The study conducted by researchers at the University of Wisconsin-Madison and Vanderbilt University focused on mapping the genetic blueprints, appetites, and environments of over 1,000 species of yeasts to understand why some species are generalists and others are specialists. The results indicate that internal factors are the primary drivers of variation in the types of carbon yeasts can eat, and there are no trade-offs involved in metabolic versatility. Some yeasts are found to be jacks-of-all-trades and masters of each when it comes to their ability to consume different foods.
The researchers embarked on a decade-long project to build a comprehensive database mapping the relationship between genomes and traits of yeasts, which are as genetically diverse as all animals. By sequencing the genomes and studying the metabolisms of a group of yeasts distantly related to baker’s yeast, the team could identify traits that have been gained and lost multiple times, leading to both generalist and specialist species within the group. Machine learning tools were used to identify which genes are associated with traits, such as niche breadth, which determines the range of resources an organism can use or conditions it can tolerate.
The existence of generalist and specialist species has been a topic of interest for scientists since Charles Darwin’s time, and two broad models have been proposed to explain this phenomenon. While some theories suggest that generalists are jacks-of-all-trades but masters of none, others propose a combination of internal and external factors driving niche variation. The study on yeast metabolism found no evidence of trade-offs, and generalists were found to be better across all the carbon sources they can utilize. Environmental factors were also found to play a limited role, with generalists and specialists found in various habitats such as soil and flowers.
The team acknowledges that the data has limitations, and further research is needed to better understand the ecological influence on niche breadth. While the study provides insights into why some yeasts are generalists and others specialists, it does not provide a definitive answer as to why all yeasts are not generalists if there are no trade-offs involved. One theory suggests that genes often disappear during evolution, and as long as the mutation is not essential for survival, it can be passed on and take over a population. Consequently, specialists may continuously evolve from generalists through this process.
Overall, the findings of the study shed light on the evolution of yeasts and the factors influencing their metabolic capabilities. By understanding why some species are generalists and others specialists, researchers can potentially identify or create yeasts that are better at converting plant sugars into biofuels, aiding in the development of alternative sources of energy. Further research, including studying yeasts in their natural environments, could provide additional insights into the ecological factors influencing niche breadth and the evolution of yeasts over millions of years.