Tadeusz Kawecki on Conceptual Issues in Local Adaptation
Emerging Research Front Commentary, August 2010
|
Article: Conceptual issues in local adaptation
Authors: Kawecki, TJ;Ebert, D |
Tadeusz J. Kawecki talks with ScienceWatch.com and answers a few questions about this month's Emerging Research Front paper in the field of Environment/Ecology.
Does the paper describe a new discovery,
methodology, or synthesis of knowledge?
With our paper we attempted to synthesize the concepts related to the theory of local adaptation and empirical approaches used to study it.
Would you summarize the significance of your paper
in layman’s terms?
Local adaptation refers to the hypothesis that, in a spatially heterogeneous environment, each population should respond to local natural selection by becoming better adapted to the local conditions.
Although at first sight this might seems an obvious default prediction from Darwinian evolution, in reality local adaptation is opposed by factors such as gene flow, genetic drift, or inbreeding. Thus, it had been recognized that by testing the local adaptation hypothesis in natural populations we can get insights into ecological and evolutionary processes operating both within the local populations and at the level of the global (meta-) population.
"In my laboratory we are currently using experimental evolution, with Drosophila as a model system, to understand adaptive evolution. In particular, we concentrate on two very different traits: tolerance to chronic nutritional stress and learning ability. We are aiming to understand how and under what circumstances could natural selection improve these traits..."
However, there had been some confusion as to how the local adaptation hypothesis should be tested, resulting in part from insufficient links between the field studies and the mathematical theory of evolution in metapopulations. Different authors often assumed different statistical criteria for local adaptation, apparently without realizing they may lead to different conclusions.
Our paper first pointed out the confusion and then attempted to clarify it, and propose a conceptual framework for studies of local adaptation, grounded in the population genetic theory.
We proposed a statistical criterion for testing the pattern of local adaptation in reciprocal transplant experiments, based on a systematic comparison, within each site, of the Darwinian fitness of local and foreign (transplanted) individuals. Many past studies had concentrated instead on comparing, for each population, its fitness in its home site with its fitness in other sites, which often leads to different conclusions.
We also discussed different types of experimental design used to study local adaptation, the units of replication, and the technical difficulties associated with measuring fitness and minimizing confounding effects. Finally, we discussed a number of ways the processes underlying local adaptation could be studied.
Why do you think your paper is highly
cited?
I believe at the time the field of local adaption was in need of a conceptual synthesis, so one may say that the paper filled an empty ecological niche. It also provides a convenient source for people doing empirical studies of local adaptation where various issues relevant to their research were discussed in one place.
Even if they do not agree with our conclusions or recommendations, they present their opinion in opposition to our paper—so the paper gets cited.
How did you become involved in this research, and
how would you describe the particular challenges, setbacks, and
successes that you've encountered along the way?
The paper resulted from long discussions with my colleague and coauthor Dieter Ebert. We realized that, in the context of local adaptation, we often understood the same concepts differently, and that we often became confused or unconvinced about each other's arguments. This repeatedly forced us to clarify the concepts, rethink our intuitions and ground them better in the formal theory.
Only after some time did we decide to wrap up the results of our musings as a paper. Gestation of this paper lasted several years, even though it does not contain any new data, methodology or theory.
Do you foresee any social or political
implications for your research?
The importance of local adaptation is increasingly recognized in conservation biology. For example, on the one hand, migration corridors between local populations may help prevent inbreeding, but on the other, the resulting gene flow may disrupt local adaptation. The degree of local adaptation is also likely to affect the success of reintroduction programs.
However, in conservation management there is sometimes a tendency to assume that any genetic differentiation between populations is evidence for local adaptation, with consequences for management decisions. Thus, conservation biology is one applied field that would profit from rigorous thinking about local adaptation.
Where do you see your research leading in the
future?
In my laboratory we are currently using experimental evolution, with
Drosophila as a model system, to understand adaptive evolution. In
particular, we concentrate on two very different traits: tolerance to
chronic nutritional stress and learning ability. We are aiming to
understand how and under what circumstances could natural selection improve
these traits, and what, if any, trade-offs would be
involved.
Tadeusz J. Kawecki
Associate Professor
Department of Ecology and Evolution
University of Lausanne
Lausanne, Switzerland
KEYWORDS: ADAPTIVE DEME FORMATION, ADAPTIVE EVOLUTION, COEVOLUTION, HETEROGENEOUS ENVIRONMENTS, GENE FLOW, METAPOPULATIONS, NATURAL SELECTION, POPULATION DIFFERENTIATION, RECIPROCAL TRANSPLANT, REVIEW, SOURCE-SINK POPULATIONS, LIFE HISTORY EVOLUTION, TRAIT LOCUS ANALYSIS.