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Introduction
Publications
Publications (209)
Prediction of future ice-sheet behavior in Antarctica and its contribution to sea-level rise depends on accurate understanding of ice-sheet response to a warm climate. Examination of how the ice sheet reacted to past warm episodes affords a means of assessing its tolerances to climate change. The West Antarctic Ice Sheet (WAIS), in particular, is t...
Chimpanzees (Pan troglodytes) are patrilocal, with males remaining in their natal group and females dispersing when they reach sexual maturity. However, the details of female chimpanzee dispersal, such as their possible origin, are difficult to assess, even in habituated groups under long-term study. To assess intergroup differences and sex-biased...
The Red Sea was witness to important events during human history, including the first long steps in a trade network (the spice route) that would drive maritime technology and shape geopolitical fortunes for thousands of years. Punt was a pivotal early node in the rise of this enterprise, serving as an important emporium for luxury goods, including...
We report on an accumulation of mummified southern elephant seals (Mirounga leonina) from Inexpressible Island on the Victoria Land Coast (VLC), western Ross Sea, Antarctica. This accumulation is unusual, as elephant seals typically breed and molt on sub‐Antarctic islands further north and do not currently occupy the VLC. Prior ancient DNA analyses...
Stable isotopes are important ecological tools, because the carbon and nitrogen isotopic composition of consumer tissue reflects the diet. Measurements of isotopes of individual amino acids can disentangle the effects of consumer physiology from spatiotemporal variation in dietary isotopic values. However, this approach requires knowledge of assimi...
The arrival of humans to Antarctica’s Ross Sea (100+ years ago) led to a slow, but sustained increase in human activities in the area. To investigate if human presence has influenced the structure of the ecosystem over the last century, we compared historical (ca 100 years old) and modern samples of a sentinel species, the Weddell seal (Leptonychot...
We investigate resource and habitat use by apex predators through stable isotope analysis at two Spanish Late Miocene localities: Los Valles de Fuentidueña (~9.6 Ma, LVF) and Cerro de los Batallones (~9.1 Ma, BAT). The temporal window represented by LVF and BAT was crucial in the shaping of the current Iberian mammalian structure because it corresp...
Scat is frequently used to study animal diets because it is easy to find and collect, but one concern is that gross fecal analysis (GFA) techniques exaggerate the importance of small-bodied prey to mammalian mesopredator diets. To capitalize on the benefits of scat, we suggest the analysis of scat carbon and nitrogen isotope values (δ¹³C and δ¹⁵N)....
Correlations by dietary proxy.
Correlations between scat C:N ratio, δ15N and δ13C and frequency of animal material occurrence (left column), percent volume animal material (middle column) and mean proportion meat consumed (right column).
(EPS)
Δ15N by diet type.
Boxplots depicting nitrogen discrimination factors for four different types of mammalian feeders: herbivores, omnivores, carnivores and insectivores.
(EPS)
Coyote diet-space corrections.
Organism- and tissue-specific isotope discrimination factors applied to coyote food source δ13C and δ15N values before input into the SIAR mixing model.
(DOCX)
Test of the effects of rinsing following acidification.
δ15N values measured in split scat samples that were either rinsed (dark grey) or not rinsed (light grey) after acidification. The mean sample difference is -0.1‰, which is indistinguishable from instrumental error (± 0.1‰).
(EPS)
Mixing model input.
Isotope values and digestible [C] and [N] values measured in items identified in each scat sample for input into the mixing models. Food source δ13C and δ15N values are converted to coyote diet space using discrimination factors listed Table S2.
(DOCX)
Published diet-to-feces Δ15N values in mammals.
(DOCX)
We assessed the effects of herbivory on competition, water stress, and potentially biological nitrogen fixation on three species of endemic shrubs using variations in the stable isotope ratios (13C/12C and 15N/14N) in leaves of chaparral shrubs in a long-term field experiment. While variations in isotopic ratios of plants are often attributed to ab...
