MORPHOLOGICAL IDENTIFICATION OF TROPHIC TRIBOLIUM CASTANEUM POPULATIONS HERBST (COLEOPTERA, TENEBRIONIDAE) IN WEST AFRICA.

Tribolium castaneum, the primary pest of stored commodities, is a cosmopolitan and polyphagous beetle. Its ability to unfold its development cycle on various food substrates has led to reflections on its morphological adaptability. This study aimed to identify morphologically T. castaneum populations in the West African zone. In each West African country, two populations were defined according to the cereal (millet or rice) on which T. castaneum unfolded its development cycle. Each of the populations consists of 30 adult males. On each adult, 19 variables were measured. The distances between the eyes dorsally and ventral (Dyd, Dyv), the width of the femur_3 (lf3) are eliminated from the analysis because they do not present any variability between the different individuals. The remaining 16 variables are used for Principal Component Analysis (PCA) and Discriminant Analysis (DA). Size is the first factor that discriminates between millet and rice trophic populations in all West African countries. Following the logarithmic transformation of the data, the biplots (PCA and DA) showed a difference in form between these two populations. Most of the transformed log-variables revealed significant mean differences between the two trophic populations in all West African countries. The hierarchic classification ascendant (HCA) combined the morphology of almost all individuals in the millet trophic population with that of group _1 and the morphology of most individuals in the rice trophic population with that of morphological groups _2 and _3. There is a morphological structure of T. castaneum populations in the West African zone. These observed differences would probably be related to a morphological adaptation of individuals or the phenotypic expression of new mutants.