SECTION 7. INVERTEBRATES, WITH THE MAIN EMPHASIS PLACED ON MILLIPEDES.

By Line Louise Sørensen.

7.1. Abstract.

This section deals with the invertebrate fauna of the Ulugurus with the main emphasis placed on millipedes. A complete checklist of millipede species known from the Ulugurus is presented, including 14 taxa collected during The Uluguru Biodiversity Survey 1993, mainly at Kimhandu.

No less than 23 (86 %) of 28 millipede taxa known from the Ulugurus are endemic to these mountains (at least 36 species occur here but not all could be included in the calculation of endemism percentage). All the endemics depend strictly on the survival of moist forest habitat. The high endemicity in the Ulugurus in millipedes and certain other invertebrate groups (exemplified by linyphiid dwarf spiders, harvestmen, pselaphids, earwigs, montane butterflies and montane ground-beetles) is discussed.

7.2. Introduction: Earlier invertebrate surveys in the Uluguru Mountains.

Invertebrates make up the largest group of animals, but are poorly studied in many areas. This is also the case in the Uluguru Mountains.

Our knowledge of the invertebrate fauna of the Uluguru Mountains is primarily based on two entomological expeditions. The first was carried out in 1957 by P. Basilewsky and N. Leleup: Mission Zoologique de l'I.R.S.A.C. en Afrique Orientale (Leleup 1965). They found the Uluguru Mountains very interesting from an entomological point of view, and this led to a second expedition in 1971: Mission Entomologique de Musée Royal de l'Afrique Centrale aux Monts Uluguru, Tanzania (Berger et al. 1975 and 1976). In 1981 a Danish expedition (Scharff et al. 1982) surveyed the avifauna and the invertebrate fauna, mainly spiders (Araneae) and caddisflies (Trichoptera), of the Uluguru Mountains. In April 1983 (rainy season) millipedes were collected intensively in Kimboza F.R., a list of 10 species is presented in Rodgers et al. (1983).

Beside the above-mentioned expeditions, there has been some sporadic collecting, but still only part of the mountains has been investigated thoroughly and only a few groups of invertebrates are well investigated. The best-known invertebrate groups are:

Ground-beetles (Coleoptera: Carabidae) (Basilewsky 1976).

Pselaphids (Coleoptera: Pselaphidae) (Leleup 1976).

Earwigs (Dermaptera) (Brindle 1975).

Montane butterflies (Lepidoptera) (de Jong and Congdon 1993).

Linyphiid dwarf spiders (Araneae: Linyphiidae) (Scharff 1993).

Harvestmen (Arachnida: Opiliones) (Lawrence 1963).

During the survey in 1993, several groups of invertebrates were collected (with the main emphasis placed on millipedes), but at present, only the millipede specimens have been identified to species.

7.3. Methods used on this survey (confer Table 2.1).

Millipedes were collected by the author along a transect from about 1500 to 2600 m in the Kimhandu area with samples gathered at every 100 m altitude. Standing stumps, trunks, fallen and decaying logs and branches were examined systematically for cryptic and free-living fauna. The lower vegetation, litter and dirt of the forest floor were examined as well. Specimens from different habitats were kept separate and habitat and altitude were noted (data on habitat type and altitude are, however, not presented in this paper). The specimens were preserved in 70 % alcohol.

The collection was made towards the end of the dry season. Most of the millipedes were therefore found inside logs or deep in the earth. This caused a patchy distribution of the animals and it was therefore difficult to follow a narrow transect.

A few specimens were collected (sporadically) at Lanzi and Tegetero by other team members. Important literature used for identification is: Demange (1977), Hoffman (1990), Krabbe (1982), Kraus (1958, 1960 and 1966) and Mauriès (1989). Taxonomy follows Hoffman (1979) and Enghoff (1983).

7.4. Results (confer Table 7.1).

Table 7.1 presents a list of all millipede species known from the Uluguru Mountains, compiled from the literature and the field survey work undertaken by the author. Because of identification problems (see a in Table 7.1) only 14 different taxa were identified in the material from the 1993 survey.

The Table 7.1 shows that 23 (86 %) of 28[1] millipede taxa known from the Uluguru Mountains are endemic. A further four are endemic to Tanzania. The last of the 28 species is Epibolus pulchripes which is not restricted to forest habitat.

7.5. Discussion.

7.5.1. Endemicity among millipedes known to occur in the Ulugurus.

There is a high degree of millipede endemicity in the Uluguru Mountains (86%). This is believed to be due to the facts that most millipedes have a strong tendency to speciate, are strongly dependent on humid microclimate and have very limited ability to disperse (Hopkin and Read 1992). All the 36 taxa except Epibolus pulchripes must be considered true forest species.

In relation to the millipedes of the Eastern Arc mountains, Hoffman (1993) concluded for the Oxydesmidae that:

1. ‘With a few exceptions most of the genera occurring in mountains are endemic, so that lines of affinity with regions must be sought at the level of tribe or higher’.

2. ‘In most cases such genera appear to be the result of derivation from formerly widespread ancestral stocks’.

3. ‘The post glacial condensation of montane forest to higher mountains surrounded by seasonally arid savanna or shrub forest has resulted in profuse local speciation on individual ranges or close clusters’.

In general, the species found in the more arid lowlands surrounding the forests show a wide distribution with low levels of endemism. These species are adapted to more arid climates and therefore their dispersal is less hindered by physical barriers than is the case for the true forest species.

7.5.2. Endemicity of other invertebrate groups occurring in the Ulugurus (confer Table 7.2).

As well as the endemism in the millipedes I have also reviewed, the literature to assess the levels of endemism in selected other invertebrate groups (Table 7.2). Most of the groups in Table 7.2 are mainly found on the forest floor and are dependent on a humid microclimate.

