Isozyme Polymorphisms in Boll Weevils1 and Thurberia Weevils from Arizona2

Abstract

Results of electrophoretic analyses for isozyme gene frequency differences showed high heterozygosity and high levels of polymorphism at isozyme loci in samples from three populations of insects as follows: (1) thurberia weevils, Anthonomus grandis thurberiae Pierce, from bolls of a wild cotton, Gossypium thurberi Todaro, collected in the Santa Rita Mountains of Arizona; (2) boll weevils, A. grandis grandis Boheman, from bolls of Pima cotton, G. barbadense L. collected at Three Points, Ariz.; and (3) boll weevils from pheromone traps positioned around a field of short staple stub cotton, G. hirsutum L., at Theba, Ariz. The three collection points were separated by distances of 50 to 210 km. Of the loci, 60% were significantly different in genotypic distributions in the three collections. Analysis of allelic frequency differences showed that these populations are not from the same random mating population. Calculated genetic distances between the three collections ranged from a value of 0.068 between the thurberia weevils and boll weevils from short-staple stub cotton up to 0.206 between thurberia weevils and the boll weevils from Pima cotton. These genetic distance values are higher than similar values found between pheromone races of insects but lower than genetic distances measured between sibling species of insects and may indicate that host races of boll weevils exist in Arizona.