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Title: Genetic structure of Tribolium castaneum (Coleptera: Tenebrionidae) populations in mills

Author
item SEMEAO, ALTAIR - Kansas State University
item Campbell, James - Jim
item Beeman, Richard
item LORENZEN, MARCE - North Carolina State University
item WHITWORTH, ROBERT - Kansas State University
item SLODERBECK, PHILLIP - Kansas State University Extension Center

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2011
Publication Date: 3/1/2012
Citation: Semeao, A.A., Campbell, J.F., Beeman, R.W., Lorenzen, M.D., Whitworth, R.J., Sloderbeck, P.E. 2012. Genetic structure of Tribolium castaneum (Coleptera: Tenebrionidae) populations in mills. Environmental Entomology. 41(1): 188-199. doi: http://dx.doi.org/10.1603/EN11207.

Interpretive Summary: Food products made from processed grain can become infested by the red flour beetle, Tribolium castaneum, either at the mills where flour is produced or at subsequent points in the food distribution channel, so tools to identify source of infestation would be useful for the targeting of pest management. Variation in molecular markers – variable sections of DNA – was used to estimate how beetle populations from mills differ from each other, and how accurately beetles could be assigned to the mill from which they originated. Red flour beetles collected from nine wheat or rice mills ranging from 0.3 to 5,700 km apart were evaluated. Using molecular population genetic analyses it was shown that populations did differ from each other, but the majority of the variation occurred within a mill, rather than between mills which suggests limited isolation of the populations. It was also found that the difference in variation between two mills did not increase with how far apart the mills were from each other, which is what would be predicted if beetles were dispersing back and forth between the mills due to their own behavior. Only 56% of the collected beetles could be correctly assigned to their source population. Results of this research show that there is structure to the populations, but either there is significantly more movement of beetles among the mills than was predicted or more suitable molecular markers are needed to accurately assign beetles to their source mill.

Technical Abstract: The red flour beetle, Tribolium castaneum, is primarily found associated with human structures such as wheat and rice mills, which are spatially isolated resource patches with apparently limited immigration that could produce genetically structured populations. We investigated genetic diversity and differentiation among nine populations of T. castaneum collected from wheat and rice mills ranging from 0.3 to 5,700 km apart, using eight polymorphic loci (microsatellites and other insertion-deletion polymorphisms), each with 3 to 14 alleles. We evaluated 72 locus-by-population combinations, of which 31 deviated significantly from Hardy-Weinberg equilibrium, all due to a deficiency of heterozygotes. AMOVA analysis indicated that 8.3% of the variation in allele frequency resulted from comparisons among populations. Genetic differentiation among populations was significant, with FST values varying from 0.018 to 0.149, but genetic distance was not significantly correlated with geographic distance. Correct assignment to the source population was successful for only 56% of individuals collected. Our results provide evidence that populations of T. castaneum show spatial genetic structure, with 97% of pairwise comparisons being significant. However, the unexpected low levels of genetic differentiation found here require further refinement of techniques for understanding forces driving the spatial structure of T. castaneum populations.