Saccharomyces paradoxus is mostly isolated from deciduous trees (oak, maple, birch), and in some rare occasions on insects and fruits.[2][3][4][5] It is often found in sympatry with other Saccharomyces species.[6][7][8] Like Saccharomyces cerevisiae, it has a worldwide distribution and it is mesophilic, which limits its natural distribution to low latitudes. However, Saccharomyces paradoxus typically grows at lower temperatures than Saccharomyces cerevisiae, resulting in a slight shift in its distribution toward cooler regions, like British islands and Eastern Canada.[2][8][9]
Biogeography
Saccharomyces paradoxus worldwide distribution. Populations are represented in different colours. Green asterisks indicate recent introductions of the European type.Phylogeny of main Saccharomyces paradoxus populations.[10]
Unlike most other Saccharomyces species, there is no evidence that Saccharomyces paradoxus has been domesticated by humans.[3][11] Accordingly, its biogeography is mostly marked by natural processes like limited migration,[3] glacial refugia[12] and adaptation to climate.[10] At least four genetically and phenotypically distinct populations of Saccharomyces paradoxus have been identified, corresponding to main geographical divisions: Europe (including West Siberia), Far East Asia (Japan, Eastern Siberia), North America (North American East and West coasts, Great Lakes region) and North-East America (Gaspé Peninsula, Saint Lawrence Valley and Appalaches), respectively.[3][9][10][11] Representative strains of these populations exhibit partial post-zygotic isolation.[12][13] A fifth population is represented by a singleton isolate from Hawaii.[3][11] Some strains from the European population are found in North America and New Zealand and likely result from recent colonization events.[14][15] Two isolates from South America, described as Saccharomyces cariocanus,[16] are genetically indistinguishable but exhibit post-zygotic isolation when crossed to strains from the American population, due to chromosomal translocations.[13]
Reproduction
Saccharomyces paradoxus is naturally homothallic, and is mostly found as diploid in the environment. Reproduction is mostly clonal and 99% of sexual reproduction occurs between spores from the same ascus.[17] This purges recessive deleterious mutations that accumulated during clonal expansion, in a process known as "genome renewal".[18][19]Post-zygotic isolation between strains of Saccharomyces paradoxus is commonly observed and could be either due to genetic divergence between populations or to chromosomal changes within populations.[12][13]
Like in other Saccharomyces species, heterothallism can be restored using standard genetic tools, to obtain stable haploid strains for experimental purposes.
^Naumov, GI; Naumova, ES; Sniegowski, PD (1998). "Saccharomyces paradoxus and Saccharomyces cerevisiae are associated with exudates of North American oaks". Canadian Journal of Microbiology. 44 (11): 1045–50. doi:10.1139/w98-104. PMID10029999.
^Mortimer, Robert K.; Romano, Patrizia; Suzzi, Giovanna; Polsinelli, Mario (December 1994). "Genome renewal: A new phenomenon revealed from a genetic study of 43 strains ofSaccharomyces cerevisiae derived from natural fermentation of grape musts". Yeast. 10 (12): 1543–1552. doi:10.1002/yea.320101203. PMID7725789. S2CID11989104.
