Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

The World Health Organisation estimates that the warming and precipitation trends due to anthropogenic climate change of the past 30 years already claim over 150,000 lives annually. Many prevalent human diseases are linked to climate fluctuations, from cardiovascular mortality and respiratory illnesses due to heatwaves, to altered transmission of infectious diseases and malnutrition from crop failures. Uncertainty remains in attributing the expansion or resurgence of diseases to climate change, owing to lack of long-term, high-quality data sets as well as the large influence of socio-economic factors and changes in immunity and drug resistance. Here we review the growing evidence that climate-health relationships pose increasing health risks under future projections of climate change and that the warming trend over recent decades has already contributed to increased morbidity and mortality in many regions of the world. Potentially vulnerable regions include the temperate latitudes, which are projected to warm disproportionately, the regions around the Pacific and Indian oceans that are currently subjected to large rainfall variability due to the El Nino/Southern Oscillation sub-Saharan Africa and sprawling cities where the urban heat island effect could intensify extreme climatic events.

https://faculty.washington.edu/jhannah/geog270aut07/readings/ClimateChange/Patz%20-%20impact%20of%20climate%20change%20on%20health.pdf

Impact of regional climate change on human health

Evolutionary adaptation can be rapid and potentially help species counter stressful conditions or realize ecological opportunities arising from climate change. The challenges are to understand when evolution will occur and to identify potential evolutionary winners as well as losers, such as species lacking adaptive capacity living near physiological limits. Evolutionary processes also need to be incorporated into management programmes designed to minimize biodiversity loss under rapid climate change. These challenges can be met through realistic models of evolutionary change linked to experimental data across a range of taxa.

http://www.indiaenvironmentportal.org.in/files/climate%20change_1.pdf

Climate change and evolutionary adaptation

Hybridization between species is commonplace in plants, but is often seen as unnatural and unusual in animals. Here, I survey studies of natural interspecific hybridization in plants and a variety of animals. At least 25% of plant species and 10% of animal species, mostly the youngest species, are involved in hybridization and potential introgression with other species. Species in nature are often incompletely isolated for millions of years after their formation. Therefore, much evolution of eventual reproductive isolation can occur while nascent species are in gene-flow contact, in sympatry or parapatry, long after divergence begins. Although the relative importance of geographic isolation and gene flow in the origin of species is still unknown, many key processes involved in speciation, such as 'reinforcement' of post-mating isolation by the evolution of assortative mating, will have ample opportunity to occur in the presence of continuing gene flow. Today, DNA sequence data and other molecular methods are beginning to show that limited invasions of the genome are widespread, with potentially important consequences in evolutionary biology, speciation, biodiversity, and conservation.

https://www.ucl.ac.uk/taxome/jim/pap/mallethyb05.pdf

Hybridization as an invasion of the genome

Hybridization has many and varied impacts on the process of speciation. Hybridization may slow or reverse differentiation by allowing gene flow and recombination. It may accelerate speciation via adaptive introgression or cause near-instantaneous speciation by allopolyploidization. It may have multiple effects at different stages and in different spatial contexts within a single speciation event. We offer a perspective on the context and evolutionary significance of hybridization during speciation, highlighting issues of current interest and debate. In secondary contact zones, it is uncertain if barriers to gene flow will be strengthened or broken down due to recombination and gene flow. Theory and empirical evidence suggest the latter is more likely, except within and around strongly selected genomic regions. Hybridization may contribute to speciation through the formation of new hybrid taxa, whereas introgression of a few loci may promote adaptive divergence and so facilitate speciation. Gene regulatory networks, epigenetic effects and the evolution of selfish genetic material in the genome suggest that the Dobzhansky-Muller model of hybrid incompatibilities requires a broader interpretation. Finally, although the incidence of reinforcement remains uncertain, this and other interactions in areas of sympatry may have knock-on effects on speciation both within and outside regions of hybridization.

/pdf/hybridization-and-speciation-5ctx8t0ugf.pdf

Hybridization and speciation

Aedes albopictus, an arbovirus vector: from the darkness to the light.

Background 
Chikungunya and dengue viruses emerged in Gabon in 2007, with large outbreaks primarily affecting the capital Libreville and several northern towns. Both viruses subsequently spread to the south-east of the country, with new outbreaks occurring in 2010. The mosquito species Aedes albopictus, that was known as a secondary vector for both viruses, recently invaded the country and was the primary vector involved in the Gabonese outbreaks. We conducted a retrospective study of human sera and mosquitoes collected in Gabon from 2007 to 2010, in order to identify other circulating arboviruses.


