Aedes aegypti bears the common name “the yellow fever mosquito,” although, today, it is of more concern as the major vector of dengue, chikungunya, and, most recently, Zika viruses. In the present article, we review recent work on the population genetics of this mosquito in efforts to reconstruct its recent (approximately 600 years) history and relate these findings to epidemiological records of occurrences of diseases transmitted by this species. The two sources of information are remarkably congruent. Ae. aegypti was introduced to the New World 400–550 years ago from its ancestral home in West Africa via European slave trade. Ships from the New World returning to their European ports of origin introduced the species to the Mediterranean region around 1800, where it became established until about 1950. The Suez Canal opened in 1869 and Ae. aegypti was introduced into Asia by the 1870s, then on to Australia (1887) and the South Pacific (1904).

Aedes albopictus, the “Asian tiger mosquito,” is an aggressive biting mosquito native to Asia that has colonized all continents except Antarctica during the last ~30–40 years. The species is of great public health concern as it can transmit at least 26 arboviruses, including dengue, chikungunya, and Zika viruses. In this study, using double‐digest Restriction site‐Associated DNA (ddRAD) sequencing, we developed a panel of ~58,000 single nucleotide polymorphisms (SNPs) based on 20 worldwide Ae. albopictus populations representing both the invasive and the native range. We used this genomic‐based approach to study the genetic structure and the differentiation of Ae. albopictus populations and to understand origin(s) and dynamics of the recent invasions. Our analyses indicated the existence of two major genetically differentiated population clusters, each one including both native and invasive populations. The detection of additional genetic structure within each major cluster supports that these SNPs can detect differentiation at a global and local scale, while the similar levels of genomic diversity between native and invasive range populations support the scenario of multiple invasions or colonization by a large number of propagules. Finally, our results revealed the possible source(s) of the recent invasion in Americas, Europe, and Africa, a finding with important implications for vector‐control strategies.

Aedes aegypti, the major vector of dengue, yellow fever, chikungunya, and Zika viruses, remains of great medical and public health concern. There is little doubt that the ancestral home of the species is Africa. This mosquito invaded the New World 400‐500 years ago and later, Asia. However, little is known about the genetic structure and history of Ae. aegypti across Africa, as well as the possible origin(s) of the New World invasion. Here, we use ~17,000 genome‐wide single nucleotide polymorphisms (SNPs) to characterize a heretofore undocumented complex picture of this mosquito across its ancestral range in Africa. We find signatures of human‐assisted migrations, connectivity across long distances in sylvan populations, and of local admixture between domestic and sylvan populations. Finally, through a phylogenetic analysis combined with the genetic structure analyses, we suggest West Africa and especially Angola as the source of the New World's invasion, a scenario that fits well with the historic record of 16th‐century slave trade between Africa and Americas.

Phylogenetic analysis of the genus Euscorpius (Scorpiones: Euscorpiidae) across the Mediterranean region (86 specimens, 77 localities, four DNA markers: 16S rDNA, COI, COII, and ITS1), focusing on Greek fauna, revealed high variation, deep clade divergences, many cryptic lineages, paraphyly at subgenus level, and sympatry of several new and formerly known lineages. Numerous specimens from mainland and insular Greece, undoubtedly the least studied region of the genus' distribution, have been included. The reconstructed phylogeny covers representative taxa and populations across the entire genus of Euscorpius. The deepest clades detected within Euscorpius correspond (partially) to its current subgeneric division, outlining subgenera Tetratrichobothrius and Alpiscorpius. The rest of the genus falls into several clades, including subgenus Polytrichobothrius and a paraphyletic subgenus Euscorpius s.s. Several cryptic lineages are recovered, especially on the islands. The inadequacy of the morphological characters used in the taxonomy of the genus to delineate species is discussed. Finally, the time frame of differentiation of Euscorpius in the study region is estimated and the distributional patterns of the lineages are contrasted with those of other highly diversified invertebrate genera occurring in the study region.

