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Experimental Evolution

As part of our series of ‘CSEE Reviews’, the 2015 Canadian Society for Ecology and Evolution (CSEE) biannual prizewinner Professor Graham Bell explores the opportunities of lab based experimental macroevolution.

We spoke with Professor Bell to find out more about the potential insights that could be gained through experimental techniques and where limitations to such studies lie.

What is meant by macroevolution?

It’s a little vague.  The most common meaning is probably ‘evolution above the species level’, or in other words evolutionary change that leads to the appearance of a higher taxonomic category.  In my article, I use the term to mean the evolution of an innovation that makes a new way of life possible (such as the feathers of birds), or adaptation to a new way of life that facilitates the radiation of species (such as a freshwater animal invading the sea, or vice versa).

How is it different to microevolution?

Perhaps it isn’t.  The distinction was originally made because it was felt that macroevolution required processes extending beyond the changes in allele frequency caused by natural selection.  The contrary point of view is that macroevolution is simply the result of microevolutionary change extended in time.

Why is studying macroevolution in the lab so difficult?

It was generally imagined for a hundred years after the publication of the Origin that it was not worthwhile studying even microevolution in the lab, because change would take place too slowly to be detected.  We know now that this is not true, and that the real question is where the limits to experimental evolution might lie.  My article is a preliminary discussion of these limits.

How can experimentation be used to resurrect ancestral states?

Most simply, in three stages.  The first is to reconstruct the ancestral state of a protein from a knowledge of related living species, using phylogenetic techniques.  The second is to engineer a gene to produce the predicted ancestral protein.  The third stage is to express this gene in a suitable model organism and observe the phenotype it produces.

How do selection processes provide insight into ranges of variation and predict future descendants?

In some cases it is possible to create a lineage through experimental evolution that is able to pursue a way of life beyond the capacity of its ancestor.  Multicellular types, for example, can evolve in the laboratory from unicellular ancestors.  Experiments like this can be used to investigate the general principles guiding major ecological transitions.

What are the main limitations to experimental macroevolution?

Obviously, we cannot literally recapitulate the major events in the history of life, such as the transition from lobe-finned fish to terrestrial amphibians.  Rather, experiments can be used to show how, or to what extent, the principles that govern events we understand, typically occurring on short time scales, can be extended to less well-understood events, typically on much longer time scales.

The Canadian Society for Ecology and Evolution Reviews are published annually in Proceedings B.

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