Explaining COVID-19 related mortality disparities in American Indians and Alaska Natives

American Indian and Alaska Native (AI/AN) individuals are more likely to die with COVID-19 than other groups, but there is limited empirical evidence to explain the cause of this inequity. The objective of this study was to determine whether medical comorbidities, area socioeconomic deprivation, or access to treatment can explain the greater COVID-19 related mortality among AI/AN individuals. The design was a retrospective cohort study of harmonized electronic health record data of all inpatients with COVID-19 from 21 United States health systems from February 2020 through January 2022. The mortality of AI/AN inpatients was compared to all Non-Hispanic White (NHW) inpatients and to a matched subsample of NHW inpatients. AI/AN inpatients were more likely to die during their hospitalization (13.2% versus 7.1%; odds ratio [OR] = 1.98, 95% confidence interval [CI] = 1.48, 2.65) than their matched NHW counterparts. After adjusting for comorbidities, area social deprivation, and access to treatment, the association between ethnicity and mortality was substantially reduced (OR 1.59, 95% CI 1.15, 2.22). The significant residual relation between AI/AN versus NHW status and mortality indicate that there are other important unmeasured factors that contribute to this inequity. This will be an important direction for future research.

Racial and Educational Disparities in Cumulative Exposure to Hardships of the 2008 Great Recession and Inflammation

OBJECTIVE

This cross-sectional analysis examined self-reported economic hardships of the 2008 Great Recession, race/ethnicity, educational attainment, and psychological well-being (PWB) as predictors of systemic inflammatory physiology at midlife. We also tested for differential vulnerability in the relationship between recession hardship and inflammatory physiology by race/ethnicity, education, and PWB.

METHODS

Adults from the Midlife in the United States Refresher sample completed a survey and biomedical assessments after the recession ( n = 592 non-Hispanic White respondents, n = 158 Black/African American respondents, n = 108 respondents with other race/ethnicity). Cumulative recession hardship was the sum of financial, housing, and employment-related events. Outcomes included circulating levels of interleukin 6 and C-reactive protein. General linear regression models tested main effects interactions between primary predictor variables.

RESULTS

Educational attainment was inversely associated with recession hardships ( b = -0.18, 95% confidence interval = -0.26 to -0.11, p < .001). Black/African American respondents reported more recession hardships than White respondents ( b = 1.17, 95% confidence interval = 0.67 to 1.68, p < .001). More recession hardships predicted higher levels of interleukin 6 ( b = 0.06, p < .001) and C-reactive protein ( b = 0.04, p = .004). Analyses did not support race/ethnicity, education, and PWB as moderators of the association between recession hardship and inflammatory markers.

CONCLUSIONS

Race/ethnicity and education independently predicted disparities in cumulative recession hardship exposure. Recession hardship predicted higher blood levels of inflammatory proteins associated with long-term health. The lack of findings for differential vulnerability in the relationship between recession hardship and inflammatory markers by race/ethnicity, education, or PWB was possibly due to the limited sample size.

Factors associated with 60-day readmission among inpatients with COVID-19 at 21 United States health systems

Identifying patients at risk for readmission after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection could facilitate care planning and prevention. This retrospective cohort study of 60-day readmission included 105 543 COVID-19 patients at 21 US healthcare systems who were discharged alive between February 2020 and November 2021. Generalized linear mixed regression analyses tested predictors of 60-day readmission and severity. The all-cause readmission rate was 15% (95% confidence interval [CI] = 10%-21%), with 22% (95% CI = 18%-26%) of readmitted patients needing intensive care, and 6% (95% CI = 05%-07%) dying. Factors associated with readmission included male sex, government insurance, positive smoking history, co-morbidity burden, longer index admissions, and diagnoses at index admission (e.g., cancer, chronic kidney disease, and liver disease). Death and intensive care rates at readmission declined postvaccine availability. Receiving at least two COVID-19 vaccine doses, which were more common among older patients and those with comorbid conditions, was not independently associated with readmission but predicted a reduced risk of death at readmission. This retrospective cohort study identified factors associated with all-cause readmission for patients re-admitted to the same health system after hospitalization with SARS-CoV-2 infection. Patients who are male, who smoke, who have a higher comorbidity burden, and have government insurance may benefit from additional postacute care planning.

Relations of Current and Past Cancer with Severe Outcomes among 104,590 Hospitalized COVID-19 Patients: The COVID EHR Cohort at the University of Wisconsin

BACKGROUND

There is mixed evidence about the relations of current versus past cancer with severe COVID-19 outcomes and how they vary by patient and cancer characteristics.

