Late Quaternary Mammal Research Articles

Late Quaternary mammal introduction and extinction records from archaeological cave deposits in Timor-Leste

Late Quaternary mammal introduction and extinction records from archaeological cave deposits in Timor-Leste

Small brains predisposed Late Quaternary mammals to extinction

The Late Quaternary witnessed a dramatic wave of large mammal extinctions, that are usually attributed to either human hunting or climatic change. We hypothesized that the large mammals that survived the extinctions might have been endowed with larger brain sizes than their relatives, which could have conferred enhanced behavioral plasticity and the ability to cope with the rapidly changing Late Quaternary environmental conditions. We assembled data on brain sizes of 291 extant mammal species plus 50 more that went extinct during the Late Quaternary. Using logistic, and mixed effect models, and controlling for phylogeny and body mass, we found that large brains were associated with higher probability to survive the Late Quaternary extinctions, and that extant species have brains that are, on average, 53% larger when accounting for order as a random effect, and 83% when fitting a single regression line. Moreover, we found that models that used brain size in addition to body size predicted extinction status better than models that used only body size. We propose that possessing a large brain was an important, yet so far neglected characteristic of surviving megafauna species.

Phylogenetic and functional clustering illustrate the roles of adaptive radiation and dispersal filtering in jointly shaping late‐Quaternary mammal assemblages on oceanic islands

Islands frequently harbour unique assemblages of species, yet their ecological roles and differences are largely ignored in island biogeography studies. Here, we examine eco-evolutionary processes structuring mammal assemblages on oceanic islands worldwide, including all extant and extinct late-Quaternary mammal species. We find island mammal assemblages tend to be phylogenetically clustered (share more recent evolutionary histories), with clustering increasing with island area and isolation. We also observe that mammal assemblages often tend to be functionally clustered (share similar traits), but the strength of clustering is weak and generally independent from island area or isolation. These findings indicate the important roles of in situ speciation and dispersal filtering in shaping island mammal assemblages under pre-anthropogenic conditions, notably through adaptive radiation of a few clades (e.g. bats, with generally high dispersal abilities). Our study demonstrates that considering the functional and phylogenetic axes of diversity can better reveal the eco-evolutionary processes of island community assembly.

Resurrection of the Island Rule: Human-Driven Extinctions Have Obscured a Basic Evolutionary Pattern.

Islands are or have been occupied by unusual species, such as dwarf proboscideans and giant rodents. The discussion of the classical but controversial island rule-which states that mammalian body sizes converge on intermediate sizes on islands-has been stimulated by these unusual species. In this study, we use an unprecedented global data set of the distributions and body sizes of late Quaternary mammal species and a novel analytical method to analyze body size evolution on islands. The analyses produced strong support for the island rule. Islands have suffered massive human-driven losses of species, and we found that the support for the island rule was substantially stronger when the many late Quaternary extinct species were also considered (particularly the tendency for dwarfing in large taxa). The decisive support for the island rule in this study confirms that evolution plays out in a markedly different way on islands and that human impact may obscure even fundamental evolutionary patterns.

Exploring the influence of ancient and historic megaherbivore extirpations on the global methane budget

Globally, large-bodied wild mammals are in peril. Because "megamammals" have a disproportionate influence on vegetation, trophic interactions, and ecosystem function, declining populations are of considerable conservation concern. However, this is not new; trophic downgrading occurred in the past, including the African rinderpest epizootic of the 1890s, the massive Great Plains bison kill-off in the 1860s, and the terminal Pleistocene extinction of megafauna. Examining the consequences of these earlier events yields insights into contemporary ecosystem function. Here, we focus on changes in methane emissions, produced as a byproduct of enteric fermentation by herbivores. Although methane is ∼ 200 times less abundant than carbon dioxide in the atmosphere, the greater efficiency of methane in trapping radiation leads to a significant role in radiative forcing of climate. Using global datasets of late Quaternary mammals, domestic livestock, and human population from the United Nations as well as literature sources, we develop a series of allometric regressions relating mammal body mass to population density and CH4 production, which allows estimation of methane production by wild and domestic herbivores for each historic or ancient time period. We find the extirpation of megaherbivores reduced global enteric emissions between 2.2-69.6 Tg CH4 y(-1) during the various time periods, representing a decrease of 0.8-34.8% of the overall inputs to tropospheric input. Our analyses suggest that large-bodied mammals have a greater influence on methane emissions than previously appreciated and, further, that changes in the source pool from herbivores can influence global biogeochemical cycles and, potentially, climate.

