Are black flies of the subgenusWilhelmia(Diptera: Simuliidae) multiple species or a single geographical generalist? Insights from the macrogenome

Abstract

Organisms with vast distributions often represent geographical mosaics of cryptic species. The black fly Simulium (Wilhelmia) lineatum is among the most widely distributed members of the family Simuliidae, ranging from the British Isles to eastern China. Rather than viewing S. lineatum as a possible aggregate of multiple species, taxonomists have suggested a more inclusive taxon with additional synonyms. Accordingly, S. lineatum is an ideal candidate for testing the hypothesis that a wide geographical distribution signals the presence of more than one species. A cytogenetic approach was used to probe the macrogenome of S. lineatum and other taxa proposed by taxonomists as conspecific. The banding patterns in the polytene chromosomes of 480 larvae from 15 countries across the Palearctic Region revealed 128 rearrangements of the complement. All rearrangements were autosomal and 89% were inversions nonrandomly distributed among species and among chromosome arms. The analyses clarify long-standing confusion over previously proposed names and reveal a longitudinal succession of four species sequentially replacing one another from west to east: Simulium lineatum s.s., Simulium balcanicum, Simulium turgaicum, and Simulium takahasii. Thus, S. turgaicum is recalled from synonymy and the other three species are validated. Within the most-represented species, S. balcanicum, the frequency of inversions follows a longitudinal gradient with a north-south bias; as the distance between the sites increases along this north-west-south-east axis, the similarity of inversion frequencies between sites decreases. Validation of the concept that broadly distributed black flies are composites of structurally similar species provides a framework for guiding discovery of additional biodiversity.

Vietnam, a Hotspot for Chromosomal Diversity and Cryptic Species in Black Flies (Diptera: Simuliidae)

“…Larvae in Carnoy’s fixative were sorted into morphotaxa, based on their key characters and those of associated life stages [ 18 ]. Polytene chromosomes were prepared according to standard Feulgen-staining procedures [ 23 ].…”

Genetic variation in a colonization specialist, Simulium ruficorne (Diptera: Simuliidae), the world’s most widely distributed black fly

“…Broad geographic distributions often signal the presence of cryptic biodiversity in the Simuliidae [ 34 , 35 ]. Simulium ruficorne has the largest geographic range of any simuliid in the world [ 20 ], and has been a prime candidate for hidden diversity, now confirmed by the discovery of chromosomally distinct segregates.…”

Overview of Zoonotic Diseases in Turkey: The One Health Concept and Future Threats

“…Black flies are distributed worldwide with the exception of Antartica and some oceanic islands. The black fly Simulium (Wilhelmia) lineatum is among the most widely distributed members of the Simuliidae family, ranging from the British Isles to eastern China (432,433). Occasionally, some severe infestations of black flies at the level of disasters also lead to devastating economic losses in some countries.…”

“…Black flies can also cause multideaths of animals, which are seen suddenly, particularly in cattle due to simulotoxicosis and toxic shock (434). In Turkey, some Simulium species have been reported, which showed pest characteristics and caused outbreaks (432,433,435,436). In contrast, in a study that was performed for molecular detection of blood-feeding preferences of Simulium species in Central Kizilirmak Basin of Turkey, Onchocerca sp and Leucocytozoon sp were detected in the samples of Simulium spp.…”