Effects of environment, life-history and phylogeny on germination strategy of 789 angiosperms species on the eastern Tibetan Plateau

Germination strategies vary widely among species and significantly influence individual fitness and community diversity. Germination strategies are known to be influenced by environmental conditions, life-history traits and evolutionary history, but how these factors influence germination across species under natural conditions is poorly understood. Here, we characterized germination strategies of 789 angiosperm species from the eastern Tibetan Plateau based on germination time courses and the final germination proportion expressed in the field under three light treatments: high (i.e., natural) light, medium light and low light. Based on results of correlation analysis and cluster analysis, we found two major dimensions of germination strategies [early (fast) versus late (slow) germination and high versus low germination proportions]. We also characterized a “dormant” germination strategy (species with final germination proportion < 5%). Low light availability altered the frequencies of germination strategies, and tended to canalize germination strategy into the extreme categories of early germination or high levels of dormancy. Germination strategy varied significantly based on species life-history traits (seed mass and adult longevity) and local habitat conditions (elevation, water habitat and light habitat). Finally, germination strategy exhibited strong phylogenetic signal, such that related taxa exhibited similar germination strategies. In sum, the diversity of germination strategies we observed among these species is maintained by a combination of local habitat conditions, evolutionary history and the correlated selection acting on germination and key life-history traits.