Microbial communities associated with mounds of the Orange-footed scrubfowl Megapodius reinwardt

Abstract

Megapodius reinwardt, the orange-footed scrubfowl, belongs to a small family of birds that inhabits the Indo-Australian region. Megapodes are unique in incubating their eggs in mounds using heat from microbial decomposition of organic materials and solar radiation. Little is known about the microorganisms involved in the decomposition of organic matter in mounds. To determine the source of microbes in the mounds, we used 16S and 18S rRNA gene sequencing to characterize the microbial communities of mound soil, adjacent soil and scrubfowl faeces. We found that the microbial communities of scrubfowl faeces were substantially different from those of the mounds and surrounding soils, suggesting that scrubfowls probably do not use their faeces to inoculate their mounds although a few microbial sequence variants were present in both faeces and mound samples. Further, the mound microbial community structure was significantly different to the adjacent soils. For example, mounds had a high relative abundance of sequence variants belonging to Thermomonosporaceae, a thermophilic soil bacteria family able to degrade cellulose from plant residues. It is not clear whether members of Thermomonosporaceae disproportionately contribute to the generation of heat in the mound, or whether they simply thrive in the warm mound environment created by the metabolic activity of the mound microbial community. The lack of clarity in the literature between designations of heat-producing (thermogenic) and heat-thriving (thermophilic) microbes poses a challenge to understanding the role of specific bacteria and fungi in incubation.

Keywords: Megapode; Microbial communities; Mound; Orange-footed Scrubfowl; Soil microbes; Thermogenesis; Thermomonosporaceae.

Figure 1. Taxa plot.

Percentage of contribution of each bacterial (A) and fungal (B) phylum for each sample category (mound, shallow soil, deep soil, faeces). Taxa shown are those that contributed to greater than one percent of all samples.

Figure 2. Non-metric Multidimensional scaling (nMDS) graph.

Unrarefied bacterial (A) and fungal (B) communities sampled at each mound location (labelled A–D) from each sample category (mound, shallow soil, deep soil, faeces). Bacterial community stress = 0.1, and fungal community stress = 0.18. Number of dimensions for each nMDS graph = 2, N = 30.

Figure 3. Relative abundance heat map of the top 50 most abundant bacterial taxa.

Sampled at each mound location (labelled A–D) from each sample category (mound, shallow soil, deep soil, faeces). Bacterial SVs are assigned to the family where possible, but if family is not resolved, then SVs are assigned to orders.

Figure 4. Relative abundance heat map of the top 50 most abundant fungal taxa.

Sampled at each mound location (labelled A–D) from each sample category (mound, shallow soil, deep soil, faeces). Fungal SVs are assigned to the family where possible, but if family is not resolved, then SVs are assigned to orders.