An atmospheric pCO2 reconstruction across the Cretaceous-Tertiary boundary from leaf megafossils

The end-Cretaceous mass extinctions, 65 million years ago, profoundly influenced the course of biotic evolution. These extinctions coincided with a major extraterrestrial impact event and massive volcanism in India. Determining the relative importance of each event as a driver of environmental and biotic change across the Cretaceous-Tertiary boundary (KTB) crucially depends on constraining the mass of CO(2) injected into the atmospheric carbon reservoir. Using the inverse relationship between atmospheric CO(2) and the stomatal index of land plant leaves, we reconstruct Late Cretaceous-Early Tertiary atmospheric CO(2) concentration (pCO(2)) levels with special emphasis on providing a pCO(2) estimate directly above the KTB. Our record shows stable Late Cretaceous/Early Tertiary background pCO(2) levels of 350-500 ppm by volume, but with a marked increase to at least 2,300 ppm by volume within 10,000 years of the KTB. Numerical simulations with a global biogeochemical carbon cycle model indicate that CO(2) outgassing during the eruption of the Deccan Trap basalts fails to fully account for the inferred pCO(2) increase. Instead, we calculate that the postboundary pCO(2) rise is most consistent with the instantaneous transfer of approximately 4,600 Gt C from the lithic to the atmospheric reservoir by a large extraterrestrial bolide impact. A resultant climatic forcing of +12 W.m(-2) would have been sufficient to warm the Earth's surface by approximately 7.5 degrees C, in the absence of counter forcing by sulfate aerosols. This finding reinforces previous evidence for major climatic warming after the KTB impact and implies that severe and abrupt global warming during the earliest Paleocene was an important factor in biotic extinction at the KTB.     

Placental mammal diversification and the Cretaceous-Tertiary boundary

Competing hypotheses for the timing of the placental mammal radiation focus on whether extant placental orders originated and diversified before or after the Cretaceous-Tertiary (KT) boundary. Molecular studies that have addressed this issue suffer from single calibration points, unwarranted assumptions about the molecular clock, andor taxon sampling that lacks representatives of all placental orders. We investigated this problem using the largest available molecular data set for placental mammals, which includes segments of 19 nuclear and three mitochondrial genes for representatives of all extant placental orders. We used the ThorneKishino method, which permits simultaneous constraints from the fossil record and allows rates of molecular evolution to vary on different branches of a phylogenetic tree. Analyses that used different sets of fossil constraints, different priors for the base of Placentalia, and different data partitions all support interordinal divergences in the Cretaceous followed by intraordinal diversification mostly after the KT boundary. Four placental orders show intraordinal diversification that predates the KT boundary, but only by an average of 10 million years. In contrast to some molecular studies that date the rat-mouse split as old as 46 million years, our results show improved agreement with the fossil record and place this split at 16-23 million years. To test the hypothesis that molecular estimates of Cretaceous divergence times are an artifact of increased body size subsequent to the KT boundary, we also performed analyses with a "KT body size" taxon set. In these analyses, interordinal splits remained in the Cretaceous.     

Smokeless tobacco consumption in Grant County, New Mexico.

A telephone survey was conducted in order to assess the prevalence of smokeless tobacco consumption in Grant County, New Mexico. Systematic random sampling was used, and 1 out of 25 phone numbers were selected from the county telephone directory. One hundred seventy-eight respondents were surveyed. Thirty-three percent of 96 males and 7% of 82 females identified themselves as smokeless tobacco users.     

Distributions of Sharks across a Continental Shelf in the Northern Gulf of Mexico