Methodology/Principal Findings 
Sample collections, including 4312 sera from patients presenting with painful febrile disease, and 4665 mosquitoes belonging to 9 species, split into 247 pools (including 137 pools of Aedes albopictus), were screened with molecular biology methods. Five human sera and two Aedes albopictus pools, all sampled in an urban setting during the 2007 outbreak, were positive for the flavivirus Zika (ZIKV). The ratio of Aedes albopictus pools positive for ZIKV was similar to that positive for dengue virus during the concomitant dengue outbreak suggesting similar mosquito infection rates and, presumably, underlying a human ZIKV outbreak. ZIKV sequences from the envelope and NS3 genes were amplified from a human serum sample. Phylogenetic analysis placed the Gabonese ZIKV at a basal position in the African lineage, pointing to ancestral genetic diversification and spread.


Conclusions/Significance 
We provide the first direct evidence of human ZIKV infections in Gabon, and its first occurrence in the Asian tiger mosquito, Aedes albopictus. These data reveal an unusual natural life cycle for this virus, occurring in an urban environment, and potentially representing a new emerging threat due to this novel association with a highly invasive vector whose geographic range is still expanding across the globe.

/pdf/zika-virus-in-gabon-central-africa-2007-a-new-threat-from-29349zd560.pdf

Zika Virus in Gabon (Central Africa) – 2007: A New Threat from Aedes albopictus?

Background 
A Chikungunya (CHIK) outbreak hit La Reunion Island in 2005–2006. The implicated vector was Aedes albopictus. Here, we present the first study on the susceptibility of Ae. albopictus populations to sympatric CHIKV isolates from La Reunion Island and compare it to other virus/vector combinations.


Methodology and Findings 
We orally infected 8 Ae. albopictus collections from La Reunion and 3 from Mayotte collected in March 2006 with two Chikungunya virus (CHIKV) from La Reunion: (i) strain 05.115 collected in June 2005 with an Alanine at the position 226 of the glycoprotein E1 and (ii) strain 06.21 collected in November 2005 with a substitution A226V. Two other CHIKV isolates and four additional mosquito strains/species were also tested. The viral titer of the infectious blood-meal was 107 plaque forming units (pfu)/mL. Dissemination rates were assessed by immunofluorescent staining on head squashes of surviving females 14 days after infection. Rates were at least two times higher with CHIKV 06.21 compared to CHIKV 05.115. In addition, 10 individuals were analyzed every day by quantitative RT-PCR. Viral RNA was quantified on (i) whole females and (ii) midguts and salivary glands of infected females. When comparing profiles, CHIKV 06.21 produced nearly 2 log more viral RNA copies than CHIKV 05.115. Furthermore, females infected with CHIKV 05.115 could be divided in two categories: weakly susceptible or strongly susceptible, comparable to those infected by CHIKV 06.21. Histological analysis detected the presence of CHIKV in salivary glands two days after infection. In addition, Ae. albopictus from La Reunion was as efficient vector as Ae. aegypti and Ae. albopictus from Vietnam when infected with the CHIKV 06.21.


Conclusions 
Our findings support the hypothesis that the CHIK outbreak in La Reunion Island was due to a highly competent vector Ae. albopictus which allowed an efficient replication and dissemination of CHIKV 06.21.

/pdf/two-chikungunya-isolates-from-the-outbreak-of-la-reunion-3ot05801sz.pdf

Two Chikungunya isolates from the outbreak of La Reunion (Indian Ocean) exhibit different patterns of infection in the mosquito, Aedes albopictus.

Chikungunya fever is a viral disease transmitted to human beings by Aedes genus mosquitoes. From 1972 to 1986 in Kedougou, Senegal, 178 Chikungunya virus strains were isolated from gallery forest mosquitoes, with most of them isolated from Ae. furcifer-taylori (129 strains), Ae. luteocephalus (27 strains), and Ae. dalzieli (12 strains). The characteristics of the sylvatic transmission cycle are a circulation periodicity with silent intervals that last approximately three years. Few epidemics of this disease have been reported in Senegal. The most recent one occurred in 1996 in Kaffrine where two Chikungunya virus strains were isolated from Ae. aegypti. The retrospective analysis of viral isolates from mosquitoes, wild vertebrates, and humans allowed to us to characterize Chikungunya virus transmission cycles in Senegal and to compare them with those of yellow fever virus.

/pdf/vectors-of-chikungunya-virus-in-senegal-current-data-and-u21v65ztip.pdf

Didier Fontenille

Papers

Aedes albopictus, an arbovirus vector: from the darkness to the light.

Zika Virus in Gabon (Central Africa) – 2007: A New Threat from Aedes albopictus?

Two Chikungunya isolates from the outbreak of La Reunion (Indian Ocean) exhibit different patterns of infection in the mosquito, Aedes albopictus.

Vectors of Chikungunya virus in Senegal: current data and transmission cycles.

Aedes albopictus as an epidemic vector of chikungunya virus: another emerging problem?