Evidence through crossmating experiments of a species complex in Anopheles pseudopunctipennis sensu lato: a primary malaria vector of the American continent

The insupportable validity of mosquito subspecies (Diptera: Culicidae) and their exclusion from culicid classification

Beginning about 80 years ago, the recognition of morphological varieties of mosquitoes was gradually replaced by the recognition of subspecies. As an examination of revisionary and detailed taxonomic studies of mosquitoes clearly shows, subspecies are untenable concepts which have been synonymized with nominotypical forms or recognized as distinct species. Thus, from our perspective, subspecies is not a functional or practical taxonomic rank. Consequently, in this study we critically assessed the taxonomic status of the 120 nominal taxa distinguished as subspecies before now to determine whether they should be recognized as separate species or synonymous names. As a result, 96 subspecies are formally elevated to specific rank, 22 are relegated to synonymy with nominotypical forms, one is considered a nomen dubium, one a species inquirenda and the names of four nominal species regarded as synonyms are revalidated. The subspecies and their new status are listed in a conspectus. The revalidated species include Anopheles argentinus (Brèthes, 1912), from synonymy with An. pseudopunctipennis Theobald, 1901c; An. peruvianus Tamayo, 1907, from synonymy with An. pseudopunctipennis as nomen dubium; Culex major Edwards, 1935, from synonymy with Cx. annulioris consimilis Newstead, 1907; and Trichoprosopon trichorryes (Dyar & Knab, 1907), from synonymy with Tr. compressum Lutz, 1905. Additionally, the type locality of Anopheles sergentii Theobald, 1907 is restricted to El Outaya, Biskra Province, Algeria. A complete list of species to be retained, added to or removed from the Encyclopedia of Life, with a few corrections, is provided.

Demographic history and population structure of Anopheles pseudopunctipennis in Argentina based on the mitochondrial COI gene

Background

Anopheles pseudopunctipennis is an important malaria vector in the Neotropical region and the only species involved in Plasmodium transmission in the Andean foothills. Its wide geographical distribution in America, high preference for biting humans and capacity to rest inside dwellings after feeding, are attributes contributing to its vector status. Previous reports have tried to elucidate its taxonomic status, distinguishing populations from North, Central and South America. In the present study we used a mitochondrial marker to examine the demographic history of An. pseudopunctipennis in northwestern Argentina.

Methods

Twelve localities were selected across 550 km of the distribution of this species in Argentina, including two near the Bolivian border and several in South Tucumán, for sampling. A fragment of the cytochrome oxidase I (COI) gene was sequenced and haplotype relationships were analyzed by a statistical parsimony network and a Neighbor-Joining (NJ) tree. Genetic differentiation was estimated with F_ST. Historical demographic processes were evaluated using diversity measures, neutrality tests and mismatch distribution.

Results

Forty-one haplotypes were identified, of which haplotype A was the most common and widely distributed. Neither the network nor the NJ tree showed any geographic differentiation between northern and southern populations. Haplotype diversities, Tajima’s D_T and Fu & Li’s F and D neutrality tests and mismatch distribution supported a scenario of Holocene demographic expansion.

Conclusion

The demographic pattern suggests that An. pseudopunctipennis has undergone a single colonization process, and the ancestral haplotype is shared by specimens from all localities, indicating mitochondrial gene flow. Genetic differentiation was minimal, observed only between one northern and one southern locality. The estimated time of the population expansion of this species was during the Holocene. These data suggest that regional vector control measures would be equally effective in both northern and southern localities sampled, but also that insecticide resistant genes may spread rapidly within this region.

Development of Exon-Primed Intron-Crossing (EPIC) PCR primers for the malaria vector Anopheles pseudopunctipennis (Diptera: Culicidae)

Using the Anopheles gambiae Giles genome as a template, we designed, screened and identified 14 novel Exon-Primed Intron-Crossing (EPIC) PCR primer pairs for Anopheles pseudopunctipennis Theobald 1901, a major vector of human Plasmodium sp. in South America. These primers were designed to target the conserved regions flanking consecutive exons of different genes and enabled the amplification of 17 loci of which nine were polymorphic. Polymorphisms at these loci ranged from two to four alleles. Intron length polymorphism analysis is a useful tool, which will allow the study of the population structure of this mosquito species, which remains poorly understood.

