Urbanization is associated with reduced genetic diversity in marine fish populations

Abstract

The economic and ecological benefits of living by the ocean have led many coastal settlements to grow into large densely populated cities. Large coastal cities have had considerable environmental effects on marine ecosystems through resource extraction, waste disposal, and use for transportation. Thus, it is important to understand the consequences of urbanization and human activities on evolutionary processes and biodiversity in marine fishes. Using published population genetic datasets for marine fishes amounting to 75,496 individuals sampled from 73 species at 1143 sample sites throughout the world’s oceans, we evaluated how human population density and a composite measure of cumulative human impacts affected genetic diversity and differentiation. We found that genetic diversity was significantly lower in marine fish populations associated with denser human populations regardless of species and locality. The effects of cumulative human impacts on genetic diversity were less prominent, perhaps due to this measure capturing more spatially varying processes. Urbanization in coastal regions has degraded marine biodiversity in a way that erodes adaptive potential for marine fish populations. This highlights the need to mitigate threats from human activities and focus efforts on sustainable urban planning and resource use to conserve marine biodiversity sustaining coastal fisheries and ecosystems.

The global protected area network does not harbor genetically diverse populations

“…Intraspecific genetic diversity is the most fundamental level of biodiversity, underlying the microevolutionary processes that contribute to populations' adaptive capacity and resilience to environmental change (Lande & Shannon, 1996). The growing human environmental footprint is associated with the erosion of genetic diversity across many species on land and in oceans (DiBattista, 2008;Karachaliou et al, 2024;Leigh et al, 2019;Pinsky & Palumbi, 2014;Schmidt et al, 2020). The expansion of protected areas buffering populations from environmental change and exploitation could be a powerful tool for limiting further genetic diversity losses.…”

“…We used previously compiled databases of publicly archived, georeferenced microsatellite genetic data from terrestrial mammals and marine fish (Karachaliou et al, 2024;Schmidt, Mäkinen, et al, 2023). Detailed methods on database compilation can be found in (Karachaliou et al, 2024;Schmidt, Mäkinen, et al, 2023). Briefly, we obtained a list of species names for terrestrial mammals and marine fish from the IUCN Red List database (https://www.iucnredlist.org/).…”