Blood Variation Implicates Respiratory Limits on Elevational Ranges of Andean Birds.

AbstractThe extent to which species ranges reflect intrinsic physiological tolerances is a major question in evolutionary ecology. To date, consensus has been hindered by the limited tractability of experimental approaches across most of the tree of life. Here, we apply a macrophysiological approach to understand how hematological traits related to oxygen transport shape elevational ranges in a tropical biodiversity hot spot. Along Andean elevational gradients, we measured traits that affect blood oxygen-carrying capacity-total and cellular hemoglobin concentration and hematocrit, the volume percentage of red blood cells-for 2,355 individuals of 136 bird species. We used these data to evaluate the influence of hematological traits on elevational ranges. First, we asked whether the sensitivity of hematological traits to changes in elevation is predictive of elevational range breadth. Second, we asked whether variance in hematological traits changed as a function of distance to the nearest elevational range limit. We found that birds showing greater hematological sensitivity had broader elevational ranges, consistent with the idea that a greater acclimatization capacity facilitates elevational range expansion. We further found reduced variation in hematological traits in birds sampled near their elevational range limits and at high absolute elevations, patterns consistent with intensified natural selection, reduced effective population size, or compensatory changes in other cardiorespiratory traits. Our findings suggest that constraints on hematological sensitivity and local genetic adaptation to oxygen availability promote the evolution of the narrow elevational ranges that underpin tropical montane biodiversity.

Increased Pass Rates in Introductory Biology: Benefits and Potential Costs of Implementing a Mathematics Prerequisite in a Community College Setting.

We explored the impacts of a mathematics prerequisite on student success in Introductory Biology, focusing on students historically underserved in science, technology, engineering, and mathematics (STEM). Specifically, we studied Introductory Biology student outcomes 5 years before and 6 years after adding the prerequisite. Students who had not previously passed Intermediate Algebra had a 54.91% chance of passing Introductory Biology, compared with a ​​69.25% chance for students who had passed this math course. Furthermore, we found a disproportionate benefit of passing the math course for Pell Grant recipients. When considering pre- versus post-prerequisite terms of Introductory Biology, we found pass rates were significantly higher after the mathematics prerequisite was required, but grades were not. After the mathematics prerequisite, enrollments in Introductory Biology temporarily decreased in comparison to a similar chemistry course and the college's overall enrollments, a potential cost to students. Pell Grant recipients and women took Introductory Biology at the same rate as before, and contrary to our hypothesis, we saw the proportion of persons excluded due to ethnicity or race (PEER) students enrolled in Introductory Biology was higher after the implementation. This study provides a model for assessing prerequisites in a local context and contributes evidence that mathematical prerequisites can benefit students.

Predictable evolution toward flightlessness in volant island birds.

Birds are prolific colonists of islands, where they readily evolve distinct forms. Identifying predictable, directional patterns of evolutionary change in island birds, however, has proved challenging. The "island rule" predicts that island species evolve toward intermediate sizes, but its general applicability to birds is questionable. However, convergent evolution has clearly occurred in the island bird lineages that have undergone transitions to secondary flightlessness, a process involving drastic reduction of the flight muscles and enlargement of the hindlimbs. Here, we investigated whether volant island bird populations tend to change shape in a way that converges subtly on the flightless form. We found that island bird species have evolved smaller flight muscles than their continental relatives. Furthermore, in 366 populations of Caribbean and Pacific birds, smaller flight muscles and longer legs evolved in response to increasing insularity and, strikingly, the scarcity of avian and mammalian predators. On smaller islands with fewer predators, birds exhibited shifts in investment from forelimbs to hindlimbs that were qualitatively similar to anatomical rearrangements observed in flightless birds. These findings suggest that island bird populations tend to evolve on a trajectory toward flightlessness, even if most remain volant. This pattern was consistent across nine families and four orders that vary in lifestyle, foraging behavior, flight style, and body size. These predictable shifts in avian morphology may reduce the physical capacity for escape via flight and diminish the potential for small-island taxa to diversify via dispersal.

Cutaneous dermatomyositis in the era of biologicals.

