Cytotaxonomy of the Simulium damnosum complex from central and northeastern Tanzania

Abstract

A cytotaxonomic study of the medically important insect vector, Simulium damnosum s.l., revealed the presence of seven and possibly eight distinct taxa from central and northeastern Tanzania. Larval salivary gland polytene chromosome maps are presented for the first time for five cytotypes and one sibling species, which include the Nkusi form, the Sanje form, the Kisiwani form, Ketaketa C1 and C2, and the Kibwezi form. Inversion disequilibrium in males of the Kibwezi form indicate population substructuring is occurring and that this population may be in the early stages of speciation. Adults of the sibling species S. damnosum Kibwezi form and cytotype of the S. damnosum Nkusi form were identified using Malpighian tubule polytene chromosomes. The taxonomic status of the populations under study are discussed in relation to previously published papers and unpublished reports. Dimorphisms for centromere band enhancement occur on all three polytene chromosomes of the complement. The same centromere band can be polymorphic, sex linked, fixed, or lost in various cytotypes. In constructing a partial phylogeny, a hypothetical intermediate is proposed to account for the diverse fate of these centromere band dimorphisms and other inversion polymorphisms in different members of this nearly pan African complex. This pattern of chromosome restructuring is consistent with that seen for other species complexes within the Simuliidae.

The cytotaxonomy and morphotaxonomy ofSimulium mengense(Diptera: Simuliidae)

“…The sibling-species identifications for the Mount-Cameroon samples have already been published (Post et al, 2003). As the pattern of fixed and polymorphic inversions present in the S. mengense collected was found to differ from that described by Vajime and Dunbar (1977), the results for the Cameroonian S. mengense were compared against chromosome maps, idiograms and descriptions of the East African cytospecies that have been reported to share inversions with S. mengense (Dunbar, 1969;Dunbar and Vajime, 1981;Procunier et al, 1987;Maegga and Cupp, 1993;Procunier and Muro, 1993).…”

“…Vajime and Dunbar (1977) also located the breakpoints of IIL-34 incorrectly in their artificial chromosome map. Inversion IIL-34 was supposedly shared with the 'Kibwezi' cytotype but neither Vajime nor Dunbar ever published chromosome maps for 'Kibwezi', and IIL-34 was found to have different breakpoints in later material examined by Procunier and Muro (1993).…”

“…2) is distinguished from IIIL-19 of 'Kibwezi' by the inclusion of section 86, which, according to Procunier and Muro (1993), is not part of IIIL-19. Inversion IIIL-109 was present in the figures published by Vajime and Dunbar (1977) but seems to have been mis-identified as IIIL-19.…”

Phylogenetic relationships among the black fly species (Diptera: Simuliidae) of Thailand based on multiple gene sequences

“…Species can be very difficult to discriminate morphologically (Crosskey 1981) so considerable effort has been devoted to the resolution of simuliid taxonomy by cytotaxonomic studies of the polytene chromosomes of larval salivary glands (Vajime and Dunbar 1975;Rothfels 1979;Bedo 1977Bedo , 1979Boakye 1993;Procunier and Muro 1993;Kuvangkadilok et al 1998Kuvangkadilok et al , 1999aKuvangkadilok et al , b, 2003Kuvangkadilok et al , 2008Phasuk et al 2005;Jitklang et al 2008). Only a few broad cladistic phylogenetic studies of the family are available.…”

Cytotaxonomic description ofSimulium kaffaense, a new member of theS. damnosumcomplex (Diptera: Simuliidae) from south–western Ethiopia

“…Although there is much information available on the taxonomy of the S. damnosum complex, the members of the complex that occur in western Africa, especially in the area formerly covered by the World Health Organization's Onchocerciasis Control Programme (OCP), are better described than those to be found in East and Central Africa (Vajime and Dunbar, 1975;Post, 1986;Boakye, 1993;Boakye et al, 1993). In East Africa, studies of the complex have concentrated mostly on the species within Tanzania Cupp, 1993, 1994;Procunier and Muro, 1993) and Uganda (Krü ger et al, 1998;Krü ger and Garms, 1999).…”