Results

Within this project we successfully implemented an innovative and transdisciplinary approach to studying the evolutionary and ecological consequences of anthropogenic disturbance. More specifically, the main objective of the research was to test how anthropogenic change affects the biology of Mediterranean mussels (Mytilus galloprovincialis), including the ecology, phenotypic traits, and genetic characteristics of the species, particularly in relation to contemporary events. A combination of evolutionary and eco-toxicological approaches and modern genomic technologies (i.e. ‘next-generation-sequencing’ NGS) yielded insights into the biological responses of this species to various environmental pressures, including pollution. One of our core conclusions is that environmental pressures, likely including pollution, can have rapid effects on specific regions of the genome, even when gene flow among populations is high.

We gathered comprehensive data on mussel fitness, physiology, morphology, genomic variation, and epigenomic variation. By integrating this multifaceted data with information on environmental variables we are working to increase understanding of contemporary and historical processes in the evolution of this species. Specifically, results from natural populations have been successfully combined with those derived from controlled transplant experiments (in the wild and in lab mesocosms) to understand the evolutionary responses of mussel populations to different environments.

Five key insights have already emerged, and further analyses are underway. First, genome wide differentiation of mussel populations along the Croatian coast is weak, supporting a history of high levels of gene flow and little genome wide structure. Second, although genome wide structure is weak, we have robustly identified numerous genomic regions exhibiting enhanced differentiation among populations (i.e., so-called ‘outlier loci’); these loci are candidates for this subject to divergent selection rather than stochastic processes. Third, we have pinpointed several environmental factors, including bioaccumulated pollutants, as underlying drivers of outlier loci. The collective results provide evidence for local adaptation despite high gene flow. Fourth, transplant experiments are still being analyses but results to date have shown that exposure to pollution has population dependent impacts on fitness. Genome-wide responses to selection are being inferred through extensive analyses of allelic frequency changes in these experimental populations, and these patterns will be compared to those from natural populations to test for matching patterns between natural and experimental settings. Such matching patterns would provide particularly robust evidence for selection and local adaptation. Fifth, extensive phenotypic variation within and among mussels populations has been quantified, associated with environmental variation, and shown to have a highly polygenic nature and modest to low heritability using modern genome wide association mapping. Thus, partial genetic but also induced effects on phenotypic variation are evident. The collective results will help address a key question in biology; namely the associations between environment, fitness, phenotype, and genotype. These extensive genetic studies are being combined with data on epigenomic variation to yield comprehensive insight into these associations. Beyond providing general biology insights, the results can be used to formulate approaches for improving aquaculture practices, and thus have applied significance.

This project was developed using a robust research program as a platform for improving the scientific capacity of Croatian researchers, especially in the cutting edge field of evolutionary genomics. This goal was achieved beyond expectations, due to the remarkable willingness of members of the project leader’s lab to share their time, knowledge, and expertise in evolutionary and computational biology with Croatia scientists, but also due to remarkable devotion of young Croatian scientists in embracing and implementing these new tools. Thus, three young Croatian researchers have been widely trained in the cutting edge computational and analytical approaches in evolutionary genomics. Moreover, this project enabled the training of one UK master student and eight Croatian master students (that volunteered on the project) in the field of evolutionary ecology. A collaborative sprit in the project team, in conjunction with the opportunity to attend several congresses and workshops, greatly enhanced scientific networking of the Croatian researchers. These factors have combined to facilitate the development of the scientific group into one posed for future productivity in terms of high-profile publications and project applications.

Project workshop was held 15-19 September 2014 at island Mljet, Croatia. 20 scientists and students from United Kingdom and Croatia participated. To download the program click HERE.

Main overview of the project and the evolutionary and genomic methods used within the project were presented at the Workshop on Marine Evolutionary Genomics and Proteomics, 14-16 October 2014, Vigo, Spain

During the 2015 project results were presented at:

SMBE Satellite meeting SMBEBA 2015, Investigating biological adaptation with NGS: data and models, May 26-29 2015, Hameau de l’étoile’, France

ESEB 2015 – meeting of the European Society for Evolutionary Biology, August 9-15 2015, Lausanne, Switzerland

12th Croatian Biological Congress with international participation, Sv. Martin, Croatia, September 18-23 2015