Robert S. Feranec

Isotopic discrimination of resource partitioning among ungulates in C3-dominated communities from the Miocene of Florida and California

Abstract Stable isotope analysis of mammalian tooth enamel is a valuable method for examining resource partitioning in modern and ancient environments where there is a mixture of C3 and C4 plants. However, before 7 Ma North American ecosystems were composed predominantly of C3 plants, complicating isotopic assessment of resource partitioning. Study of modern African and North American ecosystems has shown that niche partitioning among mammals may be discerned in communities dominated by C3 plants, suggesting that a similar approach may work for ancient C3 ecosystems. Here, such analyses are applied to explore resource use and niche partitioning in two ancient C3-dominated communities, one from California and one from Florida. Each locality, Black Hawk Ranch (California) and the Love Bone Bed (Florida), occurs in Miocene deposits that accumulated prior to the rapid increase in C4 ecosystems 7 Myr ago. δ13C and δ18O values were obtained from the tooth enamel of eight species from Black Hawk Ranch, and 15 species from the Love Bone Bed. Results from the 197 bulk isotope samples showed significant differences in δ13C among taxa at the Love Bone Bed, but no significant differences were observed among taxa at Black Hawk Ranch. At both localities, equids generally have more positive δ13C values than co-occurring taxa, suggesting that equids occupied more open habitats, whereas antilocaprids, camelids, and proboscideans have more negative values, implying utilization of more closed communities. One result of note is the positive δ13C values of Pediomeryx (Yumaceras) hamiltoni from the Love Bone Bed, which suggests that P. (Y.) hamiltoni incorporated abundant fiber, possibly grass, in the diet similar to the horses from this locality. The lack of significant differences among taxa at Black Hawk Ranch may indicate a relatively homogeneous flora, or presence of abundant resources permitting niche overlap, whereas the opposite is implied by the presence of significantly different isotope values among taxa at the Love Bone Bed. The results from this study highlight the utility of isotopic techniques allowing discernment of resource partitioning in C3-dominated landscapes such as those that persisted for the millions of years before the rapid increase in C4 ecosystems that occurred during the late Miocene.

Stable isotopes, hypsodonty, and the paleodiet of Hemiauchenia (Mammalia: Camelidae): a morphological specialization creating ecological generalization

Abstract Morphological adaptations may indicate increased specialization (narrowing of ecological niche) or expansion of the suite of lifestyles available to an organism (increasing niche breadth). Hypsodonty in mammals generally has been interpreted as a specialization into a grazing niche from a browsing niche. Here I examine the feeding strategy of the extinct hypsodont camel Hemiauchenia through an analysis of stable carbon isotope values from its tooth enamel, which was used to clarify its feeding strategy and to resolve conflicting interpretations of dental versus muzzle attributes. The paleodiet of Hemiauchenia is then used to test whether hypsodonty correlates to grazing within fossil Lamini. This study focuses on fossils from Florida, which is geographically ideal because unlike other regions of the country almost all extant plants on which animals browse use the C3 photosynthetic pathway. In contrast, most of the grasses and sedges utilized by grazers use the C4 photosynthetic pathway. If Hemiauchenia was an obligate grazer, the stable carbon isotope values of tooth enamel should reflect primarily a diet of C4 grass and sedge (>−1.3‰). If Hemiauchenia was mainly a browser, the isotopic value should be considerably more negative reflecting ingestion primarily of C3 browse (<−7.9‰). The mean δ13C values for Hemiauchenia during each time interval average more negative than −8.0‰, indicating a dominantly C3 browse diet, and there is no evidence for abandonment of the browsing niche from the Hemphillian through the Rancholabrean North American Land Mammal Ages. However, an increase in the range of isotopic values indicates a diet with a higher proportion of C4 grasses and sedges through time. This study therefore suggests that Hemiauchenia was a hypsodont intermediate feeder with preference for browse during the past 5 million years. Hypsodonty is not strictly associated with obligate grazing; instead it may, in this case, represent an adaptation to widen niche breadth that allowed grazing as well as browsing.

Effects of global warming on ancient mammalian communities and their environments.