METHODS

Electronic health record data of 104,590 adult hospitalized patients with COVID-19 were obtained from 21 United States health systems from February 2020 through September 2021. In-hospital mortality and ICU admission were predicted from current and past cancer diagnoses. Moderation by patient characteristics, vaccination status, cancer type, and year of the pandemic was examined.

RESULTS

6.8% of the patients had current (n = 7,141) and 6.5% had past (n = 6,749) cancer diagnoses. Current cancer predicted both severe outcomes but past cancer did not; adjusted odds ratios (aOR) for mortality were 1.58 [95% confidence interval (CI), 1.46-1.70] and 1.04 (95% CI, 0.96-1.13), respectively. Mortality rates decreased over the pandemic but the incremental risk of current cancer persisted, with the increment being larger among younger vs. older patients. Prior COVID-19 vaccination reduced mortality generally and among those with current cancer (aOR, 0.69; 95% CI, 0.53-0.90).

CONCLUSIONS

Current cancer, especially among younger patients, posed a substantially increased risk for death and ICU admission among patients with COVID-19; prior COVID-19 vaccination mitigated the risk associated with current cancer. Past history of cancer was not associated with higher risks for severe COVID-19 outcomes for most cancer types.

IMPACT

This study clarifies the characteristics that modify the risk associated with cancer on severe COVID-19 outcomes across the first 20 months of the COVID-19 pandemic. See related commentary by Egan et al., p. 3.

The first 20 months of the COVID-19 pandemic: Mortality, intubation and ICU rates among 104,590 patients hospitalized at 21 United States health systems

Main objective

There is limited information on how patient outcomes have changed during the COVID-19 pandemic. This study characterizes changes in mortality, intubation, and ICU admission rates during the first 20 months of the pandemic.

Study design and methods

University of Wisconsin researchers collected and harmonized electronic health record data from 1.1 million COVID-19 patients across 21 United States health systems from February 2020 through September 2021. The analysis comprised data from 104,590 adult hospitalized COVID-19 patients. Inclusion criteria for the analysis were: (1) age 18 years or older; (2) COVID-19 ICD-10 diagnosis during hospitalization and/or a positive COVID-19 PCR test in a 14-day window (+/- 7 days of hospital admission); and (3) health system contact prior to COVID-19 hospitalization. Outcomes assessed were: (1) mortality (primary), (2) endotracheal intubation, and (3) ICU admission.

Results and significance

The 104,590 hospitalized participants had a mean age of 61.7 years and were 50.4% female, 24% Black, and 56.8% White. Overall risk-standardized mortality (adjusted for age, sex, race, ethnicity, body mass index, insurance status and medical comorbidities) declined from 16% of hospitalized COVID-19 patients (95% CI: 16% to 17%) early in the pandemic (February-April 2020) to 9% (CI: 9% to 10%) later (July-September 2021). Among subpopulations, males (vs. females), those on Medicare (vs. those on commercial insurance), the severely obese (vs. normal weight), and those aged 60 and older (vs. younger individuals) had especially high mortality rates both early and late in the pandemic. ICU admission and intubation rates also declined across these 20 months.

Conclusions

Mortality, intubation, and ICU admission rates improved markedly over the first 20 months of the pandemic among adult hospitalized COVID-19 patients although gains varied by subpopulation. These data provide important information on the course of COVID-19 and identify hospitalized patient groups at heightened risk for negative outcomes.

Trial registration

ClinicalTrials.gov Identifier: NCT04506528 (https://clinicaltrials.gov/ct2/show/NCT04506528).

Smoking Status, Nicotine Medication, Vaccination, and COVID-19 Hospital Outcomes: Findings from the COVID EHR Cohort at the University of Wisconsin (CEC-UW) Study

INTRODUCTION

Available evidence is mixed concerning associations between smoking status and COVID-19 clinical outcomes. Effects of nicotine replacement therapy (NRT) and vaccination status on COVID-19 outcomes in smokers are unknown.

METHODS

Electronic health record data from 104 590 COVID-19 patients hospitalized February 1, 2020 to September 30, 2021 in 21 U.S. health systems were analyzed to assess associations of smoking status, in-hospital NRT prescription, and vaccination status with in-hospital death and ICU admission.

RESULTS

Current (n = 7764) and never smokers (n = 57 454) did not differ on outcomes after adjustment for age, sex, race, ethnicity, insurance, body mass index, and comorbidities. Former (vs never) smokers (n = 33 101) had higher adjusted odds of death (aOR, 1.11; 95% CI, 1.06-1.17) and ICU admission (aOR, 1.07; 95% CI, 1.04-1.11). Among current smokers, NRT prescription was associated with reduced mortality (aOR, 0.64; 95% CI, 0.50-0.82). Vaccination effects were significantly moderated by smoking status; vaccination was more strongly associated with reduced mortality among current (aOR, 0.29; 95% CI, 0.16-0.66) and former smokers (aOR, 0.47; 95% CI, 0.39-0.57) than for never smokers (aOR, 0.67; 95% CI, 0.57, 0.79). Vaccination was associated with reduced ICU admission more strongly among former (aOR, 0.74; 95% CI, 0.66-0.83) than never smokers (aOR, 0.87; 95% CI, 0.79-0.97).