BACKGROUND: The pace and magnitude of human-caused global change has accelerated dramatically over the past 50 years, overwhelming the capacity of many ecosystems and species to maintain themselves as they have under the more stable conditions that prevailed for at least 11,000 years. The next few decades threaten even more rapid transformations be...
Sharks migrate annually over large distances and occupy a wide variety of habitats, complicating analysis of lifestyle and diet. A biogeochemical technique often used to reconstruct shark diet and environment preferences is stable isotope analysis, which is minimally invasive and integrates through time and space. There are previous studies that fo...
Wild members of Camelidae live in some of the most arid environments, including North Africa, Arabia, the Gobi Desert of China and Mongolia and high elevation environments in the Andes Mountains. A better understanding of the paleoecology of the three most abundant Pleistocene camelids (Camelops, Hemiauchenia, and Palaeolama) may clarify modern ada...
The ability of salmon to navigate from the ocean back to their river of origin to spawn acts to reinforce local adaptation and maintenance of unique and heritable traits among salmon populations. Here, the extent to which Chinook salmon Oncorhynchus tshawytscha from the same freshwater breeding groups associate together in the ocean at regional and...
The end of the Pleistocene was marked by the extinction of almost all large
land mammals worldwide except in Africa. Although the debate on Pleistocene
extinctions has focused on the roles of climate change and humans, the
impact of perturbations depends on properties of ecological communities,
such as species composition and the organization of ec...
Humans now play a major role in altering Earth and its biota. Finding ways to ameliorate human impacts on biodiversity and to sustain and restore the ecosystem services on which we depend is a grand scientific and societal challenge. Conservation paleobiology is an emerging discipline that uses geohistorical data to meet these challenges by develop...
Our recent paper used artistic depictions of animals and fossil evidence to examine the community-level effects of local extinction events over 6,000 y of Egyptian history (1). We found that local extinctions were nonrandom, that changes to community structure (quantified by the species predator/prey ratio) seemed to correspond to local aridificati...
Climatic variation alters biochemical and ecological processes, but it is difficult both to quantify the magnitude of such changes, and to differentiate long-term shifts from inter-annual variability. Here, we simultaneously quantify decade-scale isotopic variability at the lowest and highest trophic positions in the offshore California Current Sys...
Significance
The composition of animal communities directly impacts the stability of ecosystems. Here, we use historical information of species extinctions in Egypt over 6,000 years to reconstruct predator–prey interactions and determine to what extent observed changes in species composition influence predictions of community stability. Our study r...
Background/Question/Methods
As studies using stable isotopes to infer the diets and foraging behaviors of wild animals increase, the importance of species-specific diet-to-tissue discrimination factors is becoming more apparent. Many authors have shown that different tissues have different isotopic values, due either to isotopic routing or to var...
2014): The effects of sex, tissue type, and dietary components on stable isotope discrimination factors (Δ 13 C and Δ 15 N) in mammalian omnivores makes every effort to ensure the accuracy of all the information (the "Content") contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representa...
We used carbon (delta C-13) and nitrogen (delta N-15) stable isotopes derived from the tissues of American black bears (Ursus americanus) to estimate the proportion of human-derived foodstuffs and food waste ("human foods") in the diets of human food-conditioned bears over the past century in Yosemite National Park, located in central-eastern Calif...
Genetic diversity provides the raw material for populations to respond to changing environmental conditions. The evolution of diversity within populations is based on the accumulation of mutations and their retention or loss through selection and genetic drift, while migration can also introduce new variation. However, the extent to which populatio...
During the Late Cretaceous, central Nevada may have been a high elevation plateau, the Nevadaplano; some geodynamic models of the western US require thickened crust and high elevations during the Mesozoic to drive the subsequent tectonic events of the Cenozoic while other models do not. To test the hypothesis of high elevations during the late Meso...
