Abstract Detail

Ecophysiology

McKown, Athena D. [1], Drewes, Eric C. [1], Azam, Md. Shofiul [1], Guy, Robert D. [1].

Inherent adaptation in Cottonwood poplar (Populus trichocarpa) along geographic clines.

Species with wide variation in geography may show local adaptation and selection for adaptive traits in relation to local growing season and climate.  The genomically sequenced Cottonwood poplar (Populus trichocarpa) is a widespread tree in western North America and there is strong interest in understanding the ecophysiology of this species, as it represents a model tree species with potential use in the agro-biofuels industry.  This study investigated inherent trait variation within P. trichocarpa using trees selected along a latitudinal cline from Alaska to Oregon.  Over 2000 trees (representing replicate plantings of 499 collected genotypes in 150 provenance localities) were grown in a common garden in Vancouver, BC and studied for numerous traits relating to seasonal (phenological) events, biomass accumulation and growth rates, and photosynthetic traits.  Traits were analyzed in relation to photoperiodic and climatic (temperature/ precipitation) clines, and in trait-trait combinations to understand relationships between plant structure and plant performance. All genotypes showed strong correlation between phenological events and latitude.  Total biomass was greater in southern genotypes, despite faster incipient growth rates in northern genotypes, because these trees set bud and entered “fall phase” earlier.  Photosynthesis and conductance, and related gas exchange traits, were higher in northern genotypes compared to southern genotypes, and showed correlation with leaf thickness and stomatal densities.  Thus, despite faster rates of growth and photosynthesis in northern genotypes, response to photoperiod shortened the active growing season and resulted in smaller trees with less accumulation in biomass.  Analysis of traits against photoperiodic or climate clines showed that most traits associate with latitude, but some further correlate with climate clines.  Numerous traits measured in this study point to photoperiod as a strong driver of adaptation in P. trichocarpa, and multiple lines of evidence from the common garden experiment suggest that northern genotypes show selection for specific traits relating to maximizing a shortened active growing season, compared to southern genotypes.

Broader Impacts:

1 - University of British Columbia, Department of Forest Sciences, Forest Sciences Centre, 2424 Main Mall, Faculty of Forestry, Vancouver, BC, V6T 1Z4, Canada

Keywords:
poplar
adaptation
Latitude
photoperiod
phenology
climate
Photosynthesis.

Presentation Type: Oral Paper:Papers for Topics
Session: 30
Location: 551B/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 11:30 AM
Number: 30012
Abstract ID:678