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

Abstract

The management of the remainder of Europe’s once extensive forests is hampered by a poor understanding of the character of the vegetation and drivers of change before the onset of clearance for farming. Pollen data indicate a closed-canopy, mixed-deciduous forest, contrasting with the assertion that large herbivores would have maintained a mosaic of open grassland, regenerating scrub and forested groves. Coprophilous fungal spores from sedimentary sequences are increasingly used as a proxy for past herbivore impact on vegetation, but the method faces methodological and taphonomical issues. Using pollen trap data from a long-running experiment in Chillingham Wild Cattle Park, UK, we investigate the first steps in the mechanisms connecting herbivore density to the incorporation of fungal spores in sediments and assess the effects of environmental variables on this relationship. Herbivore utilisation levels correlate with dung fungal spore abundance. Chillingham is densely populated by large herbivores, but dung fungal spore influx is low. Herbivores may thus be present on the landscape but go undetected. The absence of dung fungal spores is therefore less informative than their presence. Dung fungal spores likely enter the sediment record through a different pathway from wind-borne pollen and thus dung fungal abundance is better expressed as influx rates than as percentage of total pollen. Landscape openness, vegetation type and site wetness do not distort the impact of utilisation levels on dung fungal spore representation. However, dung fungal spore influx varies markedly between seasons and years. Spores travel, leading to a background level of spore deposition across the landscape, and at times a depletion of spores, especially under wet weather conditions. Animal behaviour, as well as husbandry practices, can lead to the accumulation of dung, and thus fungal spores, in specific locations on the landscape that do not directly reflect grazing pressure.

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

“…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. Besides megaherbivore abundance, other factors affect spore abundance (van Asperen et al, 2019). These factors include (1) moisture availability for fungal growth and hydrology (Wood and Wilmshurst, 2011), (2) shoreline morphology, (3) seasonality of climate and wind impacting fungal growth and dispersal (van Asperen, 2017), (4) taphonomic effects including the sedimentary environment and spore preservation, and (5) laboratory procedures (van Asperen et al, 2016).…”

On the Use of Spores of Coprophilous Fungi Preserved in Sediments to Indicate Past Herbivore Presence

“…When herbivores engage in coprophagy, they simultaneously consume the fungal fruitbodies (with spores inside) that grow on the surface of faeces, and plant material with attached spores [14,20]. The spores have thick melanised walls that act as protective layers, allowing them to travel through the digestive system without being harmed [16,32]; the thick wall also improves the likelihood of SCF being preserved in sedimentary records [35]. Having passed through the digestive track of an animal, ultimately dung and the incorporated spores will then be ejected and the spores are left to germinate and grow on the dung substrate [16,19,32,35].…”

“…The spores have thick melanised walls that act as protective layers, allowing them to travel through the digestive system without being harmed [16,32]; the thick wall also improves the likelihood of SCF being preserved in sedimentary records [35]. Having passed through the digestive track of an animal, ultimately dung and the incorporated spores will then be ejected and the spores are left to germinate and grow on the dung substrate [16,19,32,35]. At a mature stage of fructification, the fungi eject spores away from the dung onto the surrounding herbage for the cycle to repeat itself [13,14,16].…”

Archaeobotanical evidence for the emergence of pastoralism and farming in southern Africa

“…Increase in spores of coprophilous fungi Abundant fungal spores (e.g., Sordaria, Sporormiella, Gelasinospora) commonly associated with dung were recovered in sediment pollen archives in the Savanna, Grasslands and IOCB Biomes, possibly indicating the presence of pastoralism across South Africa, Botswana, and Mozambique beginning as early as 2000-1500 BP (Neumann et al, 2014;Ekblom et al, 2014b;Cordova et al, 2017;Hahn et al, 2021). Palaeoecological studies focused on dung fungal spores have shown that their presence is often associated with the dung of herbivores (Cugny et al, 2010;Baker et al, 2013;Cheruiyot et al, 2020;van Asperen et al, 2020), though some fungal taxa (e.g., Gelasinospora) grow rapidly on other substrates (Cheruiyot et al, 2020;van Asperen et al, 2020). Thus, a significant increase in dung fungal spores is a potential indicator of grazing particularly during known periods of pastoralism in the archaeological record especially if spores of coprophilous fungi co-occur with e.g., pollen of crops and weeds.…”