Interspecific variation in seed mass and the co-existence of conifer species: A null model test

In many plant communities, there is remarkable variation in seed mass among co-existing species. Plant ecologists have focused on explaining the evolu tion of this variation but have directed relatively little attention toward s examining its significance for species co-existence. This study represent s the first empirical attempt to link variation in seed mass with species c o-existence. Recent models have suggested that variation in seed mass may p romote species co-existence if seedlings compete and if a trade-off exists between seed number and seed mass. We used a null model to test whether the pattern of interspecific variation in seed mass in 124 assemblages of mont ane conifer species was random or non-random. In most assemblages (mountain ranges), the variation appeared to be random. However, in assemblages cons isting solely of pine species, seed masses were more evenly spaced than exp ected by chance alone. We therefore conclude that variation in seed mass is not important to species co-existence in diverse conifer assemblages but i t may promote co-existence among pine species. Further empirical tests are needed before ecologists can come to a consensus opinion concerning the rol e of variation in seed mass in species co-existence.