Abstract

Declines in shark populations have sparked researchers and fishery managers to investigate more prudent approaches to the conservation of these fish. As managers strive to improve data collection for stock assessment, fisheries-independent surveys have expanded to include data-deficient areas such as coastal regions. To that end, a catch series from a nearshore survey off Alabama was combined with data from a concurrent offshore survey with identical methodology to examine the depth use of sharks across the continental shelf (2–366 m). The combined data set contained 22 species of sharks collected from 1995 to 2008: 21 species in the offshore data set (1995–2008) and 12 species in the nearshore data set (2006–2008). Depth was a significant factor determining species' distributions, primarily for Atlantic sharpnose Rhizoprionodon terraenovae, blacknose Carcharhinus acronotus, and blacktip C. limbatus sharks. Blacknose sharks had the highest catch per unit effort (CPUE) in the middepth stratum (10–30 m), blacktip sharks had consistently higher CPUE in the shallow depth stratum (<10 m), and Atlantic sharpnose sharks showed high abundance throughout both the shallow and middepth strata. Length frequency and sex ratio analyses suggest that Atlantic sharpnose and blacknose sharks are using waters greater than 30 m deep for parturition, whereas adult blacktip sharks are probably using shallow waters for parturition. Our abundance patterns illustrate a continuum of depth use across the inner continental shelf. Surveys that do not encompass the entirety of this ecosystem fail to accurately characterize the distributions of these important predators.     

From the Cover: Persistent ecological shifts in marine molluscan assemblages across the end-Cretaceous mass extinction

Contemporary biodiversity loss and population declines threaten to push the biosphere toward a tipping point with irreversible effects on ecosystem composition and function. As a potential example of a global-scale regime shift in the geological past, we assessed ecological changes across the end-Cretaceous mass extinction based on molluscan assemblages at four well-studied sites. By contrasting preextinction and postextinction rank abundance and numerical abundance in 19 molluscan modes of life—each defined as a unique combination of mobility level, feeding mode, and position relative to the substrate—we find distinct shifts in ecospace utilization, which significantly exceed predictions from null models. The magnitude of change in functional traits relative to normal temporal fluctuations at far-flung sites indicates that molluscan assemblages shifted to differently structured systems and faunal response was global. The strengths of temporal ecological shifts, however, are mostly within the range of preextinction site-to-site variability, demonstrating that local ecological turnover was similar to geographic variation over a broad latitudinal range. In conjunction with varied site-specific temporal patterns of individual modes of life, these spatial and temporal heterogeneities argue against a concerted phase shift of molluscan assemblages from one well-defined regime to another. At a broader ecological level, by contrast, congruent tendencies emerge and suggest deterministic processes. These patterns comprise the well-known increase of deposit-feeding mollusks in postextinction assemblages and increases in predators and predator-resistant modes of life, i.e., those characterized by elevated mobility and infaunal life habits.Recognizing nonlinear responses and tipping points in complex biological systems has raised concerns over the effects of global change, the extinction of species, and future global-scale shifts in the state of ecosystems (1, 2). Severe perturbations of the earth system, coupled with significant losses of biodiversity, have occurred a few times in earth history. These episodes of mass extinction provide the opportunity to study the ecological and evolutionary dynamics of the earth system when exposed to critical stress. Mass extinctions do not only devastate biodiversity—they also fundamentally restructure the variety of functions performed by the biota (3, 4). The analysis of ancient mass extinctions allows establishing the circumstances and the degree of system-level change in the geological past and thus could be informative of future changes in ecosystems due to anthropogenically driven biodiversity loss.The extinction event at the Cretaceous–Paleogene boundary (KPB, 66 million years before present) was the most recent mass extinction with an estimated 70% species loss (5). Similar to other mass extinctions it was associated with a profound disruption of the global carbon cycle (6). The ultimate trigger was probably the impact of an asteroid at Chicxulub in present-day Mexico (7), whereas Deccan Trap volcanism may have been an additional stressor (8). The most likely proximate killing mechanism was a crisis in primary productivity and global collapse of food webs owing to the suppression