The megaherbivore syndrome: alternative life style or different time frame?

Owen‐Smith, Norman

doi:10.1007/978-94-009-2605-9_22

Cited by 4 publications

(4 citation statements)

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“…We are using here this restricted definition from Owen-Smith [45], [46] rather than the more broad advanced by Martin and Klein [36] (>44 kg) because of its biological basis. In South America, megafauna include primarily the large terrestrial mammals (proboscideans, extinct xenarthrans, and extinct orders such as Notoungulata)[47].…”

Section: Introductionmentioning

confidence: 99%

“…These are faunistic elements (taxa) of the frugivore communities interacting with a given plant species that characteristically have a large (>1000 kg) body mass [36] , [45] – [46] . We are using here this restricted definition from Owen-Smith [45] , [46] rather than the more broad advanced by Martin and Klein [36] (>44 kg) because of its biological basis. In South America, megafauna include primarily the large terrestrial mammals (proboscideans, extinct xenarthrans, and extinct orders such as Notoungulata) [47] .…”

Section: Introductionmentioning

confidence: 99%

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Seed Dispersal Anachronisms: Rethinking the Fruits Extinct Megafauna Ate

2008

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BackgroundSome neotropical, fleshy-fruited plants have fruits structurally similar to paleotropical fruits dispersed by megafauna (mammals >103 kg), yet these dispersers were extinct in South America 10–15 Kyr BP. Anachronic dispersal systems are best explained by interactions with extinct animals and show impaired dispersal resulting in altered seed dispersal dynamics.Methodology/Principal FindingsWe introduce an operational definition of megafaunal fruits and perform a comparative analysis of 103 Neotropical fruit species fitting this dispersal mode. We define two megafaunal fruit types based on previous analyses of elephant fruits: fruits 4–10 cm in diameter with up to five large seeds, and fruits >10 cm diameter with numerous small seeds. Megafaunal fruits are well represented in unrelated families such as Sapotaceae, Fabaceae, Solanaceae, Apocynaceae, Malvaceae, Caryocaraceae, and Arecaceae and combine an overbuilt design (large fruit mass and size) with either a single or few (<3 seeds) extremely large seeds or many small seeds (usually >100 seeds). Within-family and within-genus contrasts between megafaunal and non-megafaunal groups of species indicate a marked difference in fruit diameter and fruit mass but less so for individual seed mass, with a significant trend for megafaunal fruits to have larger seeds and seediness.Conclusions/SignificanceMegafaunal fruits allow plants to circumvent the trade-off between seed size and dispersal by relying on frugivores able to disperse enormous seed loads over long-distances. Present-day seed dispersal by scatter-hoarding rodents, introduced livestock, runoff, flooding, gravity, and human-mediated dispersal allowed survival of megafauna-dependent fruit species after extinction of the major seed dispersers. Megafauna extinction had several potential consequences, such as a scale shift reducing the seed dispersal distances, increasingly clumped spatial patterns, reduced geographic ranges and limited genetic variation and increased among-population structuring. These effects could be extended to other plant species dispersed by large vertebrates in present-day, defaunated communities.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seed Dispersal Anachronisms: Rethinking the Fruits Extinct Megafauna Ate

2008

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“…Hypothesis 2 states that facial armor evolution was driven by feeding injuries in environments with many Sympatric Dangerous Herbivores (SDHs), which we define in this study as any herbivore coexisting with armor-faced theropods that had a high capacity to inflict injury on an attacking predator (Figure 1B). Herbivorous dinosaurs were classified as SDHs if they either exhibited obvious defensive weaponry such as horns, spikes, osteoderms, etc., or if they weighed over 1,000kg, because even unarmed megaherbivores in modern ecosystems can be very dangerous to potential predators due to their large size and strength (18). The weight cutoff for SDHs only applies to herbivores that did not bear obvious defensive weaponry, such as large duck-billed hadrosaurs and the long-necked sauropods (17).…”

Section: Introductionmentioning

confidence: 99%

Preliminary investigation of Allosauroidea facial integument and the evolution of theropod facial armor

Kearns,

Kearns

2022

J Emerg Invest

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In amniotes, the growth of specialized facial integument, or external skin tissues, has a close relationship with the texture and morphology of underlying cranial bones. Osteological correlates of facial skin structures have been used before to reconstruct the integument of several extinct dinosaurian lineages but not for theropods from the clade Allosauroidea, whose members exhibit exceptionally rugose and heavily ornamented skulls. This study aims to investigate, in a preliminary sense, the facial integument of Allosauroidea by examining osteological correlates from high-resolution photographs of fossil material. We compared the inferred integument of allosauroids to analogous structures in modern animals in order to discuss potential biological and behavioral implications, with soft-tissue adaptations suggesting headbutting or sparring in some taxa. Allosauroids display an evolutionary trend for increasing cranial cornification throughout their history, and their most derived members exhibit greater development of facial armor than other tetanurans. We developed three hypotheses to explain the selective pressures that may have driven the independent evolution of this dermal armor in several unrelated theropod clades, namely abelisaurids, carcharodontosaurids, and tyrannosaurids. Empirical tests of paleoecological data did not support any of the three hypotheses of intraspecific conflict, competition from other carnivores, or dangerous prey items as the main pressure that drove the evolution of theropod facial armor. We suggest that more sampling of armor-faced theropods and their associated ecosystems, especially those from the Southern Hemisphere, is needed to reveal the reasons behind the convergent evolution of this integument.

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“…Instead of being trapped in woody plant tissues for decades or centuries, as it is the case in forested ecosystems, organic carbon in the form of grass blades, seeds and underground storage organs can be easily consumed by different kinds of herbivores (e.g., Dominy et al, 2008), and the CO 2 incorporated by the plants is rapidly recycled as CO 2 in the atmosphere, with an impact on the greenhouse gas content and the temperature. On the other hand, a significant amount of carbon is stored in the biomass of the megaherbivores themselves, which are organisms with long lifespans and essentially beyond the reach of animal predators (Owen-Smith, 1989). …”

Section: Ecological Functions Of Megaherbivoresmentioning

confidence: 99%

The Rise of the Anthroposphere since 50,000 Years: An Ecological Replacement of Megaherbivores by Humans in Terrestrial Ecosystems?

Bocherens

2018

Front. Ecol. Evol.

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Megaherbivores fulfilled a number of important ecological functions in terrestrial ecosystems and behaved as ecological engineers since 300 million years until around 12,000 years ago. These essential ecological functions include opening vegetation cover, selective seed dispersal and nutrient recycling and spreading. Thanks to these effects, megaherbivores change the vegetation structure where they live, with cascading effects on smaller herbivores and also on climate. The late Pleistocene extinction strongly impacted the megaherbivores almost all over the world and led to the loss of these important ecological functions in terrestrial ecosystems. These functions were partially restored by agriculturist humans through an ecological replacement that occurred through an ecological shift within the species Homo sapiens. A better understanding of the differences and similarities between the ecological impacts of megaherbivores and those of agricultural humans should help to predict the future of terrestrial ecosystems.

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The megaherbivore syndrome: alternative life style or different time frame?

Cited by 4 publications

References 50 publications

Seed Dispersal Anachronisms: Rethinking the Fruits Extinct Megafauna Ate

Seed Dispersal Anachronisms: Rethinking the Fruits Extinct Megafauna Ate

Preliminary investigation of Allosauroidea facial integument and the evolution of theropod facial armor

The Rise of the Anthroposphere since 50,000 Years: An Ecological Replacement of Megaherbivores by Humans in Terrestrial Ecosystems?

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