CONCLUSIONS

Former but not current smokers hospitalized with COVID-19 are at higher risk for severe outcomes. SARS-CoV-2 vaccination is associated with better hospital outcomes in COVID-19 patients, especially current and former smokers. NRT during COVID-19 hospitalization may reduce mortality for current smokers.

IMPLICATIONS

Prior findings regarding associations between smoking and severe COVID-19 disease outcomes have been inconsistent. This large cohort study suggests potential beneficial effects of nicotine replacement therapy on COVID-19 outcomes in current smokers and outsized benefits of SARS-CoV-2 vaccination in current and former smokers. Such findings may influence clinical practice and prevention efforts and motivate additional research that explores mechanisms for these effects.

Scientific imperatives vis-à-vis growing inequality in America

A landmark article published in the American Psychologist (Adler et al., 1994) encouraged psychologists to engage in research on socioeconomic inequality and health. Numerous contributions followed to fill in psychosocial and behavioral pathways. Specifically, we review advances on health inequalities research from a large public-use study (Midlife in the United States [MIDUS]). The Great Recession of 2007 to 2009 and its lingering effects are then reviewed to underscore widening inequality in access to education, employment, and income. Two MIDUS national samples of same-aged adults recruited 2 decades apart are then compared to assess historical changes in socioeconomic, physical health, and well-being profiles from the 1990s to postrecession. Despite historical gains in educational attainment over time, we show that indicators of socioeconomic status, health, and well-being are more compromised in the postrecession sample relative to the 1990s sample. Building on these preliminary findings, we elaborate opportunities for further inquiry by the scientific community to examine whether widening socioeconomic inequalities exacerbated by the Great Recession translate to widening health inequalities. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Hardships of the Great Recession and health: Understanding varieties of vulnerability

The Great Recession of 2007–2009 is regarded as the most severe economic downturn since World War II. This study examined relationships between reported recession hardships and physical health in a national survey of American adults (N = 1275). Furthermore, education and psychological resources (perceived control, purpose in life, and conscientiousness) were tested as moderators of the health impacts of the recession. A greater number of hardships predicted poorer health, especially among the less educated. Psychological resources interacted with education and hardships to predict health outcomes. Although typically viewed as protective factors, such resources became vulnerabilities among educationally disadvantaged adults experiencing greater recession hardships.

Comparing Visible and Invisible Social Support: Non-evaluative Support Buffers Cardiovascular Responses to Stress

Previous research suggests that in contrast to invisible social support, visible social support produces exaggerated negative emotional responses. Drawing on work by Bolger and colleagues, this study disentangled social support visibility from negative social evaluation in an examination of the effects of social support on negative emotions and cardiovascular responses. As part of an anticipatory speech task, 73 female participants were randomly assigned to receive no social support, invisible social support, non-confounded visible social support or visible social support as delivered in a 2007 study by Bolger and Amarel. Twelve readings, each for systolic blood pressure, diastolic blood pressure and heart rate were taken at 5-min intervals throughout the periods of baseline, reactivity and recovery. Cardiovascular outcomes were tested by incorporating a series of theoretically driven planned contrasts into tests of stress reactivity conducted through piecewise growth curve modelling. Linear and quadratic trends established cardiovascular reactivity to the task. Further, in comparison to the control and replication conditions, the non-confounded visible and invisible social support conditions attenuated cardiovascular reactivity over time. Pre- and post-speech negative emotional responses were not affected by the social support manipulations. These results suggest that appropriately delivered visible social support may be as beneficial as invisible social support.

Post-albumin, a foetal-specific rat plasma protein: Purification, physicochemical and immunological studies

1. The foetal-specific post-albumin of rat plasma was purified by electrophoresis on a Pevicon block. 2. The sedimentation coefficient, diffusion coefficient and molecular weight were determined for this protein and found to be similar to those of adult rat plasma albumin. 3. Foetal post-albumin and adult albumin were compared immunologically and shown, with rabbit antisera, to share no antigenic determinants, suggesting different genetic control of the production of each. 4. It is suggested that the disappearance of post-albumin in the newborn animal may result from the disappearance of haemopoietic tissue from the rat liver with advancing age.

