Saccharomyces eubayanus population genomics: wild diversity and contributions to domesticated hybrids
2020-04-20T22:03:35Z (GMT) by
1230C How evolution drives diversification within and between species and the consequences of hybridization between independently evolving species are fundamental question in biology. The genus Saccharomyces is becoming an ideal model to address questions of evolutionary genomics. In this one genus, differing evolutionary trajectories, i.e. domestication versus wild diversity, can be studied; as well as the dynamics and interaction of variation within and between species. Presented here is a deep characterization of the landscape of diversity within one species, Saccharomyces eubayanus. The Patagonian region of South America is a hotspot of diversity for this species, where five subpopulations exists in some sympatry; but a subset of this diversity is globally distributed. Isolates from North America are dominated by an admixed lineage that showed almost 50-50 contributions from two Patagonian populations and, surprisingly, showed the exact same patterns of local ancestry across their genomes. These strains come from four distant locations in North America and show that all individuals originated from a single hybridization event and that this admixed lineage then successfully invaded regions across North America, where S. eubayanus is scarce. The even rarer subpopulation found only in the Holarctic ecozone is the wild progenitor of Saccharomyces cerevisiae × S. eubayanus hybrids that are used for cold-temperature lager-brewing, yet no pure S. eubayanus have yet been found in Europe the origin of lager-brewing. The two lager-brewing lineages have maintained variation still segregating in the wild, indicating complex origins of these lineages. Other Saccharomyces hybrids are frequently isolated from fermentation environments, including strains with up to four contributing species. Both wild diversity and pre-domestication have led to evolutionary innovations that have influenced the persistence of these hybrids in industrial settings, notably cold-tolerance from a wild parent and flavor-profile from a domesticated parent. This work enlightens our understanding of yeast diversity in the wild and the evolutionary consequences of hybridization and domestication, with parallels to hybridization in other organisms across the tree of life.