Zoology Department Seminar: Two Tales of Anthropogenic Hybridization in Human-Altered Marine Habitats

Speaker: Dr Nicolas Bierne, Université de Montpellier.

Title: Two Tales of Anthropogenic Hybridization in Human-Altered Marine Habitats

Abstract: Human transport of species across the Anthropocene ocean has increased hybridization in human-altered habitats. This hybridization blends divergent genomes into new genomic mosaics and provides valuable natural experiments for understanding selective processes in hybrid genomes, yet it remains understudied, especially in marine environments. I will present results from two marine systems: Ciona sea-squirts and Mytilus mussels. Introgression from the North Pacific Ciona robusta into the native North Atlantic C. intestinalis was proven to be adaptive, localized to a genomic region on chromosome 5. Using long-read and linked-read sequencing, we investigated the molecular variation conferring this advantage. Hybridization between the invasive Mytilus galloprovincialis and the native M. edulis led to a new ecotype, known as the “dock mussel”, in French commercial ports. Analysis of over 300 dock mussels with a 60K SNP array revealed two chromosomal islands of native parental ancestry, suggesting adaptive introgression. However, contrary to expectations for admixture between two species at the end of the speciation continuum, the dock mussel genome was found to be fully admixed. This finding is consistent with a multigenic fitness landscape model with parental maladaptation, which predicts selection for enhanced ancestry heterozygosity. Admixture and adaptive introgression may be common evolutionary pathways in novel human-altered habitats such as ports. Future work must integrate phenotypic and environmental data to better understand the evolutionary forces shaping hybrid mosaic genomes.

Our Departmental Seminars run weekly on Thursdays during term time. They cover recent research on a wide variety of topics from evolutionary genetics through behavioural ecology to ecology and natural history.  

Everyone in Zoology is invited, and Part II undergraduate zoologists are particularly encouraged to attend.  Please click here for a list of all of this term's seminars.