Background Current global warming affects the composition and dynamics of mammalian communities and can increase extinction risk; however, long-term effects of warming on mammals are less understood. Dietary reconstructions inferred from stable isotopes of fossil herbivorous mammalian tooth enamel document environmental and climatic changes in ancient ecosystems, including C3/C4 transitions and relative seasonality. Methodology/Principal Findings Here, we use stable carbon and oxygen isotopes preserved in fossil teeth to document the magnitude of mammalian dietary shifts and ancient floral change during geologically documented glacial and interglacial periods during the Pliocene (∼1.9 million years ago) and Pleistocene (∼1.3 million years ago) in Florida. Stable isotope data demonstrate increased aridity, increased C4 grass consumption, inter-faunal dietary partitioning, increased isotopic niche breadth of mixed feeders, niche partitioning of phylogenetically similar taxa, and differences in relative seasonality with warming. Conclusion/Significance Our data show that global warming resulted in dramatic vegetation and dietary changes even at lower latitudes (∼28°N). Our results also question the use of models that predict the long term decline and extinction of species based on the assumption that niches are conserved over time. These findings have immediate relevance to clarifying possible biotic responses to current global warming in modern ecosystems.

Understanding specifics in generalist diets of carnivorans by analyzing stable carbon isotope values in Pleistocene mammals of Florida

Abstract Within ancient ecosystems, it is generally difficult to determine the specific diets of species from higher trophic levels, which in turn hinders our understanding of trophic relationships and energy flow through these systems. To better understand the ecology of taxa at higher trophic levels, we used analysis of tooth enamel stable carbon isotope values to infer the dietary preferences of Canis edwardii and Smilodon gracilis from the Leisey Shell Pit 1A (LSP 1A) and Inglis 1A, two Pleistocene localities in Florida. The goals of the analyses were to (1) determine whether these carnivorans specialized in particular prey types or maintained a generalist diet; (2) ascertain whether carbon isotope values support what was previously suggested about the ecology of these species; and (3) establish what ecological details of ancient food webs can be discovered by carbon isotope analyses at higher trophic levels. Results show that the sampled carnivoran carbon isotope values are distributed among suspected prey isotope values, suggesting that varied prey were taken at the study localities. Prey compositions were modeled for each carnivoran species by using Stable Isotope Analysis in R (SIAR). The modeled diets indicate that each studied carnivoran had a generalist diet; however, there are differences in how these taxa achieved dietary generalization. At the glacial Inglis 1A locality, sampled individuals of C. edwardii and S. gracilis show similar isotope values and modeled dietary prey proportions, although both carnivorans do show a preference for grazing prey species. The similar isotopic values, and calculated prey proportions, observed between these species may imply greater interspecific competition for food. At the interglacial LSP 1A locality, C. edwardii shows values similar to those observed at Inglis 1A. In contrast, the data for S. gracilis shows a preference for consuming browsing prey species. Further, its restricted range of carbon isotope values suggests that S. gracilis may have concentrated its feeding within a particular habitat. Examination of stable carbon isotope values among species at higher trophic levels reveals that some intricacies of ancient food webs can be discerned.

AMS RADIOCARBON DATES FROM PLEISTOCENE AND HOLOCENE MAMMALS HOUSED IN THE NEW YORK STATE MUSEUM, ALBANY, NEW YORK, USA

To obtain the appropriate samples, the preparation procedures generally follow Brown et al. (1988) and Bronk Ramsey et al. (2004). Samples were first decalcified using 0.5N HCl to obtain collagen, generally for 24–48 hr. Once decalcified, collagen was then gelatinized at 58 C for 16 hr. Afterwards, the gelatin solution was filtered to remove any remaining solids. The solution was then ultrafiltered to remove the 30-kD fraction, which was then lyophilized. In general, lyophilized collagen appeared similar to a white cotton ball. Graphitization and analysis were conducted at the National Oceanic Sciences Accelerator Mass Spectrometry (NOSAMS) facility. All dates were calibrated using the online CALIB 5.0.2 program (Stuiver et al. 2005). The calibrated dates reported below represent the 2-age range.

Exploring the Potential of Laser Ablation Carbon Isotope Analysis for Examining Ecology during the Ontogeny of Middle Pleistocene Hominins from Sima de los Huesos (Northern Spain).

Laser ablation of tooth enamel was used to analyze stable carbon isotope compositions of teeth of hominins, red deer, and bears from middle Pleistocene sites in the Sierra de Atapuerca in northern Spain, to investigate the possibility that this technique could be used as an additional tool to identify periods of physiological change that are not detectable as changes in tooth morphology. Most of the specimens were found to have minimal intra-tooth variation in carbon isotopes (< 2.3‰), suggesting isotopically uniform diets through time and revealing no obvious periods of physiological change. However, one of the two sampled hominin teeth displayed a temporal carbon isotope shift (3.2‰) that was significantly greater than observed for co-occurring specimens. The δ13C value of this individual averaged about -16‰ early in life, and -13‰ later in life. This isotopic change occurred on the canine crown about 4.2 mm from the root, which corresponds to an approximate age of two to four years old in modern humans. Our dataset is perforce small owing to the precious nature of hominid teeth, but it demonstrates the potential utility of the intra-tooth isotope profile method for extracting ontogenetic histories of human ancestors.

