Temperature preference biases parental genome retention during hybrid evolution

Interspecific hybridization can introduce genetic variation that aids in adaptation to new or changing environments. Here we investigate how the environment, and more specifically temperature, interacts with hybrid genomes to alter parental genome representation over time. We evolved Saccharomyces cerevisiae x Saccharomyces uvarum hybrids in nutrient-limited continuous culture at 15°C for 200 generations. In comparison to previous evolution experiments at 30°C, we identified a number of temperature specific responses, including the loss of the S. cerevisiae allele in favor of the cryotolerant S. uvarum allele for several portions of the hybrid genome. In particular, we discovered a genotype by environment interaction in the form of a reciprocal loss of heterozygosity event on chromosome XIII. Which species haplotype is lost or maintained is dependent on the parental species temperature preference and the temperature at which the hybrid was evolved. We show that a large contribution to this directionality is due to temperature sensitivity at a single locus, the high affinity phosphate transporter PHO84 . This work helps shape our understanding of what forces impact genome evolution after hybridization, and how environmental conditions may favor or disfavor hybrids over time.