Plant communities on granite outcrops are prone to water and nutrient limitations because of the shallow soils and high summer-temperatures characteristic of that habitat. Thus, resource availability is expected to influence plant performance on these sites. Here, we sought to determine if low resource-availability (water and nutrients) acts as a selective agent in natural populations of Helianthus porteri (Porter's Sunflower), a granite-outcrop endemic. We conducted field observations of growth and survival for 3 years in 3 populations spanning the species' range. We found that survival to flowering was correlated with soil-water availability (estimated by plant predawn water-potentials; Ψpd), and that drought severity (estimated by survival and Ψpd) differed among populations, suggesting the populations could be adaptively differentiated for resource-use traits. However, in a greenhouse common-garden experiment, the population that experienced the greatest drought severity in the field did not exhibit traits associated with greater drought resistance, and all 3 populations responded similarly to water and nutrient limitations. Thus, although drought influences survival in Porter's Sunflower, populations do not appear to be adaptively differentiated with respect to resource availability.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 15 • No. 3