Friday, October 2, 2015

On hybrid speciation and genomic architecture in sparrows: visit and talks by two guest from CEES in Oslo

 Posted by Erik Svensson

Next week on the EXEB-meeting on Tuesday October 6 (10.00, as usual) we will have a visit by two PhD-students from  the Centre of Ecological and Evolutionary Synthesis (CEES) at Oslo University, who will give short talks (about 15 minutes) about their researchers. Our two guests are briefly introduced below, and Abstracts of their talks are also provided.

 Caroline and Angelica are PhD-students of Fabrice Eroukhmanoff and Anna Runemark, two
 former EXEB-members who did their PhD in Lund (2010 and 2012, respectively), and who are
 now working on hybrid speciation in Passer sparrows together with Glenn-Peter Saetre and 
 other researchers in the big sparrow project in Oslo.

 "Fika" will be provided and time and place as usual: "Argumentet" at 10.00.


    Caroline Øien Guldvog
 "As I come from the Oslo area, I did both my bachelor and my MSc here at UiO. For my PhD, I have continued on working with the same research group as I did for my MSc, Glenn-Peter Sætre’s group investigating homoploid hybrid speciation in the Italian sparrow. The work this group is doing originally appealed to be as I find evolutionary genetics very fascinating and would love to continue working within this field in the future. The title of my MSc thesis was «Clock genes and their role in migratory phenotype among Passer sparrows» where I studied genotype-phenotype interactions for migratory behavior among migratory and sedentary populations of birds among the hybrid Italian sparrow and its parentals, the house sparrow and Spanish sparrow. Through this work, I was introduced to genomics and bioinformatics and I am very happy to be able to continue using these skills and learning more through my PhD which has the title "The repeatability of the genomic architecture in a homoploid hybrid species»."


Hybridization has increasingly been recognized as a source of novel variation. The genetic variation resulting from hybridization differs from that from mutations, as large co-adapted complexes can be transferred by hybridization. In addition, variants derived from hybridization have already been tested by selection, further contributing to the potential to form viable new combinations through recombination of genetic elements derived from either parent species. Hybridization will only contribute to adaptation if resulting genotypes are better fit in some environments than the parental species. However, the combination of differentiated genomes typically results in the great majority of recombinants being unfit. In that regard, an interesting question is whether different genomic combinations of the parental species can be produced or if this process is constrained to only result in one or a few viable forms.

The Italian sparrow (Passer italiae) is a homoploid hybrid species resulting from hybridization between the Spanish sparrow (P. hispaniolensis) and house sparrow (P. domesticus). The Italian sparrow is a mix of its parents both on the phenotypic and genetic level. It inhabits the Italian peninsula as well as a few Mediterranean islands including Crete, Corsica and Sicily. The island-living populations differ phenotypically and appear to be derived from different hybridization events and/or to have evolved independently in different directions, making this an excellent system for the study of the repeatability of genomic architecture in a hybrid species. I will present the preliminary plan for my recently started PhD in which the main objective is to study the constraint of the mosaicism of the genome of the Italian sparrow. Populations that differ in both genotype and phenotype will be informative on general processes affecting the hybrid genome such as associations between phenotype and genotype, genetic admixture, patterns of linkage disequilibrium and the role of transposable elements in molding the hybrid genome.

Angelica Maria Cuevas Pulido

"My primary research interest lies in the field of evolutionary ecology and genomics of natural populations. I am particularly interested in how variation in genetic architecture affects the
adaptive potential of natural populations and determine the ways in which evolutionary forces
might act on a population. For my PhD I am working on the evolvability of genomic architecture during speciation, using the Italian sparrow as a model species. My project focuses on the genetic basis of adaptive traits in the hybrid species Passer italiae and its parental species. I currently hold a B.Sc. degree in Biology from the Colombian National University and a M.Sc. in Ecology and Evolutionary Biology from the University of Groningen (The Netherlands) and Ludwig Maximilian University of Munich (Germany). I have participated in research projects in different institutions including the Centre d’Ecologie Fonctionnelle et Evolutive, CNRS (France), Harvard University (USA) and Natural History Museum of London (UK)." 


Secondary contact between closely related species can have important evolutionary consequences, including ecological character displacement due to competition. This may be especially true for encounters between a hybrid species and its parents, where strong isolation mechanisms need to evolve for the hybrid to remain stable. Besides the evolution of pre-­‐zygotic isolation and intrinsic reproductive barriers, competition could also play an important role. Some adaptive radiations in birds (e.g. Darwin’s finches) are related to high levels of competition and diversification through beak shape, a trait playing an important role in diet and habitat choice. In the case of hybrid linages, genomic variability may boost evolutionary potential, which could allow rapid evolution in response to species interactions.

I study a population of Italian sparrow (a homoploid hybrid species) before and after a recent secondary contact with one of its parental species, the Spanish sparrow. I show that over just a couple of generations the size of this hybrid population has declined by 60% following the arrival of its parent. Body condition in the Italian sparrow has dramatically decreased and there is strong habitat segregation between the species. The Italian sparrow occupies an animal-­‐farming habitat while its parent is mainly concentrated close to cereal fields. This may reflect severe competition for resources. Beak shape has also changed considerably; the morphospace currently occupied by the Italian sparrow is a subset of the one prior to secondary contact. Hence, this hybrid species appears to be evolving under a very small spatio-­‐temporal scale in response to species interactions.

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