ABSTRACT

An understanding of boll weevil (Anthonomus grandis, Boheman) dispersal behavior is essential to characterizing and re-sponding to the threat of migration into eradicated zones. Variation in boll weevil mitochondrial DNA (mtDNA) was sam-pled and analyzed to make inferences on the magnitude and geographic pattern of genetic differentiation among weevil populations. PCR-RFLP analysis was conducted on a large fragment of mtDNA from each of 419 individuals from 20 locations across northeast Mexico and eight US states. A total of 28 distinct mtDNA haplotypes, 17 of which were unique to single locations, were identified from restriction reactions of ten informative endonucleases. The value of within-location haplotype diversity varied from 0 to 0.81, and nucleotide diversity ranged from 0 to 0.36%. Nucleotide sequence divergence among weevil populations ranged from -0.01 to 0.68% with a mean value of 0.13%. Haplotype and nucleotide diversity was generally greater in eastern than western populations, and haplotype frequencies differed greatly in these two regions. Phyloge-netic reconstruction of populations revealed two major clades corresponding to eastern and western regions, and is consistent with historical boll weevil range expansion into the southeastern U.S. from Mexico, and a secondary colonization of the High Plains. Evidence suggests that gene flow between eastern and western populations is limited. However, it appears that migration between populations separated by < 200 km is frequent.