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1. Population histories of variable reproductive success and low winter precipitation correlate with risk‐averse seed germination in a mediterranean‐climate winter annual

   https://doi.org/10.1002/ajb2.16412  

   Vergara, Isabella H; Geber, Monica A; Moeller, David A; Eckhart, Vincent M (October 2024, American Journal of Botany)

   Abstract PremiseSeed germination involves risk; post‐germination conditions might not allow survival and reproduction. Variable, stressful environments favor seeds with germination that avoids risk (e.g., germination in conditions predicting success), spreads risk (e.g., dormancy), or escapes risk (e.g., rapid germination). Germination studies often investigate trait correlations with climate features linked to variation in post‐germination reproductive success. Rarely are long‐term records of population reproductive success available. MethodsSupported by demographic and climate monitoring, we analyzed germination in the California winter‐annualClarkia xantianasubsp.xantiana. Sowing seeds of 10 populations across controlled levels of water potential and temperature, we estimated temperature‐specific base water potential for 20% germination, germination time weighted by water potential above base (hydrotime), and a dormancy index (frequency of viable, ungerminated seeds). Mixed‐effects models analyzed responses to (1) temperature, (2) discrete variation in reproductive success (presence or absence of years with zero seed production by a population), and (3) climate covariates, mean winter precipitation and coefficient of variation (CV) of spring precipitation. For six populations, records enabled analysis with a continuous metric of variable reproduction, the CV of per‐capita reproductive success. ResultsPopulations with more variable reproductive success had higher base water potential and dormancy. Higher base water potential and faster germination occurred at warmer experimental temperatures and in seeds of populations with wetter winters. ConclusionsGeographic variation in seed germination in this species suggests local adaptation to demographic risk and rainfall. High base water potential and dormancy may concentrate germination in years likely to allow reproduction, while spreading risk among years. 

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2. Physical Seed Dormancy in Legumes: Molecular Advances and Perspectives

   https://doi.org/10.3390/plants13111473  

   Wen, Zhaozhu; Lu, Xuran; Wen, Jiangqi; Wang, Zengyu; Chai, Maofeng (June 2024, Plants)

   Physical dormancy of seeds is a form of dormancy due to the presence of an impermeable seed coat layer, and it represents a feature for plants to adapt to environmental changes over an extended period of phylogenetic evolution. However, in agricultural practice, physical dormancy is problematic. because it prevents timely and uniform seed germination. Therefore, physical dormancy is an important agronomical trait to target in breeding and domestication, especially for many leguminous crops. Compared to the well-characterized physiological dormancy, research progress on physical dormancy at the molecular level has been limited until recent years, due to the lack of suitable research materials. This review focuses on the structure of seed coat, factors affecting physical dormancy, genes controlling physical dormancy, and plants suitable for studying physical dormancy at the molecular level. Our goal is to provide a plethora of information for further molecular research on physical dormancy. 

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3. Bacteria-phage coevolution with a seed bank

   https://doi.org/10.1038/s41396-023-01449-2  

   Schwartz, Daniel A.; Shoemaker, William R.; Măgălie, Andreea; Weitz, Joshua S.; Lennon, Jay T. (June 2023, The ISME Journal)

   Abstract Dormancy is an adaptation to living in fluctuating environments. It allows individuals to enter a reversible state of reduced metabolic activity when challenged by unfavorable conditions. Dormancy can also influence species interactions by providing organisms with a refuge from predators and parasites. Here we test the hypothesis that, by generating a seed bank of protected individuals, dormancy can modify the patterns and processes of antagonistic coevolution. We conducted a factorially designed experiment where we passaged a bacterial host (Bacillus subtilis) and its phage (SPO1) in the presence versus absence of a seed bank consisting of dormant endospores. Owing in part to the inability of phages to attach to spores, seed banks stabilized population dynamics and resulted in minimum host densities that were 30-fold higher compared to bacteria that were unable to engage in dormancy. By supplying a refuge to phage-sensitive strains, we show that seed banks retained phenotypic diversity that was otherwise lost to selection. Dormancy also stored genetic diversity. After characterizing allelic variation with pooled population sequencing, we found that seed banks retained twice as many host genes with mutations, whether phages were present or not. Based on mutational trajectories over the course of the experiment, we demonstrate that seed banks can dampen bacteria-phage coevolution. Not only does dormancy create structure and memory that buffers populations against environmental fluctuations, it also modifies species interactions in ways that can feed back onto the eco-evolutionary dynamics of microbial communities. 

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4. Subalpine tree seed availability and germination at Niwot Ridge, 2015 - ongoing.

   https://doi.org/10.6073/pasta/39fe0926fb860aa1c0f3e53d093403e4  

   Andrus, Robert A (March 2025, Environmental Data Initiative)

   These data were collected to assess how seed availability and site limitations affect conifer germination across species distributions. Our study focused on areas above alpine treeline where subalpine tree species must migrate to track movement of suitable climate, but we also included sites in the core and at the lower ecotone of subalpine forests. We monitored seed availability and germination of new seedlings for four subalpine tree species from 2015-present at Niwot Ridge, Colorado, USA. Seed availability was collected in 66-95 seed traps in 14-17 sites (6-12 traps per site; see data for count per site), depending on year. In the lab, seeds were counted by species. In the field, new germinants were counted by species 3-5 weeks after snow disappearance (i.e., peak germination) and again in late September from 2015 to 2018 only. Only one census of new germinants was conducted from 2019 to 2023. New germinants from prior years were censused in subsequent summers. 

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5. Decadal survival of tropical pioneer seeds in the soil seed bank is accompanied by fungal infection and dormancy release

   https://doi.org/10.1111/1365-2435.14476  

   Zalamea, Paul‐Camilo; Sarmiento, Carolina; Arnold, A_Elizabeth; Kuo, Venus; Delevich, Carolyn; Davis, Adam_S; Brown, Thomas_A; Dalling, James_W (December 2023, Functional Ecology)

   Abstract Pioneer trees require high‐light environments for successful seedling establishment. Consequently, seeds of these species often persist in the soil seed bank (SSB) for periods ranging from several weeks to decades. How they survive despite extensive pressure from seed predators and soil‐borne pathogens remains an intriguing question.This study aims to test the hypotheses that decades‐old seeds collected from the SSB in a lowland tropical forest remain viable by (i) escaping infection by fungi, which are major drivers of seed mortality in tropical soils, and/or (ii) maintaining high levels of seed dormancy and seed coat integrity when compared to inviable seeds.We collected seeds ofTrema micranthaandZanthoxylum ekmaniiat Barro Colorado Island, Panama, from sites where adult trees previously occurred in the past 30 years. We used carbon dating to measure seed age and characterized seed coat integrity, seed dormancy and fungal communities.Viable seeds from the SSB ranged in age from 9 to 30 years forT. micrantha, and 5 to 33 years forZ. ekmanii. We found no evidence that decades‐old seeds maintain high levels of seed dormancy or seed coat integrity. Fungi were rarely detected in fresh seeds (no soil contact), but phylogenetically diverse fungi were detected often in seeds from the SSB. Although fungal infections were more commonly detected in inviable seeds than in viable seeds, a lack of differences in fungal diversity and community composition between viable and inviable seeds suggested that viable seeds are not simply excluding fungal species to survive long periods in the SSB.Synthesis.Our findings reveal the importance of a previously understudied aspect of seed survival, where the impact of seed–microbial interactions may be critical to understand long‐term persistence in the SSB. Read the freePlain Language Summaryfor this article on the Journal blog. 

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