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An integrative gene-to-ecosystem understanding of the ecological consequences of climate change

Predicted anthropogenic climate changes include increased average temperatures, more variable precipitation regimes, and increased frequency and intensity of climate extremes (e.g., heat waves, drought). These are expected to interact to influence a complex array of ecological interactions and evolutionary processes through chronic alterations in resource availability and increased stress. Natural plant populations will respond initially to these altered environmental conditions through observed phenotypic changes (Smith et al. 2009). Plant phenotypic responses to changing environmental conditions are achieved through the regulation of gene expression at transcriptional and post-transcriptional levels, which results in changes in metabolism and physiology. However, in comparison to these downstream phenotypic variables, gene expression is expected to be a more sensitive indicator of response to altered environmental conditions. Evaluating functional responses of plants at the genetic and biochemical level can increase our understanding of underlying genetic bases of responses that limit growth and survivorship, which could over time influence fitness variation, selection and adaptative responses. Individual responses also could affect community and ecosystem structure and function, particularly if the impacted species is dominant (common) in the system or if species differ in their ability to cope with changing environmental conditions (Smith et al. 2009).

Until recently, the molecular basis of plant responses to changing environmental conditions in natural systems was often relegated to a black box status (Leakey et al. 2009). However, with genomics and other molecular tools (e.g., metabolomics), we can begin to shed light on these molecular mechanisms and assess their importance in more realistic field settings. The integration of genomics into ecological research represents an important emerging field (Leakey et al. 2009), one that I have been on the forefront of with support from the DOE, enabling me to assemble a multidisciplinary team of scientists. Our approach is to utilize the functional genomic information from a model organism (Zea mays) to determine how genomic responses of two closely related, ecologically important C4 grass species, Andropogon gerardii and Sorghastrum nutans, may underlie community and ecosystem responses to climate change. These grasses co-dominant in native tallgrass prairie but differ in their sensitivity to changes in temperature and water availability (Swemmer et al. 2006, Nippert et al. 2009). We believe it is these differential responses that likely drive observed community and ecosystem responses to climate change.

Over the past four years, my lab has been assessing for the first time the genomic responses (i.e., transcriptional profiles via cDNA microarrays, target gene responses via real-time PCR) of individuals of both grass species to experimental warming and more variable rainfall patterns within a long-term collaborative field experiment, the Rainfall Manipulation Plots (RaMPs), located at the Konza Prairie Biological Station in northeastern KS. We have found that A. gerardii and S. nutans differ in fundamental ways in their leaf-level genomic responses to alterations in temperature and soil water availability imposed by the RaMPs treatments, with, for example, regulation of genes associated with biosynthesis and stress response pathways more sensitive to variation in temperature in A. gerardii and more sensitive to water stress in S. nutans (Travers et al. 2007, in revision, Yuan et al. in prep). While we are continuing to assess these linkages using a novel analytical framework, these differential gene-level responses appear to have important consequences for individual performance (altered physiology, reduced growth, Nippert et al. 2009), population structure (reductions in genotypic diversity and population abundances, Avolio et al. submitted), community diversity (increased abundance of uncommon species), and ecosystem functioning (reduced productivity, Knapp et al. 2002).

Other Current Initiatives