Why birds with deferred sexual maturity are sedentary on islands: a systematic review

Background

Island faunas have played central roles in the development of evolutionary biology and ecology. Birds are among the most studied organisms on islands, in part because of their dispersal powers linked to migration. Even so, we lack of information about differences in the movement ecology of island versus mainland populations of birds.

Methodology/Principal Findings

Here we present a new general pattern indicating that large birds with deferred sexual maturity are sedentary on islands, and that they become so even when they are migratory on the mainland. Density-dependent variation in the age at first breeding affects the survivorship of insular populations and this, in turn, affects the movement ecology of large birds. Because density-dependent variation in the age of first breeding is critical to the long-term survival of small isolated populations of long-lived species, migratory forms can successfully colonize islands only if they become sedentary once there. Analyses of the movement ecology of continental and insular populations of 314 species of raptors, 113 species of Ciconiiformes and 136 species of passerines, along with individual-based population simulations confirm this prediction.

Conclusions

This finding has several consequences for speciation, colonization and survival of small isolated population of species with deferred sexual maturity.     

Comprehensive DNA barcode coverage of North American birds

DNA barcoding seeks to assemble a standardized reference library for DNA-based identification of eukaryotic species. The utility and limitations of this approach need to be tested on well-characterized taxonomic assemblages. Here we provide a comprehensive DNA barcode analysis for North American birds including 643 species representing 93% of the breeding and pelagic avifauna of the USA and Canada. Most (94%) species possess distinct barcode clusters, with average neighbour-joining bootstrap support of 98%. In the remaining 6%, barcode clusters correspond to small sets of closely related species, most of which hybridize regularly. Fifteen (2%) currently recognized species are comprised of two distinct barcode clusters, many of which may represent cryptic species. Intraspecific variation is weakly related to census population size and species age. This study confirms that DNA barcoding can be effectively applied across the geographical and taxonomic expanse of North American birds. The consistent finding of constrained intraspecific mitochondrial variation in this large assemblage of species supports the emerging view that selective sweeps limit mitochondrial diversity.     

Soil-mediated indirect impacts of an invasive predator on plant growth

While several studies have shown that invasive plant effects on soil biota influence subsequent plant performance, corresponding studies on how invasive animals affect plants through influencing soil biota are lacking. This is despite the fact that invasive animals often indirectly alter the below-ground subsystem. We studied 18 offshore islands in northern New Zealand, half of which have been invaded by rats that are predators of seabirds and severely reduce their densities, and half of which remain non-invaded; invasion of rats thwarts seabird transfer of resources from ocean to land. We used soil from each island in a glasshouse experiment involving soil sterilization treatments to determine whether rat invasion indirectly influences plant growth through the abiotic pathway (by impairing seabird-driven inputs to soil) or the biotic pathway (by altering the soil community). Rat invasion greatly impaired plant growth but entirely through the abiotic pathway. Plant growth was unaffected by the soil community or its response to invasion, meaning that the responses of plants and soil biota to invasion are decoupled. Our results provide experimental evidence for the powerful indirect effects that predator-instigated cascades can exert on plant and ecosystem productivity, with implications for the restoration of island ecosystems by predator removal.     

A review of the systematic position of the North American species of the genusGlyptotendipes

The systematic position of the North American species of the genusGlyptotendipes is reviewed using morphological characters from all life history stages. The cladistic analysis revealed adult characters which support the monophyly of the three species groups (A, B and C) of PINDER and REISS (1983, 1986) for pupae and larvae. These species groups are given formal subgeneric status, with Group A becomingGlytotendipes, s.s., placingPhytotendipes Goetghebuer, 1937 in synonymy, Group B is namedCaulochironomus (type-species,Tendipes caulicola Kieffer, 1913) and Group C is namedTrichotendipes (type-species,Tendipes signatus Kieffer, 1911).     

