scholarly journals Evaluating the role of contracting and expanding rainforest in initiating cycles of speciation across the Isthmus of Panama

2012 ◽  
Vol 279 (1742) ◽  
pp. 3520-3526 ◽  
Author(s):  
Brian Tilston Smith ◽  
Amei Amei ◽  
John Klicka
Keyword(s):  
Bird Species ◽  
Tropical Regions ◽  
Isthmus Of Panama ◽  
Species Pairs ◽  
The Matrix ◽  
High Species Richness ◽  
The Rich ◽  
The Tropics ◽  
The Impact

Climatic and geological changes across time are presumed to have shaped the rich biodiversity of tropical regions. However, the impact climatic drying and subsequent tropical rainforest contraction had on speciation has been controversial because of inconsistent palaeoecological and genetic data. Despite the strong interest in examining the role of climatic change on speciation in the Neotropics there has been few comparative studies, particularly, those that include non-rainforest taxa. We used bird species that inhabit humid or dry habitats that dispersed across the Panamanian Isthmus to characterize temporal and spatial patterns of speciation across this barrier. Here, we show that these two assemblages of birds exhibit temporally different speciation time patterns that supports multiple cycles of speciation. Evidence for these cycles is further corroborated by the finding that both assemblages consist of ‘young’ and ‘old’ species, despite dry habitat species pairs being geographically more distant than pairs of humid habitat species. The matrix of humid and dry habitats in the tropics not only allows for the maintenance of high species richness, but additionally this study suggests that these environments may have promoted speciation. We conclude that differentially expanding and contracting distributions of dry and humid habitats was probably an important contributor to speciation in the tropics.

scholarly journals The Interactions between Polyphenols and Microorganisms, Especially Gut Microbiota

Antioxidants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 188
Author(s):  
Małgorzata Makarewicz ◽  
Iwona Drożdż ◽  
Tomasz Tarko ◽  
Aleksandra Duda-Chodak
Keyword(s):  
Intestinal Bacteria ◽  
Research Data ◽  
Bioactive Metabolites ◽  
Human Organism ◽  
Comprehensive Knowledge ◽  
Bidirectional Relationship ◽  
The Matrix ◽  
Intestinal Pathogens ◽  
The Impact

This review presents the comprehensive knowledge about the bidirectional relationship between polyphenols and the gut microbiome. The first part is related to polyphenols’ impacts on various microorganisms, especially bacteria, and their influence on intestinal pathogens. The research data on the mechanisms of polyphenol action were collected together and organized. The impact of various polyphenols groups on intestinal bacteria both on the whole “microbiota” and on particular species, including probiotics, are presented. Moreover, the impact of polyphenols present in food (bound to the matrix) was compared with the purified polyphenols (such as in dietary supplements) as well as polyphenols in the form of derivatives (such as glycosides) with those in the form of aglycones. The second part of the paper discusses in detail the mechanisms (pathways) and the role of bacterial biotransformation of the most important groups of polyphenols, including the production of bioactive metabolites with a significant impact on the human organism (both positive and negative).

The Economic Consequence of Labor Mobility in China's Regional Development

2009 ◽  
Vol 8 (2) ◽  
pp. 85-114 ◽  
Author(s):  
Ding Lu
Keyword(s):  
Capital Stock ◽  
Demographic Transition ◽  
Labor Mobility ◽  
Labor Movements ◽  
Income Levels ◽  
The Rich ◽  
Marginal Returns ◽  
Technology Level ◽  
The Impact

Factor mobility plays an important role in the convergence of regional income levels. This paper examines the role of labor mobility in China's regional economic development in the context of phases of demographic transition and the existence of institutional barriers. Our findings show that the two most important sources of interregional income disparity are per worker capital stock and technology level. The fact that the richest provincial economies are at the later phase of demographic transition provides a major reason for why those economies have accumulated higher per worker capital stock and achieved higher productivity levels. We also discover that regional per capita income levels have not displayed convergence since the mid 1990s. Two observations explain this phenomenon. One observation is that capital and labor movements have played only a limited role in equalizing their marginal returns across regions despite the fact that labor mobility has substantially strengthened this role since 2000. The other observation is that the impact of demographic changes on income growth has been distinctly uneven between the rich and poor regions. This phenomenon can be attributed to some particular features of China's interregional labor migration.

