Sökresultat

Filtyp

Din sökning på "*" gav 532049 sökträffar

Local host specialization, host-switching, and dispersal shape the regional distributions of avian haemosporidian parasites

The drivers of regional parasite distributions are poorly understood, especially in comparison with those of free-living species. For vector-transmitted parasites, in particular, distributions might be influenced by host-switching and by parasite dispersal with primary hosts and vectors. We surveyed haemosporidian blood parasites (Plasmodium and Haemoproteus) of small land birds in eastern North A

Rickettsial agents in avian ixodid ticks in northeast Brazil

Birds are important in the maintenance and spread of ticks and tick-borne diseases. In this context we screened birds in the Atlantic forest north of the São Francisco River and Caatinga in northeast Brazil. In the Atlantic forest Amblyomma longirostre, Amblyomma nodosum, Amblyomma varium and Amblyomma auricularium were identified. A. longirostre was infected by ". Candidatus Rickettsia amblyommii

A blurring of life-history lines : Immune function, molt and reproduction in a highly stable environment

Rufous-collared sparrows (Zonotrichia capensis peruviensis) from valleys in the Atacama Desert of Chile, live in an extremely stable environment, and exhibit overlap in molt and reproduction, with valley-specific differences in the proportion of birds engaged in both. To better understand the mechanistic pathways underlying the timing of life-history transitions, we examined the relationships amon

Epaulet size and current condition in red-winged blackbirds : Examining a semistatic signal, Testosterone, Immune function, And parasites

Some sexually selected signals are thought to convey information about the current condition and genetic/epigenetic quality of the individual signaling, including the ability to resist parasites. However, it is unclear whether semistatic sexual signals that develop periodically and remain stable over protracted periods, such as avian breeding plumage, can relate to measures of current condition an

Specialized avian Haemosporida trade reduced host breadth for increased prevalence

Parasite specialization on one or a few host species leads to a reduction in the total number of available host individuals, which may decrease transmission. However, specialists are thought to be able to compensate by increased prevalence in the host population and increased success in each individual host. Here, we use variation in host breadth among a community of avian Haemosporida to investig

The ecology of host immune responses to chronic avian haemosporidian infection

Host responses to parasitism in the wild are often studied in the context of single host–parasite systems, which provide little insight into the ecological dynamics of host–parasite interactions within a community. Here we characterized immune system responses to mostly low-intensity, chronic infection by haemosporidian parasites in a sample of 424 individuals of 22 avian host species from the sam

Mixed species flock, nest height, and elevation partially explain avian haemoparasite prevalence in Colombia

The high avian biodiversity present in the Neotropical region offers a great opportunity to explore the ecology of host-parasite relationships. We present a survey of avian haemoparasites in a megadiverse country and explore how parasite prevalences are related to physical and ecological host characteristics. Using light microscopy, we documented the presence of haemoparasites in over 2000 individ

Breaking down seasonality : Androgen modulation and stress response in a highly stable environment

Previous studies show that most birds inhabiting temperate regions have well defined life history stages, and they modulate the production of testosterone (T) and corticosterone (CORT) in response to changes in seasonality. In this study we aimed to examine baseline and stress-induced levels of CORT and circulating T in relation with life history stages in the rufous-collared sparrow, Zonotrichia

Changes in immunocompetence and other physiological measures during molt in brown-headed cowbirds (Molothrus ater)

We tested one of the foundational hypotheses of the field of ecological immunology: that it is difficult for animals to simultaneously carry out two or more especially demanding physiological processes at optimal levels because of energy needs or other factors that cause tradeoffs among competing components of life history. We investigated possible effects of molt (a costly life-history stage that

Cultural evolution and long-term song stability in a dialect population of Brown-headed Cowbirds

Knowing the extent to which the acoustic structure of songs is temporally stable is essential to understanding how cultural evolution affects song dialects in oscines. The acoustic structure of the most prevalent variant of the flight-whistle song recorded from male Brown-headed Cowbirds (Molothrus ater) in the Mammoth dialect (Mammoth Lakes, California) from 2005 to 2009 differed significantly an

Construction firms in public–private partnerships: a place to grow

Public–Private Partnerships (PPPs) constitute a crucial vehicle in delivering infrastructure. In the transport sector the primary project sponsors are construction companies, which over the last few decades have transformed to strong international actors. In order to study growth strategies stemming from the PPP agreement, a conceptual game theoretic model built on four institutional rationalitiesPublic–Private Partnerships (PPPs) constitute a crucial vehicle in delivering infrastructure. In the transport sector the primary project sponsors are construction companies, which over the last few decades have transformed to strong international actors. In order to study growth strategies stemming from the PPP agreement, a conceptual game theoretic model built on four institutional rationalities

Sarcopenia and relationships between muscle mass, measured glomerular filtration rate and physical function in patients with chronic kidney disease stages 3–5.

Background Sarcopenia and poor physical function are common in patients with chronic kidney disease (CKD). Our aim was to investigate the relationships between muscle mass and measured glomerular filtration rate (GFR) and between muscle mass and strength and balance, respectively, in patients with CKD stages 3–5. Methods This is a baseline data analysis of a randomized controlled clinical trial.

Are REDD+ community forest projects following the principles for collective action, as proposed by Ostrom?

Forested countries in the global south that have agreed to engage in REDD+, a policy mechanism for addressing climate change, are receiving support to improve laws, policies, systems and structures. As a mechanism initiated at the global level and seeking to use forests to address a global commons crisis (atmospheric carbon concentration), understanding how REDD+ translates into implementation at

Laser diagnostics for the study of heterogeneous catalysis

In heterogeneous catalysis the reactions occur on the surface of a catalyst. To understand the reaction pathways, a detailed understanding on an atomic level is critical. However, the gas atmosphere surrounding the surface dictates the interaction between the surface and the gas. At low pressures this is often neglected, but as the community turns to higher pressures it becomes important to consid

Recent development of methods based on structured illumination for combustion studies

Structured illumination is an imaging method most commonly employed within the field of microscopy. However, recently the technique has spread into other scientific fields, such as for combustion research, where it has revealed new measurement opportunities. This paper describes how structured illumination can be employed for spray- and combustion research and highlights some of the recent progres

New data-driven estimation of terrestrial CO2 fluxes in Asia using a standardized database of eddy covariance measurements, remote sensing data, and support vector regression

The lack of a standardized database of eddy covariance observations has been an obstacle for data-driven estimation of terrestrial CO2 fluxes in Asia. In this study, we developed such a standardized database using 54 sites from various databases by applying consistent postprocessing for data-driven estimation of gross primary productivity (GPP) and net ecosystem CO2 exchange (NEE). Data-driven est