of photosynthesis (9–11). Other factors with devastating effects for marine ecosystems may have been metal poisoning (12), the acidification of oceanic surface waters (13), and short-lived global cooling (14).Major biotic changes associated with regime shifts can involve diversity loss, changes in biomass and trophic interactions, and the establishment of novel species assemblages (1). The contrast among different states in ecosystems is usually caused by a shift in dominance among organisms with different modes of life (15). Here we quantify the ecological change across the KPB in shallow marine benthic soft-bottom assemblages. These fossil assemblages are dominated by bivalve and gastropod mollusks, which not only have an excellent fossil record but also represent many different modes of life (MOLs), yielding unique insights into the ecological dynamics of the extinction and subsequent recovery. We compare molluscan ecospace occupation—as defined by the mobility, feeding mechanisms, and living positions of species (16)—in latest Cretaceous (Late Maastrichtian) preextinction times with that in earliest Paleogene (Danian) postextinction times.Previous studies showed an Early Danian increase in infaunal deposit feeders and mobility levels in some environments at some sites (17–21), whereas at other sites, either infaunal or epifaunal suspension feeders dominated and mobility levels and benthic tiering structure displayed no trends (21–25). Increased predation pressure after the KPB has been inferred from the radiation of predatory carnivores, in particular neogastopods (3, 18, 21, 26–28), elevated gastropod drilling frequencies (29, 30), and a trend toward deeper burrowing in bivalves (31), but predatory interactions did not increase universally (21, 25). One study demonstrated that Cretaceous–Paleogene spatial variation in functional group composition exceeded any changes through time (32), but otherwise this topic is largely unexplored. Some workers have questioned the presence of general ecological patterns (25), whereas others argued that ecological effects were habitat specific, with significant restructuring occurring in offshore assemblages and siliciclastic environments but not in shallow subtidal habitats and oligotrophic carbonate settings (20, 21).We studied mollusk-dominated siliciclastic shelf ecosystems at four well-studied sites before and after the KPB (SI Text S1). At each site, sedimentological evidence suggests that external environmental conditions were similar before and after the KPB (SI Text S1 and SI Text S2). The successions at three sites (Brazos River, Bajada del Jagüel, and Seymour Island) formed in a middle-to-outer shelf environment, whereas the fourth site (San Ramón) represents a tide-dominated delta. We estimated the ecological importance of each MOL in pre- and postextinction assemblages by its respective proportion based on counts of individuals. For this purpose, all Late Maastrichtian samples at a site were combined into a preextinction assemblage and all Danian samples into a postextinction assemblage. Specimen-level data were not available for the Maastrichtian of Seymour Island, and here the KPB comparison resides on the number of occurrences, i.e., counts of the presence of species of a particular MOL. In addition to comparing aggregate pre- and postextinction assemblages we used permutation tests and ordination techniques to compare the between-sample variation in ecological structure before and after the extinction event. Specifically, we tested whether these ecosystems experienced large, temporally abrupt, and persistent changes in ecological structure across the KPB. First, we examined whether postextinction assemblages constitute a fundamentally different assembly of functional groups. Differences to preextinction assemblages can be expected from previous work, but it is not clear whether they were beyond those of ordinary background fluctuations. Second, we explored whether any ecological disparity of postextinction assemblages reflects the ecospace occupation displayed by those taxa of preextinction assemblages that survived the extinction event. This scenario would suggest extinctions as the primary cause of ecological shifts. Third, we analyzed how consistently ecological patterns changed across sites. Congruence would suggest that the ecological systems responded deterministically to environmental change. Finally, we contrasted faunal shifts in time with the site-to-site variability to evaluate the spatiotemporal dimensions of ecological change.To test the significance of our results, we generated random species assemblages from the individual samples at each site for which we then calculated their ecological dissimilarity. By repeating this procedure many times we obtained a null distribution of ecological dissimilarity for “pre-” and “postextinction” assemblages (Materials and Methods). Comparison of the observed pattern with the prediction of the permuted null model allowed us to evaluate the significance of ecological change.     

