Biology, Systematics, Taxonomy, and Evolution of Insect Vectors

Established populations of Aedes aegypti, a mosquito vector of multiple major arthropod-borne viruses, were first found in three California (CA) cities in 2013. From 2013 to April 2021, Ae. aegypti thwarted almost all control efforts to stop its spread and expanded its range to 308 cities, including Exeter, in 22 counties in CA. Population genomic analyses have suggested that multiple genetically distinct Ae. aegypti populations were introduced into CA. However Ae. aegypti collected for the first time in 2014 in Exeter, appeared to be different from three major genetic clusters found elsewhere in CA. Due to intense control efforts by the Delta Vector Control District (DVCD), Ae. aegypti was thought to have been eliminated from Exeter in 2015. Unfortunately, it was recollected in 2018. It was not clear if the reemergence of Ae. aegypti in Exeter was derived from the bottlenecked remnants of the original 2014 Exeter population or from an independent invasion from a different population derived from surrounding areas. The goal of this work was to determine which of these scenarios occurred (recovery after bottleneck or reintroduction after elimination) and if elimination and reintroduction occurred to identify the origin of the invading population using a population genomic approach. Our results support the reintroduction after elimination hypothesis. The source of reintroduction, however, was unexpectedly from the southern CA cluster rather than from other two geographically closer central CA genetic clusters. We also conducted a knockdown resistance mutation profile, which showed Exeter 2014 had the lowest level of resistant alleles compared to the other populations, could have contributed towards DVCD’s ability to locally eliminate Ae. aegypti in 2014.

The Rhodniini tribe is one of the five tribes in the subfamily Triatominae and is notorious for its domestic blood-sucking pests and vectors of Trypanosoma cruzi across Latin America. The human and economic costs of the Chagas disease in the American tropics are considerable, and these insects are of unquestionable importance to humans. We used mitochondrial rDNA (16S), nuclear ribosomal RNA (28S) and wingless (Wg) sequences to perform phylogenetic analysis to derive trees based on parsimony and maximum likelihood. Nucleotide sequences were used in molecular-clock analyses to estimate time divergence between species of Rhodniini. The potential distribution of each species was modeled and compared with Kappa statistic. Multivariate niches with bioclimatic variables were used to describe differences between the species using discriminant analysis. The results of this study indicate that the Rhodniini originated 17.91 Mya ago. Rhodnius domesticus is the oldest species having its origin at 9.13 Mya. Rhodniini are closely related to Salyavatinae that are specialist termite predators and diverged from this subfamily 30.43 Mya. Most species are clearly allopatric and have distinct bioclimatic niches. The colonization of bromeliads, palms trees and bird nests represent important events for the speciation of these taxa. The hematophagous habit can be described as a scenario where Rhodniini’s ancestor could be pre-adapted for the invasion of bromeliads, palm trees, and bird nests where they would find significant water availability and thermal damping. These environments are widely used by vertebrate inquilines that would be the source of food for the species of Rhodniini. Lastly, our results show an alternative position of Psammolestes in the phylogenetic tree.