A SNP in the gene encoding lactase (LCT) (C/T-13910) is associated with the ability to digest milk as adults (lactase persistence) in Europeans, but the genetic basis of lactase persistence in Africans was previously unknown. We conducted a genotype-phenotype association study in 470

/pdf/convergent-adaptation-of-human-lactase-persistence-in-africa-4exuxz9ryv.pdf

Convergent adaptation of human lactase persistence in Africa and Europe

Gene drives may be capable of addressing ecological problems by altering entire populations of wild organisms, but their use has remained largely theoretical due to technical constraints. Here we consider the potential for RNA-guided gene drives based on the CRISPR nuclease Cas9 to serve as a general method for spreading altered traits through wild populations over many generations. We detail likely capabilities, discuss limitations, and provide novel precautionary strategies to control the spread of gene drives and reverse genomic changes. The ability to edit populations of sexual species would offer substantial benefits to humanity and the environment. For example, RNA-guided gene drives could potentially prevent the spread of disease, support agriculture by reversing pesticide and herbicide resistance in insects and weeds, and control damaging invasive species. However, the possibility of unwanted ecological effects and near-certainty of spread across political borders demand careful assessment of each potential application. We call for thoughtful, inclusive, and well-informed public discussions to explore the responsible use of this currently theoretical technology.

/pdf/concerning-rna-guided-gene-drives-for-the-alteration-of-wild-2la0voj6g0.pdf

Concerning RNA-guided gene drives for the alteration of wild populations

Engineered gene drives - the process of stimulating the biased inheritance of specific genes - have the potential to enable the spread of desirable genes throughout wild populations or to suppress harmful species, and may be particularly useful for the control of vector-borne diseases such as malaria. Although several types of selfish genetic elements exist in nature, few have been successfully engineered in the laboratory thus far. With the discovery of RNA-guided CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-CRISPR-associated 9) nucleases, which can be utilized to create, streamline and improve synthetic gene drives, this is rapidly changing. Here, we discuss the different types of engineered gene drives and their potential applications, as well as current policies regarding the safety and regulation of gene drives for the manipulation of wild populations.

/pdf/cheating-evolution-engineering-gene-drives-to-manipulate-the-429dkalaqo.pdf

Cheating evolution: engineering gene drives to manipulate the fate of wild populations

宏生态学是生态学与其他宏观学科不断交叉和融合后的产物.它以个体、种群和物种的生态特征在大时空尺度上的格局和变化规律为主要研究内容,它比其他生态学更强调归纳和推论,也更依赖数据的积累.近年来,宏生态学在对物种-面积关系进行探讨的基础上,对生物类群间的物种数量的协同变化以及物种和高级分类单元间的关系等进行了新的研究;宏生态学试图将有机论和个体论结合来探讨和总结群落结构中的物种组成规律;并对物种多度和分布格局间的关系从生态位和异质种群角度进行新的解释;个体大小频次分布规律是宏生态学一重要内容,对其深入研究和探讨已与物种多度、能量、分布面积、历史起源等多方面特征相结合,并得到一些普遍性规律;最后,宏生态学还探讨物种在地理区域上的普遍性的分布模式,并对其假说进行检验和探讨.宏生态学在中国还处于刚起步阶段,但中国具有资源的优势,并具有一定的数据积累, 将在宏生态学研究中发挥越来越重要的作用.

宏生态学（Macroecology）及其研究

Background
Although a vaccine could be available as early as 2016, vector control remains the primary approach used to prevent dengue, the most common and widespread arbovirus of humans worldwide. We reviewed the evidence for effectiveness of vector control methods in reducing its transmission.

