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Summary Intraspecific variation in functional traits may mediate tree species' drought resistance, yet whether trait variation is due to genotype (G), environment (E), or G×E interactions remains unknown. Understanding the drivers of intraspecific trait variation and whether variation mediates drought response can improve predictions of species' response to future drought.Using populations of quaking aspen spanning a climate gradient, we investigated intraspecific variation in functional traits in the field as well as the influence of G and E among propagules in a common garden. We also tested for trait‐mediated trade‐offs in growth and drought stress tolerance.We observed intraspecific trait variation among the populations, yet this variation did not necessarily translate to higher drought stress tolerance in hotter/drier populations. Additionally, plasticity in the common garden was low, especially in propagules derived from the hottest/driest population. We found no growth–drought stress tolerance trade‐offs and few traits exhibited significant relationships with mortality in the natural populations, suggesting that intraspecific trait variation among the traits measured did not strongly mediate responses to drought stress.Our results highlight the limits of trait‐mediated responses to drought stress and the complex G×E interactions that may underlie drought stress tolerance variation in forests in dry environments.
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Changes in phenology can alter patterns of natural selection: the joint evolution of germination time and postgermination traits
Summary The timing of a developmental transition (phenology) can influence the environment experienced by subsequent life stages. When phenology causes an organism to occupy a particular habitat as a consequence of the developmental cues used, it can act as a form of habitat tracking. Evolutionary theory predicts that habitat tracking can alter the strength, direction, and mode of natural selection on subsequently expressed traits.To test whether germination phenology altered natural selection on postgermination traits, we manipulated germination time by planting seedlings in seven germination cohorts spanning 2 yr. We measured selection on postgermination traits relating to drought, freezing, and heat tolerance using a diverse combination ofArabidopsis thalianamutants and naturally occurring ecotypes.Germination cohorts experienced variable selection: when dry, cold, and hot environments were experienced by seedlings, selection was intensified for drought, freezing, and heat tolerance, respectively. Reciprocally, postgermination traits modified the optimal germination time; genotypes had maximum fitness after germinating in environments that matched their physiological tolerances.Our results support the theoretical predictions of feedbacks between habitat tracking and traits expressed after habitat selection. In natural populations, whether phenological shifts alter selection on subsequently expressed traits will depend on the effectiveness of habitat tracking through phenology.
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- Award ID(s):
- 2118654
- PAR ID:
- 10399798
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- New Phytologist
- Volume:
- 238
- Issue:
- 1
- ISSN:
- 0028-646X
- Page Range / eLocation ID:
- p. 405-421
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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