HYBRAD

The Impact of Hybridization on Functional Diversification - Experimental Evolution with Sexual Microbes

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 Obiettivo del progetto (Objective)

'An underexplored aspect in the evolution of biodiversity is the role of interspecific hybridization. Hybridization is hypothesized to increase the functional diversity of adaptive radiations, potentially yielding ecological speciation. Yet, direct evidence for this is lacking. We propose to apply a large-scale, quantitative approach using experimental evolution with yeast to test this fundamental theory of quantitative genetics. Yeast is a powerful system because it permits the simulation of eukaryotic evolutionary processes while allowing easy access to information on geno- and phenotype. First, we will generate artificial radiations from hybrid and non-hybrid ancestors and expose them to diversifying selection using high-throughput phenotypic microarrays, simulating a heterogeneous fitness landscape. We will then compare the functional diversity obtained in radiations with and without hybrid background. Second, we will test if phenotypic novelty (transgressive segregation) observed in hybrids increases with genetic and phenotypic distance between their parents. Third, to test if there are stereotypical genetic changes accompanying divergence during adaptive radiation we will resequence parallel and divergent selected strains of yeast. Besides theoretical aspects, these data may reveal applications for commercial exploitation of phenotypic novelty in yeast. An improved understanding of genetic exchange in fungi can also be crucial for medical/veterinary sciences, epidemiology, and conservation biology. Training in experimental evolution and state of the art technology (SOLiD sequencing and metabolic fingerprinting) are of key importance to the future competitiveness of the fellow. This project delivers the following aspects of the work program: Improvement of EU scientific excellence through new scientific networks, training of a future research group leader both directly and through mobility, and enhancing EU competitiveness through high profile output'

Introduzione (Teaser)

Extreme man-made changes to the environment are bringing many species to the point of extinction. EU-funded research has investigated, using real-time experiments, how hybridisation may increase the ability to survive in adverse environments.

Descrizione progetto (Article)

Looking at evolutionary trees, there is indirect evidence that when different varieties of organisms interbreed, the resulting transgressive or extreme phenotypes may be able to withstand harsher environments than their parents. The HYBRAD project has presented direct experimental evidence from yeast (Saccharomyces) crosses for the ecological divergence of transgressive hybrids.

The research team crossed phenotypically and genetically different yeast strains and compared the resulting hybrids with their parents in harsh environments. These new situations mimicked various increasingly stressful pollution events. The transgressive hybrids could outcompete against their parents in a wide range of environments and were up to three times as fit, in the evolutionary sense.

HYBRAD also tested the survival mechanism known as 'evolutionary rescue' by looking at interspecific hybridisation where more distant relatives of yeast interbreed. Hybridisation increased the probability of evolutionary rescue compared to both parental lineages and intraspecific crosses. This is attributed to the fact that hybridisation boosts the genetic variance and phenotypic novelty available to natural selection.

Looking at even more distinct parents and the results of crosses, HYBRAD selected the hybrids from 10 increasingly stressful environments. Sampling genotypes and using a project-modified restriction site associated DNA (RAD)-tag protocol, they have promising preliminary results. The method allows for mass screening of many genotypes for recombinant events as well as radical genetic change such as aneuploidy, the addition or loss of whole chromosomes.

Results of project experiments have featured in peer-reviewed journals Journal of Evolutionary Biology and Evolutionary Applications. Overall, HYBRAD has delivered a series of important experimental evolutionary models that mimic the trend of an increasingly polluted environment. Moreover, the project devised state of the art technological improvements in genomic protocols that will no doubt help to give European research a competitive edge.