PARENT SESSION
Contributed Oral Session 102: Herbivory: Effects of Photosynthesis; Nutrients
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 520 B, Level 5, Palais des congrès de Montréal
Soil characters influence the survival of a native plant via indirect effects on herbivory.
McCall, Andrew*,1, Lau, Jennifer1, 2, Wright, Jessica1, 3, Davies, Kendi1, McKay, John1, 1 University of California, Davis, CA, USA2 University of Minnesota, St. Paul, MN, USA3 U.S. Forest Service, Institute of Forest Genetics, Davis, CA, USA
ABSTRACT- The edaphic factors that affect plant fitness in heterogeneous environments are poorly understood. Important characteristics such as soil minerals and soil moisture may affect plant fitness directly; there may also be strong indirect effects of soil variables that are mediated by other community members, such as herbivores. We used 3 years of detailed soil and biotic data from a heterogeneous serpentine/nonserpentine landscape to create a model elucidating what characters limit the distribution of the common woodland herb, Collinsia sparsiflora. We then empirically tested this model by planting 1600 seeds from 2 serpentine and 2 non-serpentine source populations throughout the landscape and measured herbivory and fitness in one growing season. Interestingly, we found no direct effects of edaphic factors on plant survival, but we did observe a significant indirect negative effect of high Ca/Mg ratio on survival, as mediated through increased herbivory on high Ca/Mg ratio sites. The serpentine and non-serpentine ecotypes differed in their susceptibility to herbivory, with serpentine-derived plants receiving consistently higher levels of herbivory than non-serpentine plants, perhaps due to past herbivory pressure at the sites of seed origin. Although we now know that edaphic factors often influence plant population dynamics and persistence directly, we show here that the effects of soil properties may be indirect and mediated by important biotic processes, such as herbivory.
Key words: herbivory, serpentine, indirect effects, niche