Mealybug (Hemiptera: Coccomorpha: Pseudococcidae) diversity in agroecosystems can be shaped by multi-trophic interactions involving host plants and mutualistic symbiotic ants, yet the mealybug species composition and the evolutionary drivers of ant symbiosis and the host plant communities remain understudied in Taiwan. Morphological analyses were performed to characterize diagnostic morphological features and identify mealybug and ant specimens. We used DNA barcoding and phylogenetic approaches to identify mealybugs and their associated ants from Southern Taiwan to assess whether their associations are more consistent with tight coevolution or opportunistic ecological networking. We examined 30 mealybug-ant-host plant triads from agricultural fields in Southern Taiwan (Chiayi and Kaohsiung). We used cytochrome c oxidase subunit I (COI) sequences as a barcoding gene. BLASTn results identified six mealybug and four ant species across the 30 sampled triads. Phylogenetic reconstruction and ASAP species delimitation aligned with BLAST results, resolving six mealybug species (Planococcus minor, Dysmicoccus brevipes, Dysmicoccus neobrevipes, Paracoccus marginatus, Phenacoccus madeirensis, and Maconellicoccus hirsutus) and four ant species (Pheidole megacephala, Tetramorium wroughtonii, Technomyrmex albipes, and Tetraponera sp., which exhibits 94.32% COI similarity with Tetraponera allaborans). The ant-mealybug assemblages were dominated by generalist taxa. Furthermore, the analyses for co-phylogeny (Procrustes SS, m2 = 0.899, p = 0.771) and Shannon diversity (H'; Mealybug diversity associated with ants (0.9557–1.4942); ant diversity associated with mealybugs (0.5004–1.3297)) suggest that the ant-mealybug symbiosis in our study area is not strictly structured by coevolution but is more consistent with opportunistic associations. These findings highlight the importance of ecological networking in shaping mealybug diversity in Southern Taiwan and provide a molecular baseline for future community-level and network analyses.
Hemipteran agriculture pests, Cophylogeny, COI gene species delimitation, Ecological adaptation, Symbiosis
