The ecological and evolutionary significance of seed shape and volume for the germination of 383 species on the eastern Qinghai-Tibet plateau

Seed shape and seed volume are functionally important traits which are associated with seed germination. To study the ecological and evolutionary significance of seed shape and volume in relation to germination, a database comprising seed information for 383 species within 50 families from an alpine meadow on the eastern Qinghai-Tibet plateau was compiled. The independent and interactive effects of seed traits on germination and whether these effects are controlled by phylogeny are discussed. The results show the following: (1) Elongated seeds had higher percentage and faster speed of germination than compact seeds whereas smaller seeds tended to have higher germinability compared to larger ones; (2) Seed volume and shape evolved together but had independent effects on seed germination. Seed volume had no significant influence on seed germination among species with compact seeds, but had a significant effect on those among species with elongated seeds; seed germination of larger seeded species was affected by seed shape, but not by seed volume. These results might be related to their predation pressure and ability to germinate from deeper soil layers. Lastly, (3) Phylogenetic conservation plays an important role in the co-evolution of seed traits and germination characteristics. Species with similarly shaped seeds on a large scale might reflect a common selective pressure, but related species within a family might be more dependent on phylogenetic conservation.