Habitat quality and among-population differentiation in reproductive effort and flowering phenology in the perennial herb <Emphasis Type="Italic">Primula farinosa</Emphasis> |
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Authors: | Per Toräng Johan Ehrlén Jon Ågren |
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Institution: | 1.Department of Plant Ecology, Evolutionary Biology Centre,Uppsala University,Uppsala,Sweden;2.Department of Botany,Stockholm University,Stockholm,Sweden |
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Abstract: | In heterogeneous environments, selection on life-history traits and flowering time may vary considerably among populations
because of differences in the extent to which mortality is related to age or size, and because of differences in the seasonal
patterns of resource availability and intensity of biotic interactions. Spatial variation in optimal reproductive effort and
flowering time may result in the evolution of genetic differences in life-history traits, but also in the evolution of adaptive
phenotypic plasticity. The perennial herb Primula farinosa occurs at sites that differ widely in soil depth and therefore in water-holding capacity, vegetation cover, and frost-induced
soil movement in winter. We used data from eight natural populations and a common-garden experiment to test the predictions
that reproductive allocation is negatively correlated with soil depth while age at first reproduction and first flowering
date among reproductive individuals are positively correlated with soil depth. In the common-garden experiment, maternal families
collected in the field were grown from seed and monitored for 5 years. In the field, reproductive effort (number of flowers
in relation to rosette area) varied among populations and was negatively related to soil depth. In the common-garden experiment,
among-population differences in age at first reproduction, and reproductive effort were statistically significant, but relatively
small and not correlated with soil depth at the site of origin. Flowering time varied considerably among populations, but
was not related to soil depth at the site of origin. Taken together, the results suggest that among-population variation in
reproductive effort observed in the field largely reflects phenotypic plasticity. They further suggest that among-population
differentiation in flowering time cannot be attributed to variation in environmental factors correlated with soil depth. |
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