Unveiling Genetic Variation in the Seed Bug Spilostethus pandurus (Scopoli, 1763) (Hemiptera: Lygaeidae) in Thailand Using Mitochondrial CO1 Sequence

<i>Spilostethus pandurus</i> is a phytophagous insect widely distributed across Asia, Europe, and Africa, yet its genetic variation remains poorly understood. This study presents the first comprehensive analysis of the genetic diversity and structure of <i>S. pandurus</i> in Thailand using mitochondrial cytochrome c oxidase subunit 1 (<i>CO1</i>) sequences from 202 individuals across 27 localities. A total of 58 haplotypes were identified, with high haplotype and nucleotide diversity observed, suggesting substantial genetic variation. The haplotype network revealed a star-like topology, indicating recent population expansion or ongoing gene flow. Neutrality tests and mismatch distribution analyses showed no strong signal of recent demographic expansion. Phylogenetic analysis confirmed that all Thai specimens clustered within a well-supported <i>S. pandurus</i> clade along with sequences from India, Namibia, and Europe. Analysis of Molecular Variance (AMOVA) revealed significant genetic differentiation among four continental groups, indicating that geographic isolation and restricted gene flow have shaped genetic divergence at a broad biogeographic scale. Further research using highly polymorphic nuclear markers is recommended to better resolve the population structure and evolutionary history of <i>S. pandurus</i> in Thailand and beyond.