Low host-pathogen specificity in the leaf-cutting ant-microbe symbiosis
Stephen J Taerum1, Matías J Cafaro, Ainslie E F Little
1Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA.
Proceedings. Biological Sciences
|June 7, 2007
Summary
Fungus-growing ants face diverse Escovopsis parasites. Despite broad coevolution, leaf-cutter ants experience frequent parasite host-switching, requiring constant defense of their fungal gardens.
Area of Science:
- Ecology
- Evolutionary Biology
- Mycology
Background:
- Host-parasite dynamics drive coevolutionary processes.
- Fungus-growing ants engage in complex symbiotic relationships with fungi, including antagonistic interactions with the parasitic microfungus Escovopsis.
- Previous research indicates congruent evolutionary histories between ants, their fungal cultivars, and Escovopsis at deep phylogenetic levels.
Purpose of the Study:
- To investigate host-parasite specificity within the Escovopsis-leaf-cutter ant symbiosis at finer phylogenetic scales.
- To determine if host-switching occurs between different leaf-cutter ant species and genera.
- To assess the experimental host range of Escovopsis strains against leaf-cutter cultivars.
Main Methods:
- Molecular phylogenetic analysis of Escovopsis isolates from leaf-cutter ant gardens (Atta spp. and Acromyrmex spp.).
- Phylogenetic comparison of Escovopsis strains with their associated ant hosts.
- In vitro experimental assays to test the infectivity of diverse Escovopsis strains on various leaf-cutter cultivars.
Main Results:
- Molecular phylogeny confirmed broad phylogenetic specificity of Escovopsis but revealed frequent host-switching events within leaf-cutter ants.
- Escovopsis strains from Acromyrmex and Atta gardens clustered together phylogenetically, with closely related strains infecting both genera.
- Experimental results demonstrated low host-parasite specificity, as diverse Escovopsis strains could overgrow all tested leaf-cutter cultivars.
Conclusions:
- The Escovopsis-leaf-cutter ant association exhibits lower specificity at finer phylogenetic levels than previously observed.
- Leaf-cutter ants must continuously defend their fungal cultivars against a diverse range of Escovopsis garden pathogens due to frequent host-switching.
- This highlights the dynamic nature of coevolutionary adaptations in specialized symbiotic systems.
Related Concept Videos
02:40Epiphytes, Parasites, and Carnivores
Plants often form mutualistic relationships with soil-dwelling fungi or bacteria to enhance their roots’ nutrient uptake ability. Root-colonizing fungi (e.g., mycorrhizae) increase a plant’s root surface area, which promotes nutrient absorption. While root-colonizing, nitrogen-fixing bacteria (e.g., rhizobia) convert atmospheric nitrogen (N2) into ammonia (NH3), making nitrogen available to plants for various biological functions. For example, nitrogen is essential for the biosynthesis of the...
01:25Microbial Interactions: Mutualism
Mutualism is a symbiotic interaction in which all participating organisms benefit. These relationships can be obligate or facultative and are fundamental to ecosystem functions across diverse biological systems.Plant–Fungi MutualismOne well-known example is the association between plant roots and mycorrhizal fungi, such as Rhizophagus species. The fungal hyphae penetrate the root hairs and the epidermis, forming an extensive hyphal network that establishes a symbiotic association. Through this...
01:26Microbial Interactions: Cooperation
Microbial cooperation involves beneficial interactions in which different species work together for individual or mutual advantage. These interactions can profoundly influence ecological dynamics and evolutionary processes, and they are essential to many pathogenic and symbiotic relationships.Nematode–Bacteria CooperationA striking example is the relationship between the Gram-negative bacterium Xenorhabdus nematophila and the parasitic nematode Steinernema carpocapsae. Juvenile nematodes...
01:22Microbial Interactions: Parasitism
Parasitism is a form of microbial interaction in which parasitic microbes exploit a host organism for nutrients and shelter, often at the host's expense. Unlike mutualistic relationships, where both organisms benefit, parasitism benefits only the parasite and harms the host.Classification of ParasitesMicrobial parasites are broadly classified based on their location relative to the host.Ectoparasites remain on the host’s surface, such as the skin or outer tissues, drawing nutrients...
01:09Microbe-Plant Interactions
Microbe-plant interactions represent a dynamic spectrum of associations shaped by intricate chemical signaling. These interactions can be neutral, beneficial, or detrimental, and profoundly influence plant physiology, growth, and ecosystem function. The plant microbiome, comprising bacteria, fungi, archaea, protists, and viruses, plays a pivotal role in mediating these effects through surface colonization, internal colonization, or systemic symbiosis.Mutualistic associations, particularly with...
01:25Colonisation of Pathogens
Pathogen colonization of host tissues is a critical step in the development of infectious diseases. Various pathogenic microorganisms, including bacteria, fungi, viruses, and protozoa, have evolved complex strategies to attach to, invade, and persist within host environments. These mechanisms enable pathogens to establish infections, evade immune responses, and resist antimicrobial treatments.Attachment to Host CellsIn bacteria, colonization typically begins with adherence to host epithelial...