Genetic and morphological polymorphisms of Aedes scapularis (Diptera: Culicidae), vector of filariae and arboviruses

Abstract

Background Aedes scapularis is a neotropical mosquito that is competent to vector viruses and filariae. It is reputed to be highly morphologically and genetically polymorphic, facts that have raised questions about whether it is a single taxonomic entity. In the last five decades, authors have posed the hypothesis that it could actually be a species complex under incipient speciation. Due to its epidemiological importance, its taxonomic status should be determined with confidence.

Aim and method Our objective was to investigate more deeply the polymorphism of Ae. scapularis to detect any evidence of incipient speciation of cryptic species. We then compared populational samples from the Southeastern, Northern and Northeastern regions of Brazil. The biological markers used in the comparison were: the complete mitochondrial DNA, the isolated mitochondrial gene cytochrome oxidase subunit I (COI) and wing geometry.

Results and discussion As expected, high morphological/genetic polymorphism was observed in all Ae. scapularis populations, however it was not indicative of segregation or incipient speciation. There was no correlation between wing shape and the geographical origin of the populations analysed. A congruent observation resulted from the analysis of the COI gene, which revealed a high number of haplotypes (51) and no clusterization of populational samples according to the original biomes. In the phylogenetic analysis of the 13 mitochondrial protein-coding genes, the Ae. scapularis clade clustered with maximum support (100% bootstrap support and posterior probability of 1). No significant internal structure was observed in the Ae. scapularis clade, which was nearly a polytomy. Taken together, our results indicate that this species is not a species complex.

Conclusion We conclude that there was no indication, in the analysed regions, of the occurrence of more than one taxon in the species Ae. scapularis, despite it being highly polymorphic. By ruling out the former species complex hypothesis, our phylogenetic results reinforce that Ae. scapularis is a single taxonomic unit and should be monitored with standardized surveillance and control methods.