Author(s): Sylvia (Sieun) Lee
Mentor(s): Rodolfo Probst
Institution U of U
Ant-plant mutualisms are common ecological interactions which have evolved over 100 million years. While much is known about systems where host plants provide nutritional rewards to ants, mutualisms where the plants lack such resources remain understudied. In these systems, associated insects (Hemiptera: Coccoidea) like mealybugs (Pseudococcidae), soft scales (Coccidae), and armored scales (Diaspididae), act as intermediaries, supplying honeydew – a nutrient-rich plant sap exudate – as primary food source for their host ants. However, the taxonomy and co-evolutionary history of these insects associates in ant-plant interactions are poorly understood. A major obstacle to identifying Coccoidea species is their morphological uniformity, which hampers species differentiation. DNA barcoding offers a molecular approach to address this challenge, providing a more objective means of identification. Focusing on 21 colonies of 10 species of the Neotropical ant genus Myrmelachista, we employed nanopore sequencing to generate DNA minibarcodes (313 base pairs) from their associated Coccoidea. Our objectives were to identify the taxonomy of these insects and explore their specific interactions with Myrmelachista hosts. We successfully obtained DNA minibarcodes for 20 mealybugs, four soft scales, and one armored scale. We used BLAST (Basic Local Alignment Search Tool) to search for match in identity of these sequences in the NCBI (National Center for Biotechnology Information) database and recovered an average match similarity of 92% across all our specimens, linking them to taxa from the Old World, which suggests the likely presence of undescribed Neotropical species of Coccoidea in this ant-plant mutualistic system. Phylogenetic trees of both the ant host and their associated insects were reconstructed and visualized with a tanglegram to illustrate association patterns. We identified one putative armored scale species, two putative species of soft scales, and four putative mealybug species in our Coccoidea tree based on clustering patterns. Regarding Myrmelachista-Coccoidea associations, armored scales were exclusively associated with Myrmelachista nigrocotea, while soft scales were found with four Myrmelachista species, including a unique association between one soft scale species and Myrmelachista longiceps. Mealybugs were associated with eight Myrmelachista species, with one mealybug species showing an exclusive interaction with Myrmelachista osa. These findings reveal distinct associations between certain Myrmelachista species and their insect partners, providing valuable evolutionary insights in the complexity of ant-plant mutualisms. Our study highlights the utility of DNA minibarcoding in unraveling the taxonomy of Coccoidea and exploring the evolutionary dynamics of these interactions within complex ecological networks.