To produce many small or a few large seeds: size-dependent germination strategies of herbs in a species-rich natural alpine grassland.

Seeds are the product of plant sexual reproduction and experience strong selection regarding resource investment. Seed germination strategy in response to environmental cues usually depends on seed mass and is believed to be strongly selected for successful seedling establishment. Selection for germination strategy and resource allocation pattern may be functionally interlinked; however, little is known about whether and how such interaction contributes to the diversity of plant communities. This study investigated resource allocation pattern and germination strategy of 75 flowering herbs from a species-rich alpine grassland. We measured seed mass and seed number per fruit and germinated seeds under temperature and light fluctuations simulating the natural growing season. Final germination proportion (FGP) and germination synchrony (uncertainty index, UNC) were calculated. The relationship between seed size and number and the influences on FGP and UNC across germination conditions were analysed using phylogenetic approaches. The results revealed a strong trade-off between seed mass and seed number per fruit across the investigated species. FGP for smaller seeds was more sensitive to environmental cues than for larger seeds. The response of germination UNC to environmental cues was independent of seed mass. In this alpine grassland, species producing many small seeds showed greater germination sensitivity to environmental cues, while those producing few large seeds required more stable conditions for germination. The differences in seed germination strategies among species with varied seed masses may enhance population regeneration of diverse species in unpredictable conditions.