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<p>Understanding the evolutionary relationships and population structure of South American silversides (<i>Odontesthes</i> spp.) is crucial for elucidating speciation, hybridization, and biogeographic patterns. Habitat transitions, salinity, and connectivity strongly influence gene flow and lineage formation. Using ddRADseq, we analyzed 364 individuals sampled across the Atlantic and Pacific basins to assess phylogeny, population structure, and species boundaries. Phylogenetic reconstructions revealed two major clades corresponding to basin distributions. Several species (<i>O. ledae, O. mirinensis, O. mauleanum, O. brevianalis, O. regia, O. gracilis</i>) were resolved as non-monophyletic, suggesting historical admixture, whereas <i>O. nigricans</i> was included for the first time in a genomic-scale phylogenetic analysis. STRUCTURE, DAPC, and PCA analyses revealed clear differentiation in <i>O. smitti</i>, coastal <i>O. argentinensis</i>, and <i>O. perugiae</i>, whereas southern Brazilian species and Chilean species <i>O. regia/O. gracilis</i> formed intermixed clusters, consistent with ongoing gene flow. Isolation-by-distance was detected in <i>O. bonariensis</i> and the southern Brazilian species group. These results demonstrate that geographic isolation, habitat connectivity, and hybridization jointly shape population structure and evolutionary history in <i>Odontesthes</i>. This study provides the first genomic-scale perspective for several lesser-known species and highlights admixture as a key factor influencing genetic diversity and lineage boundaries in South American silversides.</p>

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Phylogenomic insights into species boundaries and population structure in South American silversides (Odontesthes, Atherinopsidae)

  • 期刊论文

  • 发表日期：

    2026年7月14日

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  • Yanina F. Briñoccoli,
  • Mariano González-Castro,
  • Eva C. Rueda,
  • Gustavo M. Somoza,
  • Guillermo Ortí,
  • Yamila P. Cardoso

摘要

Understanding the evolutionary relationships and population structure of South American silversides (Odontesthes spp.) is crucial for elucidating speciation, hybridization, and biogeographic patterns. Habitat transitions, salinity, and connectivity strongly influence gene flow and lineage formation. Using ddRADseq, we analyzed 364 individuals sampled across the Atlantic and Pacific basins to assess phylogeny, population structure, and species boundaries. Phylogenetic reconstructions revealed two major clades corresponding to basin distributions. Several species (O. ledae, O. mirinensis, O. mauleanum, O. brevianalis, O. regia, O. gracilis) were resolved as non-monophyletic, suggesting historical admixture, whereas O. nigricans was included for the first time in a genomic-scale phylogenetic analysis. STRUCTURE, DAPC, and PCA analyses revealed clear differentiation in O. smitti, coastal O. argentinensis, and O. perugiae, whereas southern Brazilian species and Chilean species O. regia/O. gracilis formed intermixed clusters, consistent with ongoing gene flow. Isolation-by-distance was detected in O. bonariensis and the southern Brazilian species group. These results demonstrate that geographic isolation, habitat connectivity, and hybridization jointly shape population structure and evolutionary history in Odontesthes. This study provides the first genomic-scale perspective for several lesser-known species and highlights admixture as a key factor influencing genetic diversity and lineage boundaries in South American silversides.