Contrasting impacts of highly invasive plant species on flower-visiting insect communities

Invasive alien plants threaten biodiversity, ecosystems and service provision worldwide. They can have positive and negative direct and indirect effects on herbivorous insects, including those that provide pollination services. Here, we quantify how three highly invasive plant species (Heracleum mantegazzianum, Impatiens glandulifera and Fallopia japonica) influence the availability of floral resources and flower-visiting insect communities. We compared invaded with comparable uninvaded areas to assess floral resources and used pan-trapping to quantify insect communities. Only F. japonica influenced floral resource availability: sites invaded by this species had a higher flowering plant species richness and abundance of open floral units than uninvaded sites, probably due to its late flowering and the paucity of other flowering species at this time of year. Fallopia japonica was also associated with higher abundances of bumblebees, higher overall insect diversity and higher hoverfly diversity than uninvaded areas. Differences in pollinator communities were also associated with I. glandulifera and H. mantegazzianum, despite there being no detectable differences in floral resources at these sites. Specifically, there were more bumblebees and solitary bees in I. glandulifera sites, and a higher overall diversity of insects, particularly hoverflies. By contrast, H. mantegazzianum sites had a lower abundance of solitary bees and hoverflies. These findings confirm that invasive plant species have a range of species-specific effects on ecological communities. This supports the emerging view that control of invasive species, as required under international obligations, is not simple and that potential losses and gains for biodiversity must be carefully evaluated on a case-by-case basis.     

Population density of North American elk: effects on plant diversity

Large, herbivorous mammals have profound effects on ecosystem structure and function and often act as keystone species in ecosystems they inhabit. Density-dependent processes associated with population structure of large mammals may interact with ecosystem functioning to increase or decrease biodiversity, depending on the relationship of herbivore populations relative to the carrying capacity (K) of the ecosystem. We tested for indirect effects of population density of large herbivores on plant species richness and diversity in a montane ecosystem, where increased net aboveground primary productivity (NAPP) in response to low levels of herbivory has been reported. We documented a positive, linear relationship between plant-species diversity and richness with NAPP. Structural equation modeling revealed significant indirect relationships between population density of herbivores, NAPP, and species diversity. We observed an indirect effect of density-dependent processes in large, herbivorous mammals and species diversity of plants through changes in NAPP in this montane ecosystem. Changes in species diversity of plants in response to herbivory may be more indirect in ecosystems with long histories of herbivory. Those subtle or indirect effects of herbivory may have strong effects on ecosystem functioning, but may be overlooked in plant communities that are relatively resilient to herbivory.     

Diet niche relationships among North American grassland and shrubsteppe birds

Summary We consider the dietary relationships of the numerically dominant breeding bird species in four North American grassland/shrubsteppe habitats, sampled over 2–3 consecutive years. Overall, the diets of these species contained primarily insects: orthopterans comprised 29% of the diet biomass, coleopterans 24%, and lepidopteran larvae 23%, while seeds contributed 15% of the average diet. These diets varied substantially, however, and we evaluated several aspects of this variation. Intersexual differences in diets within a species were few, despite the occurrence of significant sexual size dimorphism in several species. For many species, however, there were substantial shifts in dietary composition between years at a given location; overall, the average between-year similarity of species' dietary composition was 70%. Different species exhibited rather different diet patterns. Horned Larks were relatively omnivorous, had broad diet composition niches, and varied considerably in diets between different locations. Meadowlarks were also broad-niched and geographically variable in their diets, but were the most highly carnivorous of the species we considered. Dietary niche breadths of Grasshopper Sparrows were intermediate, but diet composition was rather stable, both between years and between locations. Chestnut-collared Longspurs exhibited narrow diet niches, but substantial annual variation: each year this species apparently exploited a different but limited set of prey types rather heavily. Larger avian predators generally consumed a broader array of functional groups of prey, but did not differ in the taxonomic variety of their diets from small birds. Variation in diet composition between individuals within local populations was considerable; in most species, an individual contained on the average 30–40% of the prey taxa represented in entire population smaples.Patterns of dietary overlap among species were quite inconsistent from year to year at most locations, although at the shrubsteppe site overlap among all species present was consistently quite high. Relatively few cooccurring species pairs exhibited low diet overlap. The degree of diet niche overlap was unrelated to body size differences of the birds, despite as much as six-fold differences in weight among some coexisting species. Relationships of the bird species on another dimension of the trophic niche, prey size, also differed substantially between sites and years. The ranking of co-occurring species by the mean sizes of the prey they consumed generally did not parallel their rankings by body sizes, and in some cases the smallest and the largest species present ate prey of similar sizes. At the shrubsteppe site, all the breeding species exhibited quite similar frequency distributions of prey sizes in their diets.As species number and diversity increased in the breeding avifaunas, diet niche breadths generally decreased, species packing by prey size decreased, and diet composition niche overlap remained relatively unchanged. These trends are in at least partial agreement with predictions of diffuse competition theory, but the patterns were derived from broad inter-site comparisons of overall site averages, and the relationships generally did not hold within local assemblages of species. In general, our attempts to match values of dietary niche features with site characteristics failed to demonstrate close agreement with the predictions of prevailing ecological theory based upon assumptions of resource limitation and competition. Instead, our findings seem generally most consistent with the suggestion that food is not normally limiting to bird populations in these systems, and individuals and populations are exploiting the food resources in an opportunistic fashion, which leads to considerable individual, between-year, and between-location variation in diet compositions and interspecific overlaps.Our attempts to discern clear relationships that accord with theoretical expectations in these avian assemblages are thwarted by our lack of detailed information on the resource base and by the lack of clear tests that will separate alternative hypotheses of community organization and structuring. We suggest that these complications may compromise the findings of many community studies.     

