Abstract: Seriphidium desert grassland is widely distributed across the northern Xinjiang region and is known for its abundant plant diversity. We collected the seeds of 88 plant species from this grassland and measured seed mass, shape index and life form. We also analyzed the phylogenetic signal of seed mass and the shape index using phylogenetic comparative methods, in order to identify seed adaptation types for desert and semi-desert environments. Results showed that the seed mass of plants can be divided into four classes: A (0.01-0.10 mg), B (0.10-1.00 mg), C (1.00-10.00 mg) and D (10.00-50.00 mg), with classes B and C being dominant in quantity. The plant species divided into six life forms, of which the dominant are annual, perennial and ephemeral herbaceous. The shape index of seeds was determined by the variance of three dimensions (length, width and height), with the index scores ranging between 0.00 and 0.20. The shape of 42 species was close to sphericity while the remaining 46 species were flat or enlongated. There were significant differences in seed size and shape between families and between species of the same family, as well as seed heteromorphism within the same species. We found that seed mass had no significant phylogenetic signal and showed stability. However, seed shape had a significant phylogenetic signal and showed instability. Most seeds evidenced very strong adaptability to the extreme environment through seed heteromorphism, mucilaginous diaspore, appendages for seed dispersal, specialized life forms and endozoochorous dispersal by animals.

Key words: Serphidium desert, seed mass, seed shape, variation, adaptation to environment