Natural variation in colony inbreeding does not influence susceptibility to a fungal pathogen in a termite.

Reduced genetic diversity through inbreeding can negatively affect pathogen resistance. This relationship becomes more complicated in social species, such as social insects, since the chance of disease transmission increases with the frequency of interactions among individuals. However, social insects may benefit from social immunity, whereby individual physiological defenses may be bolstered by collective-level immune responses, such as grooming or sharing of antimicrobial substance through trophallaxis. We set out to determine whether differences in genetic diversity between colonies of the subterranean termite, Reticulitermes flavipes, accounts for colony survival against pathogens. We sampled colonies throughout the United States (Texas, North Carolina, Maryland, and Massachusetts) and determined the level of inbreeding of each colony. To assess whether genetically diverse colonies were better able to survive exposure to diverse pathogens, we challenged groups of termite workers with two strains of a pathogenic fungus, one local strain present in the soil surrounding sampled colonies and another naïve strain, collected outside the range of this species. We found natural variation in the level of inbreeding between colonies, but this variation did not explain differences in susceptibility to either pathogen. Although the naïve strain was found to be more hazardous than the local strain, colony resistance was correlated between two strains, meaning that colonies had either relatively high or low susceptibility to both strains regardless of their inbreeding coefficient. Overall, our findings may reflect differential virulence between the strains, immune priming of the colonies via prior exposure to the local strain, or a coevolved resistance toward this strain. They also suggest that colony survival may rely more upon additional factors, such as different behavioral response thresholds or the influence of a specific genetic background, rather than the overall genetic diversity of the colony.

A Lab-Based Study of Temperate Forest Termite Impacts on Two Common Wood-Rot Fungi.

Termites and fungi are the primary decomposers of dead wood. Interactions between wood-feeding termites and wood-rot fungi are inevitable given their shared food source. Termites have developed multiple defense strategies against infectious fungi, such as Metarhizium spp., that include antifungal proteins in their saliva and fungal inhibition properties in their gut. The antifungal properties of termite salivary secretions depend on ß-1,3-glucanases that are likely to be effective against a broad spectrum of filamentous fungi. Given the overlap in niches, there is opportunity for interference competition between termites and wood-rot fungi to occur. Here we demonstrate that ß-1,3-glucanases in the saliva and the antifungal properties of the gut of the eastern subterranean termite Reticulitermes flavipes (Kollar) (Blattodea: Rhinotermitidae) affects the growth of two common wood-rot fungi, Gloeophyllum trabeum Persoon (Murrill) (Gloeophyllales: Gloeophyllaceae) and Phanerochaete chrysosporium (Burdsall) (Polyporales: Phanerochaetaceae).