A systematic review of mechanisms by which natural products of plant origin evoke vasodilatation

This article reviews the body of work aimed at elucidating the mechanisms of action by which natural products of plant origin exert a vasodilatory effect at the level of the vasculature. The search was restricted to 4 mechanisms: the nitric oxide system and (or) reactive oxygen species, the eicosanoid system, potassium channel function, and calcium channel function. The National Library of Medicine database was searched using "PubMed" without restriction to language. The search generated 266 references on 15 November 2005. Most studies were in vitro in nature and of these, most involved studies in the rat aorta. Many of the natural products evoked vasodilatation through an endothelium-dependent mechanism. The vasodilatation was attenuated or abolished by a nitric oxide synthase inhibitor and, in some of these studies, by an inhibitor of guanylate cyclase. A few studies reported a cyclooxygenase component, but most found no effect of the cyclooxygenase inhibitor, indomethacin. The vasorelaxation evoked by several natural products was attenuated by various potassium channel blocking agents, suggesting that some natural products exerted their effect either directly or indirectly through activation of potassium channels. Finally, a significant number of natural products evoked vasodilatation either through blockade of calcium channels or by inhibiting the release of calcium from intracellular stores. Many natural products evoked vasodilatation through multiple mechanisms. The information in this review on mechanisms of action should facilitate good clinical practice by increasing the predictive capabilities of the practitioner, notably the ability to predict adverse effects and interactions among medications. The knowledge should also help to provide leads to the ultimate goal of developing new therapeutic medications.     

Variable effects of climate change on six species of North American birds

Many recent studies have shown that birds are advancing their laying date in response to long-term increases in spring temperatures. These studies have been conducted primarily in Europe and at local scales. If climate change is a large-scale phenomenon, then we should see responses at larger scales and in other regions. We examined the effects of long-term temperature change on the laying dates and clutch sizes of six ecologically diverse species of North American birds using 50 years of nest record data. As predicted, laying dates for most (four of six) species were earlier when spring temperatures were warmer. Over the long-term, laying dates advanced over time for two species (red-winged blackbirds, Agelaius phoeniceus and eastern bluebirds, Sialia sialis). Laying date of song sparrows (Melospiza melodia) also advanced with increasing temperature when the analysis was restricted to eastern populations. Neither laying date nor clutch sizes changed significantly over time in the remaining species (American coot, Fulica americana, killdeer, Charadrius vociferous, and American robin, Turdus migratorius), an unsurprising result given the lack of increase in temperatures over time at nest locations of these species. This study indicates that the relationship between climate change and breeding in birds is variable within and among species. In large-scale analyses of North American birds, four of seven species have shown advances in laying dates with increasing temperature (including song sparrows in the east). These variable responses within and among species highlight the need for more detailed studies across large spatial scales.     

Cellular and molecular mechanisms of acute exposure to sulfur mustard: a systematic review

Context: Mustard gas (e.g. sulfur mustard (SM)) has been used as a chemical agent in several battles and is still a potential worldwide menace. Besides local absorption, particularly in the skin, eyes and lungs, systemic spread of the agent also has detrimental effects on gonads, bone marrow and nervous system. Moreover, chronic exposure of SM to respiratory system causes death. Inducing oxidative stress, and disturbing DNA and tissue repair systems, inflammation and cell death signaling pathways have been introduced as molecular mechanisms of the injury.

