Genetic differentiation of southeastern boll weevil and thurberia weevil populations of Anthonomus grandis (Coleoptera : Curculionidae) using mitochondrial DNA

The southeastern boll weevil, the Mexican boll weevil. and the thurberia we evil are considered to be morphologically similar but behaviorally differen t variants of the same species, Anthonomus grandis Boheman. A polymerase ch ain reaction (PCR)-amplified 9.2-kb section of the mitochondrial DNA was cl eaved with restriction enzymes. RFTPs of weevils from three cotton growing locations in Texas and one in northeastern Mexico were compared with thurbe ria weevil from three sites in Arizona. Six haplotypes were observed in the Texas/Mexico collections and 12 haplotypes were found among the thurberia weevil. There were no shared haplotypes between these two groups. Polymorph ism was observed within the weevil types. The three thurberia weevil locati ons exhibit some geographic isolation and exhibit differences in both the h aplotypes present and the relative frequencies of the haplotypes. Only one haplotype was recovered at all three Arizona sites. The Texas/ Mexico sampl es showed less genetic variability with the northern most site having the l owest polymorphism. 52/53 of these weevils appear to be genetically southea stern boll weevil. Two haplotypes were shared by all four of these populati ons and comprised 72% of the insects examined. The range of genetic distanc es between haplotypes was <0.001-0.022. The Mexican boll weevil was not exp licitly examined; however, three individuals were discovered that appear to represent a genetically distinct third population. One was from Mexico and the other two were from a thurberia weevil site. These three individuals m ay represent the Mexican boll weevil. The results include apparent diagnost ic restriction fragment differences between the thurberia weevil and the so utheastern boll weevil that could be used to help determine whether future weevils found in Arizona or California cotton are thurberia weevil. southea stern boll weevil. or another population of weevils.