A urethropexy technique for surgical treatment of urethral prolapse in the male dog

Urethral prolapse is an uncommon condition affecting young male dogs, most commonly English bulldogs. Current described techniques for surgical treatment of urethral prolapse involve manual reduction of prolapsed mucosa and placement of a temporary purse-string suture at the penile tip, or resection of the prolapsed tissue and apposition of urethral and penile mucosa. The incidence of recurrence of urethral prolapse following resection of the prolapse is not known. This report describes a technique for surgical treatment of urethral prolapse in the male dog that minimizes surgical and anesthetic time, is simple to perform, requires minimal equipment, is effective, and is not associated with significant complications or recurrence. Three cases are described.

Convergence and divergence in the evolution of aquatic birds

Aquatic birds exceed other terrestrial vertebrates in the diversity of their adaptations to aquatic niches. For many species this has created difficulty in understanding their evolutionary origin and, in particular, for the flamingos, hamerkop, shoebill and pelecaniforms. Here, new evidence from nuclear and mitochondrial DNA sequences and DNA-DNA hybridization data indicates extensive morphological convergence and divergence in aquatic birds. Among the unexpected findings is a grouping of flamingos and grebes, species which otherwise show no resemblance. These results suggest that the traditional characters used to unite certain aquatic groups, such as totipalmate feet, foot-propelled diving and long legs, evolved more than once and that organismal change in aquatic birds has proceeded at a faster pace than previously recognized.

Pericardial effusion associated with metastatic disease from an unknown primary tumor in a dog

A 6.5-year-old, spayed female Siberian husky presented with signs of cardiac tamponade and weakness. Pleural, pericardial, and abdominal effusion were identified with radiographs and ultrasound. Pericardiocentesis relieved signs of tamponade, and the dog was clinically improved. Pericardial effusion recurred, and pericardiectomy was performed. Histopathological examination of excised tissues failed to reveal evidence of infectious or neoplastic disease. After pericardiectomy, clinically apparent thoracic effusion persisted. The dog was euthanized, and postmortem histopathological examination revealed emboli of metastatic carcinoma cells in the epicardium. The location of intrathoracic disease in this dog made antemortem diagnosis difficult, if not impossible.

Total evidence, consensus, and bat phylogeny: A distance-based approach

Resolution of the total evidence (i.e., character congruence) versus consensus (i.e., taxonomic congruence) debate has been impeded by (1) a failure to employ validation methods consistently across both tree-building and consensus analyses, (2) the incomparability of methods for constructing as opposed to those for combining trees, and (3) indifference to aspects of trees other than their topologies. We demonstrate a uniform, distance-based approach which allows for comparability among the results of character- and taxonomic-congruence studies, whether or not an identical suite of taxa has been included in all contributing data sets. Our results indicate that total-evidence and consensus trees differ little in topology if branch lengths are taken into account when combining two or more trees. In addition, when character-state data are converted to distances, our method permits their combination with information produced by techniques which generate distances directly. Moreover, treating all data sets or trees as distance matrices avoids the problem that different numbers of characters in contributing studies may confound the conclusions of a total-evidence or consensus analysis. Our protocol is illustrated with an example involving bats, in which the three component studies based on serology, DNA hybridization, and anatomy imply distinct phylogenies. However, the total-evidence and consensus trees support a fourth, somewhat different, topology resolved at all but one node and which conforms closely to the currently accepted higher category classification of Chiroptera.

The platypus is not a rodent: DNA hybridization, amniote phylogeny and the palimpsest theory

We present DNA-hybridization data on 21 amniotes and two anurans showing that discrimination is obtained among most of these at the class and lower levels. Trees generated from these data largely agree with conventional views, for example in not associating birds and mammals. However, the sister relationships found here of the monotremes to marsupials, and of turtles to the alligator, are surprising results which are nonetheless consistent with the results of some other studies. The Marsupionta hypothesis of Gregory is reviewed, as are opinions about the placement of chelonians. Anatomical and reproductive data considered by Gregory do not unequivocally preclude a marsupial-monotreme special relationship, and there is other recent evidence for placing turtles within the Diapsida. We conclude that the evidential meaning of the molecular data is as shown in the trees, but that the topologies may be influenced by a base-compositional bias producing a seemingly slow evolutionary rate in monotremes, or by algorithmic artefacts (in the case of turtles as well).

