Evolution and Species Boundaries

Understanding how gene flow is prevented in sympatry is greatly informative about the nature of species differences and the speciation process. In addition to the five cichlid genomes sequenced at the Broad Institute, we have sequenced the genomes of four additional species of Neolamprologus in collaboration with colleagues at the CEES and the NSC in Oslo. These new genomes have provided considerable insight into how speciation progresses at the genome level and how the recombination landscape shapes the evolution of reproductive isolation and the rate of hybridization. We report some of the first empirical data that support the impacts of genome architecture, recombination landscapes and selection at linked sites on rates of introgression and differentiation. Relevant to understanding how speciation can progress in the face of gene flow, collinear chromosomal regions can be protected from gene flow and harbor incompatibility genes if they reside in lowly recombining regions, and coupling can evolve between non-physically linked genomic regions (chromosome centers in particular). Simultaneously, chromosome peripheries appear as more dynamic, evolvable regions where introgression is higher and adaptation polymorphisms can evolve.


PacBio sequencer in action at the Norwegian Sequencing Centre in Oslo


In addition to the genomic approaches above we have investigated the nature of species boundaries and hybridization in different freshwater fish systems using other types of molecular data, including barbels, nases and roaches, with several teams from different countries.


Luciobarbus bocagei from the Tejo River Basin, one of the Iberian species involved in interspecific gene flow.


Having a phylogenetic hypothesis of a group of interest is fundamental for understanding the evolution of species traits, species relations in space and time, and factors promoting their diversification. We used phylogenomic tools and new genome data of Neolamprologus cichlids to disentangle their species tree from the effects of hybridization and incomplete lineage sorting. We have investigated this in detail in a number of other fish groups, such as Iberian nases and Iberian and Italian barbels.



Last updated: October 30th, 2018

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