The origin of groundnut infestation by the seed beetle Caryedon serratus (Olivier) (Coleoptera: Bruchidae): Results from cytochrome B and ITS1 gene sequences

Caryedon serratus, the groundnut seed beetle, is a major pest of groundnut (Arachis hypogaea), an introduced legume of the subfamily Papilionoideae. Native hosts of C. serratus in Senegal include Bauhinia rufescens, Cassia sieberiana, Piliostigma reticulatum and Tamarindus indica, all of which belong to the legume subfamily Caesalpinioideae. To determine the extent of isolation between native forms and forms feeding on groundnut, we analysed cytochrome B (Cyt. B) and ITS1 sequences within and among 24 Senegalese populations of C. serratus feeding on its five major host plants. Results show a strong differentiation of insects from different host trees, with specimens from C. sieberiana possibly representing a sibling species and insects from B. rufescens and T. indica a distinct host race. Groundnut and P. reticulatum populations are indistinguishable on the basis of sequence sets.