Differentiation in habitat response in taxodium distichum,taxodium mucronatum,platanus occidentalis,and liquidambar styraciflua from the United States and Mexico |
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Authors: | Calvin McMillan |
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Institution: | (1) Department of Botany and Plant Ecology Research Laboratory, University of Texas, Austin, Texas |
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Abstract: | Summary Habitat specialization in populations of three broadly distributed trees includes adaptive differentiation to day length and
temperature. Low sensitivity to environmental cues is the adaptive strategy of the southernmost populations (from northeastern
Mexico). Early cessation of growth and sensitivity to the environment is adaptive for the northernmost populations (southern
Illinois). Intermediate responses characterize trees of Texas. In a comparison under four photoperiod-temperature conditions,
the Mexico plants were adapted to the longest growing season. Under out-of-doors conditions in central Texas, these trees
from Mexico continue to demonstrate adaptive strategies different from those of Texas or Illinois trees. Stipule production
and leaf area inPlatanus showed modifications correlated with latitude. Northernmost trees had the smallest leaves and did not produce stipules under
12-h day lengths and 24–15 °C temperatures. The Mexico trees had stipules under each of the four experimental conditions.
The results suggest that populations of deciduous trees in a given climate are selected toward convergence in some responses
to that climate. As a result, populations of the three trees resemble each other in behavior in a given ecosystem.
Research funds were provided by a grant from the U.S. Forest Service and from National Science Foundation Grant GB-6097. I
acknowledge help of David S. May and George J. Williams. |
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Keywords: | Adaptation Habitat response Illinois Mexico Phenology Photoperiod Stipules Temperature Texas |
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