The rapid growth of Egypt’s agricultural output, 1890–1914, as an early example of the green revolutions of modern South Asia: some implications for the writing of global history

2006 ◽  
Vol 1 (1) ◽  
pp. 81-99 ◽  
Author(s):  
Roger Owen
Keyword(s):  
Green Revolution ◽  
Global History ◽  
British India ◽  
Late Twentieth ◽  
Late Nineteenth ◽  
The Rich ◽  
The Impact ◽  
Late Twentieth Century

The article uses comparative Indian material from British India and later, the Pakistani Punjab to ask new questions of the standard accounts of Egypt’s post-1890 cotton boom. It also argues for the particular relevance of the rich Punjabi green revolution data to the Egyptian case, and more generally, for the rewards to be obtained from an academic dialog between selected aspects of late nineteenth and of late twentieth century globalization. Topics analyzed include the impact of the various agricultural revolutions on social and regional inequalities, the issue of sustainability, the role of experts and the impact on health of long-term environmental degradation.

scholarly journals Are ICTs Prerequisites for the Eradication of Poverty?

2007 ◽  
Vol 7 ◽  
pp. 283-294
Author(s):  
H P P Lötter
Keyword(s):  
Decision Making ◽  
Information And Communication Technologies ◽  
Communication Technologies ◽  
Knowledge And Skills ◽  
Information And Communication ◽  
The Rich ◽  
Effective Use ◽  
The Impact ◽  
The Relationship

I provide a philosophical analysis of the claim that ICTs are necessary preconditions for the eradication of poverty. What are the links between information and communication technologies (ICTs) and poverty? I first define technology and then give a brief depiction of ICTs. Thereafter I define poverty and give a brief expla-nation of its context and causes. Next I discuss the relationship between poverty and ICTs in three paradigm cases: [i] the role of ICTs in poor societies, [ii] the effect of poor ICT knowledge and skill of individuals in highly developed technological societies, and [iii] the impact of impoverished ICT knowledge and skills on the rich, powerful, and intelligent ones in society. I propose a procedure for decision making about the appropria-tion of ICTs by individuals and societies. I assess the claim that both access to ICTs and effective use of them are preconditions for the eradication of poverty.

scholarly journals Mathematical Modeling of the Coinfection Dynamics of Malaria-Toxoplasmosis in the Tropics

2019 ◽  
Vol 56 (2) ◽  
pp. 139-163
Author(s):  
Oluwatayo M. Ogunmiloro
Keyword(s):  
Reproduction Number ◽  
Model System ◽  
Host Population ◽  
Globally Asymptotically Stable ◽  
Susceptible Host ◽  
Tropical Regions ◽  
First Order ◽  
Mathematical Techniques ◽  
The Tropics ◽  
The Impact

SummaryCoinfection by Plasmodium species and Toxoplasma gondii in humans is widespread, with its endemic impact mostly felt in the tropics. A mathematical model is formulated as a first-order nonlinear system of ordinary differential equations to describe the coinfection dynamics of malaria-toxoplasmosis in the mainly human and feline susceptible host population in tropical regions. Comprehensive mathematical techniques are applied to show that the model system is bounded, positive and realistic in an epidemiological sense. Also, the basic reproduction number (Romt) of the coinfection model is obtained. It is shown that if Romt < 1, the model system at its malaria-toxoplasmosis absent equilibrium is both locally and globally asymptotically stable. The impact of toxoplasmosis and its treatment on malaria, and vice versa, is studied and analyzed. Sensitivity analysis was performed to investigate the impact of the model system parameters on the reproduction number of the transmission of malaria-toxoplasmosis coinfection. Simulations and graphical illustrations were made to validate the results obtained from the theoretical model.

scholarly journals Exploring the adjustment to parasite pressure hypothesis: differences in uropygial gland volume and haemosporidian infection in palearctic and neotropical birds

2020 ◽  
Author(s):  
Sergio Magallanes ◽  
Anders Pape Møller ◽  
Charlene Luján-Vega ◽  
Esteban Fong ◽  
Daniel Vecco ◽  
...  
Keyword(s):  
Body Size ◽  
Relative Size ◽  
Bird Species ◽  
Uropygial Gland ◽  
Gland Volume ◽  
Selective Forces ◽  
Species Richness And Abundance ◽  
Additional Support ◽  
The Tropics

