Friday, August 8, 2008

PS 79-80: Soils as agents of selection: Feedbacks between plants and soils alter seedling survival and performance.

Clara C. Pregitzer, University of Tennessee, Joe Bailey, University of Tennessee, Stephen C. Hart, Northern Arizona University, and Jennifer A. Schweitzer, University of Tennessee - Knoxville.


Soils are one of the first selective environments a seed experiences and yet little is known about the evolutionary consequences of plant soil feedbacks.  Using field soils from different origins within a drainage and seed from 20 different Populus angustifolia genetic families, we examined two related hypotheses: 1) soils can act as agents of selection, differentially affecting seedling survival and the heritability of plant traits that convey fitness advantages; and 2) seedlings are locally adapted to their native soils.


We found that plants grown in their native soil had 32% higher survival, were 24% taller, had 11% more leaves that were 27% longer and had 29% greater biomass than plants grown in non-native soil.  Narrowsense heritability of these plant traits among families were highest when trees were grown in their native soil, relative to soils outside of their natural range; trees grown in non-native soils, overall had higher mortality, reducing the genetic variation for selection to act upon.  Estimates of natural selection (S) and estimated response to selection (R) tended to be greater on seedlings in their native soils versus non-native soils due to increased genetic variance.  Soil microbial biomass explained more of the variation in seedling performance than soil texture, pH, or nutrient availability, suggesting strong microbial interactions and feedbacks between plants, soils, and associated microbial communities.  Overall, these data suggest that a “home-field advantage” helps maintain genetic variance in P. angustifolia seedlings and the potential for populations to respond to future environmental selection events.