Improved reference genome of the arboviral vector Aedes albopictus

Genome biology · 2020 · 138 citations

• Biology
• Genetics
• Computational biology

BACKGROUND: The Asian tiger mosquito Aedes albopictus is globally expanding and has become the main vector for human arboviruses in Europe. With limited antiviral drugs and vaccines available, vector control is the primary approach to prevent mosquito-borne diseases. A reliable and accurate DNA sequence of the Ae. albopictus genome is essential to develop new approaches that involve genetic manipulation of mosquitoes. RESULTS: We use long-read sequencing methods and modern scaffolding techniques (PacBio, 10X, and Hi-C) to produce AalbF2, a dramatically improved assembly of the Ae. albopictus genome. AalbF2 reveals widespread viral insertions, novel microRNAs and piRNA clusters, the sex-determining locus, and new immunity genes, and enables genome-wide studies of geographically diverse Ae. albopictus populations and analyses of the developmental and stage-dependent network of expression data. Additionally, we build the first physical map for this species with 75% of the assembled genome anchored to the chromosomes. CONCLUSION: The AalbF2 genome assembly represents the most up-to-date collective knowledge of the Ae. albopictus genome. These resources represent a foundation to improve understanding of the adaptation potential and the epidemiological relevance of this species and foster the development of innovative control measures.

Species delimitation and invasion history of the balsam woolly adelgid, <i>Adelges</i> ( <i>Dreyfusia</i> ) <i>piceae</i> (Hemiptera: Aphidoidea: Adelgidae), species complex

Systematic Entomology · 2020 · 18 citations

• Biology
• Zoology
• Ecology

Abstract The Adelges ( Dreyfusia ) piceae (Ratzeburg) species complex is a taxonomically unstable group of six species. Three of the species are cyclically parthenogenetic [ Ad . nordmannianae (Eckstein), Ad . prelli (Grossmann), and Ad . merkeri (Eichhorn)] and three are obligately asexual [ Ad . piceae , Ad . schneideri (Börner), and Ad . nebrodensis (Binazzi &amp; Covassi)]. Some species are high‐impact pests of fir ( Abies ) trees, so stable species names are needed to communicate effectively about management. Therefore, to refine species delimitation, guided by a reconstruction of their biogeographic history, we genotyped adelgids from Europe, North America, and the Caucasus Mountains region with 19 microsatellite loci, sequenced the COI DNA barcoding region, and compared morphology. Discriminant analysis of principal components of microsatellite genotypes revealed four distinct genetic clusters. Two clusters were morphologically consistent with Ad . nordmannianae . One of these clusters consisted of samples from the Caucasus Mountains and northern Turkey, and the other included samples from this region as well as from Europe and North America, where Ad . nordmannianae is invasive. A third cluster was morphologically consistent with Ad . piceae , and included individuals from Europe, where it is native, and North America, where it is invasive. In North America, the majority of Ad . piceae individuals were assigned to two geographically widespread clones, suggesting multiple introductions. The fourth cluster included individuals morphologically consistent with Ad . prelli or Ad . merkeri . However, based on genetic assignments, hybrid simulations, and approximate Bayesian computation, we find it likely that these are contemporary hybrids between Ad . nordmannianae and Ad . piceae that arose independently in Europe and North America, so we propose that Ad . prelli and Ad . merkeri are invalid. Finally, we synonymise Ad . schneideri (syn.n.) with Ad . nordmannianae and designate Ad . nebrodensis as subspecies Ad . piceae nebrodensis (stat.n.) . Our revised taxonomy therefore recognises two species: Ad . nordmannianae and Ad . piceae , which we estimate to have diverged recently, during one of the last two interglacial periods. Finally, we comment on this species complex being in the midst of transition between sexual and asexual reproduction, a pattern that is probably common in Adelgidae.