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Plant morphological change; a result of climate change, predation or both?

May 21, 2012

As I run through the tropical forest in Oregon, I take time to take look at the plants and how they have changed over the years. I stop and think about what caused such change. I have learned through my biology courses, morphological change takes time and must occur through evolutionary adaptation that is passed on from parent to offspring.

When I look at all of the changes over the years, I consider global warming, an undeniable phenomena that is occurring over the world. It’s common knowledge, plants are affected by CO2. Plants uptake CO2 through the earth’s atmosphere and then releases it as O2. It is also well known the increase in CO2 in the atmosphere has aided in global warming.  What has increase in CO2 has done to the plants?

As I began to look into this I was able to find a study that looks at CO2 effect on species interaction and an evolutionary adaptation on plant population. In Vannette and Hunter (2011) study on Asclepias syriaca (Milkweed, a native to North America), evolutionary adaptation to elevated CO2; results showed that the plant, under elevated CO2, may have caused changes in:

  • Biomass and,
  • Defensive phenotype: Possible indicate a shift to a different ontogenetic stage where plants rely on tolerance and physical defenses rather than chemical defense.

Vannette and Hunter (2011) also found heritable intraspecific variation in the expression of defense phenotype and found that the effect of CO2 on the expression of defenses was often genotype-specific. Elevated CO2 increased plant tolerance to herbivory by mitigating the negative effect of herbivory on the number of bud meristems produced on plant rhizomes (Vannette and Hunter 2011). Vannette and Hunter (2011) were able to conclude that elevated Co2 does not directly change genotype frequencies within the population of A. syriaca; rather, insect herbivory acting on altered defensive phenotype will likely shape the evolution of this plant population instead. Thus, presenting the question what are the key roles of interactions evolutionary adaptation to global climate change; specifically herbivory and genetic composition of the plant population defensive phenotype.

If herbivory and pathogen interaction to plant and climate change intrigues you stay tuned for post three.

File:Asclepias syriaca.jpg

Photo credit: Common milkweed, Wikipedia

Credits:

Vannette and Hunter 2011: Genetic Variation in expression of defense phenotype may mediate evolutionary adaptation of Asclepias syriaca to elevated CO2; Rachel L. Vannette and Mark D. Hunter. Department of Ecology and Evolutionary Biology, University of Michigan. Global Change Biology (2011) 17, 1277-1288

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