, Darren R.; Ehleringer, James R.
- Abstract
Previous studies of the desert shrub Encelia farinosa have shown variation of morpholological and physiological integration that appears to match environmental differences among populations. Such findings led us to ask if there is a genetic basis for such differentiation that may be related to physiological control of intercellular CO2 concentrations as indicated by carbon isotope discrimination (Δ) values, and if genetic variance for Δ is detectable within populations. Under common environment conditions, Δ values were compared between two populations of E. farinosa from desert regions with contrasting rainfall patterns: Superior, Ariz., a region with high annual rainfall and droughts of short duration, and Oatman, Ariz. a region with lower annual rainfall and longer drought periods. Superior plants had consistently greater mean Δ values than Oatman plants across a broad range of soil water potentials, indicating that there is a genetic basis for Δ variation between these populations. At the intrapopulation level only Oatman plants showed detectable genetic variance of Δ based on: (1) consistent individual-rank values for Δ among soil-drought stages, and (2) evidence of heritable genetic variance for Δ during one drought stage. No genetic variance in Δ was evident for the Superior population. It is hypothesized that the high spatio-temporal heterogeneity of water availability at Oatman may facilitate the maintenance of genetic variance for carbon isotope discrimination within this population. Both the inter- and intra-population level findings suggest that selection associated with rainfall and drought has resulted in genetic divergence of the physiological factors involved in Δ determination for these populations. There appears to be strong differences of water-use and carbon-gain strategies among populations, and broader functional breadth among plants in the habitat of greatest environmental heterogeneity.
- Subjects
OATMAN (Ariz.); ARIZONA; ISOTOPES; CARBON dioxide; PLANTS
- Publication
Oecologia, 2003, Vol 134, Issue 4, p463
- ISSN
0029-8549
- Publication type
Article
- DOI
10.1007/s00442-002-1129-8