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

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