Feasting yeast and the sweetness of diversity

The idea that a spreading species can lose genetic diversity goes back to early work by Ernst Mayr in 1942 on founder effects for introduced populations (1). Here, reduced diversity of a spreading population arises from the small number of individuals who are initially introduced into a region (founders). A small number of founders will not represent the full genetic diversity of the population, and then the diminished diversity will be propagated as these few individuals grow and spread, passing on their genotypes.

The question arises, however, as to the outcome for genetic diversity if small groups of individuals do not fare well and only larger groups manage to thrive and spread. Perhaps the smaller groups will die out and the larger groups will be sufficient in size to pass on their population diversity to successive generations. While theoreticians (2, 3) and mathematicians (4⇓–6) have postulated that such an effect should exist, and there has been some empirical support from field studies (7), it has been difficult to connect the theory to experimental observation. However, a recent paper by Gandhi et al. (8) sheds light on how cooperation can preserve diversity. Their work investigates the genetic diversity of expanding yeast (Saccharomyces cerevisiae) populations. By manipulating the food substrate for spreading populations of yeast cells on test plates, Gandhi et al. experimentally demonstrated how cooperative feeding dynamics can actually help combat declines in genetic diversity when populations undergo spatial expansion. Using a number of ingenious techniques, the authors were …

↵¹Email: Mark.lewis{at}ualberta.ca.