Global seed dormancy patterns are driven by macroclimate but not fire regime

Abstract

Summary Seed dormancy maximizes plant recruitment in habitats with variation in environmental suitability for seedling establishment. Yet, we still lack a comprehensive synthesis of the macroecological drivers of nondormancy and the different classes of seed dormancy: physiological dormancy, morphophysiological dormancy and physical dormancy. We examined current geographic patterns and environmental correlates of global seed dormancy variation. Combining the most updated data set on seed dormancy classes for > 10 000 species with > 4 million georeferenced species occurrences covering all of the world's biomes, we test how this distribution is driven by climate and fire regime. Seed dormancy is prevalent in seasonally cold and dry climates. Physiological dormancy occurs in relatively dry climates with high temperature seasonality (e.g. temperate grasslands). Morphophysiological dormancy is more common in forest‐dominated, cold biomes with comparatively high and evenly distributed precipitation. Physical dormancy is associated with dry climates with strong seasonal temperature and precipitation fluctuations (e.g. deserts and savannas). Nondormancy is associated with stable, warm and wetter climates (e.g. tropical rain forest). Pyroclimate had no significant effect on the distribution of seed dormancy. The environmental drivers considered in this study had a comparatively low predictive power, suggesting that macroclimate is just one of several global drivers of seed dormancy.

Dormancy, germination, and associated seed ecological traits of 25 Fabaceae species from northern India

“…Thus, compared to the dry zone of Sri Lanka, species tend to produce more PY seeds under the drier conditions in Rajgir (Nalanda), India. This interpopulation variation is acceptable as many researchers have reported an increasing trend of PY with dryness of the environment (Tweddle et al 2003;Baskin & Baskin 2014;Jaganathan et al 2017;Rosbakh et al 2023). The observed change in the "level" of dormancy could be due to genetic, environmental, or maternal effects (Jaganathan 2016).…”

Global patterns in the evolutionary relations between seed mass and germination traits

“…For example, this may be explained by the potential competition from neighbouring and maternal plants that exists in the forest understory which in turn may select for long-distance dispersal or increased level of seed dormancy, requiring smaller and lighter seeds to easily disperse or to enter deeper soil layers to form a soil seed bank. Additionally, most tree species exhibit PD (Rosbakh et al, 2023) which favors delayed germination and requires dormancy breaking agents (i.e, stratification and after ripening) to overcome dormancy, leading to cueing of germination to periods suitable conditions (Escobar et al, 2021; Maleki et al, 2022; Just et al, 2023). Interestingly, this hypothesis is consistent with our findings about small seeds of species with PD showing higher levels of seed dormancy (Fig 3; Table 2).…”

“…To test whether was a relationship between seed mass and germination traits, principal component analysis (PCA) implemented within the R environment (FACTOMINER package) was employed (Le et al, 2008; Rosbakh et al, 2023). We first quantified the potential relationship for each growth form through fitting univariate models.…”

“…To answer the long-standing question of how seed mass interacts with differing levels of seed dormancy, we used Bayesian logistic phylogenetically informed generalized mixed models, following Rosbakh et al (2023). In the models, we treated seed dormancy (the response variable) as binary data.…”

Large dataset analyses advance knowledge of seed ecology and evolutionary biology

“…Data used in the analysis (species distribution data and corresponding seed dormancy classes) of Rosbakh et al . (2023) original study are available at Zenodo: https://zenodo.org/records/10207191 (DOI 10.5281/zenodo.10207190).…”