Animal nutrition plays an important role in many ecological interactions by affecting their life-history, nutrient cycling, and trophic interactions. Despite this, there remains considerable obstacles to assessing the nutritional state (i.e., presence and type of limitation) of animals as they are found in ecosystems. Inferring the nutritional state of animals could use new tools based on the characterization of molecular features (e.g., transcriptomic properties) of animals that are known to be sensitive to different types of dietary nutrient limitation. Here we describe patterns of differential gene expression to poor nutrition in an aquatic invertebrate, Daphnia, and show how these responses (individually or together) can be used as biomarkers of their nutritional stress in different types of ecological studies. To do so, we used transcript sequencing and differential gene expression analysis to determine patterns of gene expression in animals exposed to several common forms of nutritional stress.
Results/Conclusions
We found unique patterns of gene expression that were associated with particular forms of nutritional limitation. We further identified limited sets of gene responses that could correctly categorize the nutritional state of animals having an unknown diet. For animals exposed to two forms of limitation (calcium and phosphorus) at the same time, we found blended phenotypes that indicated that animals could detect and physiologically respond to low supplies of two nutrients at once. We also found compelling links between predicted molecular function and nutrient sensitivity of selected genes, further contributing to our understanding of the effects of poor nutrition on consumer molecular physiology. While further development of this approach is needed to verify the uniqueness of responses, robustness to confounding environmental stressors, and stability across ontogenetic stage or among multiple genotypes, the application of this approach has the potential to transform the study of nutrients in ecology from organismal to ecosystem level scales by providing new types of information about the presence and intensity of animal consumers in ecosystems.
