Morphometric characterization and comparison of the African rhinoceros beetle (AfRB) Oryctes monoceros Olivier (Coleoptera: Dynastidae) populations from different agro-ecological zones in Ghana

The African rhinoceros beetle (AfRB), Oryctes monoceros (Olivier) (Coleoptera: Scarabaeidae), is a very destructive coconut pest in Africa and Asia. Proper identification of a target pest is essential for developing integrated pest management strategies. Therefore, we morphologically characterized and compared AfRB populations from Coastal savannah, Transitional, Evergreen, and Deciduous forest agro-ecological zones in Ghana. Linear measurements of 24 morphological traits were selected, measured, and analyzed using t-test, ANOVA, MANOVA, PCA and the UPGMA method. The results showed variations in AfRB males and females, with males consistently larger than females. The AfRBs differed across the agro-ecological zones, with those from the Coastal savannah being the smallest. Beetles from the Transitional zone appeared larger, whereas those from the Deciduous forest were intermediate. Principal component analyses of the males and females from the agro-ecological zones showed overlaps of AfRB populations, with no clear separation. However, dendrogram formed by the UPGMA method using squared Euclidean distance of female AfRB populations showed that the Deciduous and Evergreen samples were similar but distinct from Coastal savannah and Transitional zones. Here we report that three subgroups can be morphologically separated within female AfRB populations in this study: (1) Deciduous and Evergreen, (2) Coastal savannah and (3) those from the Transitional zone. Our findings show that the morphometric variations of AfRB are influenced by the agro-ecological zones, which may effect the fitness parameters and dispersal potential of the pest.