Elevation filters seed traits and germination strategies in the eastern Tibetan Plateau

Seeds are the colonizing propagules for many plants and may therefore contribute to the filtering of species during the process of colonization and community assembly. Environmental filtering of seed traits may occur among species and influence community composition, or within species and influence the environmental breadth that a given species inhabits. To test for evidence of such filtering of seed traits, we measured morphological and germination traits of seeds of 408 angiosperm species collected across an elevational gradient in the eastern Tibetan Plateau grasslands. We tested for elevational filtering of traits at the species level, as well as within 22 of those species that occurred at different elevations, in order to test whether within-species variation reflected among-species patterns. Elevational patterning occurred in both seed morphology and seed germination. Seeds were smaller, more elongated, and had a higher surface area:volume ratio and shorter germination times at hi...