Mechanisms of behavioral control:
How do parasites control the behavior of the hosts they infect? We are exploring this with fungi in the genus Ophiocordyceps . Some species in this genus cause the well known zombie ant extended phenotype in ant hosts where ants are instructed to bite into leaves before dying. Other species induce less severe effects and related species in other insects such as beetles do not manipulate at all.
We are therefore in a position to understand the mechanisms of behavioral control using the comparative approach and tools such as phylogenomics, transciptomics and metabolomics. We are developing a number of precise technical approaches that will allow us to understand the mechanisms. Earlier work established that the zombie ant phenmenon was due to an atrophy of ant muscles controlling the mandibles.
We are using Laser Capture Microdissection to sample fungi at the the interface of ant neurons and muscles for both transcriptomics and metabolomics. Charissa de Bekker (Marie Curie Fellow in the lab) is an expert on LCM and single celled transcriptomics of fungi and we are ultimately working towards a artificial ant system that allows a fine detailed proximate understanding of manipulation and its temporal aspects.
We have also begun adding other systems such as nematodes, cestodes and strepsipterans in ants (which all manipulate behavior). You can see this in the video below which recounts the liver fluke manipulation (ignore the terrible narration)
Ultimately we want to understand how convergently evolved extended phenotypes of parasites cope with the common challenge of ant neurobiology
Disease spread in societies:
Behavioral manipulation of ant behavior is engaging but what makes the system of greater interest is that manipulation has evolved because ant societies establish complex conditions for parasite evolution and transmission. Such enormous groups living in close proximity has selected for effective disease defense forcing many parasite to exit the colony to transmit. Social insect societies range in complexity from 10 workers to more than 10 million.
We are interested in exploring this defense in the lab and field (Pennsylvania and Brazilian Amazon). We are merging cage experiments with field manipulations and spatial mathematical modeling (with Matt Ferrari and Marcel Salathe of CIDD). We are also working with folk in Architecture on use building software to map ant cities (nests and foraging trails) and relate that to disease spread (with Darla Lindberg of CIDD)
Biodiversity of manipulative parasites
Recent and excellent work by people like Amrand Kuris, Kevin Lafferty, Robert Poulin and others have demonstrated very clearly that parasites are dominant components of ecosystems both in terms of species numbers but also biomass. Most parasites don’t manipulate behavior (why is that?) and a question we are asking is how dominant are the group of fungi that do control ant behavior? We are addressing this study with alpha-taxonomy, phylogenetics, biotic surveys and genomics. We are working in Australia, SE Asia, West Africa, Sth America and Nth America with a range of excellent mycologists such as Harry Evans, Joey Spatafora, Tatiana Sanjuan and Roger Shivas.
Ants as agricultural pests:
Ants pose a significant threat to agriculture through their mutusalisms with phloem feeding insects such as hemipterans. Much of the disease incidence and spread of diseases on plants is due to the hundreds of thousands of ants that protect plant-feeding insects that vector disease. Ants farm these sucking insects and ‘milk’ them for the by-product sugar they excrete. This is a strong mutualism and ant protection increases the populations of plant feeding insects, and in turn, this greatly increases the rate of disease spread between plants as the bugs transmit viral and bacterial infections and the hundreds of thousands of ant legs and mandibles introduce fungi and psuedo-fungi (oomycetes) into leaf tissue. Reflecting the successful integration found inCIDD I am interested in bringing diverse approaches to study agricultural diseases. We are working now on Cassva and Cocoa in Ghana. You see further details in my recent lecture.