Abstracts (first author)

Talk 

The genetic basis of adaptation to ocean acidification in Emiliania huxleyi , a key phytoplankton species

Author(s): Reusch TBH, Lohbeck KT, Riebesell U, Esser D, Rosenstiel P

Summary:

Ocean acidification, the drop in seawater pH due to the uptake of anthropogenic CO2, is a major threat to marine calcifying organisms. In a long-term evolution experiment, we found that the biogeochemically important unicellular algae Emiliania huxleyi partly restored calcification and growth rates at elevated CO2 owing to adaptive evolution, compared to control lines kept at ambient CO2 levels. In order to unravel the genetic basis of adaptive change we re-sequenced replicated control and adapted populations to a high coverage. We identified SNPs and other polymorphisms that diverged with respect to CO2 selection treatments via mapping to the existing genome of E. huxleyi. We were particularly interested whether or not the same genes or metabolic pathways were affected, and how consistent these changes were across replicates. These data provide first insights into the dynamics and the parallelism of de novo mutations in an ecologically important phytoplankton species.


Video


Abstracts (coauthor)

Genomic islands of divergence: a comparison of five parapatric lake-river population pairs of three-spined sticklebacks

Author(s): Feulner, PGD, Chain FJJ, Panchal M, Huang Y, Eizaguirre C, Kalbe M, Lenz T, Samonte I, Stoll M, Bornberg-Bauer E, Reusch T, Milinski M

Summary:

Sticklebacks have recently colonized various freshwater habitats and have since undergone recurrent phenotypic divergence. Here, we sample five geographically distinct lake-river population pairs of the three-spined stickleback for investigating patterns of population divergence at varying stages of ecological speciation. Using 60 whole genome sequences (15x coverage each) we identify genomic islands of divergence between parapatric lake-river ecotypes. This allows us to evaluate the number, size and distribution of genomic islands of divergence between several population pairs and to assess the extent of population differentiation across our samples. We identify different genes and genomic regions potentially associated with ecological differentiation in the five lake-river comparisons. This suggests that divergence patterns between lakes and rivers can involve multiple molecular pathways. Interestingly, we find some associations between genomic structural variations and islands of divergence. This is based on our extensive set of structural variations including deletions, copy-number variations, inversions, and translocations. Combined with estimates of the recombination rates across the genomes, we provide insights into the relevance of the genomic architecture and the role of genomic islands during adaptive divergence.

Male pregnancy and immune defence anomaly

Author(s): Roth, O, Haase D, Wegber M, Reusch TBH

Summary:

The major histocompatibility complex (MHC) - mediated adaptive immune system was claimed to be the hallmark of vertebrate immune defence. Now recent work suggests that vertebrate immune systems and in particular the MHC - mediated immunity are much more plastic than previously assumed. Based on deep-transcriptome sequencing, we report the loss of the MHC class II immune pathway in the sex-role reversed pipefish Syngnathus typhle. In contrast, MHC class I genes were present, and their diversity correlates with the efficiency of immunity and male mate choice behavior. We identify “sex-role reversal” as a potential selection factor for loss of MHC II and other surprising anomalies in the pipefish immune defence, and give an outlook of how this can affect host-parasite coevolution.

Genome evolution and structural variation in sticklebacks across different stages of divergence

Author(s): Chain, FJJ, Feulner PGD, Panchal M, Huang Y, Eizaguirre C, Kalbe M, Lenz TL, Samonte IE, Stoll M, Bornberg-Bauer E, Reusch TBH, Milinski M

Summary:

Deciphering the genetic architecture underlying population differentiation and adaptation is crucial for better understanding the process of ecological speciation. To reveal patterns of genome evolution across different stages of population divergence, we characterized genetic variation in three-spined sticklebacks using 66 whole genomes (15x coverage each) from geographically and ecologically distinct populations. This fish species has recently colonized freshwater habitats and undergone substantial and recurrent phenotypic divergence associated with their habitat. We have evaluated the relative importance of several types of genetic variation (SNPs, INDELs, CNVs, inversions and translocations) in the differentiation of genomes across populations and ecotypes. Structural variations cover a larger proportion of the genome than the ~10 million single nucleotide variants. Whereas the majority of variants are shared across several populations, we detect genomic regions of high differentiation between closely related populations. Lineage-specific genes and RNA genes often differ in copy number between individuals and between populations, suggesting a potential role of structural variation such as CNVs in ecological adaptations. We also investigate the relationship between CNVs and different categories of duplicate genes, and evaluate the molecular rates of gene evolution using interspecific data. Taken together, our findings demonstrate extensive genomic differentiation within only a few thousand generations and support a mechanism for the birth and death of new genes via duplication, highlighting the dynamic nature of genomes. Due to our population sampling design we are able to shed some light on the interplay of ecological and genomic features of populations during adaptive evolution and at different stages of ecological speciation.

Summary:

The biological impacts of climate change and the associated acidification of the surface ocean are intensely studied, with likely consequences for biodiversity and ecosystem functioning emerging as a consensus. However, evolutionary responses have only recently been considered. Marine microbes with short generation times and large population size are good candidates for testing the evolutionary potential to respond to ocean acidification. We used the globally important marine phytoplankton species Emiliania huxleyi for a 1000 generation selection experiment in elevated CO2 and found that adaptive evolution to ocean acidification is possible and likely fast enough to act on time scales relevant to climate change. Replicate populations selected under high CO2 consistently revealed higher fitness than control populations under ocean acidification conditions. To investigate whether such phenotypic convergence involves the same or different mutations, we exposed adapted populations to a novel environment where pleiotropic effects can serve as a proxy for divergent genetic bases of previous adaptation to high CO2. We identified divergent functional genetic bases in replicate high CO2 adapted but not in control populations. This indicates that many evolutionary trajectories to high CO2 adaptation are possible in E. huxleyi but also suggests that pleiotropy may constrain adaptation of natural E. huxleyi populations to ocean acidification. Our results highlight the urgent need to consider evolutionary processes when assessing the responses of marine microbes to future ocean conditions.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
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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