PARENT SESSION
Symposium #7: Long-term perspectives on ecological questions: A symposium in tribute to Margaret Davis.
Sponsored by ESA Paleoecology Section
Organized by: L.B. Brubaker, V. Card, and L.J. Graumlich.
Tuesday, August 7, 2001. 8:00 AM to 12:00 PM. Lecture Hall

Plant species and quaternary climate: Disparate histories and potential responses to future change.

Davis, Margaret¹, Shaw, Ruth¹, ¹

ABSTRACT- Paleoecologists have downplayed the role of evolutionary response to climate change, believing that shifts in range occur more readily than adaptation. However, experiments in which trees are grown in climates different from the source environment demonstrate adaptive differentiation in most tree species, even populations recently established at high latitudes. As climate warms and ranges begin to shift, evolutionary changes inevitably occur throughout a species range as selection favors traits than enhance fitness in the novel climate, and genes recombine that influence physiological traits, such as sensitivity to photoperiod. Recent discussion has emphasized limited seed dispersal as a restriction on biotic responses to new environments, but because of gene flow from the central population, populations at the leading edge may already harbor genetic variation that would support adaptation to a warmer climate. Populations at the trailing edge are at greater risk, because they would not receive seeds or pollen from newly extirpated populations further south. Barring genetic change, populations in the center of the range are likely to display lowered productivity, as reduced growth rates are frequently found when trees are transplanted to climates different from the source environment. Past extinctions often occurred during periods of rapid climate change, perhaps because rapid change challenged the process of adaptation by increasing the difference between existing phenotype distributions and fitness optima.

KEY WORDS: migration, refuges, genetics, climate change