Domination by Reptiles in a Terrestrial Food Web of the Bahamas Prior to Human Occupation

Human activities in the Bahamas and other oceanic islands have damaged terrestrial ecosystems irreparably through the extinction of indigenous species. Tortoise and crocodile bones from Abaco Island in the Bahamas sampled for 14C-dating revealed a small overlap between the last occurrence of these large reptiles and early human settlement in the Bahamas. Before their extermination approximately 1,000 years ago, the dominant herbivore and carnivore on Abaco Island were the endemic Albury's Tortoise (Chelonoidis alburyorum) and the formerly widespread Cuban Crocodile (Crocodylus rhombifer). Stable isotope data from carbon (δ13C) and nitrogen (δ15N) in bone collagen from Late Holocene fossils suggest that these large reptiles were part of a terrestrial rather than marine or estuarine food web. Our proposal that Cuban Crocodiles were once the apex terrestrial predator in the Bahamas is supported by comparisons with published δ13C values for modern marine/estuarine crocodylians as compared to those of nonmarine reptilian and mammalian carnivores. For reptiles to occupy terrestrial trophic roles distinguishes Bahamian Islands from nearby Greater Antillean Islands (Cuba, Jamaica, Hispaniola, Puerto Rico) where endemic mammals represent the largest herbivores and carnivores in prehuman times. This distinction is even greater when compared with Late Quaternary mammals of prehuman vertebrate communities in neighboring North America.

A Life-History Approach to the Late Pleistocene Megafaunal Extinction

A major criticism of the "overkill" theory for the late Pleistocene extinction in the Americas has been the seeming implausibility of a relatively small number of humans selectively killing off millions of large-bodied mammals. Critics argue that early Paleoindian hunters had to be extremely selective to have produced the highly size-biased extinction pattern characteristic of this event. Here, we derive a probabilistic extinction model that predicts the extinction risk of mammals at any body mass without invoking selective human harvest. The new model systematically analyzes the variability in life-history characteristics, such as the instantaneous mortality rate, age of first reproduction, and the maximum net reproductive rate. It captures the body size-biased extinction pattern in the late Pleistocene and precisely predicts the percentage of unexpectedly persisting large mammals and extinct small ones. A test with a global late Quaternary mammal database well supports the model. The model also emphasizes that quantitatively analyzing patterns of variability in ecological factors can shed light on diverse behaviors and patterns in nature. From a macro-scale conservation perspective, our model can be modified to predict the fate of biota under the pressures from both climate change and human impacts.

Radiocarbon dates of late quaternary mammals in the Archangelsk Region and their contribution to reconstructions of the last glaciation in Eastern Europe

Twelve new AMS (Accelerator Mass Spectrometry) dates of large Quaternary mammal remains were reported: mammoth (Mammuthus primigenius, bison (Bison priscus), and musk ox (Ovibos pallantis) found in the Archangelsk Region. The absolute age of the identified samples varies from 46 000 to 22 000 calibrated years ago. These data suggest that a substantial part of the Archangelsk Region was not covered by ice during the indicated time interval.

Identification and importance of critical depositional gaps in pitfall cave environments: The fossiliferous deposit of Cuvieri Cave, eastern Brazil