Cigarette smoking and lung cancer in New Mexico

We have used population-based data for the state of New Mexico to calculate cigarette-smoking-specific incidence rates for lung cancer, cumulative incidence rates for lung cancer, and estimates of the proportion of lung cancer cases attributable to smoking. For white New Mexicans, the incidence of lung cancer increased with age and was markedly higher in smokers than in nonsmokers. From 25 through 84 yr of age, the cumulative incidence of lung cancer was 0.9% in nonsmoking males and 0.5% in nonsmoking females. The cumulative incidence rates were much higher for smokers; for males who smoked 20 or more cigarettes daily from age 25, the cumulative risk of lung cancer through age 84 was 31.7%. For females with the same cigarette smoking history, the estimate of cumulative incidence through age 84 years was 15.3%. The population-attributable risks for lung cancer associated with cigarette smoking were 89.5% for males and 85.5% for females.     

Epizootic vesicular stomatitis in Colorado, 1982: epidemiologic studies along the northern Colorado front range

Epidemiologic evaluations were made of farm personnel on vesicular stomatitis-affected premises along the front range of the Rocky Mountains in Colorado during the 1982 epizootic. A similar antibody prevalence was noted to that of veterinarians and research and regulatory personnel who were involved with the same epizootic. Risk of infection resulted from intimate physical contact with infected horses or cows. Incidence and infection rates in horses were 45%; rates in cows were much lower, only 5%. Some epidemiologic clues were gained by a detailed study of an equine ranch. The pasture was incriminated as the area of highest risk, where 100% infection rates were noted. Horses in open pens and barns were at lower risk. Severe clinical disease in horses resulted in higher neutralizing antibody titers than inapparent or mild infection. Maternal antibody was detected in foals up to 4 months of age, and the level of antibody in the foal was a reflection of the dam's antibody level.     

Inhalant abuse and juvenile delinquency: a control study in Albuquerque, New Mexico

This paper examines the relationship between inhalant abuse and delinquency among juveniles in Albuquerque, New Mexico. The arrest records of 100 juvenile delinquents identified as chronic inhalant abusers are compared with two control groups (N = 100 each) of other delinquents from Albuquerque. One control group was stratified on age, sex, and ethnicity, and the other was a simple random sample. The demographic characteristics of inhalant abusers indicated an overrepresentation of young, male Hispanics from large, poor, disrupted families where siblings were involved in both the abuse of inhalants and a variety of other delinquent activities. The inhalant abusers were much more likely to be arrested for virtually every type and category of delinquent activity. Specifically, inhalant abusers are considerably more criminal regarding total offenses committed, status offenses, crimes against property, crimes against persons, and criminal and violent offenses. Therefore, this study has indicated a strong relationship between inhalant abuse and juvenile delinquency.     

Disentangling environmental effects on adult life span in a butterfly across the metamorphic boundary

Life span is a central life history trait often showing tremendous variation within populations. Much of this variation can be attributed to environmental factors. In holometabolous insects life stages differ strikingly in physiology and energetic demands, and environmental variation before and after metamorphosis may not necessarily yield identical responses. In this study, we adopted a full-factorial experimental design with two larval and two adult temperatures as well as two larval and three adult feeding treatments (n_total = 1151). Identical temperatures yielded qualitatively different results depending on the developmental stage. While the lower compared to the higher developmental temperature slightly reduced adult life span, a lower adult temperature substantially increased life span. Food stress in the larval stage slightly reduced life span, as did food stress during the adult stage. Females lived generally longer than males. All factors investigated were involved in interactions with other factors, both within and across life stages. For instance, the qualitative impact of larval food stress depended on adult feeding treatment and adult temperature. Our results suggest that much insight into the causes of variation in life span is to be gained by explicitly considering environmental impacts across developmental stages and potential interactions among different environmental factors.     

Colorado tick fever: clinical, epidemiologic, and laboratory aspects of 228 cases in Colorado in 1973-1974.

During 1973 and 1974, we looked for cases of Colorado tick fever throughout Colorado; 228 cases were identified. Although 90% of the patients reported exposure to ticks before illness, only 52% were aware of an actual tick bite. Typical symptoms of fever, myalgia, and headache were common, but gastrointestinal symptoms were also prominent in 20% of the patients. Twenty percent were hospitalized; no deaths or permanent sequelae were noted. Persistent viremia (greater than or equal to 4 weeks) was found in about half of the cases; this finding was not associated with the occurrence of prolonged symptoms (greater than or equal to 3 weeks), which were also reported in half of the cases. One patient became reinfected with the virus. Increasing tourism in endemic areas and the frequent occurrence of prolonged or biphasic illnesses provide the potential for patients with Colorado tick fever to seek medical care anywhere in the United States.     

Lung cancer risk and vitamin A consumption in New Mexico

The association between dietary intake of vitamin A and lung cancer risk was examined in a population-based, case-control study of 447 patients and 759 control subjects in New Mexico. A food frequency interview was used to measure usual consumption of total vitamin A retinol, preformed vitamin A, and carotene. With all respondents combined, the odds ratios for lung cancer increased as intakes of total vitamin A and carotene declined but did not vary with intake of preformed vitamin A. When the subjects were stratified by ethnic group, Hispanic or non-Hispanic (Anglo) white, significant effects of vitamin A consumption were limited to the Anglos. In the Anglos, the protective effects of total vitamin A and carotene consumption were present in males and females, but varied strongly with cigarette smoking habits. In Anglo smokers, significant increases in the odds ratios with declining intake were observed in former but not in current smokers. Among the former smokers, significant effects of total vitamin A and carotene consumption were present only in those who had stopped smoking for 6 to 15 yr. Limitation of the protective effect of vitamin A and carotene consumption to past smokers has important implications for the design of clinical trials and for cancer control strategies.     

pfcrt Polymorphism and the spread of chloroquine resistance in Plasmodium falciparum populations across the Amazon Basin

The widespread occurrence of drug-resistant malaria parasites in South America presents a formidable obstacle to disease control in this region. To characterize parasite populations and the chloroquine-resistance profile of Plasmodium falciparum in the Amazon Basin, we analyzed a DNA segment of the pfcrt gene, spanning codons 72-76, and genotyped 15 microsatellite (MS) markers in 98 isolates from 6 areas of Brazil, Peru, and Colombia where malaria is endemic. The K76T mutation, which is critical for chloroquine resistance, was found in all isolates. Five pfcrt haplotypes (S[tct]MNT, S[agt]MNT, CMNT, CMET, and CIET) were observed, including 1 previously found in Asian/African isolates. MS genotyping showed relatively homogeneous genetic backgrounds among the isolates, with an average of 3.8 alleles per marker. Isolates with identical 15-loci MS haplotypes were found in different locations, suggesting relatively free gene flow across the Amazon Basin. Allopatric isolates carrying SMNT and CMNT haplotypes have similar genetic backgrounds, although parasites carrying the CIET haplotype have some exclusive MS alleles, suggesting that parasites with CIET alleles were likely to have been introduced into Brazil from Asia or Africa. This study provides the first evidence of the Asian pfcrt allele in Brazil and a detailed analysis of P. falciparum populations, with respect to pfcrt haplotypes, in the Amazon Basin.     

Ischemic heart disease mortality in Hispanics, American Indians, and non-Hispanic whites in New Mexico, 1958-1982

To describe trends in mortality from ischemic heart disease in New Mexico's Hispanic, American Indian, and non-Hispanic white populations, we used vital records data collected from 1958 through 1982. We calculated age-adjusted and age-specific mortality rates for ischemic heart disease for each of the state's principal ethnic groups. Death certificate data were used in combination with population estimates based on the censuses of 1960, 1970, and 1980. Age-adjusted mortality rates for ischemic heart disease among Hispanics, American Indians, and non-Hispanic white men were consistent with nationwide patterns of rising mortality rates during the 1960s followed by declining rates. Mortality rates from ischemic heart disease in all three ethnic groups in New Mexico were lower than national rates for whites. Rates for Hispanics in New Mexico were lower than for non-Hispanic whites; rates for American Indians were the lowest among the three groups. These data support previous observations that Hispanics and American Indians in the Southwest are at decreased risk for mortality from ischemic heart disease in comparison with U.S. whites.     

New quinolone, grepafloxacin, inhibits Cl- secretion across bovine airway epithelium in culture

OBJECTIVE: Transepithelial ion transport plays an important role in the regulation of the amount and the rheological properties of bronchial secretion. The effect of grepafloxacin (GPFX), a new quinolone agent, on bioelectrical properties of airway epithelium was determined. METHODOLOGY: Electrical properties of bovine tracheal epithelium cultured under an air-liquid interface condition were measured by the short-circuit technique. RESULTS: Addition of GPFX (100 microg/mL) to the mucosal side decreased short-circuit current (Isc) from 14.4 +/- 1.3 to 5.6 +/- 0.6 microA/cm2 (P < 0.001), and the response was accompanied by corresponding decreases in transepithelial potential difference and cell conductance. This effect was concentration dependent, and a similar response was also noted when GPFX was added to the submucosal side. The GPFX-induced decrease in Isc was not altered by the Na+ channel blocker amiloride, but was inhibited by the Cl- channel blocker diphenylamine-2-carboxylate or Cl(-)-free medium (P < 0.001, in each case). Furthermore, GPFX reduced Cl- conductance (P < 0.01) without affecting Na+ conductance of the epithelium. CONCLUSIONS: Grepafloxacin selectively inhibits Cl- secretion across tracheal epithelial cells, which may result in the inhibition of water secretion and, hence, the reduction of airway secretion.     