Base-compositional biases and the bat problem. III. The questions of microchiropteran monophyly

Using single-copy DNA hybridization, we carried out a whole genome study of 16 bats (from ten families) and five outgroups (two primates and one each dermopteran, scandentian, and marsupial). Three of the bat species represented as many families of Rhinolophoidea, and these always associated with the two representatives of Pteropodidae. All other microchiropterans, however, formed a monophyletic unit displaying interrelationships largely in accord with current opinion. Thus noctilionoids comprised one clade, while vespertilionids, emballonurids, and molossids comprised three others, successively more closely related in that sequence. The unexpected position of rhinolophoids may be due either to the high AT bias they share with pteropodids, or it may be phylogenetically authentic. Reanalysis of the data with varying combinations of the five outgroups does not indicate a rooting problem, and the inclusion of many bat lineages divided at varying levels similarly discounts long branch attraction as an explanation for the pteropodid-rhinolophoid association. If rhinolophoids are indeed specially related to pteropodids, many synapomorphies of Microchiroptera are called into question, not least the unitary evolution of echolocation (although this feature may simply have been lost in pteropodids). Further, a rhinolophoid-pteropodid relationship--if true--has serious implications for the classification of bats. Finally, among the outgroups, an apparent sister-group relation of Dermoptera and Primates suggests that flying lemurs do not represent the ancestors of some or all bats; yet, insofar as gliding of the type implemented in dermopterans is an appropriate model for the evolution of powered mammalian flying, the position of Cynocephalus in our tree indirectly strengthens the argument that true flight could have evolved more than once among bats.

Base-compositional biases and the bat problem. II. DNA-hybridization trees based on AT- and GC-enriched tracers

We conducted a series of parallel DNA-hybridization experiments on a small group of bats (species of Pteropus, Rhinolophus, Noctilio and Pteronotus) and outgroups (Lemur, Cynocephalus, Didelphis), using whole-genome labels and tracers made from extracts enriched with AT and two levels of GC content. FITCH (additive phylogenetic trees) topologies were constructed from the four sets of comparisons, indexed as both delta Tmode and delta NPHs (normalized percentage of hybridization). Based on our previous work showing that the shared AT bias of pteropodids and some microchiropterans may affect the rank-ordering of taxa based on either AT- or GC-rich labels, our expectation was that the resulting trees would show differing topologies when generated from tracers made with the variously enriched DNA extracts. Whereas there was some variation among the trees, most of them grouped the bats together, and almost all paired the representative megachiropteran and rhinolophoid microchiropteran as sister-taxa in contrast to the other microchiropterans. As the pteropodid-rhinolophoid relationship is an unexpected and unlikely one, we attribute this association to an AT bias that was not obviated even by our most GC-rich labels, and suggest that such a bias may compromise the truth of some molecular trees. Accordingly, we believe the broader issue of bat monophyly remains unresolved by DNA-hybridization and probably also by gene-sequencing studies.

DNA hybridization evidence for the principal lineages of hummingbirds (Aves:Trochilidae)

The spectacular evolutionary radiation of hummingbirds (Trochilidae) has served as a model system for many biological studies. To begin to provide a historical context for these investigations, we generated a complete matrix of DNA hybridization distances among 26 hummingbirds and an outgroup swift (Chaetura pelagica) to determine the principal hummingbird lineages. FITCH topologies estimated from symmetrized delta TmH-C values and subjected to various validation methods (bootstrapping, weighted jackknifing, branch length significance) indicated a fundamental split between hermit (Eutoxeres aquila, Threnetes ruckeri; Phaethornithinae) and nonhermit (Trochilinae) hummingbirds, and provided strong support for six principal nonhermit clades with the following branching order: (1) a predominantly lowland group comprising caribs (Eulampis holosericeus) and relatives (Androdon aequatorialis and Heliothryx barroti) with violet-ears (Colibri coruscans) and relatives (Doryfera ludovicae); (2) an Andean-associated clade of highly polytypic taxa (Eriocnemis, Heliodoxa, and Coeligena); (3) a second endemic Andean clade (Oreotrochilus chimborazo, Aglaiocercus coelestis, and Lesbia victoriae) paired with thorntails (Popelairia conversii); (4) emeralds and relatives (Chlorostilbon mellisugus, Amazilia tzacatl, Thalurania colombica, Orthorhyncus cristatus and Campylopterus villaviscensio); (5) mountain-gems (Lampornis clemenciae and Eugenes fulgens); and (6) tiny bee-like forms (Archilochus colubris, Myrtis fanny, Acestrura mulsant, and Philodice mitchellii). Corresponding analyses on a matrix of unsymmetrized delta values gave similar support for these relationships except that the branching order of the two Andean clades (2, 3 above) was unresolved. In general, subsidiary relationships were consistent and well supported by both matrices, sometimes revealing surprising associations between forms that differ dramatically in plumage and bill morphology. Our results also reveal some basic aspects of hummingbird ecologic and morphologic evolution. For example, most of the diverse endemic Andean assemblage apparently comprises two genetically divergent clades, whereas the majority of North American hummingbirds belong a single third clade. Genetic distances separating some morphologically distinct genera (Oreotrochilus, Aglaiocercus, Lesbia; Myrtis, Acestrura, Philodice) were no greater than among congeneric (Coeligena) species, indicating that, in hummingbirds, morphological divergence does not necessarily reflect level of genetic divergence.

