Chemical signaling in ant/plant mutualisms studied with isotopes, transcriptomes, and field assays

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During the first part of this project, we analyzed ant/plant mutualisms that comprises six epiphytic species in the Rubiaceae genus Squamellaria and one ant species, Philidris nagasau, as well as less specialized outgroups. The system includes the first farming mutualisms between ants and plants, wherein the ant species obligately lives inside Squamellaria, feeds on these plants´ post-anthetic sugar rewards, which are exclusively accessible to P. nagasau, plants the seeds of its hosts under tree bark (of tree species that offer rewards), and actively fertilizes yet-uninhabitable seedlings via defecation. We have phylogenetic and ecological data for both the plant and the ant sides, which enables us to infer the sequence of trait evolution. Funds are requested here to (i) quantify isotope ratios in tissue samples from a 16 months-long ant exclusion experiment, (ii) submit tissue samples (in hand) to metabolome analyses to compare specialized and generalist species, (iii) carry out field assays to assess the effect that candidate signaling compounds have on P. nagasau (in one assay, ants will be fed with 15N glycine so that we can trace their excretions), and (iv) use RNA-Seq on tissue samples already collected from domatium tissues of specialized and unspecialized plant hosts to compare gene expression in wart-like outgrowths only present in specialists and with the Coffea genome serving as a reference.