Ecological stoichiometry: A chemical approach to understanding trophic interactions across spatial gradients
Ecologists have long been interested in latitudinal diversity patterns because these reveal the influence of climate and geology on ecological systems. One clear link between latitudinal variation in climate, geology and biodiversity is spatial variation in the chemical content of living organisms. For example, variation in nitrogen (N) and phosphorus (P) availability in response to climate and geology has a strong influence on plant leaf N and P content. Leaf N and P content; in turn generally influence the stoichiometry of litter. In addition, spatial variation in plant and litter nutrient content can also affect abundance, distribution, and feeding rates of consumers, thereby influencing the pools and transfer rates of energy and nutrients between trophic levels. One of the key mechanisms here is the way in which these consumers respond to changes in nutrient content of their food resources. In fact, recent evidence from the field of ecological stoichiometry (i.e., ES; the study of the balance of multiple chemical elements in living systems) has highlighted that imbalances between the demands of nutrients by consumers and that on their resources are common in nature, and can have strong constraints on consumer-resource interactions. Despite the valuable insights provided by studies so far, to date, most studies of stoichiometric constraints on consumer-resource interactions have been conducted at local spatial scales. At present, we know relatively little about how the stoichiometry of consumers may vary across latitudinal gradients and their ecological implications. Here we present an overview about the way that chemistry mediates consumer-resource interactions at small-scale, and how can it help to understand ecological interactions at large spatial scales.
We address some of the development of ES to the understanding of food web structure and dynamics as well nutrient cycling. We discuss how ES can provide novel insights into spatial gradients of biogeochemical constraints on ecological interactions. We also touch upon how human perturbations of these stoichiometric relationships between consumers and their resources may have strong effects on the functioning of ecological systems. We conclude by pointing out some novel directions where ES likely will be useful in understanding and predicting ecological interactions along gradients in nutrient availability in a changing world.