Seed dormancy increased population persistence in permissive environments, but not in stressful environments in an annual plant
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Background and Aims
Seed dormancy can delay germination timing to more favorable growth conditions, not only increasing seedling survival, but potentially increasing lifetime fitness. As such, seed dormancy can be a form of seasonal environmental tracking. In addition, seed dormancy can act as a bet-hedging strategy by spreading the germination risk across time, within or between years. Through both environmental tracking and bet-hedging, seed dormancy can stabilize population demography, potentially enhancing long-term population persistence.
Methods
To test whether populations that express seed dormancy are more likely to persist than populations not capable of dormancy, we established genetically variable, experimental field populations of Arabidopsis thaliana that differ in their capacity to control the seasonal timing of germination through seed dormancy. Four environmental treatments were imposed to test for demographic differences across environments and to test whether dormancy mitigates the effects of environmental variation.
Key Results
Seasonal seed dormancy influenced demography and population persistence primarily via early seedling or rosette mortality. Dormant populations had larger seedling populations and higher population persistence over the three years in the most permissive environmental treatments. However, stressful environments diminished the demographic effects of dormancy. These dynamics, in turn, resulted in dormant populations unexpectedly exhibiting more variation across environmental treatments than non-dormant populations. Therefore, dormancy’s enhancement of demographic performance may be caused more by allowing populations to take advantage of favorable conditions than by helping them to escape poor conditions.
Conclusions
This study shows that seasonal seed dormancy may help populations persist over time, but not under all environmental conditions. In more permissive environments, dormancy can reduce population bottlenecks and maintain larger populations. Some conditions, however, may be too adverse for seed dormancy to overcome.