Dermatomyositis (DM) is a systemic inflammatory condition characterized by cutaneous and muscle findings, in addition to potential involvement of other organ systems. A distinct subtype of DM exists that is categorized by cutaneous findings with absent or minimal muscle involvement, referred to as clinically amyopathic dermatomyositis or dermatomyositis sine myositis. A variety of topical, immunosuppressive, and immunomodulatory therapies have been utilized to treat cutaneous DM. The advent of biological agents including tumor necrosis factor-α antagonists, intravenous immunoglobulin, rituximab, and others has allowed for the use of these agents with varying degrees of success for the treatment of cutaneous DM.

Skin Signs of Rheumatoid Arthritis and its Therapy-Induced Cutaneous Side Effects.

Rheumatoid arthritis (RA) is a systemic inflammatory disorder that primarily affects the joints, but may exhibit extra-articular, including cutaneous, manifestations such as rheumatoid nodules, rheumatoid vasculitis, granulomatous skin disorders, and neutrophilic dermatoses. A large burden of cutaneous disease may be an indication of RA disease activity and the need for more aggressive treatment. Many of the therapeutic agents used to treat RA can also result in cutaneous adverse effects, which pose their own diagnostic and therapeutic challenges. Anti-TNFα agents, in particular, have a wide variety of adverse effects including psoraisiform eruptions, granulomatous conditions, and cutaneous connective tissue disorders. Herein we provide an update on the clinical presentations and management of RA-associated cutaneous findings as well as drug-induced cutaneous effects, with particular attention to the adverse effects of biologic disease-modifying agents.

Response to Comments on "Evidence for mesothermy in dinosaurs".

D'Emic and Myhrvold raise a number of statistical and methodological issues with our recent analysis of dinosaur growth and energetics. However, their critiques and suggested improvements lack biological and statistical justification.

Dinosaur physiology. Evidence for mesothermy in dinosaurs.

Were dinosaurs ectotherms or fast-metabolizing endotherms whose activities were unconstrained by temperature? To date, some of the strongest evidence for endothermy comes from the rapid growth rates derived from the analysis of fossil bones. However, these studies are constrained by a lack of comparative data and an appropriate energetic framework. Here we compile data on ontogenetic growth for extant and fossil vertebrates, including all major dinosaur clades. Using a metabolic scaling approach, we find that growth and metabolic rates follow theoretical predictions across clades, although some groups deviate. Moreover, when the effects of size and temperature are considered, dinosaur metabolic rates were intermediate to those of endotherms and ectotherms and closest to those of extant mesotherms. Our results suggest that the modern dichotomy of endothermic versus ectothermic is overly simplistic.

Post-varicella-zoster virus granulomatous dermatitis: a report of 2 cases.

Granulomatous dermatitis (GD) is known to occur following varicella-zoster virus (VZV) infection. Lesions may appear at varying times after the acute eruption in both immunosuppressed and immunocompetent hosts. The etiology of GD is unclear, and findings of VZV in the lesions often are inconsistent. We describe 2 immunocompromised patients who presented with GD following VZV infection; their lesions were examined for the presence of VZV. We also review the literature on postzoster GD.

Metabolic 'engines' of flight drive genome size reduction in birds.

The tendency for flying organisms to possess small genomes has been interpreted as evidence of natural selection acting on the physical size of the genome. Nonetheless, the flight-genome link and its mechanistic basis have yet to be well established by comparative studies within a volant clade. Is there a particular functional aspect of flight such as brisk metabolism, lift production or maneuverability that impinges on the physical genome? We measured genome sizes, wing dimensions and heart, flight muscle and body masses from a phylogenetically diverse set of bird species. In phylogenetically controlled analyses, we found that genome size was negatively correlated with relative flight muscle size and heart index (i.e. ratio of heart to body mass), but positively correlated with body mass and wing loading. The proportional masses of the flight muscles and heart were the most important parameters explaining variation in genome size in multivariate models. Hence, the metabolic intensity of powered flight appears to have driven genome size reduction in birds.

Insular avian adaptations on two Neotropical continental islands.

