Dung fungi as a proxy for megaherbivores: opportunities and limitations for archaeological applications

Abstract

The use of spores of coprophilous fungi from sedimentary sequences as proxy evidence for large herbivore abundance has garnered pronounced attention and scrutiny over the past three decades. In response to the rapid rate at which new information is being discovered on this topic, this paper presents a brief review of the archaeological applications so far, and outlines opportunities and limitations of using Sporormiella as a proxy for herbivore abundance. Specific archaeological uses of this proxy include understanding megaherbivore extinctions and human land use patterns such as pastoralism and agriculture. We analyze how dung fungal records are formed and review the mycological literature to outline factors affecting spore reproduction and preservation. These include how strongly each commonly used dung fungal taxon relies on dung as a substrate and environmental factors affecting dung fungal reproduction and coprophilous fungi deposition. Certain laboratory preparation techniques adversely affect spore representation on pollen slides. The methods of analysis and quantification of spore records also impact on our understanding. We describe good practice to increase precision of analytical methods. Due to limitations imposed by some of these factors, it is possible that an absence of dung fungi from a palaeoecological record does not imply an absence of herbivores. However, consideration of these factors and inclusion of as wide a range of coprophilous spore records as possible increases the reliability of such inferences.

Comparison of Sporormiella dung fungal spores and oribatid mites as indicators of large herbivore presence: evidence from the Cuzco region of Peru

“…There are multiple biotic and abiotic factors affecting the representation of dung fungal spores in lake sediments, not just the presence of large herbivores in the local catchment (Parker and Williams, 2011;Perrotti and van Asperen, 2018). One key factor is the poor dispersal capability of the spores, which normally occurs close to ground-level and within a few metres of the surface of the dung source.…”

Tracking late-Quaternary extinctions in interior Alaska using megaherbivore bone remains and dung fungal spores

“…For future investigations, uncertainty regarding Sporormiella zero-counts could be avoided by more strictly adhering to the guidelines set by Etienne and Jouffroy-Bapicot (2014) recommending high exotic marker counts, independently from pollen sum. We also found that, when Sordaria, another reliable indicator of megaherbivores (Baker et al, 2013;Perrotti and van Asperen, 2019) is counted, the number of samples with indicative spores (i.e., Sporormiella and/or Sordaria) is doubled (12 vs 25 samples of 48 total). Therefore, including other dung fungal spores such as Sordaria appears to be an effective additional measure to minimise the uncertainty associated with Sporormiella zero counts.…”

Relating dung fungal spore influx rates to animal density in a temperate environment: Implications for palaeoecological studies

“…The results from this study raise some important considerations for assessing herbivore presence in palaeoecological landscapes. It is clear that a wider range of fungal types are informative when assessing past herbivore presence, rather than relying on one indicator taxon such as Sporomiella (Perrotti and Van Asperen 2019). However, even with a range of fungal spores the data presented here suggest that some levels of grazing in wetter meadows might not be detectable or may require painstaking searches for sparse fungal spores in quantities insufficient to draw robust conclusions from.…”

“…Overall, the low influx of dung fungal spores in the traps show that a landscape can be densely populated by large herbivores that do not always leave a dung fungal spore signal that is strong enough to distinguish it from background deposition rates. The absence of dung fungal spores in palaeoecological samples may therefore be less informative than their presence (Raper and Bush 2009;Jones et al 2017;Perrotti and Van Asperen 2019). Although in some cases Sporormiella spore abundance alone may indicate herbivore presence and/or abundance, the low levels of Sporormiella spore recovery, from both the Chillingham pollen traps and the dung, underline the importance of analysing all dung fungal spore taxa encountered in a palaeoecological sample, rather than limiting the analysis to a single spore type (Johnson et al 2015;Baker et al 2016;Perrotti and Van Asperen 2019).…”

“…2.3. Fungal spore taxonomy, morphology and ecologyThe genera Podospora, Sordaria and Sporormiella are generally regarded as being among the strongest indicators of dung in palaeoecological studies (e.g Baker et al 2013;Perrotti &. Van Asperen 2019).…”