Connectivity and genetic structure of marine fish populations
Author(s)
Volckaert, Filip A.M.
Momigliano, Paolo
Date Issued
2025
Type
bookPart
Journal
Ecology of Marine Fish
Abstract
Genetic diversity and structure are the foundation of species diversity and speciation. Marine fish populations show a higher genetic diversity and more subtle genetic structure than freshwater fishes. The former is related to the large population sizes, and the latter to the absence of sharp barriers. The distinction in genetic patterns of ray-finned fishes (Actinopterygii) and cartilaginous fishes (Chondrichthyes) is largely linked to their reproductive modes. In both taxa a wide range of subtle barriers such as salinity and temperature clines, current and historical biogeographic barriers, and frontal systems structure populations. Connectivity between populations, often living in closely associated units called metapopulations, shapes their genetic characteristics. Marine fish populations adapt to their local environment, sometimes in relatively short time frames. Counterintuitively, populations may adapt to a local environment despite a high exchange rate of individuals. While ray-finned fishes often have large effective population sizes, their census sizes are several orders of magnitude larger. Researchers employ a diverse scientific toolkit to understand the causes and dynamics of genetic population structure. Population genomics, which accesses full genomes, provides insight into the diversity, architecture, control, and functioning of genomes. The integration of georeferenced environmental information with genomics (i.e., seascape genomics) elucidates the spatial and temporal dynamics of populations. The integration of genomic and phenotypic information, for example as in genome-wide association studies (GWAS), provides a functional link between quantitative and population genomics to understand how selection changes phenotypes through the genotype. Hence, population genetics has and continues to contribute to the understanding of fish populations, their sustainable exploitation, and conservation, especially in view of global change.
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