E.A. Pierson
Janice E. Bowers
2001
<p>Larger seeds have been shown to convey benefits for seedling survival but the mechanisms of this process are not well understood. In this study, seed size and seedling survival were compared for 2 sympatric cactus species, <i>Carnegiea gigantea</i> (Engelm.) Britt. & Rose and <i>Ferocactus wislizeni</i> (Engelm.) Britt. & Rose, in laboratory and field experiments in the northern Sonoran Desert. Both species have small seeds, but <i>Ferocactus</i> seeds are nearly twice as long and 3 times as heavy as those of <i>Carnegiea</i>. The difference in size is perpetuated after germination: new <i>Ferocactus</i> seedlings have 4 times the estimated volume of new <i>Carnegiea</i> seedlings. In an outdoor experiment, annual survivorship of both species was low but was 6 times higher for <i>Ferocactus</i> (6 seedlings, 8.1%) than <i>Carnegiea</i> (1 seedling, 1.4%). The pattern of seedling mortality in relation to temperature and rain suggests that, after the initial flush of seed and seedling predation, drought and heat took a greater toll on <i>Carnegiea</i> than <i>Ferocactus</i> seedlings, probably because the larger seedling volume of <i>Ferocactus</i> conferred greater drought tolerance. In addition, <i>F. wislizeni</i> could become established without benefit of nurse plants whereas <i>C. gigantea</i> could not; this might reflect differential tolerance to high soil temperatures.</p>
application/pdf
10.2307/3672423
en
Southwestern Association of Naturalists
Implications of seed size for seedling survival in Carnegiea gigantea and Ferocactus wislizeni (Cactaceae)
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