Foraging is constrained by the energy within resources and the mechanics of acquisition and assimilation. Thick molar enamel, a character trait differentiating hominins from African apes, is predicted to mitigate the mechanical costs of chewing obdurate foods. The classic expression of hyperthick enamel together with relatively massive molars, term...
Although crabeater seals Lobodon carcinophaga are among the most abundant consumers of Antarctic krill Euphausia superba, their diet has rarely been studied throughout most of the species’ range. Using
Stable-isotope ratios of carbon (C-13/C-12; delta C-13) and nitrogen (N-15/N-14; delta N-15) in animal tissues are analyzed to estimate animal foraging ecology because these ratios reflect those of an animal's diet. This reflection is generally indirect, as stable-isotope ratios change with trophic level. These differences, called discrimination fa...
Climatic and environmental shifts have had profound impacts on faunal and floral assemblages globally since the end of the Miocene. We explore the regional expression of these fluctuations in southwestern Europe by constructing long-term records (from ∼11.1 to 0.8 Ma, late Miocene-middle Pleistocene) of carbon and oxygen isotope variations in tooth...
Statistical analyses comparing different mammalian taxa per MN. Student-t test was used for those MNs where we sampled two genera, whilst ANOVA test was used for those MNs with more than 2 genera. Significant differences are highlighted in bold.
(XLS)
Site, MN, age (Ma), signature, family, taxa, tooth, δ13CCO3 (‰ VPDB), δ18OCO3 (‰ VSMOW) and δ18OPO4 (‰ VSMOW) values for the whole set of fossil mammals from the Iberian Peninsula. Age from Domingo et al. [16, unpublished data]. In the “Tooth” column: M = molar, P = premolar, superscript = upper teeth, subscript = lower teeth.
(XLS)
δ13Cenamel (‰ VPDB) values of the whole set of Iberian mammalian fossil tooth enamel.
1δ13Cdiet (‰ VPDB) calculated by using the offset of 14,1‰ between δ13Cenamel and δ13Cdiet proposed by Cerling and Harris [39]. 2δ13CatmCO2 (‰ VPDB) is from Tipple et al. [40]. 3δ13Cdiet, meq (‰ VPDB) was calculated using equation (2) (see text) and using the mode...
Equations used to calculate δ18Ow values from mammalian tooth enamel δ18OPO4 values.
(XLS)
Compound-specific isotope analysis of individual amino acids (AA) is a rapidly growing tool in ecological studies to assess diet and trophic position (TP) in both modern and ancient foodwebs. We conducted the first controlled feeding study examining d15N values in AAs in a marine mammal (harbor seal Phoca vitulina). The pattern of d15N variation am...
Species interactions form food webs, impacting community structure and, potentially, ecological dynamics. It is likely that global climatic perturbations that occur over long periods of time have a significant influence on species interaction patterns. Here, we integrate stable isotope analysis and network theory to reconstruct patterns of trophic...
During the early Paleogene, climate in continental interiors is thought to have been warmer and more equable than today, but estimates of seasonal temperature variations during this period are limited. Global and regional climate models of the Paleogene predict cooler temperatures for continental interiors than are implied by proxy data and predict...
There is growing evidence for individuality in dietary preferences and foraging behaviors within populations of various species. This is especially important for apex predators, since they can potentially have wide dietary niches and a large impact on trophic dynamics within ecosystems. We evaluate the diet of an apex predator, the white shark (Car...
Photo showing annual growth bands before (left) and after drilling (right) on specimen WS101. Ages are also noted next to the growth bands.
(TIF)
The compiled prey isotope values from the literature and unpublished data used in Figure 2.
(DOC)
The ontogeny of δ13C values for the 15 white sharks analyzed for this study. Individuals are in the same A, B, and C groups as Figure 1.
(TIF)
Baboons regularly drink surface waters derived from atmospheric precipitation, or meteoric water. As a result, the oxygen isotope (δ(18)O) composition of their tissues is expected to reflect that of local meteoric waters. Animal proxies of the oxygen isotope composition of meteoric water have practical applications as paleoenvironmental recorders b...