Methods: In this systematic review, more than 1200 (2000–2014) articles focusing on gross or molecular pathological reports in the acute phase of the respiratory injury after SM exposure were reviewed, followed by two different layers of gross and molecular pathological data (clinic and laboratory) integrated together in a spatio-temporal order. Role of epithelial, neutrophil and macrophage cells and three signaling pathways of inflammation, oxidative stress and cell death are covered in details.

Results and conclusion: Our results propose a critical role of interleukin-17 producing cells in acute and chronic inflammatory responses.     

Collision mortality has no discernible effect on population trends of North American birds

Avian biodiversity is threatened by numerous anthropogenic factors and migratory species are especially at risk. Migrating birds frequently collide with manmade structures and such losses are believed to represent the majority of anthropogenic mortality for North American birds. However, estimates of total collision mortality range across several orders of magnitude and effects on population dynamics remain unknown. Herein, we develop a novel method to assess relative vulnerability to anthropogenic threats, which we demonstrate using 243,103 collision records from 188 species of eastern North American landbirds. After correcting mortality estimates for variation attributable to population size and geographic overlap with potential collision structures, we found that per capita vulnerability to collision with buildings and towers varied over more than four orders of magnitude among species. Species that migrate long distances or at night were much more likely to be killed by collisions than year-round residents or diurnal migrants. However, there was no correlation between relative collision mortality and long-term population trends for these same species. Thus, although millions of North American birds are killed annually by collisions with manmade structures, this source of mortality has no discernible effect on populations.     

Programs for invasive research in North American zoos and aquariums

Zoo-based research in North America is an emerging field, which has progressed from an ad hoc approach in a small number of zoos to a coordinated, integrated network of scientists with recognized research programs in approximately one half of the accredited institutions in North America. The disciplines most active in these programs--veterinary medicine and pathology, nutrition, reproductive biology, contraception, and behavior--are now becoming coordinated in zoos through Scientific Advisory Groups. Zoos with research programs generally establish either an institutional animal care and use committee or another committee to evaluate research proposals. In addition to scientific merit and experimental design, zoos evaluate proposals based on factors such as priority by conservation program/identified need; direct effect on species conservation, species type, and appropriateness; availability and location of animals; operational requirements/logistics; communication between institutions; and available funding. Euthanasia is considered only in rare circumstances. Zoo-based research has evolved into an integral component in animal management and conservation programs by providing practical information that is used to improve animal care, well-being, health, and reproduction. However, the degree to which zoos participate in invasive research varies considerably among institutions, due not only to resource limitations but also to how the term "invasive" is defined and accepted at each institution. A more standardized approach among zoological institutions for examining and approving research projects that are supported by zoo-based conservation programs would greatly facilitate the wildlife research efforts of North American zoos.     

Major plant communities of warm North American deserts

Abstract. A syntaxonomic study of the major plant communities in neotropical North American deserts (Sonoran, Mojave and Baja California Deserts) is presented. The field method of the Braun-Blanquet approach was combined with a numerical syntaxonomical analysis (cluster analysis and principal coordinate ordination). 21 associations are described for the first time: Ambrosio chenopodifoliae-Larreetum tridentatae, Acamptopappo sphaerocephali-Larreetum tridentatae, Hymenocleo monogyrae-Baccharidetum glutinosae, Bergerocacto emoryi-Agavetum shawii, Burseretum hindsianomicrophyllae, Cercidio microphylli-Carnegieetum giganteae, Bursero microphyllae-Cyrtocarpetum edulis, Hymenocleo salsolae-Daleetum spinosae, Echinocereo engelmannii-Agavetum deserti, Euphorbio californicae-Fouquierietum diguetii, Fouquierio splendentis-Larreetum tridentatae, Agavo cerulatae-Idrietum columnaris, Mascagnio macropterae-Lysilometum candidae, Maytenetum phyllanthoidis, Opuntio basilaris-Larreetum tridentatae, Prosopidetum torreyanae, Roso minutifoliae-Aesculetum parryi, Opuntio taponae-Agavetum subcerulatae, Tidestromio oblongifoliae-Atriplicetum hymenelytrae, Eurotio lanatae-Larreetum tridentatae and Yucco validae-Fouquierietum diguetii. Some associations include subassociations. Ecological, biogeographical and floristic bioclimatic data are given for each association.     