Methodology/Principal Findings
Studies of any design published since 1980 were included if they evaluated method(s) targeting Aedes aegypti or Ae. albopictus for at least 3 months. Primary outcome was dengue incidence. Following Cochrane and PRISMA Group guidelines, database searches yielded 960 reports, and 41 were eligible for inclusion, with 19 providing data for meta-analysis. Study duration ranged from 5 months to 10 years. Studies evaluating multiple tools/approaches (23 records) were more common than single methods, while environmental management was the most common method (19 studies). Only 9/41 reports were randomized controlled trials (RCTs). Two out of 19 studies evaluating dengue incidence were RCTs, and neither reported any statistically significant impact. No RCTs evaluated effectiveness of insecticide space-spraying (fogging) against dengue. Based on meta-analyses, house screening significantly reduced dengue risk, OR 0.22 (95% CI 0.05–0.93, p = 0.04), as did combining community-based environmental management and water container covers, OR 0.22 (95% CI 0.15–0.32, p 0.5), but insecticide aerosols (OR 2.03; 95% CI 1.44–2.86) and mosquito coils (OR 1.44; 95% CI 1.09–1.91) were associated with higher dengue risk (p = 0.01). Although 23/41 studies examined the impact of insecticide-based tools, only 9 evaluated the insecticide susceptibility status of the target vector population during the study.

Conclusions/Significance
This review and meta-analysis demonstrate the remarkable paucity of reliable evidence for the effectiveness of any dengue vector control method. Standardised studies of higher quality to evaluate and compare methods must be prioritised to optimise cost-effective dengue prevention.

Author Summary
Dengue fever has increased dramatically over the past 50 years and today is the most widespread mosquito-borne arboviral disease, affecting nearly half the world’s population in 128 countries. Until the arrival of a vaccine, control of its Aedes vectors has been the only method to prevent dengue infection. With dengue outbreaks occurring at increasing frequency and intensity, we undertook a systematic review and meta-analysis of the literature, to evaluate the evidence for effectiveness of vector control strategies currently available. Forty-one studies (from 5 months to 10 years duration) were included in the review. Most studies investigated combinations of approaches but only 9 studies were randomized controlled trials (RCTs). Remarkably, no RCTs evaluated effectiveness against dengue of insecticide space-spraying (outdoor fogging), the main response to dengue outbreaks used worldwide. Nevertheless, there was limited evidence indicating that house screening and to a lesser extent, community-based environmental management with water container covers could reduce risk of dengue infection. However, skin repellents, bed nets and mosquito traps had no effect while insecticide aerosols and mosquito coils were associated with higher dengue risk. However, the quality of the few studies eligible for inclusion was poor overall, and the evidence base is very weak, compromising the knowledge base for making recommendations on delivery of appropriate and effective control. Given this paucity of reliable evidence, standardised studies of higher quality must now be a priority.

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Is Dengue Vector Control Deficient in Effectiveness or Evidence?: Systematic Review and Meta-analysis.

The idea of introducing genetic modifications into wild populations of insects to stop them from spreading diseases is more than 40 years old. Synthetic disease refractory genes have been successfully generated for mosquito vectors of dengue fever and human malaria. Equally important is the development of population transformation systems to drive and maintain disease refractory genes at high frequency in populations. We demonstrate an underdominant population transformation system in Drosophila melanogaster that has the property of being both spatially self-limiting and reversible to the original genetic state. Both population transformation and its reversal can be largely achieved within as few as 5 generations. The described genetic construct {Ud} is composed of two genes; (1) a UAS-RpL14.dsRNA targeting RNAi to a haploinsufficient gene RpL14 and (2) an RNAi insensitive RpL14 rescue. In this proof-of-principle system the UAS-RpL14.dsRNA knock-down gene is placed under the control of an Actin5c-GAL4 driver located on a different chromosome to the {Ud} insert. This configuration would not be effective in wild populations without incorporating the Actin5c-GAL4 driver as part of the {Ud} construct (or replacing the UAS promoter with an appropriate direct promoter). It is however anticipated that the approach that underlies this underdominant system could potentially be applied to a number of species.

/pdf/first-steps-towards-underdominant-genetic-transformation-of-301rt6aham.pdf

First steps towards underdominant genetic transformation of insect populations.

