Submitted by Neil Tsutsui on
The Argentine ant, Linepithema humile, is considered one of the 100 most damaging invasive species in the world and has become established in nearly every continent except Antarctica. In addition to their formation of massive supercolonies and highly competitive abilities, another feature of Argentine ant invasive success is their mutualistic association with hemipterans such as aphids, scale insects, and mealybugs. These hemipteran partners provide Argentine ants with important carbohydrate resources via honeydew – a sugar-rich excretion that ants readily feed on – and the ants, in turn, provide the hemipterans with protection from predation, among other benefits. By tending to and defending hemipteran mutualists, Argentine ants cause indirect negative impacts on many agricultural and ornamental plants in California including vineyards, tree nuts, citrus, and oleander. The goal of this project is to better understand how Argentine ants establish and maintain mutualisms with hemipterans and how other partners, e.g., bacterial endosymbionts, influence these relationships.
A major focus of ongoing research in the Tsutsui lab is understanding the role of cuticular hydrocarbons (CHCs), which contribute to Argentine ant supercolony identity and communication. Given their role in ant colony cohesion, CHCs are likely also important for maintenance of insect mutualisms. In this new direction of inquiry, we plan to investigate the role of CHCs in ant-hemipteran mutualisms using the following methods: (1) collect Argentine ant-associated hemipterans, e.g., aphids, and establish colonies in the lab, (2) sample and identify hemipteran bacterial endosymbionts with 16S/23S rRNA sequencing, (3) experimentally manipulate endosymbiont abundance and/or composition in hemipterans via antibiotic feeding assays, (4) analyze CHC differences between hemipterans with or without endosymbionts, and (5) run behavior/choice/learning assays to determine if Argentine ants can distinguish differences between hemipterans with or without endosymbionts.
Work will involve collecting insects in the field and maintaining insect colonies in the lab. Students will learn how to collect and analyze insect cuticular hydrocarbons using gas chromatography-mass spectrometry (GC-MS). Additionally, students will assist in collecting and analyzing samples from insect endosymbionts using molecular techniques, as well as run feeding assays with hemipterans and behavior assays with Argentine ants.
Experience handling insects will be helpful but is not a strict prerequisite. Experience with basic lab techniques, e.g., pipetting, calculating and preparing dilutions, and handling/organizing large numbers of biological samples will also be beneficial.