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Investigating interactions between ecology and historical contingency in the generation of species diversity

Titel Englisch Investigating interactions between ecology and historical contingency in the generation of species diversity
Gesuchsteller/in Seehausen Ole
Nummer 106573
Förderungsinstrument Projektförderung (Abt. I-III)
Forschungseinrichtung Departement für Biologie Universität Bern
Hochschule Universität Bern - BE
Hauptdisziplin Genetik
Beginn/Ende 01.01.2005 - 31.12.2007
Bewilligter Betrag 479'000.00
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Alle Disziplinen (3)


Keywords (6)

Hybridization; Adaptive Radiation; Speciation; Disruptive selection; Sexual selection; Transgressive segregation

Lay Summary (Englisch)

Lay summary
One of the least well understood problems in evolutionary biology and biodiversity research is why some organisms have undergone massive speciation and adaptive diversification in very short time, whereas many others, often closely related and superficially similar, have not diversified at all. Intensive investigations of the processes that result in the origin of reproductive isolation, coupled with increasingly realistic computer simulations have in recent years ed to several paradigm shifts in speciation theory. Speciation with geneflow, driven by ecological processes that exert disruptive or diversifying selection is now receiving a lot of attention, and an intensive productive scientific debate is centres on the causes of disruptive selection during sympatric speciation. The question is whether diverging mating preferences, which are assumed in most of the recent models, are recruited by selection resulting from competition for ecological resources or by selection resulting from competition for mating opportunities, followed by ecological character displacement. Theoretical parameter space for sympatric speciation has been exhaustively explored, but empirical testing of model assumptions is lagging behind. In the first of the two projects that I propose here, I develop experimental tests of predictions made by these alternative models with regard to the temporal patterns of emergence of gene associations and genetic linkage groups comprising alternative sets of genes. I propose to use hybridizing populations of incipient species of lake Victoria cichlids to (i) subject different types of traits to tests of disruptive selection, and (ii) to identify chromosomal linkage groups containing “speciation traits” by association scans with AFLP markers. Another unresolved problem associated with the rapid emergence of adaptive diversity in some lineages is the source of genetic variation that allows for the unusually high rates of phenotypic evolution. One theory that has recently been revived is that hybridization upon secondary contact in novel or perturbed environments between genetically well differentiated lineages endows resulting hybrid populations with large variation in quantitative traits that allow these populations subsequently to rapidly radiate in response to diversifying selection. The concept comprises two elements, the hybrid swarm origin hypothesis which predicts that rapid radiations are often derived from more than one hybridizing ancestral taxa, and the syngameon hypothesis for the generation of functional diversity. The latter suggests that occasional or localized hybridization between emerging species during an adaptive radiation is essential to generating new adaptive trait combinations and preventing fixation at quantitative trait loci under selection. Hybridization would maintain and prolong the adaptive radiation momentum. I the second project I propose to test this syngameon hypothesis. (i) I propose to build the first comprehensive species level phylogeny for Lake Victoria cichlids from polymorphic AFLP loci and use this phylogeny to investigate the distribution of alleles that can be traced back to the hybridizing ancestral species. (ii) I propose an experimental quantification of the morphological diversity than can be generated by interspecific hybridization. (iii) I propose a series of experiments to parameterise endogenous and ecological hybrid fitness and functional hybrid diversity in relation to genetic distance of the hybridizing species. Together these investigations will provide the first comprehensive test of the potential for interspecific hybridization to sow the seeds for an adaptive radiation. Taking both projects together, the challenge is to understand the relationship between the potential for hybridization among already divergent species to generate recombinant genetic diversity that can be edited into new genotypes on the one hand, and on the other hand the requirement for mechanisms that reduce hybridization between populations during their divergence to allow for functional differentiation. Clearly, one of these facets of hybridization seems to generate diversity while the other one seems to prevent it or slow it down. I believe that the investigations proposed here, may ultimately contribute to the resolution of this conceptual conflict.
Direktlink auf Lay Summary Letzte Aktualisierung: 21.02.2013

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