Assessment of Pea Weevil Bruchus pisorum (Coleoptera: Bruchidae) Genetic Diversity Based on Mitochondrial COI Gene Sequences

Bruchus pisorum L., commonly known as the pea weevil, is a cosmopolitan insect pest of pea. Currently, its genetic diversity and population structure are still not well understood. Therefore, an examination of the pea weevil population diversity and evolutionary history will provide insight into efficient pest management strategies. In this study, we sequenced and analysed a 393 bp fragment of the mitochondrial Cytochrome C Oxidase subunit I (COI) gene from 29 samples of B. pisorum collected from the major pea-growing regions in northern Tunisia. Analysis of these sequences in addition to 18 supplementary sequences derived from six countries; Australia, China, Ethiopia, Germany, Italy and U.S.A.; led to the identification of 15 haplotypes among which nine were found in Tunisian samples, and among these, six were specific to Tunisia. The FST values reflected a weak population genetic diversity of B. pisorum in Tunisia. The haplotype network and phylogenetic analysis, including all sequences, supported the low genetic structuring of Tunisian B. pisorum and further revealed the presence of widely shared haplotypes. The presence of common haplotypes in geographically distant areas is mainly related to human intervention that facilitated the worldwide expansion of this pest, through the transportation of infested seeds, suggesting that local B. pisorum populations have different origins and may have resulted from multiple introductions.