The majority of extinct Brazilian late Quaternary mammal (i.e. megafauna) remains comes from cave deposits and was retrieved through excavations lacking detailed stratigraphical context. This poses a major problem since these deposits present multifaceted processes of formation. Based on the meticulous excavation of a pitfall site within Cuvieri Cave, Minas Gerais, eastern Brazil, this article describes a critical, albeit subtle, temporal discontinuity between different fossiliferous sedimentary facies and discusses its significance to the contextualization of the paleontological remains recovered from the site. The discontinuity was described based on sedimentary analyses, bone deposition processes, taxonomy and AMS radiocarbon chronology. Two facies were distinguished and named according to their color and texture: an upper dark brown silt-loam (BSL) and a lower dark reddish brown silt-loam (RBSL). Besides color differences, they present differences in grain size distribution and chemical composition. These analyses show that the RBSL has in its composition only half the sand and one third more the silt than BSL. It also shows that mean percent values for the RBSL in comparison to the BSL are higher for silica (42.35 versus 15.80), aluminum (18.63 versus 7.58) and iron (8.45 versus 3.79) and lower for calcium (10.07 versus 36.14) and volatiles (13.86 versus 30.10). These differences are attributed to changes in sediment source and entrance route. Differences were also observed in the faunal remain analyses. RBSL has abundant megafauna remains originally deposited within this facies, while the scarce megafauna material found in BSL is the result of mixing processes. Despite these differences, animal entrapment is considered the best scenario to explain bone accumulation in both facies. AMS radiocarbon dates indicate that the BSL was deposited during the Holocene, with dates ranging from 8580calyr BP to the present, while the RBSL deposition dates to the Holocene/Pleistocene transition (13,600–10,660calyr BP). Radiocarbon dating also indicates that the subtle erosional surface that limits both facies represents a temporal gap between a minimum age of 8.4calkyr BP and a maximum age of 11.0calkyr BP. The recognition of this discontinuity allows for a more accurate interpretation of bone accumulation, enabling the differentiation of faunal assemblages that might otherwise be considered part of a continuum.

Quaternary Mammal Communities: Relevance of the Individualistic Response and Non-Analogue Faunas

Frequent and repeated climate fluctuations of the late Quaternary serve as a “natural experiment” for the response of species to environmental change. Analysis of the FAUNMAP database documents individualistic shifts in the geographic distributions for late Quaternary mammals. However, because the individualistic response is not necessarily random and because many species share similar niche parameters, it is possible that some species appear to form coherent groups of core species. In reality their dispersals are individualistic with regard to rate and timing. The individualistic response of mammals, as well as that of other organisms, has created late Quaternary communities without modern analogues. This concept has profound implications for the design of biological reserves and for land use management with respect to future global climate change. However, the relevance of non-analogue mammal communities has been challenged by Alroy (1999), who claims that non-analogue associations were not common in the Quaternary and that they appeared to occur in both the Pleistocene and Holocene. Reexamination of his analysis shows that he employed a different definition for non-analogue faunas and that his methods of analyses created artificially low counts of non-analogue communities and consequently an underestimate of their importance.

The effects of late Quaternary climate and pCO2 change on C4 plant abundance in the south-central United States

The late Quaternary was a time of substantial environmental change, with the past 70,000 years exhibiting global changes in climate, atmospheric composition, and terrestrial floral and faunal assemblages. We use isotopic data and couple climate and vegetation models to assess the balance between C 3 and C 4 vegetation in Texas during this period. The carbon isotope composition of fossil bison, mammoth, and horse tooth enamel is used as a proxy for C 3 versus C 4 plant consumption, and indicates that C 4 plant biomass remained above 55% through most of Texas from prior to the Last Glacial Maximum (LGM) into the Holocene. These data also reveal that horses did not feed exclusively on herbaceous plants, consequently isotopic data from horses are not reliable indicators of the C 3 –C 4 balance in grassland biomes. Estimates of C 4 percentages from coupled climate–vegetation models illuminate the relative roles of climate and atmospheric carbon dioxide (CO 2 ) concentrations in shaping the regional C 4 signal. C 4 percentages estimated using observed modern climate–vegetation relationships and late Quaternary climate variables (simulated by a global climate model) are much lower than those indicated by carbon isotope values from fossils. When the effect of atmospheric CO 2 concentration on the competitive balance between C 3 and C 4 plants is included in the numerical experiment, however, estimated C 4 percentages show better agreement with isotopic estimates from late Quaternary mammals and soils. This result suggests that low atmospheric CO 2 levels played a role in the observed persistence of C 4 plants throughout the late Quaternary.

