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→Species and Phylogeny
In general, most of the cultures of kveik that have been analyzed contain more than one strain of ''S. cerevisiae''. The exact number of strains that is present in a given kveik culture is difficult to analyze; generally labs with better equipment and more time can identify more strains than others. Some kveik cultures contain multiple strains of closely related strains of ''S. cerevisiae'', while others contain a more diverse group of strains <ref name="garshol_preiss_mbaa" />. The kveik cultures with closely related strains defy what a "strain" isolate is; Richard Preiss describes these kveik cultures as being "heterogenous but related communities", meaning that there can be a lot of genetic overlap between subpopulations in a kveik culture and where one strain begins and another ends is not possible to define <ref name="preiss_strains" />. Strains within cultures probably arose due to mutations during cell division, as well as sporulation which kveik is more capable of than other domesticated yeast strains <ref>[https://www.facebook.com/groups/MilkTheFunk/posts/6929359520425536/?comment_id=6929468623747959&reply_comment_id=6933491356679019 Richard Preisse. Milk The Funk Facebook group thread about landrace yeast and sporulation. 05/16/2023.]</ref>. ''S. cerevisiae'' was the only species in all of the kveik cultures analyzed by Preiss et al. (2018). Of the 9 kveik cultures analyzed by Preiss et al. (2018), only Muri (which has since been found to be commercially available Bavarian Weizen yeast and not a landrace farmhouse yeast at all; see [[Landrace Yeast]]), Simonaitis, and Stranda contained only one strain of ''S. cerevisiae'', while all of the others contained more than one strain of ''S. cerevisiae'' up to 9 strains in the case of Granvin (see [https://www.frontiersin.org/files/Articles/409253/fmicb-09-02137-HTML-r1/image_m/fmicb-09-02137-t001.jpg this table from the paper]). A Master's Thesis by [https://nmbu.brage.unit.no/nmbu-xmlui/handle/11250/2681970?show=full Nadia Marlen Aasen from Norwegian University of Life Sciences] isolated 4-10 strains from 4 different kveik cultures: Ørjasæter, Otterdal, Gausemel and Gamlegrua. As with Preiss (2018), the only species of yeast found was ''S. cerevisiae''. While only yeast was found in Otterdal and Ørjasæter, the Gausemel also had two bacteria species, ''Acetobacter malorum'' and ''Lactobacillus plantarum'', and the Gamlegrua also had ''L. plantarum'' <ref name="Aasen">[https://nmbu.brage.unit.no/nmbu-xmlui/handle/11250/2681970?show=full Nadia Marlen Aasen. Growth, metabolism and beer brewing with kveik. Master's Thesis. Norwegian University of Life Sciences. 2020.]</ref>.
Genetically, kveik yeast strains form their own group of closely related domesticated ale strains that are a subgroup of the "Beer 1" yeasts (Belgian/Germany/UK/US yeast strains) from the [http://www.cell.com/cell/fulltext/S0092-8674(16)31071-6 Gillons/White Labs (2016)] study that sequenced previously known ale strains and found them to make up two genetically related groups called "Beer 1" and "Beer 2" (see [[Saccharomyces#History_of_Domestication|''Saccharomyces'' History of Domestication]] and [http://www.garshol.priv.no/blog/374.html "A family tree for brewer's yeast" by Lars Marius Garshol]). The closest related domesticated strains were 3 German hefeweizen strains; however, this relation is likely just due to both groups being hybrids rather than having any historic relation <ref name="Tyrawa_2017" />. None of the kveik strains sequenced by Preiss et al. (2018) contained the STA1 gene for diastatic activity, which is expected since all of the diastatic yeasts belong to the "Beer 2" group <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2445690998792433/?comment_id=2446266075401592&reply_comment_id=2446269382067928&comment_tracking=%7B%22tn%22%3A%22R5%22%7D Richard Preiss. Milk The Funk Facebook thread on kveik and the STA1 gene. 01/03/2018.]</ref>. Further genetic analysis of 35 [Landrace_Yeast|landrace] strains from Western Norway, Eastern Norway, and the Baltics, demonstrated that many (not all) farmhouse yeasts form their own third beer clade. They have a common ancestor from the Beer 1 clade, as well as an ancestor from Asia. Some other landrace yeast fall within the "mixed origin" beer yeast clade <ref>[https://link.springer.com/article/10.1007/s00253-024-13267-3 Preiss, R., Fletcher, E., Garshol, L.M. et al. European farmhouse brewing yeasts form a distinct genetic group. Appl Microbiol Biotechnol 108, 430 (2024). https://doi.org/10.1007/s00253-024-13267-3.]</ref>. See this [https://www.garshol.priv.no/blog/436.html article by Lars Marius Garshol] for a summary of this study.
Although whole genome sequencing of more kveik strains is needed in order to fully flesh out a family tree of kveik <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2277955402232661/?comment_id=2279696338725234&reply_comment_id=2279736462054555&comment_tracking=%7B%22tn%22%3A%22R%2321%22%7D Richard Preiss. Milk The Funk Facebook group comment about the two families of kveik yeast. 09/13/2018.]</ref>, based on the 6 strains that were analyzed, kveik strains seem to be divided into two related genetic groups, with the Simonatis Lithuanian strain and a Norwegian bread yeast falling outside of these two groups completely, which arguably categorizes them to not actually be considered "kveik". The two groups of kveik probably originated from two ancestors that were hybrids between a "Beer 1" yeast and wild yeast. Interestingly, the kveik cultures that have multiple strains have strains from both genetic groups of kveik. For example, Hornindal, Granvin, Laerdal, and Stordal Ebbergarden all contained strains from both genetic groups of kveik. Overall, their genetic diversity is wider than the genetic diversity of other "Beer 1" subgroups <ref name="Tyrawa_2017" />. See this [https://www.frontiersin.org/files/Articles/409253/fmicb-09-02137-HTML-r1/image_m/fmicb-09-02137-g002.jpg updated family diagram of yeast].