Effect of seed size on seedling performance in a long-lived desert perennial shrub (Ericameria nauseosa: Asteraceae)

We investigated how seed size and timing of emergence interact with environmental conditions to determine seedling performance in one population of the long-lived perennial shrub Ericameria nauseosa var. oreophila ( Asteraceae) in the sand dune ecosystem near Mono Lake, California. Size of seeds varied significantly among and within individual plants, and this variation had important consequences for size, growth, and survival of seedlings in both greenhouse and field experiments. Larger-seeded seedlings had greater biomass, greater percentage of total plant biomass allocated to roots, and longer taproots than seedlings from smaller seeds. Seedlings grown in native soil had less total biomass than seedlings grown in augmented soil but greater allocation of biomass to roots. In a field experiment following individually weighed seeds, seedlings emerging from larger seeds germinated and emerged earlier and at a higher rate than did smaller-seeded seedlings. Larger-seeded seedlings were larger at emergence, remained larger through time, and lived longer than smaller-seeded seedlings. In all stages of early seedling establishment, from germination through the first summer drought, and by all criteria, larger-seeded seedlings performed better than smaller-seeded seedlings. Given the considerable longevity of adults and the extremely small size of the wind-dispersed seeds, these aspects of seed and seedling performance have a remarkably significant impact on the survival and reproduction of subsequent life stages of E. nauseosa at this site.