Light plasticity of germination on the eastern Tibetan Plateau: Phylogeny, trait, and environmental correlates

Seeds often exhibit great plasticity of germination in response to environmental variability and uncertainty. The causes of this plasticity, however, remain poorly understood, and comparative phylogenic analyses of such plasticity are rare. Here, we analyzed a field germination dataset including 474 species exposed to three different levels of light availability, using comparative phylogenetic methods. We calculated the plasticity of germination in response to light availability (PG_GP) based on the maximum germination proportion (GP_max), PG_T50 based on the time required to reach 50% of GP_max, PG_RGV based on the relative germination velocity (RGV), and PG_Total based on all three of these germination traits. We found that closely related species shared similar light plasticity of germination behavior. Different aspects of germination plasticity in response to light availability were related to specific traits or local environment. PG_GP was associated with adult longevity and local water habitat, while PG_T50 was related to seed mass and local water habitat, and PG_RGV was marginally significantly related to plant height. PG_Total was significantly associated with adult longevity and water habitat. These results suggested that different aspects of germination plasticity were located at specific niche dimension, and local habitats with sufficient soil moisture induced great plasticity germination in response to light environment. As such, they can simplify our understanding of germination, promote the exploration of the general law of germination, and further increase our understanding of species diversity maintenance, adaptation, and evolution from the perspective of germination.