Growth rates for each individual throughout experiment. Individual symbols correspond to those used in Figure 1. Growth rates remain steady for two individuals, but the individual represented by “•” had low hematocrit values and a reduced growth rate.
The mole percents of individual AAs in plasma, RBC, and muscle with treatment are listed.
Background/Question/Methods
Coyotes (Canis latrans) have been shown to facilitate and benefit from marine subsidies and can also have cascading impacts on other predators and prey. Identifying the past and present role coyotes play in linking land and sea, and whether those links are lost or gained through time, will therefore have important impli...
Patterns of species interactions affect the dynamics of food webs. An important component of species interactions that is rarely considered with respect to food webs is the strengths of interactions, which may affect both structure and dynamics. In natural systems, these strengths are variable, and can be quantified as probability distributions. We...
The foraging ecology of elasmobranchs (sharks, skates, and rays) is difficult to study because species have spatially and temporally diverse diets. Many diet and habitat preference studies for mammals, birds, and teleosts use stable isotope analysis, but interpretations are limited for elasmobranch studies because taxon-specific isotope discriminat...
The Middle Miocene underwent profound climatic perturbations detected in worldwide marine and continental records. The Miocene Climatic Optimum (~ 17 to 14 Ma), a warm and humid period, was followed by the Middle Miocene Cooling (~ 14–13.8 Ma) characterized by a sharp drop in temperatures and an increase in aridity triggered by the reestablishment...
Population sizes and movement patterns of ungulate grazers and their predators have fluctuated dramatically over the past few centuries, largely owing to overharvesting, land-use change and historic management. We used δ(13)C and δ(15)N values measured from bone collagen of historic and recent gray wolves and their potential primary prey from Yello...
Although crabeater seals Lobodon carcinophaga are among the most abundant consumers of Antarctic krill Euphausia superba, their diet has rarely been studied throughout most of the species’ range. Using δ13C and δ15N values in vibrissae from 53 seals, we examined the trophic ecology of crabeater seals from the western Antarctic Peninsula (wAP) in 20...
The lemurs of Madagascar represent a prodigious adaptive radiation. At least 17 species ranging from 11 to 160 kg have become extinct during the past 2000 years. The effect of this loss on contemporary lemurs is unknown. The concept of competitive release favours the expansion of living species into vacant niches. Alternatively, factors that trigge...
We used genetic and stable isotope analysis of hair from free-ranging black bears (Ursus americanus) in Yosemite National Park, California, USA to: 1) identify bears that consume human food, 2) estimate the diets of these bears, and 3) evaluate the Yosemite human–bear management program. Specifically, we analyzed the isotopic composition of hair fr...
Stable isotope analysis has provided insight into the dietary and habitat patterns of many birds, mammals and teleost fish. A crucial biological parameter to interpret field stable isotope data is tissue incorporation rate, which has not been well studied in large ectotherms. We report the incorporation of carbon and nitrogen into the tissues of le...
Carbonate clumped isotope (Δ_(47)) thermometry provides an independent test of the metrics used to assess the preservation of carbonate rocks and fossils. Additionally, Δ_(47) thermometry, when combined with other geochemical and structural measurements, may establish whether diagenesis occurred under closed-system conditions, open-system condition...
Alligators and crocodiles differ in their physiological capacity to live in saline waters.
Crocodiles can tolerate high-salinity water, at least for limited timeframes, whereas alligators and
their close relatives cannot. Experiments have placed different crocodylians in various water
salinities to document physiological responses, but no study has...
Identifying individuals' foraging strategies is critical to understanding the ecology of a species, and can provide the means to predict possible ecological responses to environmental change. Our study combines stable isotope analysis and satellite telemetry to study the variability in individual foraging strategies of adult female southern elephan...
