Rhynchophorus ferrugineus Olivier and Rhynchophorus schach Olivier have long been reported as the two most common species of palm weevils in the Philippines. In 2008, surveys conducted in Agusan del Sur, Davao del Sur, Davao City and Cebu revealed more erstwhile unreported palm weevil morphotypes which led to perplexity in taxonomic classification. This study was conducted to determine and ascertain the genetic variation and phylogenetic relationship among 10 collected morphotypes, including R. ferrugineus and R. schach, using sequences of cytochrome oxidase I (COI) gene to resolve their taxonomic status. Results show that there were no marked morphometric differences among the palm weevils as supported by the COI characterization. Nucleotide sequences were subjected to phylogenetic analysis using bootstrapping, namely: neighbor-joining, parsimony and maximum likelihood. Among the phylogenetic trees generated, parsimony and maximum likelihood had similar results. Parsimony yielded low bootstrap values ranging from 2.5 to 10 while the maximum likelihood were from 1 to 7, indicating that these morphotypes can be clustered into one species. In support of these findings, low genetic variation was also observed, from 0 to 5.82% and high genetic similarity of 94.18 to 100% among morphotypes. Based on these results, it can be deduced that the morphotypes are cases of polymorphism, including the synonymy of R. ferrugineus and R. schach.
Key words: Morphotypes, polymorphism, Rhynchophorus ferrugineus, Rhynchophorus schach, synonymy.
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