An investigation into the population structure of Bactrocera Dorsalis from four Agro-Ecological zones in Ghana

Abstract

Fruit flies pose significant challenges as pests in the global cultivation of fruits and vegetables. This study reports how landmark based geometric morphometry and cuticular hydrocarbon analysis were used to discriminate populations of Bactrocera dorsalis from four Agro-ecological zones. The images of the right forewing of 706 samples were captured and imported into a TPS utility program to generate a TPS file. The TPS file was then imported into TPS Dig, version 1.40 to facilitate digitization of landmarks. Raw ‘x’ and ‘y’ coordinates were imported into Morpho J 1.07a for the analysis. For the cuticular hydrocarbon analysis, infested fruits were collected from the four Agro-ecological zones and incubated. The developing larvae were raised until they reached adulthood. Adult flies, aged 9 days, were used for Hexane extraction and Gas Chromatography–Mass Spectrometry (GCMS). Geometric morphometry utilized Procrustes ANOVA and Partial Least Square analyses to assess the significance of variation among populations. To gain better insights into population differences, Principal Component Analysis (PCA) was utilized to identify the wing feature contributing to the most variation, while Discriminant Function Analysis (DFA) was applied to determine cluster classifications of the populations. For the cuticular hydrocarbon analysis, a heat map was used to visualize the data and subjected to Principal Component Analysis (PCA). Significant variations were observed in the shape of the wing among the populations of the pest from four Agro ecological zones. Samples from the transition and coastal zones were most distant from each other while samples from Northern and Eastern Volta zones were most similar. This may have implications for population structure of the pest in Ghana.