Convergent molecular changes in populations of two pipefish species in the Baltic Sea
- 1Department of Biology, University of Copenhagen, Denmark
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.
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BibTeX
@misc{drewalowski2026convergent,
title = {{Convergent molecular changes in populations of two pipefish species in the Baltic Sea}},
author = {J. Drewalowski and E. Taub and M. Abashkina and O. Trillo and G. Rosenqvist and S. Kliver and I. Kovacic and S. S. T. Mak and J. Bogaards and C. Kvarnemo and B. Petersen and J. Nesme and B. Gouillieux and P. R. Moller and R. S. Larsen and M. T. P. Gilbert and K. B. Mobley and J. Stiller},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.23.753463},
url = {https://www.biorxiv.org/content/10.64898/2026.09.23.753463v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Convergent molecular changes in populations of two pipefish species in the Baltic Sea
AU - J. Drewalowski
AU - E. Taub
AU - M. Abashkina
AU - O. Trillo
AU - G. Rosenqvist
AU - S. Kliver
AU - I. Kovacic
AU - S. S. T. Mak
AU - J. Bogaards
AU - C. Kvarnemo
AU - B. Petersen
AU - J. Nesme
AU - B. Gouillieux
AU - P. R. Moller
AU - R. S. Larsen
AU - M. T. P. Gilbert
AU - K. B. Mobley
AU - J. Stiller
PY - 2026
DA - 2026/09/23
PB - bioRxiv
DO - 10.64898/2026.09.23.753463
UR - https://www.biorxiv.org/content/10.64898/2026.09.23.753463v1
AB - 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.
ER -