<b>Phylogeographic pattern of the assassin bug </b><b><i>Sycanus croceovittatus</i></b><b> inferred from mitochondrial genomes and nuclear genes</b>

Sycanus croceovittatus is a widely distributed assassin bug (Hemiptera: Reduviidae) in southern China. It is a potential biological control agent in agricultural ecosystems. However, its distribution pattern and evolutionary history have not been explored. This study sequenced its mitochondrial genome and nuclear ribosomal RNA genes to assess the effects of climatic oscillations and geological events on its phylogeographic patterns. The results suggested that native populations of S. croceovittatus in southern China can be divided into two phylogeographic clades which diverged during the penultimate glacial in the Middle Pleistocene: Clades A and B. Most samples from Hainan Island formed a monophyletic lineage within Clade A, which diverged during the Late Pleistocene. The Qiongzhou Strait connecting mainland China and Hainan Island might have served as a "dispersal corridor" during the Pleistocene glaciation, with the Hainan Island population becoming separated when rising sea levels submerged this land bridge. Ecological niche analysis suggested the suitability sustainably of the mainland and island populations since the last interglacial period. Demographic inferences indicated expansions of S. croceovittatus during the Middle and Late Pleistocene, likely due to climatic conditions. Our study highlights the role of Pleistocene sea-level changes in determining the distribution patterns of assassin bugs in China.