Coprophilous fungal communities in semiarid to mesic grasslands

Abstract

This investigation examined the composition of coprophilous fungal communities, with emphasis on the ascomycetous components thereof, on rabbit and cattle feces collected from short-grass (Nunn, CO), mixed-grass (Cottonwood, SD), and tall-grass (Shidler, OK) prairie ecosystems in the western United States. Fungal communities recorded for one dung type were always more similar to one another than to fungal communities from the other dung type, regardless of the grassland site from which samples were collected. The composition of the fungal community varied according to the age of the dung collected. Comparison of fungal communities on six age classes (0–54 months field exposure) of cattle dung from a semiarid grassland showed that communities were most similar on fecal collections nearest in age. The largest number of fungal species was recorded on fecal collections from the semiarid short-grass prairie. These results contrast sharply with species diversity patterns of other organism groups inhabiting these same grasslands. A hypothesis is presented that the greater species abundance of coprophilous fungal communities in semiarid grasslands is related to the slower rate of decomposition of individual fecal substrates and, thus, the availability of long-lived resource islands capable of supporting successive populations of fungal colonists. Communities on dung from the drier prairie sites (short grass and mixed grass) were more similar to one another than to communities from the more mesic tall-grass prairie. These results are contrasted with between-site comparisons of seed plants and small mammals. With one exception, decomposition dry weight losses during moist-chamber incubation for 80 days did not differ significantly (p > 0.05) among cattle dung samples regardless of the time dung was incubated in the field. Chemical analyses performed initially on field-aged cattle dung from the short-grass prairie site revealed similar percentages of various chemical components and this may account for the similarity of weight loss during moist-chamber incubation.