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

Abstract

The ability of aquatic insects to colonize Earth’s most remote freshwater habitats, such as those of islands and deserts, is limited to select taxa. Among black flies, the premiere colonization specialist is Simulium ruficorne Macquart, the only species known from both the Afrotropical and Palearctic regions. We investigated the cytogenetics of S. ruficorne to gain insight into its wide geographic distribution and ability to colonize oceanic islands and deserts. On the basis of larval polytene chromosomes from 14 locations, we documented 17 novel and previously known chromosomal rearrangements and established five cytoforms (A1, A2, B, C, and D), of which probably four (A1/A2, B, C, and D) are distinct species and two (A1 and A2) represent sex-chromosome polymorphism involving a heteroband in the long arm of chromosome III. The chromosome restructuring phenomena associated with the five cytoforms are consistent with the trend in the Simuliidae that one and the same rearrangement can assume different functions in the various descendants of a common ancestor in which the rearrangement was polymorphic. The most widely distributed cytoforms are A1 and A2, which are found in North Africa, the Canary Islands, and Majorca. Simulium ruficorne, the only known black fly in the Hoggar Mountains of the central Sahara Desert, represents a cohesive population of cytoform A1 little differentiated from other North African populations of A1 and A2. Cytoform B inhabits the West African mainland, cytoform C is on Tenerife, and cytoform D is on Cape Verde. We suggest that dispersal and colonization specialists, such as S. ruficorne, are multivoltine inhabitants of temporary streams, and must relocate as their habitats deteriorate. Simulium ruficorne, therefore, should have adaptations that contribute to successful dispersal and colonization, perhaps largely physiological in nature, such as tolerance of high temperatures and droughts.

Integrated taxonomy of black flies (Diptera: Simuliidae) reveals unexpected diversity in the most arid ecosystem of Europe

“…Other semi-arid regions in southern Spain with saline water, such as Rambla Salada in Murcia [77], should be explored for S. mellah and other simuliids. For instance, Simulium ruficorne, a characteristic species of desert environments in North Africa and the Iberian Peninsula [31], might be expected in our study area or similar ramblas.…”

“…An additional bias in our knowledge, given that black flies are linked to flowing water, is that many studies have been conducted in favorable ecosystems such as wet mountainous areas [27][28][29]. Yet, black flies also dwell in arid lowlands [6,[30][31][32][33]. Different trapping and identification methods and selection of specific habitats for sampling are needed to provide a comprehensive view of the simuliid community in any area.…”

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

“…It may be possible for different types of organisms to become reproductively isolated in different ways (Feder et al, ) . A case in point is the black fly, Simulium ruficorne s. l. with its present‐day allopatric distribution of cytotypes/siblings (Cherairia & Adler, ) .…”