Radiocarbon dates from the pleistocene fossil deposits of samwel cave, Shasta County, California, USA

Dates obtained from the collagen of 5 mammals from the fossil deposits of Samwel Cave, Shasta County, Cal- ifornia, USA, show emplacement during the last glacial maximum. These dates support the assignment of the fauna to the late Pleistocene. The Samwel Cave deposits currently do not appear to be stratified.

NEW POPULATIONS AND BIOGEOGRAPHIC PATTERNS OF THE GEOMYID RODENTS LIGNIMUS AND MOJAVEMYS FROM THE BARSTOVIAN OF WESTERN MONTANA

Abstract New dental specimens described here from the Barstovian CC South and Flint Creek localities of western Montana are determined to be of two geomyid rodent species, Lignimus transversus and Mojavemys sp. These species were known previously from sparse material and the new samples aid the clarification of their biogeography and evolution. The presence of Lignimus transversus at both localities extends the range of that species to the north. In Mojavemys, a cline of increasing tooth size from south to north is analogous to clines in extant geomyids that correlate with nutritional or climatic gradients. Comparisons of various dental morphologic features of the new material and of the previously described populations of both genera reveal that the examined traits as well as the populations themselves were not genetically linked, and suggest mosaic evolution operated in these species. The differences in dental morphology between the various depositional basins are consistent with the idea of a tectonic influence on mammalian evolution.

Using a Novel Absolute Ontogenetic Age Determination Technique to Calculate the Timing of Tooth Eruption in the Saber- Toothed Cat, Smilodon fatalis

Despite the superb fossil record of the saber-toothed cat, Smilodon fatalis, ontogenetic age determination for this and other ancient species remains a challenge. The present study utilizes a new technique, a combination of data from stable oxygen isotope analyses and micro-computed tomography, to establish the eruption rate for the permanent upper canines in Smilodon fatalis. The results imply an eruption rate of 6.0 millimeters per month, which is similar to a previously published average enamel growth rate of the S. fatalis upper canines (5.8 millimeters per month). Utilizing the upper canine growth rate, the upper canine eruption rate, and a previously published tooth replacement sequence, this study calculates absolute ontogenetic age ranges of tooth development and eruption in S. fatalis. The timing of tooth eruption is compared between S. fatalis and several extant conical-toothed felids, such as the African lion (Panthera leo). Results suggest that the permanent dentition of S. fatalis, except for the upper canines, was fully erupted by 14 to 22 months, and that the upper canines finished erupting at about 34 to 41 months. Based on these developmental age calculations, S. fatalis individuals less than 4 to 7 months of age were not typically preserved at Rancho La Brea. On the whole, S. fatalis appears to have had delayed dental development compared to dental development in similar-sized extant felids. This technique for absolute ontogenetic age determination can be replicated in other ancient species, including non-saber-toothed taxa, as long as the timing of growth initiation and growth rate can be determined for a specific feature, such as a tooth, and that growth period overlaps with the development of the other features under investigation.

A new record of ringed seal (Pusa hispida) from the late Pleistocene Champlain Sea and comments on its age and paleoenvironment

The Champlain Sea, the most recent interior seaway of northeastern North America, resulted from late Pleistocene recession of the Laurentide Ice Sheet (LIS) and subsequent isostatic depression of the Champlain and St. Lawrence valleys (Gadd, 1988; Rayburn et al., 2007; Cronin et al., 2008, 2012). This sea existed for about 4000 years, from 13.1 to 9.0 ka (Cronin et al., 2008), and Champlain Sea sediments contain abundant marine microfauna (e.g., foraminifera, ostracods; Cronin, 1988; Hunt and Rathburn, 1988) and macrofauna (e.g., bivalves, mammals; Harington, 1988; McAllister et al., 1988; Rodrigues, 1988). Here we report the discovery of a new specimen of phocid seal from southern Champlain Sea sediments (Fig. 1), and its age. We also report the age of a previously described Phoca vitulina (harbor seal) from a nearby locality (Ray, 1983), and discuss the paleoenvironmental implications of the geographic location and ages of these two phocid specimens. Institutional Abbreviations—AMNH, American Museum of Natural History, New York, New York; NYSM, New York State Museum, Albany, New York; NOSAMS, National Ocean Sciences Accelerator Mass Spectrometry Facility; SUNY, State University of New York.