Overview 

My work focuses on examining how the underlying mechanisms and drivers of species interactions can reveal the context dependency of these interactions in nature. I currently have two major components to my research program: (1) examining how communication plays a role in complex species interactions, and (2) investigating how selective pressures shape these interactions.

Ants in agroecosystems as a model for studying complex species interactions  

Ants are a highly successful group of organisms, both evolutionarily and ecologically. The approximately 13,000 described species dominate most terrestrial habitats in terms of abundance, biomass and energy turnover. They frequently live in large colonies that provide well-protected and resource rich environments. Furthermore, ants have stable and complex communication systems. Unsurprisingly then, organisms at a range of trophic levels seek close associations with ants in order to access protection or resources. This makes ants an excellent model for studying complex species interactions.

Ants are also important in agricultural systems. Ants are voracious predators and often effectively defend plants against herbivores, so much so that using ants to reduce herbivory in A.D 304 in China is the first recorded pest control practice. Therefore, understanding the dynamics of species interactions involving ants in agroecosystems can have important management implications.

Azteca and scale on coffee

How does communication play a role in complex species interactions?

             Social insects have complex and often fairly conserved communication systems that, when exploited, can provide ant associated organisms access to otherwise unavailable resources. However, few studies have examined the dynamics of these interactions outside of their pair-wise context. My dissertation research focused on examining how intraspecific communication systems can impact the dynamics of multi-species interactions in coffee agroecosystems.

The most abundant and ecologically dominant ant in the coffee agroecosystems of Southern Mexico is the aggressive arboreal ant, Azteca sericeasur. These ants nest in shade trees and prey on and remove coffee herbivores. Phorid fly parasitoids are one of the most devastating natural enemies of social insects. Species of phorid fly are often host specific, thus in order for phorid flies to successfully locate and parasitize their hosts, they need multiple cues to hone in on compatible targets. My work shows that phorid flies use a hierarchical series of multimodal cues from Azteca sericeasur to first locate and then choose a host.

In addition to phorid fly parasitoids, recently described Myrmedonota xipe beetles are also interact with Azteca sericeasur (Mathis & Eldridge 2014). Because ants are typically excellent defenders, predators may choose moments of weakness to take advantage of their prey. This hypothesis was studied with M. xipe, which preys on Azteca sericeasur ants in the presence of parasitoid flies. A combination of lab and field experiments show that M. xipe beetles selectively locate and prey upon parasitized ants. These parasitized ants are less aggressive toward beetles than healthy ants, which allows beetles to eat the parasitized ants alive without interruption. Moreover, behavioral assays and chemical analysis reveal that M. xipe are attracted to the ant’s alarm pheromone, the same cue used by the phorid fly parasitoids in host location.

How do selection pressures shape complex species interactions?

Many ant-plant interactions are mutualisms in which plants provide food directly in the form of nectar from extrafloral nectaries (EFNs), and the ants in turn protect the plants against herbivores. These mutualisms are often complex, containing multiple partner species. A key issue in understanding multispecies mutualisms is determining how variation in resources and the broader ecological network can impact these partnerships.

Ant-plant protection mutualisms in which plants contain EFNs occur in several agricultural crops including cotton, peaches, and fava bean. My current research examines how competition and management strategies impact ant community dynamics and the strength of ant-plant protection mutualisms in peach orchards.