Intra-specific responses of a dominant C-4 grass to altered precipitation patterns

摘要

The mechanisms by which global change alters the genotypic structure of populations by selection remain unclear. Key to this understanding is elucidating genotype-phenotype relationships under different environmental conditions as genotypes could differ in their plasticity or in their tolerance to changing environmental conditions. We have previously observed selection of certain genotypes of the dominant C-4 grass Andropogon gerardii L. within the on-going Rainfall Manipulation Plots (RaMPs) experiment at Konza Prairie Biological Station in Kansas. The RaMPs experiment has been experimentally imposing ambient and more variable (altered) precipitation patterns since 1998. Here, we studied phenotypic differences among six genotypes to gain insight into what drove the pattern of selection previously observed and assess potential genotype x environmental interactions. In 2008 and 2009 we sampled individuals of genotypes in the RaMPs and within unmanipulated reference plots located adjacent to the RaMPs experiment. For each individual, we measured both leaf-level (specific leaf area, stomatal conductance) and whole-plant growth (height, biomass) traits. We consistently detected differences among genotypes in the reference plots. Additionally, when focusing on two genotypes found in the altered and ambient RaMPs we observed no genotype x environment interactions. Overall, we found in an intact population of A. gerardii there exists phenotypic variability among genotypes, but no genotype x environment interactions. Thus our results demonstrate that differences in plasticity of genotypes do no explain the pattern of selection we observed.