The effects of late Quaternary climate and pCO 2 change on C 4 plant abundance in the south-central United States

The late Quaternary was a time of substantial environmental change, with the past 70,000 years exhibiting global changes in climate, atmospheric composition, and terrestrial floral and faunal assemblages. We use isotopic data and couple climate and vegetation models to assess the balance between C 3 and C 4 vegetation in Texas during this period. The carbon isotope composition of fossil bison, mammoth, and horse tooth enamel is used as a proxy for C 3 versus C 4 plant consumption, and indicates that C 4 plant biomass remained above 55% through most of Texas from prior to the Last Glacial Maximum (LGM) into the Holocene. These data also reveal that horses did not feed exclusively on herbaceous plants, consequently isotopic data from horses are not reliable indicators of the C 3–C 4 balance in grassland biomes. Estimates of C 4 percentages from coupled climate–vegetation models illuminate the relative roles of climate and atmospheric carbon dioxide (CO 2) concentrations in shaping the regional C 4 signal. C 4 percentages estimated using observed modern climate–vegetation relationships and late Quaternary climate variables (simulated by a global climate model) are much lower than those indicated by carbon isotope values from fossils. When the effect of atmospheric CO 2 concentration on the competitive balance between C 3 and C 4 plants is included in the numerical experiment, however, estimated C 4 percentages show better agreement with isotopic estimates from late Quaternary mammals and soils. This result suggests that low atmospheric CO 2 levels played a role in the observed persistence of C 4 plants throughout the late Quaternary.

BODY MASS OF LATE QUATERNARY MAMMALS

The purpose of this data set was to compile body mass information for all mammals on Earth so that we could investigate the patterns of body mass seen across geographic and taxonomic space and evolutionary time. We were interested in the heritability of body size across taxonomic groups (How conserved is body mass within a genus, family, and order?), in the overall pattern of body mass across continents (Do the moments and other descriptive statistics remain the same across geographic space?), and over evolutionary time (How quickly did body mass patterns iterate on the patterns seen today? Were the Pleistocene extinctions size specific on each continent, and did these events coincide with the arrival of man?). These data are also part of a larger project that seeks to integrate body mass patterns across very diverse taxa (NCEAS Working Group on Body Size in Ecology and Paleoecology: linking pattern and process across space, time, and taxonomic scales). We began with the updated version of D. E. Wilson and D. M. Reeder's taxonomic list of all known Recent mammals of the world (N = 4629 species) to which we added status, distribution, and body mass estimates compiled from the primary and secondary literature. Whenever possible, we used an average of male and female body mass, which was in turn averaged over multiple localities to arrive at our species body mass values. The sources are line referenced in the main data set, with the actual references appearing in a table within the metadata. Mammals have individual records for each continent they occur on. Note that our data set is more than an amalgamation of smaller compilations. Although we relied heavily on a data set for Chiroptera by K. E. Jones (N = 905), the CRC handbook of Mammalian Body Mass (N = 688), and a data set compiled for South America by P. Marquet (N = 505), these represent less than half the records in the current database. The remainder are derived from more than 150 other sources. Furthermore, we include a comprehensive late Pleistocene species assemblage for Africa, North and South America, and Australia (an additional 230 species). “Late Pleistocene” is defined as approximately 11 ka for Africa, North and South America, and as 50 ka for Australia, because these times predate anthropogenic impacts on mammalian fauna. Estimates contained within this data set represent a generalized species value, averaged across sexes and geographic space. Consequently, these data are not appropriate for asking population-level questions where the integration of body mass with specific environmental conditions is important. All extant orders of mammals are included, as well as several archaic groups (N = 4859 species). Because some species are found on more than one continent (particularly Chiroptera), there are 5731 entries. We have body masses for the following: Artiodactyla (280 records), Bibymalagasia (2 records), Carnivora (393 records), Cetacea (75 records), Chiroptera (1071 records), Dasyuromorphia (67 records), Dermoptera (3 records), Didelphimorphia (68 records), Diprotodontia (127 records), Hydracoidea (5 records), Insectivora (234 records), Lagomorpha (53 records), Litopterna (2 records), Macroscelidea (14 records), Microbiotheria (1 record), Monotremata (7 records), Notoryctemorphia (1 record), Notoungulata (5 records), Paucituberculata (5 records), Peramelemorphia (24 records), Perissodactyla (47 records), Pholidota (8 records), Primates (276 records), Proboscidea (14 records), Rodentia (1425 records), Scandentia (15 records), Sirenia (6 records), Tubulidentata (1 record), and Xenarthra (75 records).