DNA-DNA hybridization-based phylogeny for "higher" nonpasserines: reevaluating a key portion of the avian family tree

A matrix of delta T mode values for 10 birds, including 9 nonpasserines and a suboscine passerine flycatcher, was generated by DNA-DNA hybridization. Within the most derived lineages, all bootstrapped and jackknifed FITCH trees lend strong support to sister-groupings of the two swift families, of hummingbirds to swifts, and of these to a clade containing both owls and night-hawks. The outgroup duck roots the tree between the woodpecker (Piciformes) and the remaining taxa, indicating that Piciformes are among the earliest branches within nonpasserines. However, the succeeding branches to kingfisher, mousebird, and suboscine passerine flycatcher are based on short internodes that are poorly supported by bootstrapping and that give inconsistent results in jackknifing. Although these 3 orders may have arisen through rapid or near-simultaneous divergence, placement of the "advanced" Passeriformes deep within a more "primitive" radiation indicates that nonpasserines are paraphyletic, echoing the same distinction for reptiles with respect to their advanced descendants. Despite significant rate variation among different taxa, these results largely concur with those obtained with the same technique by Sibley and Ahlquist, who used the delta T50H measure and UPGMA analysis. This agreement lends credence to some of their more controversial claims.

Jackknifing of weighted trees: validation of phylogenies reconstructed from distance matrices

The jackknife strict consensus has been used to detect topological incompatibilities in phylogenetic trees derived from distance data. We here extend this approach to account for branch lengths, as well as topological relationships, when comparing jackknife pseudoreplicates. The average consensus procedure is used to derive a tree reflecting the agreement among the jackknife phylogenies. Combining the average tree with a minimum and a maximum consensus provides information about jackknife tree variability; the range consensus between the minimum and the maximum represents the topological agreement among them. We also demonstrate the effect of the number of pseudoreplicates on the resulting consensus trees by considering single and multiple deletions. The jackknife extensions that we propose are applied to both hypothetical and DNA-DNA hybridization distance data. Consideration of branch lengths reveals greater stability of the jackknife phylogeny than would be demonstrated by a strict consensus based on topology alone.

Phylogeny through brain traits: more characters for the analysis of mammalian evolution

We have assembled data on nine brain traits, in addition to the fifteen we have previously described, which provide new evidence for assessing mammalian relationships. States of these characters are tabulated as they occur in each of 152 mammalian species, providing data in numerically ordered form, useful for multiple analyses of phylogenetic relationships in programs which take into account variations in several different characters simultaneously. Derived states of each of the nine traits are characteristic of certain restricted groups of mammals; (1) mirroring of the complete SI body representation in isocortex (anthropoid primates); (2) loss of the accessory olfactory bulbs (sirenians, cetaceans, most bats, catarrhine primates); (3) Rindenkerne, clumps of cell bodies in layer 6 of cerebral cortex (sirenians); (4) posteriorly-pointing digits in the SI body representation (bats, both mega- and micro-); (5) equivalent tectopetal connections to the anterior colliculus of one side from both retinas, rather than predominantly from the contralateral retina (primates and megabats); (6) loss of lamination in dorsal cochlear nuclei (anthropoid primates, bats, seals, sirenians, cetaceans); (7) separation of claustrum from cerebral cortex (diprotodont marsupials, carnivores, artiodactyls, perissodactyls, hyracoids, cetaceans and primates), (8) presence of a complete secondary (SII) somatic sensory region of cerebral cortex (therians-all extant mammals other than monotremes), and (9) presence of a distinct external cuneate nucleus among the nuclei of the dorsal columns (all mammalian groups except monotremes and sirenians). Two examples of phylogenetic trees derived from these data are presented. These sample trees maintain the segregation of the monotremes and the marsupials, and the basic dichotomy of placentals seen in our earlier trees based entirely on brain data. They also show: an orderly sequence of bifurcations (rather than the commonly seen multifurcation near the base of the radiation) in the reconstruction of placental relationships; extremes of derivation for the Cetacea, the Chiroptera, and the Sirenia (in concordance with trees based on other data); a ferungulate association of Carnivora, Perissodactyla, Artiodactyla, Hyracoidea and Sirenia; and an assemblage of related Dermoptera, Primates, Scandentia, and Chiroptera which in this model also includes Insectivora and Macroscelidea. Analyses based on brain characters can reinforce conclusions based on other data, while at the same time introducing new ideas about relationships. Neural traits provide a source of data independent of those commonly used in phylogenetic analysis, and are extremely valuable for testing old hypotheses and for introducing new ones.(ABSTRACT TRUNCATED AT 400 WORDS)

