Is there a cost to resprouting? Seedling growth rate and drought tolerance in sprouting and nonsprouting Ceanothus (Rhamnaceae)

Many woody plant species that depend upon fire-cued seed germination lack the ability to resprout. As the ability to resprout is widely assumed to be the ancestral condition in most plant groups, the failure to sprout is an evolutionary derived trait. Models for the evolutionary loss of sprouting assume a trade-off between seedling success and vegetative resprouting ability of adults. Such models require higher seedling success rates in nonsprouters than in sprouters. On the other hand, there seem to be few a priori reasons why a strong sprouter might not also have highly competitive post-fire seedlings. To test the hypothesis that nonsprouting plants have higher growth rates and/or drought survival, we grew seedlings of Ceanothus tomentosus from sprouting and nonsprouting populations in a common garden experiment. Each of these C. tomentosus populations was paired with a sympatric Ceanothus species that differed in resprouting ability. Sprouters exhibited greater allocation to root carbohydrate storage than did nonsprouters, but overall relative growth rates did not differ. Nonsprouters had earlier onset of flowering. These results provide mixed support for models of a sprouting/nonsprouting allocation trade-off.