Palm Weevil Diversity in Indonesia: Description of Phenotypic Variability in Asiatic Palm Weevil, Rhynchophorus vulneratus (Coleoptera: Curculionidae)

Abstract

Palm weevils (Coleoptera: Curculionidae) are the most destructive pest of many palm species worldwide, including Indonesia. Accurate species identification and knowledge of their diversity is crucial for implementing management strategies. In this study, 97 out of 237 collected palm weevils from six main islands of Indonesia were found exhibiting intermediate color and markings between those of red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) and Asiatic palm weevil (APW), R. vulneratus Panzer. To test the hypothesis that intermediate occurring phenotypes in Indonesia are only phenotypic color variations of APW, extensive morphometric analyses and mating trials were carried out. Additionally, RPW from the Kingdom of Saudi Arabia (KSA) were compared to Indonesian populations. Morphology-based identification of Indonesian palm weevils recognized three putative taxa: R. ferrugineus, R. vulneratus, and the black palm weevil, R. bilineatus (Montrouzier). It was suspected that intermediate color phenotypes of APW from Indonesia had been ambiguously considered RPW. Discriminant function analysis of morphometric measurements and genitalic comparisons indicated that an intermediate weevil from Indonesia, which was previously determined to be RPW, and APW, are highly similar. The mating trials of these two putative weevils produced fertile progenies for three successive generations suggesting both are one species. Additionally, intermediate phenotype specimens from Indonesia previously identified as RPW are different from RPW from the KSA. Therefore, our findings indicate that intermediate weevils are color phenotypes of APW. Thus, in Indonesia, only two species exist, namely, R. vulneratus and R. bilineatus.