MSc Exit Seminar – Wenjing Xia (Anderson/Kohn labs)

MSc Exit Seminar

Monday September 12^th, 10:10 am – Room IB 200, University of Toronto at Mississauga

Wenjing Xia (Anderson/Kohn labs)

“Micro-Scale Diversity and Persistence of Genomic Variants of the Yeast Saccharomyces Paradoxus in a Natural Woodland Population“

Abstract

Alcohol Genetic diversity in experimental, domesticated, and wild populations of the related yeasts, Saccharomyces cerevisiae and S. paradoxus, has been well described at the global scale, but rarely on a small spatial scale.  While large-scale sampling is informative on the roles of biogeography in shaping population structure, fine scale sampling over time captures stability and flux in genome distribution and interaction, which may not be revealed in large-scaled studies.  In this thesis, I investigated the population genomics of a local population on a fine spatial scale to address two main questions. First, is there genomic variation in a S. paradoxus population at a spatial scale spanning centimeters (microsites) around individual trees to tens of meters?  Second, does the distribution of genomic variants persist over time?  My sample consisted of 42 S. paradoxus strains from 2014 and 43 strains from 2015 collected from the same 72 microsites around four host trees (Quercus rubra and Q. alba) within 1km² in a mixed hardwood forest in southern Ontario.  Six additional S. paradoxus strains recovered from adjacent maple and beech trees in 2015 are also included in the sample.  Whole-genome Illumina sequencing and genomic SNP analysis revealed five differentiated groups (clades) within the sampled area.  The signal of persistence of genotypes in their microsites from 2014 to 2015 was highly significant.  Isolates from the same tree tended to be more related than strains from different trees, with limited evidence of dispersal between trees.  The results indicate that different clades co-exist at fine spatial scale and that population structure persists over time in these wild yeasts.