The theoretical models of life-history strategy assume that there is a positive correlation between seed size and offspring survival (seed size-survival relationship). However, little research has been done on how this relationship changes with environment or with seedling traits. Therefore, a research team led by researcher Huakun Zhou belongs to Key Laboratory of Restoration Ecology for Cold regions laboratory in Qinghai monitored the seedling survival rate of 303 angiosperms collected from alpine and sub-alpine meadows in the eastern Qinghai-Tibet Plateau in the first year after emergence, and used linear model (LM) and generalized linear model of phylogenetic development (PGLM) to measure the relationship between seed size and survival rate, as well as the difference under illumination conditions. In addition, the interaction between seed size and other seedling traits (emergence time, specific leaf area, root-stem biomass ratio, biomass growth) was evaluated by path analysis (PA) and phylogenetic validation path analysis (PPA), and the ways of effect on seedling survival were revealed.
It was found that seed size was positively correlated with seedling survival rate only under medium and high-light treatment. PA and PPA showed that the positive effect of seed size on seedling survival was indirect, mainly through the growth of biomass. Under the condition of low light, the larger seeds showed a faster growth rate, which improved the survival rate of seedlings, and the direct effect of seed size on the survival of seedlings was negative. The relationship between seed size and seedling survival depends on both environmental and systemic genetics. The survival advantage of large seeds lies in their high biomass growth capacity in low-resource environments. However, the study found that larger seeds face a small but more immediate risk of death, a tradeoff that cannot be ignored. All seedling traits and their relationships were different under different light treatments. Therefore, the influence of environment on seedling traits, interaction between seedling traits and phylogeny should be considered when constructing the dynamic model of seedlings. This study has a good reference value for the understanding of the restoration potential and regulation mechanism of alpine grassland and the breeding and improvement of new herbage varieties.
The paper links: https://doi.org/10.1016/j.agee.2019.05.009
