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<p><i>Simulium asakoae</i> is a widespread species of black fly in Southeast Asia and a potential vector of parasites of medical and veterinary importance. Despite its broad distribution and diverse habitats, population genetic information remains limited. We investigated the genetic diversity, population structure, and demographic history of <i>S. asakoae</i> in Laos and examined its genetic relationships with populations from other Southeast Asian countries, using mitochondrial cytochrome c oxidase subunit I (COI) sequences. A total of 369 COI sequences (241 generated in the present study and 128 retrieved from GenBank) were analyzed. Of these, 284 sequences (241 from this study and 43 from GenBank) originated from nine locations across five provinces in Laos. Among the Laotian specimens, 51 haplotypes were identified, showing high haplotype diversity (Hd = 0.9063) and moderate nucleotide diversity (π = 0.0080). Intraspecific genetic divergence among Lao populations ranged from 0 to 2.49%, increasing slightly to 2.66% when regional sequences were included. Median-joining network analyses revealed no major genetic breaks or clear geographic structuring in Laos or across Southeast Asia, indicating extensive gene flow. Pairwise <i>F</i><sub>ST</sub> analyses, however, detected significant differentiation among some populations. Demographic analyses, including mismatch distributions and neutrality tests, supported a scenario of recent population expansion, with estimated expansion times of approximately 13,000 years ago for Lao populations and 15,000 years ago at the regional scale. These timeframes coincide with the transition from the cool dry Pleistocene to the warm humid Holocene, which might have facilitated population growth and range expansion. Our results demonstrate that <i>S. asakoae</i> forms a genetically diverse, weakly structured, and well-connected metapopulation across Laos and Southeast Asia. This extensive connectivity might enhance the ability of this species to maintain and disseminate parasites, indicating the importance of regional-scale surveillance and future studies incorporating nuclear markers and ecological data.</p>

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Population genetics of the black fly Simulium asakoae from Laos and its relationships with Southeast Asian populations

  • 期刊论文

  • 发表日期：

    2026年4月26日

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  • Bhuvadol Gomontean,
  • Wannachai Wannasingha,
  • Khamla Inkhavilay,
  • Chavanut Jaroenchaiwattanachote,
  • Peter H. Adler,
  • Pairot Pramual

摘要

Simulium asakoae is a widespread species of black fly in Southeast Asia and a potential vector of parasites of medical and veterinary importance. Despite its broad distribution and diverse habitats, population genetic information remains limited. We investigated the genetic diversity, population structure, and demographic history of S. asakoae in Laos and examined its genetic relationships with populations from other Southeast Asian countries, using mitochondrial cytochrome c oxidase subunit I (COI) sequences. A total of 369 COI sequences (241 generated in the present study and 128 retrieved from GenBank) were analyzed. Of these, 284 sequences (241 from this study and 43 from GenBank) originated from nine locations across five provinces in Laos. Among the Laotian specimens, 51 haplotypes were identified, showing high haplotype diversity (Hd = 0.9063) and moderate nucleotide diversity (π = 0.0080). Intraspecific genetic divergence among Lao populations ranged from 0 to 2.49%, increasing slightly to 2.66% when regional sequences were included. Median-joining network analyses revealed no major genetic breaks or clear geographic structuring in Laos or across Southeast Asia, indicating extensive gene flow. Pairwise FST analyses, however, detected significant differentiation among some populations. Demographic analyses, including mismatch distributions and neutrality tests, supported a scenario of recent population expansion, with estimated expansion times of approximately 13,000 years ago for Lao populations and 15,000 years ago at the regional scale. These timeframes coincide with the transition from the cool dry Pleistocene to the warm humid Holocene, which might have facilitated population growth and range expansion. Our results demonstrate that S. asakoae forms a genetically diverse, weakly structured, and well-connected metapopulation across Laos and Southeast Asia. This extensive connectivity might enhance the ability of this species to maintain and disseminate parasites, indicating the importance of regional-scale surveillance and future studies incorporating nuclear markers and ecological data.