Cytogenetic studies of alfalfa weevil (Hypera postica) strains (Coleoptera: Curculionidae)

Abstract

Chromosome karyotypes, chiasma frequencies, and Giemsa C-banding patterns were analyzed from eight weevil populations: three of the eastern strain (Beltsville, MD; State College, PA; and Washington Co., IL) and two of the western strain (Logan and St. George, UT) of the alfalfa weevil, two of the Egyptian alfalfa weevil (Yuma, AZ and Westmorland, CA), and one weevil population from Wageningen, Netherlands. All of these weevil populations have the same chromosome number, 2n = 20 + XYp, which is identical to that reported previously for five other Hypera species. The chromosome number for the clover leaf weevil, Hypera punctata (Fabricius), is 2n = 18 + neo-XY which appears to be phylogenetically different from other Hypera species. The lack of cytogenetic variations among the eight weevil populations under investigation leads us to conclude that all weevil strains in the United States are of the alfalfa weevil, H. postica (Gyllenhal), and that the use of H. brunneipennis Boheman for the Egyptian alfalfa weevil of North America should be discontinued.Key words: Hypera postica, cytogenetics, chromosomes, C-banding, alfalfa weevil.