Effects of season and fire on the diversity of hypogeous fungi consumed by a tropical mycophagous marsupial

Abstract

1. Despite the importance of fire in many natural systems, knowledge of how fire affects the relationship between hypogeous fungi and mycophagous mammals in fire-prone environments is limited. Using experimental fires, we examined consumption of hypogeous ectomycorrhizal fruit-bodies by an endangered tropical mycophagist, the northern bettong Bettongia tropica Wakefield, in north-eastern Australia. 2. Fungus was the major dietary component (56%) throughout all seasons, both before and after fire. At least 35 hypogeous taxa were consumed. Number of taxa consumed during different seasons was similar, but was significantly higher on unburnt sites than on burnt sites. Similarly, diversity of taxa per faecal sample was significantly greater on unburnt sites, but also increased irrespective of fire from wet season to dry season. 3. Cluster and principal component analyses were used to examine patterns in consumption of fungal taxa. The greatest differences in dietary composition were between the period immediately after fire on burnt sites (early wet season) and all other season and treatment combinations. This difference was due to increased consumption of taxa in the fire-adapted family Mesophelliaceae and reduced consumption of the genus Elaphomyces. Principal component analysis revealed two major gradients in consumption. The first accounted for 32% of total variance and described change in consumption of taxa with season. The second accounted for 24% of total variance and described change in consumption of taxa before and after fire. 4. Despite taxon-specific changes in consumption of hypogeous fungi, the body condition of bettongs did not change significantly between seasons or in relation to fire, suggesting that bettongs were never compromised in their optimal fungal intake. 5. Our data show that the northern bettong has a flexible response to fire and could be best thought of as a fire-adapted marsupial. We therefore propose a precautionary approach to fire management of bettong habitat; at the present time this would include maintaining the recent fire regime of low to moderately intense fires every 3-4 years.