The timing of germination has profound impacts on fitness, population dynamics, and species ranges. Many plants have evolved responses to seasonal environmental cues to time germination with favorable conditions; these responses interact with temporal variation in local climate to drive the seasonal climate niche and may reflect local adaptation. Here, we examined germination responses to temperature cues in Streptanthus tortuosus populations across an elevational gradient.
Methods
Using common garden experiments, we evaluated differences among populations in response to cold stratification (chilling) and germination temperature and related them to observed germination phenology in the field. We then explored how these responses relate to past climate at each site and the implications of those patterns under future climate change.
Results
Populations from high elevations had stronger stratification requirements for germination and narrower temperature ranges for germination without stratification. Differences in germination responses corresponded with elevation and variability in seasonal temperature and precipitation across populations. Further, they corresponded with germination phenology in the field; low‐elevation populations germinated in the fall without chilling, whereas high‐elevation populations germinated after winter chilling and snowmelt in spring and summer. Climate‐change forecasts indicate increasing temperatures and decreasing snowpack, which will likely alter germination cues and timing, particularly for high‐elevation populations.
Conclusions
The seasonal germination niche for S. tortuosus is highly influenced by temperature and varies across the elevational gradient. Climate change will likely affect germination timing, which may cascade to influence trait expression, fitness, and population persistence.
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Variation in the seasonal germination niche across an elevational gradient: the role of germination cueing in current and future climates
The timing of germination has profound impacts on fitness, population dynamics, and species ranges. Many plants have evolved responses to seasonal environmental cues to time germination with favorable conditions; these responses interact with temporal variation in local climate to drive the seasonal climate niche and may reflect local adaptation. Here, we examined germination responses to temperature cues in
Using common garden experiments, we evaluated differences among populations in response to cold stratification (chilling) and germination temperature and related them to observed germination phenology in the field. We then explored how these responses relate to past climate at each site and the implications of those patterns under future climate change.
Populations from high elevations had stronger stratification requirements for germination and narrower temperature ranges for germination without stratification. Differences in germination responses corresponded with elevation and variability in seasonal temperature and precipitation across populations. Further, they corresponded with germination phenology in the field; low‐elevation populations germinated in the fall without chilling, whereas high‐elevation populations germinated after winter chilling and snowmelt in spring and summer. Climate‐change forecasts indicate increasing temperatures and decreasing snowpack, which will likely alter germination cues and timing, particularly for high‐elevation populations.
The seasonal germination niche for
- Award ID(s):
- 1831913
- NSF-PAR ID:
- 10458301
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- American Journal of Botany
- Volume:
- 107
- Issue:
- 2
- ISSN:
- 0002-9122
- Page Range / eLocation ID:
- p. 350-363
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The seasonal timing of seed germination determines a plant’s realized environmental niche, and is important for adaptation to climate. The timing of seasonal germination depends on patterns of seed dormancy release or induction by cold and interacts with flowering-time variation to construct different seasonal life histories. To characterize the genetic basis and climatic associations of natural variation in seed chilling responses and associated life-history syndromes, we selected 559 fully sequenced accessions of the model annual species Arabidopsis thaliana from across a wide climate range and scored each for seed germination across a range of 13 cold stratification treatments, as well as the timing of flowering and senescence. Germination strategies varied continuously along 2 major axes: 1) Overall germination fraction and 2) induction vs. release of dormancy by cold. Natural variation in seed responses to chilling was correlated with flowering time and senescence to create a range of seasonal life-history syndromes. Genome-wide association identified several loci associated with natural variation in seed chilling responses, including a known functional polymorphism in the self-binding domain of the candidate gene DOG1. A phylogeny of DOG1 haplotypes revealed ancient divergence of these functional variants associated with periods of Pleistocene climate change, and Gradient Forest analysis showed that allele turnover of candidate SNPs was significantly associated with climate gradients. These results provide evidence that A. thaliana ’s germination niche and correlated life-history syndromes are shaped by past climate cycles, as well as local adaptation to contemporary climate.more » « less
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Abstract In Mediterranean climates, the timing of seasonal rains determines germination, flowering phenology and fitness. As climate change alters seasonal precipitation patterns, it is important to ask how these changes will affect the phenology and fitness of plant populations. We addressed this question experimentally with the annual plant species
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DOG1 and the flowering time geneFRI . We synthesized germination phenology data from the first experiment with fitness functions from the second experiment to project population fitness under different seasonal rainfall scenarios.Germination phenology tracked rainfall onset but was slower and more variable on sand than on soil. Many seeds dispersed on sand in spring and summer delayed germination until the cooler temperatures of autumn. The high‐dormancy
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Abstract Aim We examine how environmental variability at seasonal and interannual time‐scales influences evolutionary trajectories and the role of plasticity in response to recent and future climate change at biogeographic scales. We investigate the interplay of selection pressures at chronic (performance) and acute (thermal stress) time‐scales.
Location Colorado, USA.
Time period 1950–2099.
Major taxa studied A montane butterfly, clouded sulphur (
Colias eriphyle W.H. Edwards, 1876).Methods We leverage field and laboratory data to construct phenotype‐based models that predict fitness and evolutionary responses to recent and future climate change. Our focal phenotype, wing solar absorptivity, responds plastically to developmental (pupal) temperatures and determines adult fitness via its influence on body temperature.
Results We project that phenology accelerates with decreasing elevation and climate change, but gradients in pupal and adult temperature with climate change are modest. Fitness of the first generation is predicted to decrease at low elevations and increase at high elevations with warming. Elevational clines in optimal wing absorptivity shift towards lower absorptivities with warming. We project that temporal shifts from selection for wing darkening (to extend flight time) to selection for wing lightening (to avoid overheating) in some cool, montane locations will ultimately impose fitness costs.
Main conclusions Our analysis suggests that shifts in the balance of selection between acute and chronic responses to environmental variation will alter biogeographic responses to climate change. Evolutionary lags may ultimately confer greater sensitivity to climate change, but plasticity can reduce evolutionary lags by facilitating trait evolution.
