Phenotypic and genetic differences in a perennial herb across a natural gradient of CO2 concentration
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The atmospheric CO2 concentration [CO2] has been increasing markedly since the industrial revolution and is predicted to reach 500–1,000 μmol mol−1 by the end of this century. Although the short-term and acclimatory responses to elevated [CO2] have been well studied, much less is understood about evolutionary responses to high [CO2]. We studied phenotypic and genetic differences in Plantago asiatica populations around a natural CO2 spring, where [CO2] has been consistently high over an evolutionary time scale. Our common-garden experiment revealed that plants transferred from habitats with higher [CO2] had higher relative growth rates, greater leaf to root ratios, lower photosynthetic rates, and lower stomatal conductance. The habitat-dependent differences were partly heritable because a similar trend of leaf to root ratio was found among their offsprings. Genetic analyses indicated that selfing or biparental inbreeding might promote local adaptation in areas with high [CO2] despite substantial gene flow across the [CO2] gradient. These results indicate that phenotypic and genetic differences have occurred between high and normal [CO2] populations.
KeywordsAdaptation to elevated CO2 concentration CO2 spring Evolutionary response Plant function Plantago
We thank Yudonosan-shrine, the landowner of the CO2 spring, for permission for the study. We thank Yayoi Koizumi, Risako Akita, Tomomi Kojima and Soichiro Nagano for technical support and Roger Butlin for comments on an early draft. The study was supported in part by KAKENHI (16687001, 19370008, 20677001, 21114009), Global Environment Research Fund (D-0904) and Global COE program (J03).
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