Brian J. Enquist
University of Arizona, Tucson, Arizona USA
An ecologist wonders how biotic feedback matters to global-change research.
I have increasingly been drawn to the question of how the biotic world responds to climatic change. In the face of environmental change, biology responds — organisms often compensate, adapt and change the nature of their ecologies. But exactly how important is this biological feedback to how ecosystems respond to a warmer world?
My colleagues and I have called for a need to focus on quantifying the importance of what we call the three As — acclimation, adaptation and assembly — on ecosystem-level processes such as carbon flux.
Acclimation is a plastic response by an organism to a change in the environment, whereas adaptation is the end result of natural selection in populations. Assembly is how species come to dominate a local environment and is the result of ecological interactions. We know that all these processes are affected by changes in climate. The end result of the three As is a group of species that live in a given location and control the flow of resources and energy.
These processes operate on differing time scales and have mostly been studied in isolation. However, two fascinating papers (K. Ishikawa et al. New Phytol. 176, 356–364; 2007, and C. Campbell et al. New Phytol. 176, 375–389; 2007) assess the role of both acclimation processes and between-species adaptation in the responses of photosynthesis and respiration to changing temperature. Remarkably, they find that acclimation and adaptative responses seem to compensate for temperature-driven changes in carbon flux.
Putting these two As together with how species assemble in ecological communities will probably reveal generalities in how evolutionary biology and plant-community ecology matters in global change.
Comments
I think that adaptation process have not always been affected by temperature. To explain this point, I would like to give an example on body size pattern in homeotherms.
Geographical variation in body size of both homeotherms and ectotherms is a very common phenomenon and has been related to many environmental factors in accordance with Bergmann’s rule, which is the best known rule in zoogeography.
I have not been sure that Bergmann’s rule can be explained only climatic data since this rule has often been questioned. Therefore, it is not clearly understood, because different species of homeotherms could show different body size pattern in their distribution range.
Although some papers were published to discuss this point in the past (e.g. Yom-Tov and Geffen, Oecologia 148, 213–218; 2006), one of them is more recent and gives important conclusion about the process that determines conformity to Bergmann’s rule (Meiri et al., Global Ecol. Biogeogr. 16, 788–794; 2007). The paper assesses the key factors that determine body size in intraspecific level in the brown bear (Ursus arctos). Food availability as a strong predictor of size, which is not associated with a latitude cline, was declared as the most likely key factor.
Primary productivity, and therefore food might more affect the evolution of body size clines of homeotherms that have large distribution range for all physiological explanations of Bergmann’s rule.
Posted by: Utku Perktas | November 29, 2007 10:30 PM