Convergent molecular changes in populations of two pipefish species in the Baltic Sea
Year: 2026
Type: preprint
Abstract: While studies of molecular convergence typically focus on species that independently evolved similar phenotypes, similar questions can be asked among populations of different species adapting to the same environment. Here, we study the Baltic Sea environmental gradient and two co-distributed, ecologically similar, but distantly related pipefish species, the broadnosed pipefish ( Syngnathus typhle ) and the straightnose pipefish ( Nerophis ophidion ), to test whether independent colonization of the Baltic Sea led to similar population structure and caused convergence at different genomic levels. Using a new diploid genome for S. typhle and whole-genome resequencing data (N=99 for S. typhle ; N=81 for N. ophidion ) across seven locations from France to Finland, we identified stronger population structure in S. typhle than in N. ophidion , while both species showed differentiation between North Atlantic, Danish Straits, and Baltic Sea populations. Genetic diversity was lower in Baltic populations, particularly in S. typhle . Cross-species comparisons of Baltic populations revealed contrasting chromosome-level patterns of genomic differentiation, with differentiation spread across the genome in S. typhle but concentrated in specific chromosomal regions in N. ophidion . Nonetheless, we identified multiple orthologous genes and SNPs showing convergent differentiation in the Baltic populations of both species, including genes related to metabolism, immunity, and regulatory functions. Overall, we identified molecular convergence at the gene and nucleotide level between Baltic populations of distantly related pipefish species, while convergence was limited at broader genomic scales. These findings suggest that similar environmental pressures can repeatedly target specific genetic elements even when genomic backgrounds and population structures differ.
Authors: Jule Drewalowski, Eli Taub, Oiana Trillo, Marharyta Abashkina, Gunilla Rosenqvist, Sergei Kliver, Iva Kovačić, Sarah S.T. Mak, Jessica Bogaards, Charlotta Kvarnemo, Bent Petersen, Joseph Nesme, Benoit Gouillieux, Peter Rask Møller, Rasmus Stenbak Larsen, M. Thomas P. Gilbert, Kenyon B. Mobley, Josefin Stiller
Institutions: University of Copenhagen, University of British Columbia, Okanagan Campus, Uppsala University, University of Gothenburg, AIMST University, Technical University of Denmark, Centre National de la Recherche Scientifique, Université de Bordeaux, Environnements et Paléoenvironnements Océaniques et Continentaux, Institut Polytechnique de Bordeaux, Natural History Museum of Denmark, Norwegian University of Science and Technology, UiT The Arctic University of Norway
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7214202100