Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2001
Publication Date: 2/1/2003
Citation: BEEMAN,R.W., DISTRIBUTION OF THE MEDEA FACTOR M4 IN POPULATIONS OF TRIBOLIUM CASTANEUM (HERBST) IN THE UNITED STATES, JOURNAL OF STORED PRODUCTS RESEARCH 39: 45-51. 2003. Interpretive Summary: Insect species frequently expand or shift their ranges or alter their distribution. These changes can have important effects on pest status. New pests can appear or previously innocuous species can become significant pests. In spite of years of research, we still have only a vague understanding of the processes involved in range expansion or contraction, population mingling and gene flow in natural populations of pest insects. We noticed an unusual distribution of potentially lethal genes in natural populations of the red flour beetle, and examined the possible existence of regional subpopulations in the United States. By interbreeding field-collected beetles, we demonstrated the existence of separate southern and northern populations of this species which was previously thought to be uniform and freely intermingling. This research will lead to new genetic markers for population monitoring and better prediction and detection of infestation sources and population evolution.
Technical Abstract: The distribution of the maternal-acting, selfish gene Medea4(M4) was determined in populations of the red flour beetle, Tribolium castaneum (Herbst), collected in the Southern and Midwestern United States. We found clear evidence for the existence of two major regional subpopulations, with a boundary that roughly corresponds to 33 degrees N. latitude. All 26 strains collected in ten states north of this latitude were homozygous for the M4 allele, while only two of 29 strains collected in six states south of this latitude were homozygous for the allele. Of the remaining 27 Southern strains, 21 lacked the M4 allele entirely, while six contained a mixture of M4 and non-M4 alleles. This is the first evidence of either the existence of biotypes or the presence of major barriers to gene flow in wild populations of this ubiquitous insect species.