TY - JOUR
T1 - From fluorescence to fitness
T2 - Variation in photosynthetic rate affects fecundity and survivorship
AU - Arntz, A. Michele
AU - DeLucia, Evan H.
AU - Jordan, Nicholas
PY - 2000/9
Y1 - 2000/9
N2 - Genetic variation in photosynthetic traits within populations provides the potential for evolution, but few studies relate phenotypic variation in these traits to variation in fitness. We tested the prediction that a lower photosynthetic rate reduces fecundity and survivorship by comparing wild-type (WT) Amaranthus hybridus family lines to those having a single-gene mutation that confers resistance to atrazine (R) and lowers the rate of photosynthetic carbon assimilation. Wild-type and R family lines with nearly uniform nuclear genomes were used to minimize the confounding effects of other loci. We established experimental populations in agricultural and one-year-old field plots and measured chlorophyll fluorescence, gas exchange, and the fecundity and survivorship of WT and R genotypes for two generations. The R genotype had a lower efficiency of electron transport through photosystem II, which translated into a 20-30% decrease in photosynthetic rate at light levels above 400 μmol·m-2·s-1. Compared to the WT, the R genotype also had lower water-use efficiency, higher specific leaf area, and greater leaf nitrogen concentration on a mass, but not area, basis. In five of six replicate populations, the R genotype had lower fecundity than the WT in the first generation. Survivorship of seed over winter was similar for the two genotypes, but survivorship of R seedlings during early establishment was lower than the WT in the agricultural field. The consistent pattern of selection against the R genotype during vegetative growth stages suggests that a lower photosynthetic rate reduces fitness. This selection, paired with heritable variation for photosynthetic traits within populations, provides a more complete scenario for the evolution of photosynthetic traits.
AB - Genetic variation in photosynthetic traits within populations provides the potential for evolution, but few studies relate phenotypic variation in these traits to variation in fitness. We tested the prediction that a lower photosynthetic rate reduces fecundity and survivorship by comparing wild-type (WT) Amaranthus hybridus family lines to those having a single-gene mutation that confers resistance to atrazine (R) and lowers the rate of photosynthetic carbon assimilation. Wild-type and R family lines with nearly uniform nuclear genomes were used to minimize the confounding effects of other loci. We established experimental populations in agricultural and one-year-old field plots and measured chlorophyll fluorescence, gas exchange, and the fecundity and survivorship of WT and R genotypes for two generations. The R genotype had a lower efficiency of electron transport through photosystem II, which translated into a 20-30% decrease in photosynthetic rate at light levels above 400 μmol·m-2·s-1. Compared to the WT, the R genotype also had lower water-use efficiency, higher specific leaf area, and greater leaf nitrogen concentration on a mass, but not area, basis. In five of six replicate populations, the R genotype had lower fecundity than the WT in the first generation. Survivorship of seed over winter was similar for the two genotypes, but survivorship of R seedlings during early establishment was lower than the WT in the agricultural field. The consistent pattern of selection against the R genotype during vegetative growth stages suggests that a lower photosynthetic rate reduces fitness. This selection, paired with heritable variation for photosynthetic traits within populations, provides a more complete scenario for the evolution of photosynthetic traits.
KW - Amaranthus hybridus
KW - Atrazine resistance
KW - Genotype frequency
KW - Selection for photosynthesis
KW - Water-use efficiency
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U2 - 10.1890/0012-9658(2000)081[2567:FFTFVI]2.0.CO;2
DO - 10.1890/0012-9658(2000)081[2567:FFTFVI]2.0.CO;2
M3 - Article
AN - SCOPUS:0033850216
VL - 81
SP - 2567
EP - 2576
JO - Ecology
JF - Ecology
SN - 0012-9658
IS - 9
ER -