Nitrogen-limitation and invasive sweetclover impacts vary between two Great Plains plant communities

Yellow sweetclover is an exotic herbaceous legume common in the Great Plains of the US. Although woody legumes have been shown to affect ecosystem processes through nitrogen (N) fixation (i.e., they can be considered “transformers” sensu Richardson et al. (2000)), the same has not been shown for short-lived herbaceous species. The objectives of this study were to (1) quantify the effects of yellow sweetclover on N mineralization and nitrification and (2) assess the effects of N fertilization on two plant communities, badlands sparse vegetation and western wheatgrass prairie. We used in situ (in wheatgrass prairie) and laboratory incubations (for both plant communities) to assess N dynamics at sites with high and low sweetclover cover in the two plant communities. We found that both N mineralization and nitrification were higher in the high sweetclover plots in the sparse plant community, but not in the wheatgrass prairie. To assess fertilization effects and determine if nutrients or water were limiting at our sites, we conducted a field experiment with five resource addition treatments, (1) N, (2) N + water, (3) water, (4) phosphorus, and (5) no addition. Water was limiting in the wheatgrass prairie but contrary to expectation, N was not. In contrast, N was limiting in the sparse community, where a fertilization effect was seen in exotic forbs, especially the toxic invader Halogeton glomeratus. Our results emphasize the contingent nature of plant invasion in which effects are largely dependent on attributes of the recipient vegetation.     

Evaluation of PCR on bronchoalveolar lavage fluid for diagnosis of invasive aspergillosis: a bivariate metaanalysis and systematic review

Background

Nucleic acid detection by polymerase chain reaction (PCR) is emerging as a sensitive and rapid diagnostic tool. PCR assays on serum have the potential to be a practical diagnostic tool. However, PCR on bronchoalveolar lavage fluid (BALF) has not been well established. We performed a systematic review of published studies to evaluate the diagnostic accuracy of PCR assays on BALF for invasive aspergillosis (IA).

Methods

Relevant published studies were shortlisted to evaluate the quality of their methodologies. A bivariate regression approach was used to calculate pooled values of the method sensitivity, specificity, and positive and negative likelihood ratios. Hierarchical summary receiver operating characteristic curves were used to summarize overall performance. We calculated the post-test probability to evaluate clinical usefulness. Potential heterogeneity among studies was explored by subgroup analyses.

Results

Seventeen studies comprising 1191 at-risk patients were selected. The summary estimates of the BALF-PCR assay for proven and probable IA were as follows: sensitivity, 0.91 (95% confidence interval (CI), 0.79–0.96); specificity, 0.92 (95% CI, 0.87–0.96); positive likelihood ratio, 11.90 (95% CI, 6.80–20.80); and negative likelihood ratio, 0.10 (95% CI, 0.04–0.24). Subgroup analyses showed that the performance of the PCR assay was influenced by PCR assay methodology, primer design and the methods of cell wall disruption and DNA extraction.

Conclusions

PCR assay on BALF is highly accurate for diagnosing IA in immunocompromised patients and is likely to be a useful diagnostic tool. However, further efforts towards devising a standard protocol are needed to enable formal validation of BALF-PCR.     

Income inequality and depression: a systematic review and meta‐analysis of the association and a scoping review of mechanisms

Most countries have witnessed a dramatic increase of income inequality in the past three decades. This paper addresses the question of whether income inequality is associated with the population prevalence of depression and, if so, the potential mechanisms and pathways which may explain this association. Our systematic review included 26 studies, mostly from high‐income countries. Nearly two‐thirds of all studies and five out of six longitudinal studies reported a statistically significant positive relationship between income inequality and risk of depression; only one study reported a statistically significant negative relationship. Twelve studies were included in a meta‐analysis with dichotomized inequality groupings. The pooled risk ratio was 1.19 (95% CI: 1.07‐1.31), demonstrating greater risk of depression in populations with higher income inequality relative to populations with lower inequality. Multiple studies reported subgroup effects, including greater impacts of income inequality among women and low‐income populations. We propose an ecological framework, with mechanisms operating at the national level (the neo‐material hypothesis), neighbourhood level (the social capital and the social comparison hypotheses) and individual level (psychological stress and social defeat hypotheses) to explain this association. We conclude that policy makers should actively promote actions to reduce income inequality, such as progressive taxation policies and a basic universal income. Mental health professionals should champion such policies, as well as promote the delivery of interventions which target the pathways and proximal determinants, such as building life skills in adolescents and provision of psychological therapies and packages of care with demonstrated effectiveness for settings of poverty and high income inequality.