Using dung fungi to interpret decline and extinction of megaherbivores: problems and solutions

Johnson, Christopher N.; Rule, Susan; Haberle, Simon; Turney, Chris S. M.; Kershaw, A. Peter; Brook, Barry W.

doi:10.1016/j.quascirev.2014.12.011

Cited by 40 publications

(54 citation statements)

References 37 publications

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“…Johnson et al . () analysed Sporormiella and other fungal spores in Lynch's Crater core sediments from tropical north‐east Queensland. Spores were present in all samples, decreasing at about 40 000 a bp then persisting in reduced numbers after this time.…”

Section: Introductionsupporting

confidence: 73%

What does the occurrence of Sporormiella (Preussia) spores mean in Australian fossil sequences?

Dodson

Field²

2018

J Quaternary Science

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Understanding the loss of the final few species of Australian megafauna is beset by a paucity of data on human arrival, well‐provenanced megafauna, human/megafauna population range and distribution (coexistence and interaction), and the range, scale and impact of environmental changes spanning the human–megafauna period. To overcome these shortcomings, the occurrence and decline of coprophilous fungal spores of Sporormiella in sediments have been used as a proxy for extinct megaherbivores. The Sporormiella evidence is presented as the key indicator of extinction timing and these reports are often from locations where there is no known archaeological record or megafauna remains. However, interpreting fungal spore occurrence is not straightforward, as demonstrated by studies investigating taphonomy, taxonomy and the types of animal dung where Sporormiella occurs. No detailed studies on these problems exist for Australia and no evidence supporting the use of Sporormiella as a valid proxy has been reported. Here we examine the occurrence of Sporormiella spores from Cuddie Springs in south‐eastern Australia. Despite a well‐preserved suite of megafauna fossils, Sporormiella occurrence is sporadic and frequencies are low. We conclude that using Sporormiella alone as an indicator for the presence of megafauna is premature for the Australian context.

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Section: Introductionsupporting

confidence: 73%

What does the occurrence of Sporormiella (Preussia) spores mean in Australian fossil sequences?

Dodson

Field²

2018

J Quaternary Science

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“…2) and used to indicate the presence of megafaunal populations. As a marine sequence, the Cape Pasley record is not subject to local taphonomic biases that may occur and require consideration at terrestrial settings such as local moisture levels35, near-by herbivore activity36 and position of the core site within the basin37. In our record, Sporormiella is abundant throughout MIS 6, 5, 4 and the early part of MIS 3, and rare in the later part of MIS 3, 2 and MIS 1.…”

Section: Resultsmentioning

confidence: 86%

Humans rather than climate the primary cause of Pleistocene megafaunal extinction in Australia

et al. 2017

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Environmental histories that span the last full glacial cycle and are representative of regional change in Australia are scarce, hampering assessment of environmental change preceding and concurrent with human dispersal on the continent ca. 47,000 years ago. Here we present a continuous 150,000-year record offshore south-western Australia and identify the timing of two critical late Pleistocene events: wide-scale ecosystem change and regional megafaunal population collapse. We establish that substantial changes in vegetation and fire regime occurred ∼70,000 years ago under a climate much drier than today. We record high levels of the dung fungus Sporormiella, a proxy for herbivore biomass, from 150,000 to 45,000 years ago, then a marked decline indicating megafaunal population collapse, from 45,000 to 43,100 years ago, placing the extinctions within 4,000 years of human dispersal across Australia. These findings rule out climate change, and implicate humans, as the primary extinction cause.

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“…Increased fire activity immediately after the Pleistocene extinctions (73)(74)(75)(76)78) and so can be used to provide the ecological context of functional large herbivore collapse (73)(74)(75)(76)(77). Several pollen records from eastern North America show an increase in hardwood deciduous taxa immediately after the Sporormiella-indicated megafaunal decline, including increases in palatable and shade-tolerant woody species (74,75,78), and a more closed vegetation, consistent with release from browsing pressure.…”

Section: Evidence Of Large-herbivore Impact From the Paleoecological mentioning

confidence: 99%

Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation

Bakker

Gill

Johnson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

323

299

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Until recently in Earth history, very large herbivores (mammoths, ground sloths, diprotodons, and many others) occurred in most of the World's terrestrial ecosystems, but the majority have gone extinct as part of the late-Quaternary extinctions. How has this large-scale removal of large herbivores affected landscape structure and ecosystem functioning? In this review, we combine paleo-data with information from modern exclosure experiments to assess the impact of large herbivores (and their disappearance) on woody species, landscape structure, and ecosystem functions. In modern landscapes characterized by intense herbivory, woody plants can persist by defending themselves or by association with defended species, can persist by growing in places that are physically inaccessible to herbivores, or can persist where high predator activity limits foraging by herbivores. At the landscape scale, different herbivore densities and assemblages may result in dynamic gradients in woody cover. The late-Quaternary extinctions were natural experiments in large-herbivore removal; the paleoecological record shows evidence of widespread changes in community composition and ecosystem structure and function, consistent with modern exclosure experiments. We propose a conceptual framework that describes the impact of large herbivores on woody plant abundance mediated by herbivore diversity and density, predicting that herbivore suppression of woody plants is strongest where herbivore diversity is high. We conclude that the decline of large herbivores induces major alterations in landscape structure and ecosystem functions.browsers | ecosystem functions | herbivore diversity | landscape structure | megaherbivore During the late Quaternary, megafaunas were drastically reduced in most regions (1, 2), representing the start of an ongoing trophic downgrading that has resulted in the loss of entire functional guilds and relaxation of top-down control in today's ecosystems (3). A high proportion of the large herbivores that have survived into the Anthropocene (4) are now drastically reduced in range and abundance, rendering them functionally extinct, or have been replaced by livestock in much of their historic ranges (5-8). How has this loss of wild-living large herbivores affected landscape structure and ecosystem functioning?Contemporary large herbivores have strong effects on the abundance of woody species, plant diversity, nutrient cycling, and other biota (9). Most likely, the ecological effects of preextinction herbivores were as large, possibly much more so given the great size and diversity of the lost large herbivore assemblages (10, 11). We hypothesize that Pleistocene herbivore assemblages, including large and megaherbivore browsers, would have greatly reduced woody plant abundance and altered species composition and landscape structure, if present at sufficient densities. We review the impact of large herbivores (≥45 kg in body weight) on woody vegetation, with a focus on megaherbivores (≥1,000 kg), and combine information from ...

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Using dung fungi to interpret decline and extinction of megaherbivores: problems and solutions

Cited by 40 publications

References 37 publications

What does the occurrence of Sporormiella (Preussia) spores mean in Australian fossil sequences?

What does the occurrence of Sporormiella (Preussia) spores mean in Australian fossil sequences?

Humans rather than climate the primary cause of Pleistocene megafaunal extinction in Australia

Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation

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