Abundance patterns of Anopheles pseudopunctipennis and Anopheles argyritarsis in northwestern Argentina

Anopheles pseudopunctipennis is an important malaria vector in Argentina but the role of Anopheles argyritarsis in the transmission of the parasite is still unknown. Abundance patterns of both species and their relationship to climatic variables were studied in the subtropical mountainous forest in northwestern Argentina. Adults were collected with CDC light traps from September 2002 to November 2005 in Salta (northern area) and Tucumán (southern area) provinces, from 3 localities in each province. The abundance of both species in localities was compared using the Kruskal-Wallis test, and their changes in abundance in relation to climatic variables were analyzed by Multilevel Poisson Regression. Anopheles argyritarsis was more abundant than A. pseudopunctipennis, and both reached a peak during the spring. There were significant differences in abundance in the northern localities for A. pseudopunctipennis, and between northern and southern localities for A. argyritarsis. Temperature, rainfall and relative humidity were significant predictors of the abundance of these two species.

Laboratory colonization of Anopheles pseudopunctipennis (Diptera: Culicidae) without forced mating

Anopheles pseudopunctipennis is one of the main malaria vectors in the Andean regions of South America. Few experimental data exist on this species because it is not very available in laboratories due to its eurygamic status that makes colony maintenance difficult. Indeed, individuals do not mate in the confined space of insectary cages. To avoid this problem, forced artificial mating can be used. However, this technique is time consuming, requires a well-trained technician, and is inadequate for easy mass production, which is sometimes necessary for certain experimental works. This study presents a technique based on exposure of adult mosquitoes to a blue stroboscopic light for 20 min during several nights, which encourages them to copulate naturally under laboratory conditions. After some generations, a self-free-mating strain was obtained. The technique is simple, inexpensive and is probably effective whatever the An. pseudopunctipennis strain considered.

Anopheles (Anopheles) pseudopunctipennis Theobald (Diptera: Culicidae): neotype designation and description

Detailed morphological descriptions and illustrations are provided for the adult male and female, male genitalia, pupal, and larval stages of Anopheles (Anopheles) pseudopunctipennis Theobald, a major vector of human malaria in Central and South America. Taxonomic and related literature records, diagnostic features, distribution, and bionomics of the species are included. A neotype male for the species from the type locality of Grenada is designated.

Molecular systematics of Anopheles: from subgenera to subpopulations

The century-old discovery of the role of Anopheles in human malaria transmission precipitated intense study of this genus at the alpha taxonomy level, but until recently little attention was focused on the systematics of this group. The application of molecular approaches to systematic problems ranging from subgeneric relationships to relationships at and below the species level is helping to address questions such as anopheline phylogenetics and biogeography, the nature of species boundaries, and the forces that have structured genetic variation within species. Current knowledge in these areas is reviewed, with an emphasis on the Anopheles gambiae model. The recent publication of the genome of this anopheline mosquito will have a profound impact on inquiries at all taxonomic levels, supplying better tools for estimating phylogeny and population structure in the short term, and ultimately allowing the identification of genes and/or regulatory networks underlying ecological differentiation, speciation, and vectorial capacity.

Systematics of mosquito disease vectors (Diptera, Culicidae): impact of molecular biology and cladistic analysis

The field of medical entomology, by nature of its association with problems of human health, has been conservative in its application of molecular and computer technologies to systematic research. Recently, however, these methods have opened new interpretations for systematics of disease vectors. Medically important insects, particularly mosquitoes, are among those more thoroughly described by conventional taxonomy, and thereby provide a secure framework for testing congruencies with molecular data. In turn, molecular investigations have provided a stimulus to vector systematics in the discovery and delineation of cryptic species complexes, as well as providing new perspectives on relationships at higher taxonomic divisions. In this review, examples involving cladistic analysis, cytogenetics--in situ hybridization, isoenzymes, DNA sequencing, and restriction fragment polymorphism are drawn from the following taxa: Aedes communis; Aedes (Ochlerotatus) group G; Aedes (Stegomyia) species including A. aegypti, A. albopictus, and A. scutellaris group; Anopheles albitarsis, Anopheles dirus, Anopheles gambiae, Anopheles nuneztovari, Anopheles pseudopunctipennis, and Anopheles punctulatus groups; Culex pipiens and the Culex subgenus Melanoconion; and the tribe Sabethini.