Genetic variation in germination, growth, and survivorship of red maple in response to subambient through elevated atmospheric CO2

Genetic variation in plant response to atmospheric carbon dioxide (CO2) may have influenced paleo-vegetation dynamics and could determine how future elevated CO2 drives plant evolution and ecosystem productivity. We established how levels of relatedness - the maternal family, population, and provenance - affect variation in the CO2 response of a species. This 2-year growth chamber experiment focused on the germination, growth, biomass allocation, and survivorship responses of Acer rubrum to four concentrations of CO2: 180, 270, 360, and 600 (mu)L L^-1- representing Pleistocene through potential future conditions. We found that all levels of relatedness interacted with CO2 to contribute to variation in response. Germination responses to CO2 varied among families and populations, growth responses depended on families and regions of origin, and survivorship responses to CO2 were particularly affected by regional identities. Differences among geographic regions accounted for 23% of the variation in biomass response to CO2. If seeds produced under subambient CO2 conditions behave similarly, our results suggest that A. rubrum may have experienced strong selection on seedling survivorship at Pleistocene CO2 levels. Further, this species may evolve in response to globally rising CO2 so as to increase productivity above that experimentally observed today. Species responses to future atmospheric CO2 and the accompanying biotic effects on the global carbon cycle will vary among families, populations, and provenances.