BackgroundAedes aegypti, commonly known as “the yellow fever mosquito”, is of great medical concern today primarily as the major vector of dengue, chikungunya and Zika viruses, although yellow fever remains a serious health concern in some regions. The history of Ae. aegypti in Brazil is of particular interest because the country was subjected to a well-documented eradication program during 1940s-1950s. After cessation of the campaign, the mosquito quickly re-established in the early 1970s with several dengue outbreaks reported during the last 30 years. Brazil can be considered the country suffering the most from the yellow fever mosquito, given the high number of dengue, chikungunya and Zika cases reported in the country, after having once been declared “free of Ae. aegypti”.Methodology/Principal findingsWe used 12 microsatellite markers to infer the genetic structure of Brazilian Ae. aegypti populations, genetic variability, genetic affinities with neighboring geographic areas, and the timing of their arrival and spread. This enabled us to reconstruct their recent history and evaluate whether the reappearance in Brazil was the result of re-invasion from neighboring non-eradicated areas or re-emergence from local refugia surviving the eradication program. Our results indicate a genetic break separating the northern and southern Brazilian Ae. aegypti populations, with further genetic differentiation within each cluster, especially in southern Brazil.Conclusions/SignificanceBased on our results, re-invasions from non-eradicated regions are the most likely scenario for the reappearance of Ae. aegypti in Brazil. While populations in the northern cluster are likely to have descended from Venezuela populations as early as the 1970s, southern populations seem to have derived more recently from northern Brazilian areas. Possible entry points are also revealed within both southern and northern clusters that could inform strategies to control and monitor this important arbovirus vector.

In an attempt to control the mosquito-borne diseases yellow fever, dengue, chikungunya, and Zika fevers, a strain of transgenically modified Aedes aegypti mosquitoes containing a dominant lethal gene has been developed by a commercial company, Oxitec Ltd. If lethality is complete, releasing this strain should only reduce population size and not affect the genetics of the target populations. Approximately 450 thousand males of this strain were released each week for 27 months in Jacobina, Bahia, Brazil. We genotyped the release strain and the target Jacobina population before releases began for >21,000 single nucleotide polymorphisms (SNPs). Genetic sampling from the target population six, 12, and 27–30 months after releases commenced provides clear evidence that portions of the transgenic strain genome have been incorporated into the target population. Evidently, rare viable hybrid offspring between the release strain and the Jacobina population are sufficiently robust to be able to reproduce in nature. The release strain was developed using a strain originally from Cuba, then outcrossed to a Mexican population. Thus, Jacobina Ae. aegypti are now a mix of three populations. It is unclear how this may affect disease transmission or affect other efforts to control these dangerous vectors. These results highlight the importance of having in place a genetic monitoring program during such releases to detect un-anticipated outcomes.

BackgroundThe yellow fever mosquito Aedes aegypti transmits viral diseases that have plagued humans for centuries. Its ancestral home are forests of Africa and ~400–600 years ago it invaded the New World and later Europe and Asia, causing some of the largest epidemics in human history. The species was rarely detected in countries surrounding the Mediterranean Sea after the 1950s, but during the last 16 years it re-appeared in Madeira, Russia and in the eastern coast of the Black Sea. We genotyped Ae. aegypti populations from the Black Sea region to investigate whether this is a recent invasion (and if so, where it came from) or a remnant of pre-eradication populations that extended across the Mediterranean. We also use the Black Sea populations together with a world reference panel of populations to shed more light into the phylogeographical history of this species.ResultsMicrosatellites and ~19,000 genome-wide single nucleotide polymorphisms (SNPs) support the monophyletic origin of all populations outside Africa, with the New World as the site of first colonization. Considering the phylogenetic relationships, the Black Sea populations are basal to all Asian populations sampled. Bayesian analyses combined with multivariate analyses on both types of markers suggest that the Black Sea population is a remnant of an older population. Approximate Bayesian Computation Analysis indicates with equal probability, that the origin of Black Sea populations was Asia or New World and assignment tests favor the New World.ConclusionsOur results confirmed that Ae. aegypti left Africa and arrived in New World ~500 years ago. The lineage that returned to the Old World and gave rise to present day Asia and the Black Sea populations split from the New World approximately 100–150 years ago. Globally, the Black Sea population is genetically closer to Asia, but still highly differentiated from both New World and Asian populations. This evidence, combined with bottleneck signatures and divergence time estimates, support the hypothesis of present day Black Sea populations being remnants of older populations, likely the now extinct Mediterranean populations that, consistent with the historic epidemiological record, likely represent the original return of Ae. aegypti to the Old World.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-2933-2) contains supplementary material, which is available to authorized users.

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