AIM: Most studies of avian insular adaptations have focused on oceanic islands, which may not allow characters that are insular adaptations to be teased apart from those that benefit dispersal and colonization. Using birds on continental islands, we investigated characters that evolved in situ in response to insular environments created by late Pleistocene sea level rise. LOCATION: Trinidad and Tobago, nearby Caribbean islands and continental South America. METHODS: We weighed fresh flight muscles and measured museum skeletal specimens of seven species of birds common to the continental islands of Trinidad and Tobago. RESULTS: When corrected for body size, study species exhibited significantly smaller flight muscles, sterna and sternal keels on Tobago than on larger Trinidad and continental South America. Tobago populations were more 'insular' in their morphologies than conspecifics on Trinidad or the continent in other ways as well, including having longer bills, longer wings, longer tails and longer legs. MAIN CONCLUSIONS: We hypothesize that the longer bills enhance foraging diversity, the longer wings and tails compensate for the smaller pectoral assemblage (allowing for retention of volancy, but with a probable reduction in flight power and speed), and the longer legs expand perching ability. Each of these differences is likely to be related to the lower diversity and fewer potential predators and competitors on Tobago compared with Trinidad. These patterns of smaller flight muscles and larger bills, legs, wings and tails in island birds are not the results of selection for island dispersal and colonization, but probably arose from selection pressures acting on populations already inhabiting these islands.

Energetics, lifestyle, and reproduction in birds.

Theoretical and empirical studies of life history aim to account for resource allocation to the different components of fitness: survival, growth, and reproduction. The pioneering evolutionary ecologist David Lack [(1968) Ecological Adaptations for Breeding in Birds (Methuen and Co., London)] suggested that reproductive output in birds reflects adaptation to environmental factors such as availability of food and risk of predation, but subsequent studies have not always supported Lack's interpretation. Here using a dataset for 980 bird species (Dataset S1), a phylogeny, and an explicit measure of reproductive productivity, we test predictions for how mass-specific productivity varies with body size, phylogeny, and lifestyle traits. We find that productivity varies negatively with body size and energetic demands of parental care and positively with extrinsic mortality. Specifically: (i) altricial species are 50% less productive than precocial species; (ii) species with female-only care of offspring are about 20% less productive than species with other methods of parental care; (iii) nonmigrants are 14% less productive than migrants; (iv) frugivores and nectarivores are about 20% less productive than those eating other foods; and (v) pelagic foragers are 40% less productive than those feeding in other habitats. A strong signal of phylogeny suggests that syndromes of similar life-history traits tend to be conservative within clades but also to have evolved independently in different clades. Our results generally support both Lack's pioneering studies and subsequent research on avian life history.

Solving the measurement invariance anchor item problem in item response theory.

The efficacy of tests of differential item functioning (measurement invariance) has been well established. It is clear that when properly implemented, these tests can successfully identify differentially functioning (DF) items when they exist. However, an assumption of these analyses is that the metric for different groups is linked using anchor items that are invariant. In practice, however, it is impossible to be certain which items are DF and which are invariant. This problem of anchor items, or referent indicators, has long plagued invariance research, and a multitude of suggested approaches have been put forth. Unfortunately, the relative efficacy of these approaches has not been tested. This study compares 11 variations on 5 qualitatively different approaches from recent literature for selecting optimal anchor items. A large-scale simulation study indicates that for nearly all conditions, an easily implemented 2-stage procedure recently put forth by Lopez Rivas, Stark, and Chernyshenko (2009) provided optimal power while maintaining nominal Type I error. With this approach, appropriate anchor items can be easily and quickly located, resulting in more efficacious invariance tests. Recommendations for invariance testing are illustrated using a pedagogical example of employee responses to an organizational culture measure.

Fixed drug eruption associated with intravenous contrast media: report in a woman receiving iohexol.

Fixed drug eruption, a medication-associated mucocutaneous reaction, rarely presents as a delayed adverse reaction to intravenous non-ionic contrast media. We describe a 57-year-old woman with a history of metastatic renal cell carcinoma who repeatedly developed a sharply demarcated, erythematous patch on her left breast after receiving the iodinated non-ionic contrast media iohexol for staging computed tomography scans. Recurrent fixed drug eruption may be avoided by using another contrast medium. Prophylactic treatment with systemic corticosteroids may prevent repeated fixed drug eruption if an alternative contrast agent cannot be used.