The relationship between central Asian aridification and the evolution of the Himalayan–Tibetan orogen remains elusive. New isotopic data from pedogenic and lacustrine carbonates sampled from well-dated Neogene strata (15.7–1.8Ma) in the northeastern Qaidam basin of the northern Tibetan Plateau identify a positive shift of ~2.5‰ in δ18O values from...
Disentangling local to regional paleoclimatic signals from
paleoelevation changes in the terrestrial sedimentary record is
challenging, and can be done with confidence only by compiling spatially
and temporally distributed datasets (preferably drawing on diverse
proxies). Spatial coverage is particularly important for paleoelevation
reconstruction...
Aim We sought to quantify geographical variation in the stable isotope values of mouse lemurs (Microcebus) and to determine whether this variation reflects trophic differences among populations or baseline isotopic differences among habitats. If the latter pattern is demonstrated, then Microcebus can become a proxy for tracking baseline habitat iso...
Stable isotope analysis has the potential to expand our understanding of elasmobranch ecology. However, elasmobranchs share
unique traits (i.e., retention of urea, lack of adipose tissue, cartilaginous skeletons) that require modified preparation
techniques. Alternative tissue collection and preservation methods would allow sampling from ichthyolog...
Background/Question/Methods
The effects of long-term climatic drivers on the structure and dynamics of megafaunal food-webs are poorly understood, primarily due to the time-scale on which these processes operate. In the Fairbanks, AK region of Beringia, a series of extinctions and species introductions coincided with increasing aridity and decrea...
Species accumulation curve (± SD) of the prey observed in the diet of Haustrum scobina at Tauranga Head, constructed using feeding survey observations as the unit of sampling [34]. Gotelli N.J. & Colwell R.K. (2001). Quantifying biodiversity: procedures and pitfalls in the measurement and comparison of species richness. Ecol. Lett., 4, 379–391.
(EP...
An analysis of the New Zealand system excluding the prey Patelloida corticata (Pc). As expected, there are slight differences in original MixSIR results, however, applying prey availability data to the overlapping prey Mg and Xp results in a similar increase in the accuracy of prey contribution estimations. A) ln-ln-transformed regression of biomas...
Manipulation of the isotopic overlap of prey. A) A mixing space with 2 non-overlapping prey (green, red), two overlapping prey (blue, orange), and a single consumer (black). Here, the overlap of blue and orange prey (wblue,orange) = 1. B) MixSIR estimates of % contribution to diet for each prey associated with Fig. S.3.A. Green and red are predicte...
Bayesian mixing models have allowed for the inclusion of uncertainty and prior information in the analysis of trophic interactions using stable isotopes. Formulating prior distributions is relatively straightforward when incorporating dietary data. However, the use of data that are related, but not directly proportional, to diet (such as prey avail...
Understanding how seasonal temperatures on land respond to global greenhouse climate conditions is important for
predicting effects of climate change on ecosystem structure, agriculture and distributions of natural resources. Fossil floral
and faunal assemblages suggest winter temperatures in middle and high latitude continental interiors during th...
We are pleased that the results of Kohn (1) so strongly support our findings published earlier in PNAS (2). Both studies (1, 2) analyzed published measurements of the carbon isotope composition of plants and quantified relationships between isotopic fractionation and environmental factors at large spatial scales. These relationships will be useful...
Biostratigraphic, chemostratigraphic, and magnetostratigraphic studies of the Paleocene and early Eocene sediments in the Nanxiong Basin of Guangdong, Chijiang Basin of Jiangxi, Qianshan Basin of Anhui, Hengyang Basin of Hunan, and Erlian Basin of Nei Mongol, China, provide the first well-resolved geochronological constraints on stratigraphic frame...
Stable carbon and nitrogen isotope ratios (δ13C and δ15N) of serum, red blood cells (RBC), muscle, and blubber were measured in captive and wild northeast Pacific harbor seals (Phoca vitulina richardii) at three coastal California sites (San Francisco Bay, Tomales Bay, and Channel Islands). Trophic discrimination factors (ΔTissue-Diet) were calcula...