Determinants of loss of mammal species during the Late Quaternary 'megafauna' extinctions: life history and ecology, but not body size.

Extinctions of megafauna species during the Late Quaternary dramatically reduced the global diversity of mammals. There is intense debate over the causes of these extinctions, especially regarding the extent to which humans were involved. Most previous analyses of this question have focused on chronologies of extinction and on the archaeological evidence for human-megafauna interaction. Here, I take an alternative approach: comparison of the biological traits of extinct species with those of survivors. I use this to demonstrate two general features of the selectivity of Late Quaternary mammal extinctions in Australia, Eurasia, the Americas and Madagascar. First, large size was not directly related to risk of extinction; rather, species with slow reproductive rates were at high risk regardless of their body size. This finding rejects the 'blitzkrieg' model of overkill, in which extinctions were completed during brief intervals of selective hunting of large-bodied prey. Second, species that survived despite having low reproductive rates typically occurred in closed habitats and many were arboreal or nocturnal. Such traits would have reduced their exposure to direct interaction with people. Therefore, although this analysis rejects blitzkrieg as a general scenario for the mammal megafauna extinctions, it is consistent with extinctions being due to interaction with human populations.

Radiocarbon Chronologies and Extinction Dynamics of the Late Quaternary Mammalian Megafauna of the Taimyr Peninsula, Russian Federation

This paper presents 75 new radiocarbon dates based on late Quaternary mammal remains recovered from eastern Taimyr Peninsula and adjacent parts of the northern Siberian lowlands, Russian Federation, including specimens of woolly mammoth (Mammuthus primigenius), steppe bison (Bison priscus), muskox (Ovibos moschatus), moose (Alces alces), reindeer (Rangifer tarandus), horse (Equus caballus) and wolf (Canis lupus). New evidence permits reanalysis of megafaunal extinction dynamics in the Asian high Arctic periphery. Increasingly, radiometric records of individual species show evidence of a gap at or near the Pleistocene/Holocene boundary (PHB). In the past, the PHB gap was regarded as significant only when actually terminal, i.e., when it marked the apparent “last” occurrence of a species (e.g., current “last” occurrence date for woolly mammoth in mainland Eurasia is 9600yr bp ). However, for high Arctic populations of horses and muskoxen the gap marks an interruption rather than extinction, because their radiocarbon records resume, nearly simultaneously, much later in the Holocene. Taphonomic effects, ΔC14 flux, and biased sampling are unlikely explanations for these hiatuses. A possible explanation is that the gap is the signature of an event, of unknown nature, that prompted the nearly simultaneous crash of many megafaunal populations in the high Arctic and possibly elsewhere in Eurasia.

Defining climate's role in ecosystem evolution: Clues from late quaternary mammals

Mammalian communities alter their taxonomic composition through time as the species composing them change their biogeographic range, become extinct, or evolve into new species. When taxonomic compositions change through these processes, inevitably the links between taxa and communities change too, resulting in evolution from one ecosystem into the next. Late Quaternary examples suggest that on a timescale encompassing a few thousand to a few hundred thousand years (the “multi‐millennial timescale), climatic change is perhaps the most important driver of ecosystem evolution because it periodically forces biogeographic changes and extinction. Climatic change over this timescale, which essentially slips between “geological time”; and “ecological time”;, is not very closely in phase with population‐level evolution of a species analyzed for this study, the meadow vole Microtus pennsylvanicus; therefore climatic oscillations on the multi‐millennial timescale may not stimulate speciation much. Instead, speciati...

Late Quaternary Mammals from the Hueco Mountains, El Paso and Hudspeth Counties, Texas

Late Quaternary Mammals from the Hueco Mountains, El Paso and Hudspeth Counties, Texas