Population structure and phylogenetic relationships ofCeutorhynchus neglectus(Coleoptera: Curculionidae)

Abstract

AbstractCeutorhynchus neglectusBlatchley is a weevil that is native to, and widely distributed in, North America. It has life-history characteristics similar to its alien invasive congener,Ceutorhynchus obstrictus(Marsham), the cabbage seedpod weevil. Our study was undertaken to compare the population structure ofC. neglectusin North America to that ofC. obstrictus, which, in contrast, was introduced only recently to North America and might be expected to have a simpler population structure. We also compared the population structure ofC. neglectusto that ofPissodes strobi(Peck), which is known to possess high levels of intraspecific variation and is also a Nearctic weevil. We sequenced a 790-bp fragment of mtDNA (cytochrome oxidase I (COI) gene) and a 117-bp fragment of nuclear DNA (internal transcribed spacer region 1 (ITS1)). Nested clade analysis inferred contiguous range expansion and restricted gene flow with isolation by distance. Analysis of molecular variance also supported restricted gene flow between geographically distant populations. However, within-species variation inC. neglectuswas lower than that for other weevil species includingC. obstrictus. We also examined DNA divergences and phylogenetic relationships among 10 species ofCeutorhynchususing parsimony analysis of a 2.3-kb fragment of mtDNA (COI–COII) and a 541-bp fragment of nuclear DNA (elongation factor 1α).