Ants from the tribe Attini have mutualistic relationships with fungi and bacteria. The best known of these ants are the leaf-cutter ants (genera Atta and Acromyrmex) but also include a number of other genera that are referred to as the lower Attines. Fungus growing ants have been growing fungal gardens for about 50 million years and use this fungus as a food source. They also use bacteria to protect these gardens from a parasitic fungus. As part of a collaborative project between the Gerardo Lab at Emory University and the Currie Lab at the University of Wisconsin we are sequencing all of the players (ants, fungal cultivar, parasitic fungus and anti-fungal bacteria) in this symbiosis/parasitism system. This relationships between farming ants, their cultivated fungus, the parasitic fungus and medicinal bacteria is one of the best examples of host-pathogen and symbiosis evolution. Our work exploring the genomics of this association will elucidate the genetics that underpins these relationships.

Pea aphids are missing many of the immune components that other insects have. We have been exploring how aphids respond to immune challenges. While much of their immune response to Gram-negative bacteria is missing, it’s unclear whether aphids have other ways of dealing with Gram-negative infection. For example, aphids could respond to infection with increased reproduction rather than investing in costly immunity or might have other ways to respond to infection. We have been studying whether we can detect the costs of responding to pathogens and whether aphids alter their reproduction to immune challenge in aphids of different ages and bearing different symbiotic bacteria. Aphids are very well suited to studies of the costs of immunity because they are extremely tractable and we can monitor many of the important evolutionarily important characteristics such as onset of reproduction, lifetime reproduction and survivorship.

Phylloxera are a group of aphid-like insects that attack a number of agriculturally important plants like pecans and grapes. Grape phylloxera were introduced into Europe from the U.S. and led to the destruction of Europe’s vineyards in the 1890s. Phylloxera stand to be a valuable resource for understanding aphid evolution as they are basal to aphids and lack the intimate bacterial symbionts that aphids harbor. We are also exploring whether or not phylloxera have associations with bacteria.