Understanding the fitness consequences of different life histories is critical for explaining their diversity and for predicting effects of changing environmental conditions. However, current theory on plant life histories relies on phenomenological, rather than mechanistic, models of resource production. We combined a well‐supported mechanistic model of ontogenetic growth that incorporates differences in the size‐dependent scaling of gross resource production and maintenance costs with a dynamic optimization model to predict schedules of reproduction and prolonged dormancy (plants staying below ground for ≥1 growing season) that maximize lifetime offspring production. Our model makes three novel predictions: First, maintenance costs strongly influence the conditions under which a monocarpic or polycarpic life history evolves and how resources should be allocated to reproduction by polycarpic plants. Second, in contrast to previous theory, our model allows plants to compensate for low survival conditions by allocating a larger proportion of resources to storage and thereby improving overwinter survival. Incorporating this ecological mechanism in the model is critically important because without it our model never predicts significant investment into storage, which is inconsistent with empirical observations. Third, our model predicts that prolonged dormancy may evolve solely in response to resource allocation trade‐offs.
To cope with uncertainty and variability in their environment, plants evolve distinct life‐history strategies by allocating different fractions of energy to growth, survival and fecundity. These differences in life‐history strategies could potentially influence ecosystem‐level dynamics, such as the sensitivity of primary production to resource fluctuations. However, linkages between evolutionary and ecosystem dynamics are not well understood. We used an annual plant population model to ask, when might differences in plant life‐history strategies produce differences in the sensitivity of primary production to resource fluctuations? Consistent with existing theory, we found that a highly variable and unpredictable environment led to the evolution of a conservative strategy characterized by relatively low and invariant germination fractions, while a variable but predictable environment favoured a riskier strategy featuring more variable germination fractions. Unexpectedly, we found that the influence of life‐history strategy on the sensitivity of production to resource fluctuations depended on competitive interactions, specifically the rate at which production saturates with the number of competing individuals. Rapid saturation overwhelms the influence of life‐history strategy, but when production saturates more slowly, the risky strategy translated to high sensitivity, whereas the conservative strategy translated to low sensitivity. Empirical estimates from Sonoran Desert annual plant populations indicate that production saturates relatively rapidly with the number of individuals for most species, suggesting that life‐history differences are unlikely to alter sensitivity of production to resource fluctuations, at least in this community.
- Award ID(s):
- 1933612
- NSF-PAR ID:
- 10448304
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Ecology
- Volume:
- 109
- Issue:
- 12
- ISSN:
- 0022-0477
- Page Range / eLocation ID:
- p. 4081-4091
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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