Fungal pressures within and surrounding nests of the arboreal termite species Nasutitermes acajutlae

Samples were collected from nests of Nasutitermes acajutlae on St. John, USVI. Nasutitermes acajutlae nests in various habitats (woodland, sparse, mangrove, dry forest, moist forest) on the island that differ in their abiotic attributes. Variables such as ambient temperature and humidity, nest temperature and humidity, light, soil moisture and pH were examined for their influence on fungal amounts and diversity in each habitat, as well as within a nest. Washes of core and trail nest material, soil from underneath the nest, and cuticular washes of worker and soldier termites were plated on Potato Dextrose Agar with 25 µg/mL of the antibiotic Thiostrepton. Two plates of each sample were incubated at 25°C and 35°C for five days and fungal colony forming units counted. Cultured fungi were identified using environmental PCR. Results show that fungal growth is highest in the nest material and soil samples at 25°C, and very little grows from the cuticles of the termites. The nest core material, trail material, and soil samples all differed significantly between habitats, and core samples had the fewest fungi in all except the dry habitat. The lack of growth at 35°C may indicate the effectiveness of the high internal temperature of N. acajutlae nests for reducing fungal growth. Termites live in microbe-rich environments, many of which could be pathogenic. These results have strong implications for the role of fungal communities in nest site selection, and the influence of fungal pressures on the evolution of termite nest architecture.