Morphometric Study of the Palm Weevils, Rhynchophorus vulneratus and R. ferrugineus (Coleoptera: Curculionidae) in View of Insular and Mainland Populations of Malaysia

摘要

A morphometric analysis was conducted on Rhynchophorus vulneratus and R. ferrugineus (Coleoptera: Curculionidae) from insular and mainland populations. Twenty-three morphological characters were measured and the data were analysed using independent t-test, principal component analysis (PCA) and discrimination function analysis (DFA). Using independent t-test, all characters were found to be significant at p 0.05, except distance between eyes (ED), mesotarsus length (F2Ta) and metatarsus length (F3Ta). In PCA, cumulative variations of 80.7% were recorded from the first two principal components, resulting from high loadings in elytra length (EL), elytra width (EW) and pronotum length (PL). For DFA, a single function explained a canonical correlation of 0.952 with 100.0% of variation and the Wilk’s Lambda statistics (0.094) was strongly supported with p 0.0001. The highest character loadings were the total length (TL), elytra width (EW) and pronotum length (PL), which were useful as diagnostic characters for separating both Rhynchophorus species. Therefore, this study suggests that R. vulneratus and R. ferrugineus are morphologically distinct species. This finding proves that the insular population of R. vulneratus fits the generality of the ‘island rule’ as being larger compared to the mainland counterparts of R. ferrugineus.