Abstracts (first author)

Talk 

Divergence and gene flow in Lissotriton newts

Author(s): Babik W, Zieliński P, Stuglik MT

Summary:

Historical patterns and consequences of genetic exchange between hybridizing species are poorly understood, but new genomic and analytical tools promise a rapid progress. We will present the results of research on historical demography and genome-wide patterns of gene flow between hybridizing newts Lissotriton montandoni (Lm) and L. vulgaris (Lv). These newts are characterized by a long history of genetic exchange, as evidenced by the mitochondrial DNA (mtDNA) data. Multiple, spatially and temporally distinct introgression events from Lv resulted in complete mtDNA replacement in Lm. We used various classes of molecular nuclear markers to obtain information about the extent and historical patterns of gene flow between the two species. Fifteen microsatellite loci and 139 coding SNPs surveyed in multiple populations demonstrated a very limited recent admixture in the nuclear genome. Genome-wide patterns of long-term gene flow were assessed by analyzing of over 300 000 SNPs derived from high-throughput transcriptome sequencing. The inferences based on the joint two-population allele frequency spectrum revealed an extensive, asymmetric gene flow from Lv to Lm and models allowing for demographic changes and temporal variation in the strength of gene flow provided best fit to the data. The species distribution modeling based on contemporary and historical climatic data suggests that temporal variation in gene flow between Lm and Lv may be linked to range changes the newts experienced during the Pleistocene climatic oscillations. Sequences of over 50 nuclear markers collected throughout the species ranges and analyzed within the coalescent framework provided evidence for genomic heterogeneity in gene flow. Our study demonstrates the complexity of long-term genetic exchange between hybridizing species and the power of new sequencing technologies for a comprehensive characterization of interspecific gene flow in non-model organisms possessing huge genomes.


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Abstracts (coauthor)

Summary:

Although, a response to selection at the genomic level has been investigated for some traits, little is known about the genomics of adaptation in ecologically important traits in vertebrates. Here we compared transcriptomes of the bank voles (Myodes glareolus) selected for high swim-induced aerobic metabolism (A) with unselected controls (C). In 13th generation of selection, voles from 4 replicate A lines achieved 48% higher max rates of oxygen consumption than those from 4 C lines (means±SD; A:5.32±0.64, C:3.59±0.57 mlO2/min) and differed in several other morphophysiological and behavioral traits. Our aim was to characterize the differences in allele frequencies and the differences in expression level between A and C lines, and thus pinpoint genes contributing to phenotypic diversification. Using Illumina paired-end sequencing and de novo transcriptome assembling we constructed reference liver and heart transcriptomes. Sequences obtained for each line from pools of liver and heart RNA were mapped to the reference transcriptomes to detect SNPs and measure the expression level. On average 33.5 and 29.3 mln 100 bp reads per line were obtained for liver and heart respectively, which allowed reliable polymorphism detection in over 7 000 genes resulting in more than 80 000 SNPs. About 1 600 of these SNPs showed allele frequency ranges which did not overlap between A and C lines, about 15% more than obtained from simulations assuming the differentiation purely by drift. However, the average differences in frequencies were similar for simulations and the experiment. We also identified a modest number (10 in heart and 45 in liver) of genes that showed more than two-fold differences in expression between A and C lines. Our results show that the rapid phenotypic diversification is accompanied by only minor changes in allele frequencies or expression level making the presence of genes of large effect unlikely and indicating a highly polygenic basis of the selected trait.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
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email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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