Experimental releases of genetically modified (GM) insects are reportedly being evaluated in various countries, including Brazil, the Cayman Islands (United Kingdom), France, Guatemala, India, Malaysia, Mexico, Panama, Philippines, Singapore, Thailand, the United States of America, and Vietnam. GM mosquitoes (Aedes aegypti) have already been released for field trials into inhabited areas in the Cayman Islands (2009–?), Malaysia (2010–2011), and Brazil (2011–2012). Here, we assess the regulatory process in the first three countries permitting releases (Malaysia, US, and the Cayman Islands) in terms of pre-release transparency and scientific quality. We find that, despite 14 US government–funded field trials over the last 9 years (on a moth pest of cotton), there has been no scientific publication of experimental data, and in only two instances have permit applications been published. The world's first environmental impact statement (EIS) on GM insects, produced by US authorities in 2008, is found to be scientifically deficient on the basis that (1) most consideration of environmental risk is too generic to be scientifically meaningful; (2) it relies on unpublished data to establish central scientific points; and (3) of the approximately 170 scientific publications cited, the endorsement of the majority of novel transgenic approaches is based on just two laboratory studies in only one of the four species covered by the document. We find that it is not possible to determine from documents publically available prior to the start of releases if obvious hazards of the particular GM mosquitoes released in Malaysia, the Cayman Islands, and Brazil received expert examination. Simple regulatory measures are proposed that would build public confidence and stimulate the independent experimental studies that environmental risk assessments require. Finally, a checklist is provided to assist the general public, journalists, and lawmakers in determining, from documents issued by regulators prior to the start of releases, whether permit approval is likely to have a scientifically high quality basis

/pdf/scientific-standards-and-the-regulation-of-genetically-45n7zrrhi0.pdf

Scientific Standards and the Regulation of Genetically Modified Insects

Using underdominance to bi-stably transform local populations.

We present a phylogeographical analysis of four genera of Mesoamerican primary freshwater fish ( Brycon , Bryconamericus , Eretmobrycon , and Cyphocharax ). Three hundred and thirty-nine individuals were genotyped into one of 31 operational taxonomic units (OTUs) based on the nucleotide sequence of their mitochondrial ATPase 6 & 8 genes (842‐839 bp). Contrary to inference based on the species-level taxonomy of these genera, molecular data identified only a single case of sympatry between closely related OTUs, despite extensive parapatry. Polytomies dominate the mtDNA-based phylogenies and demonstrate multiple, noncontemporaneous waves of rapid expansion across Mesoamerica from South American sources. Analyses based on genetic distances observed among congeneric species of Mesoamerican primary freshwater fishes in comparison to divergence between transisthmian marine fishes permit the strong inference that the Pliocene rise of the Panama land bridge provided the first opportunity for the colonization of Mesoamerica by Characiform fishes. We develop a priority-effect model, based on the assumption that genetically closely related OTUs share similar ecological niches, to reconcile the general lack of contemporary sympatry between closely related OTUs with the substantial historical connectivity among Mesoamerican drainages demonstrated by the rapid expansion of Brycon , Bryconamericus , and Cyphocharax . Finally, in most cases, we infer that the westerly limits of freshwater fish distributions in Mesoamerica are more consistent with being defined by ecological factors rather than by dispersal limitation. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 235‐255.

Colonization, population expansion, and lineage turnover: Phylogeography of Mesoamerican characiform fish

There is mounting evidence consistent with a general role of positive selection acting on the Drosophila melanogaster X-chromosome. However, this positive selection need not necessarily arise from forces that are adaptive to the organism. Nonadaptive meiotic drive may exist on the X-chromosome and contribute to forces of selection. Females from a reference D. melanogaster line, containing the X-linked marker white, were crossed to males from 49 isofemale lines established from seven African and five non-African natural populations to detect naturally occurring meiotic drive. Several lines exhibited a departure from expected Mendelian transmission of X-chromosomes to the third generation (F2) offspring, particularly those from hybrid African male parents. F2 viability was not correlated with skewed chromosomal inheritance. However, a significant difference in viability between cosmopolitan and tropical African crosses was observed. Recombination analysis supports the presence of a male-acting meiotic drive element near the centromeric region of the X-chromosome and putative recessive autosomal drive suppression. There is also evidence of another female-acting drive element linked to white. The possible role meiotic drive may contribute in shaping levels of genetic variation in D. melanogaster, and additional ways to test this hypothesis are discussed.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.0014-3820.2005.tb01778.x

R. Guy Reeves

Papers

First steps towards underdominant genetic transformation of insect populations.

Scientific Standards and the Regulation of Genetically Modified Insects

Using underdominance to bi-stably transform local populations.

Colonization, population expansion, and lineage turnover: Phylogeography of Mesoamerican characiform fish

Evidence of susceptibility and resistance to cryptic X-linked meiotic drive in natural populations of Drosophila melanogaster.