The high levels of endemism are most striking in the groups, which have a low ability to disperse. However, high endemism also occurs in groups, which have some degree of mobility. The dwarf spiders are well known, and can disperse by ballooning, but the percentage endemism is high on the Ulugurus, especially in comparison with geologically younger mountains (Scharff 1992 and 1993). The montane butterflies, some of which have strong powers of flight, also show a high degree of endemism in the Ulugurus and other geologically old mountains (de Jong and Congdon 1993).

The rates of endemism in some mountain forests of eastern Africa have been calculated, and are seen to be higher on the ancient Eastern Arc mountains than on the geologically younger volcanic mountains in the region (Leleup 1965). This conclusion is supported by Scharff's (1992, 1993) dwarf spider study: In the Ulugurus there are 17 dwarf spider species of which 14 (86 %) are confined to forest and endemic to those mountains. On the geologically younger Mt. Kilimanjaro 15 dwarf spider species are known to occur, of which eight are forest species, five (63 %) of these being endemic. For Mt. Kenya there are even lower rates of endemism, from 32 species 15 are forest species and only 5 (33%) of these are endemic. The same trends are found in the butterflies (de Jong and Congdon 1993).

7.5.3. Interpretation of invertebrate endemicity.

Some of the other mountains in the Eastern Arc have received attention from entomologists, although large collection gaps still exist. The best studied are the Usambara and Uluguru Mountains. Hence, there is much to learn about the endemic species of the Eastern Arc. In particular, the Eastern Arc Mountains situated near the Uluguru Mountains (Rubehos, Ngurus and Udzungwas), are not as thoroughly investigated as the Ulugurus, and a proper investigation of these will probably show that some endemic species of the Uluguru area also occur in the nearby mountain forests. It must be stressed, however, that the Uluguru Mountains will probably still contain a fauna quite different from that of other Eastern Arc Mountains, including high numbers of endemic species.

7.6. References.

Basilewsky, P. 1976. 19. Coleoptera, Carabidae. Pp. 671-722 in Berger, L., N. Leleup and J. Debecker (eds.). Mission entomologique du Musée Royal de l'Afrique Centrale aux Monts Uluguru, Tanzanie. Revue de Zoologie Africaine 90 (3).

Berger, L., N. Leleup and J. Debecker 1975. Mission entomologique du Musée Royal de l'Afrique Centrale aux Monts Uluguru, Tanzanie. Revue de Zoologie Africaine 89: 673-760.

Berger, L., N. Leleup and J. Debecker 1976. Mission entomologique du Musée Royal de l'Afrique Centrale aux Monts Uluguru, Tanzanie. Revue de Zoologie Africaine 90:188-196, 337-356 and 671-865.

Brindle, A. 1975. Dermaptera. Pp. 681-695 in Berger, L., N. Leleup and J. Debecker (eds.): Mission entomologique du Musée Royal de l'Afrique Centrale aux Monts Uluguru, Tanzanie. Revue de Zoologie Africaine 89 (3).

Demange, J.-P. 1977. Nouveaux Myriapodes de Tanzanie. Description de deux espèces nouvelles de Diplopodes. Affinités de quelques genres d'Oxydesmidae. Bulletin du Museum National d'Histoire Naturelle Paris (Zoologique) No. 301: 507-518.

Enghoff, H. 1983. Phylogeny of millipedes - a cladistic analysis. Zeitschrift für Zoologisch Systematik und Evolutionsforschung 22: 8-26.

Hoffman, R.L. 1979. Classification of the Diplopoda. Geneve: Muséum d´Histoire Naturelle..

Hoffman, R.L. 1990. Myriapoda 4. Polydesmida: Oxydesmidae. Das Tierreich/The Animal Kingdom, No. 107: 1-512.

Hoffman, R.L. 1993. Biogeography of East African montane forest millipedes. Pp. 103-114 in Lovett, J. and S.K. Wasser (eds.). Biogeography & ecology of the rain forests of Eastern Africa. Cambridge, UK: Cambridge University Press.

Hopkin, S.P. and H.J. Read 1992. The biology of millipedes. Oxford: Oxford University Press.

de Jong, R and T.C.E. Congdon 1993. The montane butterflies of the Eastern Afrotropics. Pp. 133-172 in Lovett, J. and S.K. Wasser (eds.). Biogeography & ecology of the rain forests of Eastern Africa. Cambridge, UK: Cambridge University Press.

Krabbe, E. 1982. Systematik der Spirostreptidae (Diplopoda, Spirostreptimorpha). Abhandlungen und Verhandlungen des Naturwissenschaftlichen Vereins in Hamburg 24: 1-476.

Kraus, O. 1958. Myriapoden aus Ostafrika (Tanganyika Territory). Veröffentlichungen der Übersee-Museum in Bremen Reihe A, Band 3, Heft 1: 1-16.

Kraus, O. 1960. Äthiopische Diplopoden. 1. Monographie der Odontopygidae=Odontopyginae (Diplopoda, Spirostreptoidae). Annales du Musée Royal du Congo Belge. Serie in 8°. Sciences Zoologique 82: 1-207.

Kraus, O. 1966. Phylogenie, Chorologie und Systematik der Odontopygoideen (Diplopoda, Spirostreptomorpha). Abhandlungen der Senckenbergischen Naturforschende Gesellscaft no. 512: 1-143.

Lawrence, R.F. 1963. Opiliones. Mission Zoologique de l'I.R.S.A.C. en Afrique orientale. Resultats Scientifique. 4^e partie. