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Food web recovery from mass extinction is poorly understood. We analyzed insect-feeding damage on 14,999 angiosperm leaves from 14 latest Cretaceous, Paleocene, and early Eocene sites in the western interior United States. Most Paleocene floras have low richness of plants and of insect damage. However, a low-diversity 64.4-million-year-old flora from southeastern Montana shows extremely high insect damage richness, especially of leaf mining, whereas an anomalously diverse 63.8-million-year-old flora from the Denver Basin shows little damage and virtually no specialized feeding. These findings reveal severely unbalanced food webs 1 to 2 million years after the end-Cretaceous extinction 65.5 million years ago.

We characterize forest floor leaf litter and transported leaf samples from several depositional environments in both a temperate and a tropical forest to provide well-characterized modern analogs for the evaluation of fossil leaf localities. We compare the low-diversity, deciduous, temperate Wharton Brook forest (Connecticut, United States) with the high-diversity, evergreen, tropical Noah Creek Rainforest (Queensland, Australia) by mapping one half-hectare of each forest, collecting 25–29 leaf litter samples from four to five depositional settings in each forest and analyzing the relative abundance of species based on >31,750 leaves. In both studies, we analyze the samples as if they were fossil sites, evaluating floral composition, numerical diversity measures, rarefied richness, and climate estimates based on leaf physiognomy. We compare this analysis with data from the standing mapped forest to evaluate the biases inherent in the data derived from fossil assemblages from different depositional settings. In both forests, sample sites that were revisited over multiple years produced different species on subsequent visits, suggesting that fossil sites with close stratigraphic spacing and different composition may actually represent the same source forest. In both forests, species diversity in laterally transported samples appears to increase as the distance of transport increases. Because the species richness of a leaf sample is impacted by the diversity of the original forest, the amount of time the leaf sample spent accumulating, and the effect of transport distance, it is not possible to interpret the diversity of ancient forests without also evaluating the sedimentary facies of the fossil collections.

An extremely diverse lower Paleocene (64.1 million years ago) fossil leaf site from Castle Rock, Colorado, contains fossil litter that is similar to the litter of extant equatorial rainforests. The presence of a high-diversity tropical rainforest is unexpected, because other Paleocene floras are species-poor, a feature generally attributed to the Cretaceous-Tertiary (K-T) extinction. The site occurs on the margin of the Denver Basin in synorogenic sedimentary rocks associated with the rise of the Laramide Front Range. Orographic conditions caused by local topography, combined with equable climate, appear to have allowed for the establishment of rainforests within 1.4 million years of the K-T boundary.

A substantial portion of the literature on organizational change focuses on the effects of change but fails to consider how information about change is communicated and processed. Social information processing is used as a theoretical framework to guide the development of a causal model in which the impact of uncertainty, source competence, and source similarity were examined as precursors to employees' attitudes about organizational change. The results of this study indicate that social information had its strongest effect on employee attitudes in situations involving high source credibility and high uncertainty. A test of the path model incorporating the interaction between uncertainty and credibility provided a good fit to the data. The implications for research and theory in organizational change are discussed.

Modern biodiversity hotspots are characterized by high species diversity and by biotas facing a substantial threat of extinction, largely due to a high proportion of endemic taxa living in these regions. Theoretically, hotspots of biodiversity are areas of particular interest in the fossil record because of the relatively high quality and quantity of data that they may contribute to a global understanding of vegetational response to changes in climate, tectonic uplift, and ecological disturbance. Current models for climatic reconstruction that depend on leaf physiognomy are based on data sets in which species-rich tropical floras are less well represented, relative to temperate floras. Eight modern Neotropical floras from a range of precipitation regimes were evaluated to determine the influence that high source floral diversity has on reconstruction of mean annual temperature (MAT) and mean annual precipitation (MAP). Floras are drawn from sites in Costa Rica to southern Peru, having species richness from 55 to >400 species per plot. MAT of the sites spans a range of 24 to 28°C, and MAP ranges from ∼1600 mm to 3000 mm. By subsampling the modern floras in rank order of dominance (basal area), the importance of collecting intensity and completeness on subsequent assessments of MAT and MAP is evaluated. Biodiverse floras are good at reconstructing MAT if at least 50% of the species are included. When only 25 species are used for temperature calculations, the accuracy of the parameter is compromised, but a ±3°C error encompasses the majority of the deviation. Application to the early Paleocene Castle Rock fossil flora of Colorado confirms the validity of subsampling in high-diversity fossil applications. However, reconstruction of MAP is fraught with problems that do not appear to be related to biodiversity of the floras. Errors on estimates of MAP currently are so large as to make the values too vague to be useful in most applications. This study has accepted a 20% error as necessary, but the applicability of data with errors > 20% is questionable in situations where rainfall is >1500 mm per year. MAP estimates using leaf area are almost universally underestimates of actual MAP, and frequently are >400 mm in error. Exploration of these data indicates that effort would be well placed in investigating the relative importance of precipitation parameters in altering leaf morphology before choosing one to reconstruct climates of the past.

Using data from the Medicare Health Outcomes Survey, this article profiles the mental health status of Medicare beneficiaries enrolled in managed care by examining the association between two measures of mental health: depressed mood and the mental component summary (MCS) score of the RAND 36-Item Health Survey and sociodemographic characteristics, comorbidity, and disability. The data collection protocol includes a combination of multiple mailings and telephone followup (over a period of approximately 4 months). Mean MCS scores among elderly Medicare enrollees are somewhat higher than those for the general US population. However, MCS scores vary by demographic characteristics, health and functional status, and insurance status. Mean MCS scores are lowest among enrollees reporting low income, low levels of educational attainment, four or more chronic conditions, or three or more activities of daily living limitations, as well as the dually eligible enrollees. While females report a higher prevalence of depressed mood than males, differences in MCS scores by sex are small.

This research examines the predictors of 2-year declines in physical and mental health for beneficiaries surveyed in the Medicare Health Outcomes Survey (HOS). Regression results indicate that age, arthritis of the hip/knee, sciatica, and pulmonary diseases, comorbidity at baseline, and increased comorbidity between baseline and followup were predictors of decline in physical health; however, these account for very small amounts of variance. The number of newly diagnosed chronic conditions and depression predicted decline in mental health. Beneficiaries deceased at followup were of lower socioeconomic status, and had lower physical and mental health scores than the analytic sample.

National surveys such as the Medicare Health Outcomes Survey (HOS) provide an opportunity to examine changes in the physical and mental health of Medicare beneficiaries over time. The current study is based on results from the HOS. For the survey results on which this study is based, the HOS includes the RAND 36-Item Health Survey (RAND SF-36), which yields two distinct higher order measures of health status: the physical component summary (PCS) score and the mental component summary (MCS) score. A beneficiary is eligible for remeasurement if a PCS and MCS score can be calculated from the baseline survey. This study demonstrates that health declines remain constant over longer intervals for this elderly population. Therefore, the current HOS administrative procedure of following up on respondents after a 2-year interval appears to be sufficient for accurately documenting rates of health decline. Intervals longer than 2 years would likely result in more beneficiaries lost through attrition and therefore smaller sample sizes.