The picture below should be familiar to anyone with a background in biology. The birds shown here are members of the “Galapagos finches”, famous for inspiring the work of Charles Darwin, but also used extensively in the classroom to talk about the founder effect.
The founder effect is one of the fundamental topics of any population genetics lecture, and it used to show how random events (what is called genetic drift) shapes the genetic structure of a population. Finches and iguanas are common examples, but to be honest, most people have heard of these examples so many times that it is getting repetitious. A recent article in Science adds a new flavor to the topic of founder effect.
Recently, researchers at the University of Montreal have examined the relationship between the founder effect and fitness, or the ability to survive and pass its genes onto the next generation. What is interesting here is that their test subjects are not birds, or iguanas, but humans.
What made this study possible was the BALSAC population database, a historical record of almost 5 million events (birth and death certificates, marriage licenses, etc) spanning almost 4 centuries and focusing on the Sagueny Lac St-Jean region of Quebec (an area that was initially colonized by French immigrants in the 17th century).
In this study the researchers investigated what happens to the population immediately after it colonizes a new area and begins to expand its range. Specifically, they examined whether it was better (from a population genetics perspective) to stay in the initial area founded by the population (the range core), or to be part of the group that it expanding into new territories (the wave front). By assessing fitness based on the reproductive success (number of children produced), the researchers found that the group on the wave front of the population made a greater contribution to the genetic makeup of the population’s gene pool over time. Fitness, it seems, is correlated more with expansion than staying in one place.
There are lots of applications for this research, not only for recent human migrations, but for the historical movement of hominins across the globe. The success of Homo sapiens, it appears, may be the result of its migration and the resulting founder effects, and the influence of the individuals in the wave front of these populations on the genetic makeup of the species. If nothing else, it provides something to discuss in class other than a finch.
- ScienceDaily article “Evolution During Human Colonizations: Selective Advantage of Being There First”
- Claudia Moreau et al. Deep human genealogies reveal a selective advantage to be on an expanding wave front. Science, 2011 DOI: 10.1126/science.1212880