Laboratoire de Recherche et de Conservation des Zones Humides, Université 8 Mai 1945 de Guelma, Guelma, Algeria.
Department of Plant and Environmental Sciences, Clemson University, Clemson, South Carolina, United States of America.
PLoS One. 2018 Oct 3;13(10):e0205137. doi: 10.1371/journal.pone.0205137. eCollection 2018.
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.
水生昆虫在地球最偏远的淡水生境中（如岛屿和沙漠）的定殖能力仅限于少数特定类群。在黑蝇中，首要的定殖专家是 Simulium ruficorne Macquart，这是唯一一种已知分布在热带非洲和古北界的物种。我们研究了 S. ruficorne 的细胞遗传学，以深入了解其广泛的地理分布和在海洋岛屿和沙漠定殖的能力。基于来自 14 个地点的幼虫多线染色体，我们记录了 17 种新的和以前已知的染色体重排，并建立了五个细胞型（A1、A2、B、C 和 D），其中可能有四个（A1/A2、B、C 和 D）是不同的物种，两个（A1 和 A2）代表涉及染色体 III 长臂异带的性染色体多态性。与五个细胞型相关的染色体结构重排现象与 Simuliidae 的趋势一致，即同一个重排在一个共同祖先的不同后代中可能具有不同的功能，而在该共同祖先中，重排是多态的。分布最广的细胞型是 A1 和 A2，它们分布在北非、加那利群岛和马略卡岛。Simulium ruficorne 是撒哈拉沙漠中部 Hoggar 山脉中唯一已知的黑蝇，代表了一个与其他北非 A1 和 A2 种群差异不大的 A1 细胞型聚集体。细胞型 B 栖息在西非大陆，细胞型 C 在特内里费岛，细胞型 D 在佛得角。我们认为，像 S. ruficorne 这样的扩散和定殖专家是临时溪流的多代居民，必须在其栖息地恶化时重新定位。因此，S. ruficorne 应该具有有助于成功扩散和定殖的适应能力，这些适应能力可能在很大程度上是生理上的，例如耐受高温和干旱。
