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Harvard Forest Symposium Abstract 2014

  • Title: Variation in reproductive allocation of ragweed ecotypes in response to elevated carbon dioxide
  • Primary Author: Jennifer Albertine (Harvard Forest)
  • Additional Authors: Tristram Seidler (University of Massachusetts - Amherst ); Kristina Stinson (University of Massachusetts - Amherst )
  • Abstract:

    Assessing ecotypic variation in plant response to predicted levels of carbon dioxide (CO2) is a priority for understanding climate change effects on plant species, especially those that can affect human health. Common ragweed, a native annual North American plant, is a well-known allergenic weed that increases growth and reproduction in experimentally elevated CO2 conditions. However, it is not well known whether plants from environmentally distinct populations respond differently to elevated carbon dioxide. Ecotypic variation in CO2 response was tested here by exposing plants from 24 populations across a latitudinal gradient in the Northeastern US to three levels of CO2: 400 ppm, 600 ppm, and 800 ppm in a common garden experiment. The objective was to test for differences among ecotypes in biomass allocation to reproduction. Ecotypes showed increasing allocation to reproduction relative to shoot growth with increasing latitude. Differences among populations were not significant at ambient CO2. However, at elevated CO2, the most northern populations (VT) allocated significantly more biomass to reproduction relative to shoot size than populations located in the southern most populations (NY). When separating reproduction into male and female reproduction it became clear that northern population (VT) allocated significantly more biomass relative to shoot mass to female reproduction and this difference was magnified by elevated CO2. Allocation to male reproduction relative to shoot mass did not significantly differ across populations. However, the southern most population (NY) allocated the least to male reproduction compared to the mid- and northern- populations. This increased allocation to reproduction in response to elevated CO2 in the northern most populations is an indication of the population’s life history and the genetic control of development. In their natural range, these plants are exposed to a shorter growing season than the southern populations; more effort is placed on reproductive growth over vegetative growth to insure the plant completes its life cycle successfully during the growing season. Thus, increases in available photosynthate as a result of stimulation by elevated CO2 would likely be allocated to reproduction over vegetative growth.

  • Research Category: Physiological Ecology, Population Dynamics, and Species Interactions