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Under global change, the impact of seed banks on evolutionary rescue is uncertain. They buffer plant populations from demographic and genetic stochasticity but extend generation time and can become a reservoir of maladapted alleles. We built analytical and individual-based models to predict the effect of seed banks on the persistence of small annual plant populations facing an abrupt or sustained directional change in uni- or multivariate trait optima. Demogenetic dynamics predict that under most scenarios seed banks increase the lag yet enhance persistence to 200–250 years by absorbing demographic losses. Simulations indicate that the seed bank has a minimal impact on the genetic skew, although we suggest that this result could depend on the fitness component under selection. Our multivariate model reveals that by enlarging and reshaping the G matrix, seed banks can diminish the impact of mutational correlation and even accelerate adaptation under antagonistic pleiotropy relative to populations without a bank. We illustrate how the magnitude of optimum fluctuations, type and degree of optimum change, selection strength, and vital rates are weights that tip the scales determining persistence. Finally, our work highlights that migration from the past is not maladaptative when optimum fluctuations are large enough to create stepping stones to the new optimum.
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Negative density dependence promotes persistence of a globally rare yet locally abundant plant species Oenothera coloradensis
Identifying the mechanisms underlying the persistence of rare species has long been a motivating question for ecologists. Classical theory implies that community dynamics should be driven by common species, and that natural selection should not allow small populations of rare species to persist. Yet, a majority of the species found on Earth are rare. Consequently, several mechanisms have been proposed to explain their persistence, including negative density dependence, demographic compensation, vital rate buffering, asynchronous responses of subpopulations to environmental heterogeneity, and fine‐scale source‐sink dynamics. Persistence of seeds in a seed bank, which is often ignored in models of population dynamics, can also buffer small populations against collapse. We used integral projection models (IPMs) to examine the population dynamics ofOenothera coloradensis, a rare, monocarpic perennial forb, and determine whether any of five proposed demographic mechanisms for rare species persistence contribute to the long‐term viability of two populations. We also evaluate how including a discrete seed bank stage changes these population models. Including a seed bank stage in population models had a significantly increased modeledO. coloradensispopulation growth rate. Using this structured population model, we found that negative density‐dependence was the only supported mechanism for the persistence of this rare species. We propose that high micro‐site abundances within a spatially heterogeneous environment enables this species to persist, allowing it to sidestep the demographic and genetic challenges of small population size that rare species typically face. The five mechanisms of persistence explored in our study have been demonstrated as effective strategies in other species, and the fact that only one of them had strong support here supports the idea that globally rare species can employ distinct persistence strategies. This reinforces the need for customized management and conservation strategies that mirror the diversity of mechanisms that allow rare species persistence.
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- Award ID(s):
- 1906243
- PAR ID:
- 10630755
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Oikos
- Volume:
- 2025
- Issue:
- 1
- ISSN:
- 0030-1299
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/oik.10673
