Abstract
Interspecific hybridization can introduce genetic variation that aids in adaptation to new or changing environments. Here, we investigate how hybrid adaptation to temperature and nutrient limitation may 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 responses only observed in the colder temperature regime, 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 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 a temperature dependent fitness benefit at a single locus, the high affinity phosphate transporter gene PHO84. This work helps shape our understanding of what forces impact genome evolution after hybridization, and how environmental conditions may promote or disfavor the persistence of hybrids over time.
Highlights
Comparative genomics of thousands of plants, animals, and fungi has revealed that portions of genomes from many species are derived from interspecific hybridization, indicating that hybridization occurs frequently in nature
To test whether temperature can influence the direction of resolution of hybrid genomes, we evolved 14 independent populations of a S. cerevisiae x S. uvarum hybrid in nutrient-limited
We observe 6/6 loss of heterozygosity (LOH) events in hybrids evolved at 15 ̊C in which the S. cerevisiae allele is lost and the S. uvarum allele is maintained, suggestive of a S. uvarum cold temperature benefit
Summary
Comparative genomics of thousands of plants, animals, and fungi has revealed that portions of genomes from many species are derived from interspecific hybridization, indicating that hybridization occurs frequently in nature. Recent work has demonstrated that in hybrid genomes with a bias in parental composition like humans, in which most of the genome is comprised of modern human haplotypes with small fragments derived from archaic human, regions from the minor parent (e.g., Neanderthal or Denisovan) are decreased near functional elements and hybrid incompatibilities [11,12,13]. Hou et al utilized different carbon sources, chemicals, and temperatures to show that over one-fourth of intraspecific crosses show condition-specific loss of offspring viability [24]. This is echoed by many examples of condition specific hybrid incompatibility in plants [25,26,27,28,29,30]. There are numerous examples of environment dependent high fitness hybrid genotypes [31] [32,33,34,35,36,37,38,39,40,41], exemplified by classic research showing Darwin’s finch hybrids with different beak shapes gained a fitness benefit during and after an El Niño event [15]
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