Abstract Parasites are globally widespread pathogenic organisms, which impose important selective forces upon their hosts. Thus, in accordance with the Adjustment to parasite pressure hypothesis, it is expected that defenses among hosts vary relative to the selective pressure imposed by parasites. According to the latitudinal gradient in diversity, species richness and abundance of parasites peak near the equator. The uropygial gland is an important defensive exocrine gland against pathogens in birds. Size of the uropygial gland has been proposed to vary among species of birds because of divergent selection by pathogens on their hosts. Therefore, we should expect that bird species from the tropics should have relatively larger uropygial glands for their body size than species from higher latitudes. However, this hypothesis has not yet been explored. Here, we analyze the size of the uropygial gland of 1719 individual birds belonging to 36 bird species from 3 Neotropical (Peru) and 3 temperate areas (Spain). Relative uropygial gland volume was 12.52% larger in bird species from the tropics than from temperate areas. This finding is consistent with the relative size of this defensive organ being driven by selective pressures imposed by parasites. We also explored the potential role of this gland as a means of avoiding haemosporidian infection, showing that species with large uropygial glands for their body size tend to have lower mean prevalence of haemosporidian infection, regardless of their geographical origin. This result provides additional support for the assumption that secretions from the uropygial gland reduce the likelihood of becoming infected with haemosporidians.

scholarly journals Privatization of Biofilm Matrix in Structurally Heterogeneous Biofilms

mSystems ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Simon B. Otto ◽  
Marivic Martin ◽  
Daniel Schäfer ◽  
Raimo Hartmann ◽  
Knut Drescher ◽  
...  
Keyword(s):  
Gene Expression ◽  
Shear Stress ◽  
Content Type ◽  
Matrix Gene ◽  
Starting Point ◽  
The Matrix ◽  
Matrix Components ◽  
Biofilm Development ◽  
The Impact

ABSTRACT The self-produced biofilm provides beneficial protection for the enclosed cells, but the costly production of matrix components makes producer cells susceptible to cheating by nonproducing individuals. Despite detrimental effects of nonproducers, biofilms can be heterogeneous, with isogenic nonproducers being a natural consequence of phenotypic differentiation processes. For instance, in Bacillus subtilis biofilm cells differ in production of the two major matrix components, the amyloid fiber protein TasA and exopolysaccharides (EPS), demonstrating different expression levels of corresponding matrix genes. This raises questions regarding matrix gene expression dynamics during biofilm development and the impact of phenotypic nonproducers on biofilm robustness. Here, we show that biofilms are structurally heterogeneous and can be separated into strongly and weakly associated clusters. We reveal that spatiotemporal changes in structural heterogeneity correlate with matrix gene expression, with TasA playing a key role in biofilm integrity and timing of development. We show that the matrix remains partially privatized by the producer subpopulation, where cells tightly stick together even when exposed to shear stress. Our results support previous findings on the existence of “weak points” in seemingly robust biofilms as well as on the key role of linkage proteins in biofilm formation. Furthermore, we provide a starting point for investigating the privatization of common goods within isogenic populations. IMPORTANCE Biofilms are communities of bacteria protected by a self-produced extracellular matrix. The detrimental effects of nonproducing individuals on biofilm development raise questions about the dynamics between community members, especially when isogenic nonproducers exist within wild-type populations. We asked ourselves whether phenotypic nonproducers impact biofilm robustness, and where and when this heterogeneity of matrix gene expression occurs. Based on our results, we propose that the matrix remains partly privatized by the producing subpopulation, since producing cells stick together when exposed to shear stress. The important role of linkage proteins in robustness and development of the structurally heterogeneous biofilm provides an entry into studying the privatization of common goods within isogenic populations.

scholarly journals Strategic land-use planning instruments in tropical regions: state of the art and future research.

2021 ◽  
Author(s):  
Eduardo Oliveira ◽  
Patrick Meyfroidt
Keyword(s):  
Land Use ◽  
Land Use Planning ◽  
Smallholder Farmers ◽  
Grey Literature ◽  
Future Research ◽  
Tropical Regions ◽  
Land Systems ◽  
The Tropics ◽  
Research Domains

Abstract Human-induced activities are threatening the socio-economic and ecological sustainability of land systems globally, including in tropical regions. Authorities in these regions prepare and implement land-use plans to select and organize land uses in a way that will meet the needs of local communities while safeguarding ecosystems services. To this end, land-use planning is used to assess, manage and monitor the physical, social and economic conditions of territories and thus assist agribusiness, smallholder farmers and other land users in their land-based activities. There is, however, a lack of systematic studies identifying strategic oriented land-use planning instruments and further detailing the extent of their effectiveness in supporting land governance. Here, we contribute to address this gap by reviewing academic and grey literature with a geographic scope on tropical regions. We conclude by sketching future research domains intended to expand the role of strategic planning approaches in land governance in the tropics.