DNA hybridization evidence for the Australasian affinity of the American marsupial Dromiciops australis

DNA hybridization was used to compare representatives of the major groups of marsupials and a eutherian outgroup. Because of the large genetic distances separating marsupial families, trees were calculated from normalized percentages of hybridization; thermal-melting statistics, however, gave identical topologies for the well-supported clades. The most notable results were the association of the only extant microbiotheriid, Dromiciops australis, an American marsupial, with the Australasian Diprotodontia, and of both together with the Dasyuridae. Estimates of the rate of divergence among marsupial genomes suggest that the Dromiciops-Diprotodontia split occurred approximately 50 million years ago, well after the establishment of the major clades of marsupials but before deep oceanic barriers prohibited dispersal among Australia, Antarctica, and South America. Because Dromiciops is nested within an Australasian group, it seems likely that dispersal from Australia accounts for its present distribution.

DNA/DNA hybridization studies of the carnivorous marsupials. I: The intergeneric relationships of bandicoots (Marsupialia: Perameloidea)

A complete suite of comparisons among six bandicoot species and one outgroup marsupial was generated using the hydroxyapatite chromatography method of DNA/DNA hybridization; heterologous comparisons were also made with three other bandicoot taxa. Matrices of delta Tm's, delta modes, and delta T50Hs were generated and corrected for nonreciprocity, homoplasy, and, in the case of delta Tm's, normalized percent hybridization; these matrices were analyzed using the FITCH algorithm in Felsenstein's PHYLIP (version 3.1). Uncorrected and nonreciprocity-corrected matrices were also jackknifed and analyzed with FITCH to test for consistency. Finally, sample scores for delta Tm, delta mode, and delta T50H matrices were bootstrapped and then subjected to phylogenetic analysis. These manipulations were carried out, in part, to address criticisms of the statistics used to summarize DNA/DNA hybridization (especially T50H) and the method itself. However, with the exception of an unresolved trichotomy among the two Echymipera species and Peroryctes longicauda, all trees showed the same branchpoints. Except in the case of the tree generated from reciprocal-corrected delta Tm data, nodes were stable under jackknifing; and, again excepting the above-mentioned trichotomy, all nodes were supported by 95% or more of the bootstrapped trees. These results suggest that, despite arguments to the contrary, all three summary statistics can be valid for DNA/DNA hybridization data. Of taxonomic interest is the placement of Echymipera spp. and Peroryctes longicauda together and separate from the more distant Peroryctes raffrayanus; the genus Peroryctes is thus at least paraphyletic. The trees further grouped Echymipera-plus-Peroryctes as the sister group of Isoodon-plus-Perameles. Limited hybridizations with Macrotis lagotis suggest that its current position as representative of an entirely distinct family of perameloids is correct.

DNA hybridization, cladistics, and the phylogeny of phalangerid marsupials

Single-copy DNA/DNA hybridization experiments and numerical cladistic analyses of anatomical characters were used to investigate relationships among nine phalangerid (Marsupialia) species from four different genera. Both rate-dependent and rate-independent analyses of molecular data indicate that species of Trichosurus from one clade and that Strigocuscus, Phalanger, and Spilocuscus form a second. Within the latter group, Spilocuscus is excluded from a Strigocuscus-Phalanger clade, which, in turn, is not fully resolved on a jackknife strict consensus tree. Minimum-length Dollo, Wagner, and Camin-Sokal parisomy trees based on 35 anatomical characters, in contrast, suggest placement of Strigocuscus with Trichosurus rather than with Spilocuscus and Phalanger. However, there are two derived characters that support the alternative arrange of Strigocuscus with Spilocuscus and Phalanger and one character that further unites Strigocuscus and Phalanger. Thus, DNA hybridization results are not inconsistent with the distribution of derived character states among anatomical characters, only with minimum-length trees based on character data.

Rates of single-copy DNA evolution in phalangeriform marsupials

DNA/DNA hybridization was used to investigate the relationships of taxa representing the phalangeriform marsupial families Acrobatidae, Burramyidae, Macropodidae, Petauridae, Phalangeridae, and Pseudocheiridae and (as an outgroup) the bandicoot family Peramelidae. In the course of this, a marked rate slowdown was noted in the burramyid lineage represented by Cercartetus caudatus; ANOVA (with Tukey's test) and F-ratio tests of both corrected and uncorrected data matrices confirmed this rate disparity. As burramyids are small, short-generation-time phalangeriforms, these data present a striking counterexample to the common view that rates of change in DNA sequences are inversely correlated with generation time.

