The world is changing and has been changing drastically for quite some time. According to IPCC (2023), the climate, and thereby the environment, will continue to change with ocean acidification, increased temperatures, and increased precipitation being some factors mentioned. With the current climate situation and decline in biodiversity, marine organisms face many challenges, therefore the importance of understanding the most basic building blocks of species is key. How genomic variation links to phenotypic variation is crucial to understanding why and how organisms adapt to changes, and key to predicting how they can persist in a changing world. Important to note is that the central dogma in molecular biology states: DNA is transcribed to RNA, and RNA is translated to protein. Therefore, genomic variation does not only consist of what genes an organism has, but also how these genes are expressed. Examining organisms in an evolutionary context also provides insights in how species have persisted historically and can give important clues to what the future might hold. Littorina species are common along the coasts at the North Atlantic. Several species have different ecotypes, and different species have different modes of reproduction (pelagic eggs, ovoviviparous, egg clusters on macroalgae). The dispersal is therefore both high and low, depending on the species. Comparing ecotypes, as well as different species of Littorina, therefor provides a powerful tool to understand different types of evolution and their processes. Littorina species have been studied from many different angels since the 1980:s, so there is also much science to further bould on. A missing link however is the effect of gene expression on evolution, that is what this project will add. My projects will be as following: 1. Proteomics of Littorina saxatilis shells from two ecotypes: Performing quantitative proteomics of shells from wave and crab ecotypes of L. saxatilis from Sweden and Spain. Comparing the proteomics of the shell to transcriptome data (already acquired from college). 2. Sperm competition in Littorina species: A collaboration with Luisa Kumpitsch, PhD student. Examining sperm competition in Littorina saxatilis, species birthing live young, and Littorina fabalis, species laying eggs clusters. In both species, females mates with several males and a single brood can have different sires. Can the females choose which male's sperm to use for fertilization? Or is it a first mate = first fertilize scenario? 3. Inversions effect on phenotype and gene expression. using data genotype and phenotype data from a covariation experiment and perform RNA-seq.