scholarly journals FIRST ANNOTATED CHECKLIST OF BIRDS OF JICARÓN AND JICARITA: THE SOUTHERNMOST ISLANDS OF THE REPUBLIC OF PANAMA

Tecnociencia ◽  
2020 ◽  
Vol 22 (2) ◽  
pp. 123-149
Author(s):  
Pedro Luis Castillo-Caballero ◽  
Claudio M. Monteza-Moreno ◽  
Oscar Johnson ◽  
George R. Angehr
Keyword(s):  
Potential Role ◽  
Bird Species ◽  
Migratory Species ◽  
Land Bridge ◽  
Isthmus Of Panama ◽  
The Republic ◽  
Annotated Checklist ◽  
North And South America ◽  
North And South

The Isthmus of Panama, the narrowest land bridge between North and South America, is surrounded by a large number of islands (>1500) relatively close to the mainland. However, despite the potential role Panamanian islands have for the conservation of bird species, most avian surveys are conducted on the mainland. The islands of Jicarón and Jicarita, located in Coiba National Park, are of particular interest because these are the southernmost islands in the Republic of Panama. Additionally, previous avian surveys were restricted to Coiba Island, the largest of the park, leaving the avifauna in the rest of the islands poorly known. Here, we provide the first annotated checklist of birds for the islands of Jicarón and Jicarita, where we documented 115 and 53 species, respectively. Of these 23 species represent new records for the park. Further, we documented 10 endemic subspecies and 29 migratory species, of which 7 are warblers. The most frequently observed species were Brown-backed Dove (Leptotila plumbeiceps battyi), Rufous-tailed Hummingbird (Amazilia tzacatl) and Bananaquit (Coereba flaveola). We highlight some species of interest and discuss the potential role of these islands for conservation.

scholarly journals Privatization of biofilm matrix in structurally heterogeneous biofilms

2019 ◽  
Author(s):  
Simon B. Otto ◽  
Marivic Martin ◽  
Daniel Schäfer ◽  
Raimo Hartmann ◽  
Knut Drescher ◽  
...  
Keyword(s):  
Gene Expression ◽  
Shear Stress ◽  
Structural Heterogeneity ◽  
Matrix Gene ◽  
Starting Point ◽  
The Matrix ◽  
Matrix Components ◽  
Biofilm Development ◽  
The Impact

ABSTRACTThe self-produced biofilm provides beneficial protection for the enclosed cells, but the costly production of matrix components makes producer cells susceptible to cheating by non-producing individuals. Despite detrimental effects of non-producers, biofilms can be heterogeneous, with isogenic non-producers being a natural consequence of phenotypic differentiation processes. For instance, in Bacillus subtilis biofilm cells differ in the two major matrix components production, the amyloid fiber protein TasA and exopolysaccharides (EPS), demonstrating different expression levels of corresponding matrix genes. This raises questions regarding matrix gene expression dynamics during biofilm development and the impact of phenotypic non-producers on biofilm robustness. Here, we show that biofilms are structurally heterogeneous and can be separated into strongly and weakly associated clusters. We reveal that spatiotemporal changes in structural heterogeneity correlate with matrix gene expression, with TasA playing a key role in biofilm integrity and timing of development. We show that the matrix remains partially privatized by the producer subpopulation, where cells tightly stick together even when exposed to shear stress. Our results support previous findings on the existence of ‘weak points’ in seemingly robust biofilms as well as on the key role of linkage proteins in biofilm formation. Furthermore, we provide a starting point for investigating the privatization of common goods within isogenic populations.IMPORTANCEBiofilms are communities of bacteria protected by a self-produced extracellular matrix. The detrimental effects of non-producing individuals on biofilm development raises questions about the dynamics between community members, especially when isogenic non-producers exist within wild-type populations. We asked ourselves whether phenotypic non-producers impact biofilm robustness, and where and when this heterogeneity of matrix gene expression occurs. Based on our results we propose that the matrix remains partly privatized by the producing subpopulation, since producing cells stick together when exposed to shear stress. The important role of linkage proteins in robustness and development of the structurally heterogeneous biofilm provides an entry into studying the privatization of common goods within isogenic populations.

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