Echinococcosis in Arizona and New Mexico. Survey of hospital records, 1969-1974.

In 1974, seven cases of human echinococcosis were diagnosed in Arizona and New Mexico. A retrospective survey of Arizona and New Mexico hospitals obtained data on ten additional cases reported for the 5-year period 1969 through 1973. Sixteen cases were diagnosed as Echinococcus granulosus infections and one as E. multilocularis infection. The latter infection was in an Eskimo from Alaska, where E. multilocularis is endemic. All of the 16 E. granulosus cases were probably acquired autochthonously; 14 were diagnosed in American Indians of the Navajo (8 cases), Zuni (4 cases), and Santo Domingo (2 cases) tribes; the remaining 2 cases were diagnosed in non-Indian women. This is the first published account of echinococcosis autochthonous to Arizona and New Mexico. Evidence suggests that the infection may have been introduced only relatively recently to the areas populated by the American Indians and that parasite transmission to humans is increasing.     

Survival after cancer surgery of elderly patients in New Mexico, 1969-1982

To examine the effects of advancing age, sex, and ethnicity on estimated 30-day survival after surgery for cancer, we reviewed population-based data on 16,130 cancer cases collected by the New Mexico Tumor Registry from 1969-1982. For surgery at most sites, mortality increased with increasing age. The highest mortality was observed for sites requiring laparotomy or thoracotomy. Sex and ethnicity (Hispanic versus non-Hispanic white) had little effect on short-term survival. Comparison of short-term survival for two time periods, 1969-1975 and 1976-1982, showed a strong trend of improving survival for many sites.     

Strontium isotopes reveal distant sources of architectural timber in Chaco Canyon, New Mexico

Between A.D. 900 and 1150, more than 200,000 conifer trees were used to build the prehistoric great houses of Chaco Canyon, New Mexico, in what is now a treeless landscape. More than one-fifth of these timbers were spruce (Picea) or fir (Abies) that were hand-carried from isolated mountaintops 75-100 km away. Because strontium from local dust, water, and underlying bedrock is incorporated by trees, specific logging sites can be identified by comparing (87)Sr/(86)Sr ratios in construction beams from different ruins and building periods to ratios in living trees from the surrounding mountains. (87)Sr/(86)Sr ratios show that the beams came from both the Chuska and San Mateo (Mount Taylor) mountains, but not from the San Pedro Mountains, which are equally close. Incorporation of logs from two sources in the same room, great house, and year suggest stockpiling and intercommunity collaboration at Chaco Canyon. The use of trees from both the Chuska and San Mateo mountains, but not from the San Pedro Mountains, as early as A.D. 974 suggests that selection of timber sources was driven more by regional socioeconomic ties than by a simple model of resource depletion with distance and time.     

Spirometric prediction equations for Hispanic children and adults in New Mexico

We conducted a population-based survey of respiratory diseases and lung function in a New Mexico Hispanic community, and developed spirometric prediction equations based on data from 576 children and adults. Spirometric test procedures were followed as recommended by the American Thoracic Society. For children 6 through 18 yr of age, we used a logarithmic model to predict spirometric parameters. We used simple linear regression for adults 25 through 80 yr of age. On the basis of exploratory analyses, we excluded adult subjects who were obese, defined as a body mass index of 30 kg/m2 or greater. This report describes these regressions. We did not perform regression analysis for those subjects between 19 and 24 yr of age because of small numbers and the inappropriateness of grouping these subjects with older adults for regression analysis. As an alternative to a regression equation for this age group specifically, we propose linear interpolation between values obtained using prediction equations developed for children and for adults. Finally, we compared the percent predicted values obtained from our internal prediction equations with equations from other populations of white children and adults. In general, the comparison equations underestimated the percent predicted values in our population.