River-specific macrogenomic diversity in Simulium guianense s. l. (Diptera: Simuliidae), a complex of tropical American vectors associated with human onchocerciasis

Abstract

Simulium guianense Wise is a Latin American vector complex of black flies associated with transmission of the causal agent of human onchocerciasis (river blindness). An analysis of the chromosomal banding patterns of 607 larvae of S. guianense s. l. revealed a high level of variation involving 83 macrogenomic rearrangements across 25 populations in Brazil, French Guiana, and Venezuela. The 25 populations were assigned to 13 cytoforms (A1, A2, B1–B4, C, D, E1–E4, and F), some of which are probably valid species. Based on geographical proximity, a member of the B group of cytoforms probably represents the name-bearing type specimen of S. guianense and the primary vector in the last-remaining onchocerciasis foci in the Western Hemisphere. Cytoform B3 in Amapá State is implicated as an anthropophilic simuliid in an area currently and historically free of onchocerciasis. Distributions of cytoforms are associated with geography, elevation, and drainage basin, and are largely congruent with ecoregions. Despite extraordinarily large larval populations of S. guianense s. l. in big rivers and consequent production of female flies for dispersal, the cytoforms maintain their chromosomal distinction within individual rivers, suggesting a high degree of fidelity to the specialized breeding habitats—rocky shoals—of the natal rivers.

Phylogeography and population diversity of Simulium hirtipupa Lutz (Diptera: Simuliidae) based on mitochondrial COI sequences

“…A previous study on populations from similar regions indicated that the distributions of the cytoforms of S . guianense are also congruent with the freshwater ecoregions [ 28 ].…”

“…On one occasion we noticed a significant reduction in the river’s water flow during sampling, which might have forced the females to oviposit in or near their natal habitat instead of dispersing. In simuliids, site fidelity may play an important role in local adaptation, which may lead to isolation, population differentiation, and, ultimately to speciation [ 17 , 28 ].…”

“…Cryptic differentiation is common to many Simuliidae species [ 28 ]. Accordingly, the genus Simulium comprises several species complexes [ 1 , 6 , 14 ].…”

“…Accordingly, the genus Simulium comprises several species complexes [ 1 , 6 , 14 ]. Cryptic taxa can however display key differences that are important for ecological and epidemiological reasons, since the larvae of some species are important bioindicators and adults of some species are vectors of diseases, respectively [ 2 , 6 , 28 – 30 ]. Therefore, accurate identification at the species level is paramount for biomonitoring and control programmes [ 6 ].…”

Sympatric speciation in the Simulium arcticum s. l. complex (Diptera: Simuliidae): The Rothfels model updated

“…Our observations also suggest that extensive sampling and analysis are necessary to adequately characterize the chromosome diversity at any one site and that break points of inversions seem not to influence the origin of additional inversions. Future genomic 3D analysis (Adler, Hamada, Nascimento, & Grillet, ) of inversion hotspots within the complex should prove invaluable for defining the potential structural integrity/molecular makeup of inversions and their potential functions.…”