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<p>We investigated the phylogenetic position and cryptic diversity of the ciliate <i>Paracolpoda steinii</i> (Ciliophora, Colpodida) using modern and ancient isolates. Seven strains were obtained from Siberian permafrost deposits dated to the Holocene and Late Pleistocene, and two from contemporary forest and permafrost-affected soils. The duration of cryptobiosis in the ancient ciliates corresponds to the age of the surrounding permafrost sediments, ranging from several thousand years in surface layers to nearly 45,000&#xa0;years in deeper deposits, as determined by radiocarbon dating. To assess intra- and interspecific variation, we combined comparative morphological and&#xa0;molecular analyses of the SSU 18S rRNA gene and the ITS1–5.8S–ITS2 region, including ITS2 secondary structure and compensatory base change (CBC) patterns. Our results indicate that <i>P. steinii</i> represents a cryptic species complex. CBC analysis revealed significant genetic differentiation, enabling reconstruction of a hypothetical sequence of evolutionary events underlying lineage diversification. These findings provide new insights into the phylogenetic position and evolutionary dynamics of <i>P. steinii</i> during the Holocene and Late Pleistocene.</p>

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Paracolpoda steinii (Ciliophora, Colpodida) from ancient Siberian permafrost: insights into cryptic diversity

  • 期刊论文

  • 发表日期：

    2025年11月4日

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  • Anastasia Shatilovich,
  • Svetlana Bykova,
  • Mikhail Tribun,
  • Elena Krivina

摘要

We investigated the phylogenetic position and cryptic diversity of the ciliate Paracolpoda steinii (Ciliophora, Colpodida) using modern and ancient isolates. Seven strains were obtained from Siberian permafrost deposits dated to the Holocene and Late Pleistocene, and two from contemporary forest and permafrost-affected soils. The duration of cryptobiosis in the ancient ciliates corresponds to the age of the surrounding permafrost sediments, ranging from several thousand years in surface layers to nearly 45,000 years in deeper deposits, as determined by radiocarbon dating. To assess intra- and interspecific variation, we combined comparative morphological and molecular analyses of the SSU 18S rRNA gene and the ITS1–5.8S–ITS2 region, including ITS2 secondary structure and compensatory base change (CBC) patterns. Our results indicate that P. steinii represents a cryptic species complex. CBC analysis revealed significant genetic differentiation, enabling reconstruction of a hypothetical sequence of evolutionary events underlying lineage diversification. These findings provide new insights into the phylogenetic position and evolutionary dynamics of P. steinii during the Holocene and Late Pleistocene.