Conflict over the molecular clock

Figure 3 (p. 1310) in the report "A 115-kD polypeptide immunologically related to erythrocyte band 3 is present in Golgi membranes" by S. Kellokumpu et al. (2 Dec., p. 1308) was incorrectly printed. The correct figure is reproduced below.

Brain traits through phylogeny: evolution of neural characters

We have previously derived a hypothetical tree of the lines of mammalian descent, based upon a comprehensive numerical taxonomic cross-analysis of primitive and derived states of 15 brain traits in 38 representative species. In this communication we use this tree to describe the probable sequence of changes that have taken place in phylogenetic history. 2 characters proved to be multiply convergent, occurring in parallel in several disparate lines of descent. The remaining 9 characters each appeared in ancestors of one or another of the lineages and characterize related progeny.

Phylogeny through brain traits: the mammalian family tree

Wagner trees based on the analysis of 15 brain characters scored on 154 specimens of 134 mammalian species show consistent patterns of relationship among the taxa, i.e. (1) monotremes are the primitive complement of the group uniting marsupials and placentals; (2) among marsupials, diprotodont Australian forms are more derived; (3) placental mammals divide into two groups of orders, roughly the ferungulates (carnivores, ungulates, and subungulates) and the unguiculates-plus-gliroids (chiropterans, dermopterans, lagomorphs, rodents, primates, and insectivores including elephant shrews); (4) edentates sit at the base of or just before the placental dichotomy; (5) the tree shrew and tarsier show the same pattern of distribution of brain traits as some rodents, as do prosimians and New World monkeys.

Phylogeny through brain traits: trees generated by neural characters

Phylogenetic trees were computed by the Wagner algorithm from data on up to 15 brain characters scored on 154 specimens of 134 mammalian species. Because the data were not complete on all specimens, only one tree, of 18 taxa, was generated on all 15 features; a tree of 99 species was computed from 10 characters, and trees of 38 species from 10 and 12. The 38-taxon trees were considered best because they preserved most completely the integrity of mammalian orders. All trees consistently separated the subclasses of mammals and suggested that rodents, insectivores, and the tree shrew were most derived on the basis of brain characters. The trees' shapes are sensitive to small alterations in character scorings, largely because of the relatively few characters available and small differences in the number of states among them.

Phylogeny through brain traits: fifteen characters which adumbrate mammalian genealogy

Fifteen characters of brain organization are identified for which primitive and derived states can be distinguished, and which are thus useful in reconstructing mammalian phylogeny. The states of the characters are numerically coded in sequence from most primitive to most derived, to facilitate reciprocal comparisons in comprehensive genealogical analyses. The characters include certain features of cerebral circulation, cytoarchitecture, fiber pathways, and sensory projections. Seven characters are shared with nonmammals, a fact which makes then particularly useful for establishing their primitive vs. derived states; the other eight characters are features peculiar to mammals. Ten characters provide impressive reinforcement for traditional major grouping of the species, while five provide bases for new ideas about mammalian relationships.

Phylogeny through brain traits: the distribution of categorizing characters in contemporary mammals

The varying states of 15 characters of the central neural organization are tabulated as they occur in each of 147 mammalian species. For each character and species, scores are entered designating the primitive or derived state of the character as it is observed in that species. This tabulation provides data in numerically ordered form for multiple analyses of possible phylogenetic relationships which take into account variations in several different characters simultaneously.

Phylogeny through brain traits. Relation of lateral olfactory tract fibers to the accessory olfactory formation as a palimpsest of mammalian descent

In mammals the fibers of the dorsal lateral olfactory tract either pass under the accessory olfactory formation, or they penetrate through it separating the internal granule cells from the output cells. The use of this trait as a phylogenetic indicator in 181 specimens representing 131 species of 16 orders yielded evidence for common ancestry of Insectivora, Chiroptera, Dermoptera, Rodentia, and Primates (including Tupaia), since all share the derived trait, their dorsal lateral olfactory tract fibers passing through the accessory olfactory formation. Carnivora (including Pinnipedia), Hyracoidea, Perissodactyla, and most Artiodactyla share the primitive condition (fibers passing under) with the one order of monotremes and three marsupial orders. The Edentata and Lagomorpha may be separate from the two major placental groups and from each other, or they may represent successive stages in the evolution of the derived state through progressive alterations in the relative chronology of development of olfactory system components, or one or both orders may occupy an ancestral position with respect to the dichotomy within placental mammals.