Delineation of selected metapocyrtus species using DNA barcoding

Abstract

The genus Metapocyrtus exhibits significant variations in general shape and form, even between sexes, making its classification and identification difficult. To address this problem, combining morphological traits and molecular data would be helpful, especially for delineating closely related species. For this study, three species (Metapocyrtus (Orthocyrtus) davaoensis and Metapocyrtus spp.) found in Monkayo and Nabunturan, Davao de Oro, and Davao City were selected for DNA barcoding using the mitochondrial gene cytochrome c oxidase subunit I (COI) as the barcode marker. Molecular procedures were carried out in the University of the Philippines Mindanao Genome Center with a total of 12 specimens, four from each sampling site. The COI barcode fragment was amplified using the primer pairs LCO1490 and HCO2198 and optimized thermocycler conditions. Intra-specific and infra-specific genetic distances were calculated using the Tamura 3-parameter distance model in MEGA11 software, and the Maximum Likelihood method with Bootstrap 1000 times was used to construct the phylogenetic tree. The result shows a low interspecific genetic divergence from COI sequences, and cannot discriminate the analyzed Metapocyrtus species based on the standard genetic distance threshold values used in many studies. Even though Metapocyrtus sp. (Monkayo) is more similar to Metapocyrtus (O.) davaoensis in terms of morphological characteristics, the phylogenetic analysis result shows it is more closely related to Metapocyrtus sp. (Nabuntran). We recommend conducting more studies to evaluate the barcoding gap at the subgenus or subspecies level.