Interactions between organisms can vary broadly between mutually beneficial cooperation, bi-directional antagonism or unilateral exploitation. In extreme cases of cooperation, individuals or species can become wholly dependent on one another and cannot survive alone. In mutualistic interactions between species, the precise conditions and mechanisms that lead to the evolution of obligate dependency remain unclear.

One proposed explanation is that frequent interactions that fulfil a vital function for an organism - such as metabolism, reproduction or defence - can compensate for the subsequent loss of an organism's intrinsic capabilities. Compensated trait-loss is readily observed in "micromutualisms" (e.g. host-microbe interactions) and indeed in parasitism, but specific examples of reduced or lost gene function in "macro-"mutualistic systems remain elusive. Likewise, the prevalence of compensated trait loss in defensive relationships, where the costs and benefits for partners are dependent on pressure from other species, is hard to discern. 

My project aims to explore the role of compensated trait-loss in these systems, using perhaps the most iconic example of a defensive macromutualism: the relationship between myrmecophytes (ant-plants) and plant-ants. The most specialised myrmecophytic plants provide a combination of housing and expensive food-rewards to ant partners in exchange for protection from herbivores, pathogens and competitors. Intriguingly, some plant-ants have come to reject all food sources except those provided by a host plant, while many myrmecophytes rapidly succumb to disease or herbivory in the absence of ants. These dependencies may reflect identifiable losses in ant and plant genomes, defensive responses and metabolic networks.

Comprehensive characterisation of materials transferred between mutualists, like plant food bodies and nectar or ant oral secretions, allows contributions to partner nutrition or defence to be explicitly assessed. Combining these data with comparative analyses of ant metabolic networks and plant defensive responses allows the identification of essential pathways and responses rendered redundant in mutualist species. I aim to uncover those "compensated" genes, pathways and traits that may have undergone trait-loss across three convergently evolved systems of ants and plants. Locating and characterising these losses will help us understand the bases of transitions towards obligacy in these relationships, and factors that favour and fix interdependencies across the tree of life. 

Study Systems:

• Vachellia (Acacia s.l.) trees and Pseudomyrmex ants
• Cecropia trees and Azteca ants
• Piper plants and Pheidole bicornis ants
• (Other projects): Philidris nagasau ants and farmed Squamellaria plants
• (Other projects): Cyrtophora citricola spiders

General Research Interests:

• Molecular Ecology and Bioinformatics
• Community and Landscape Ecology
• Evolutionary Biology
• Mutualism and Species Interactions
• Sociality
• Population Genomics