R. simus senegalensis; the last two forms have limited extensions into East Africa. West African forest species, in the Sudan known only from montane forests and lower streambanks of the Imatong and nearby mountain masses of the east bank of Equatoria Province, are H. parmata, R. bequaerti, and R. kochi. The Imatong Area also harbors several specialized East African forms not found elsewhere in the Sudan. The occurrence of populations of any of the first five species listed above outside of the Raga Loka Area (Figure 328) is excep tional. It should be noted that the term West African, as here used zoogeographically, applies to elements originating in the first six of the Faunal Districts listed in Figure 1. Several species logically considered as West African from a generalized point of view and in common name terminology are not considered West Afri can in the more strictly defined zoogeographical sense of the term. For instance, H. impressum, although confined to West Africa in the generalized geographical sense, is a savannah spe cies of the East African (zoogeographical) Subregion. H. houyi appears to be common in the savannahs of both Subregions; a though it is difficult to determine in which Subregion it should be considered typical the evidence strongly suggests East Africa. M. reidi sp. nov. is tentatively included here as a species of the West African Subregion since it has been found in only a restricted sector of the Raga Loka Area (Figure 328). Further investigation may modify this concept but it is unlikely that a large amount of data will ever be amassed on this curious spe cies. The unique biological characteristics and distributional picture of the two species in this genus, combined with their localization in remote areas, confuse an interpretation of their pattern of distribution. East African Components Species limited mostly to the area politically considered as East Africa are of considerable value as zoogeographical indicators for the present study. The fact that several of these species, such as Amblyomma gemma and Rhipicephalus pulchellus, are not known to reach the Sudan, is of additional interest. Two East African species, A. lepidum and R. pravus are espe cially interesting in that they are typical of the Kapoeta Area (Figure 328) and extend to Torit but little if any further west into Equatoria Province. The reduced rainfall and consequent mod ification of vegetation in the Kapoeta Area has already been noted (pages 836,838,839). R. pravus is unknown elsewhere in the Sudan; A. lepidum does spill over via the Eastern Floodplain to the Cen tral Rainlands where it is often common. A. lepidum is a species strictly confined to East African areas with reduced rainfall while R. pravus, though most common in the same areas, has a number of restricted outlying populations in southern and western Africa. It is therefore noteworthy that A. lepidum appears to be more aggressive in its Sudanese distribution than R. pravus. pravus. Reasons for these differences should be sought among the various factors noted for uneven tick distribution (pages 845 to 848). A. cohaerens, a strictly East African species that reaches its western limits in eastern Belgian Congo, is also known in the Sudan chiefly from the Kapoeta Area and questionably from adjacent parts of the Torit Area. H. bequaerti of Torit and Raga Loka Areas is confined to East Africa except for a single known population in western Sudan; this tick belongs to a group of hyrax parasitizing species not known otherwise to occur in West Africa. R. R. appendicu latus, on the other hand, is chiefly an East African species, but in the Sudan occurs only in the Imatong forests and a small corner of the Raga Loka Area, where it is common. R. appendiculatus requires a more humid environment than many East African species and is therefore absent in most East African areas of the Sudan. Popu lations of this tick also occur in the highlands of Central and southeastern Africa, probably in part due to movements of cattle. East African components typical of arid areas not infrequently extend their range into the Southwest Arid District (south western Union of South Africa, Ovamboland, Angola). An example of this pattern is A. brumpti. The ability of this species to reach and survive in dry niches such as hyrax dens in otherwise humid areas may account for its wide distribution and presence in areas that appear unsuitable for its survival. Although A. brumpti thrives and is best known from dry areas, its range of humidity toleration may be more extensive than presently realized. The general outline of the distribution of 0. savignyi in Africa is somewhat similar to that of A. brumpti. East African components of montane forests, I. schillingsi and R. compositus, have already been mentioned (page Species not already discussed are in part too poorly known to be designated as typically East African or as typically South African. Examples are A. marmoreum (group), R. ?distinctus, and I. rasus ?subspecies, the exact relationships of which are still unknown. Others, such as R. arnoldi, R. muhlensi, and R. supertritus, are widely spread but data are so Tew and incom plete that they shed little light on ecology or distribution patterns. A certain group of species that commonly attack domestic animals and that tolerate a moderately low to medium range of humidity factors are widely distributed throughout the Ethiopian Faunal Region. They are common in much of the Union of South Africa, in western Africa, and in the Sudan. In the Sudan, their range includes the Central Rainlands and sometimes even fairly arid areas such as the Red Sea Hills and coastal plains. The outstanding examples of this group of pan Ethiopian species are R. s. simus, R. e. evertsi, R. s. sanguineus, B. decoloratus, H. 1. leachii, H. rufipes, and H. truncatum. Another important group of species is almost as widely spread as those listed above but their apparent demand for high temperature and a medium humidity range restricts them from much of the Union of South Africa and from the northern savannahs (FasherButana Area) of the Sudan. These species are often common in western and eastern Africa as far south as Mozambique. The outstanding example is A. variegatum. H. h. hoodi, H. aciculifer, and A. tholloni are other species in this group. R. supertritus and R. muhlensi might also be considered in this category. |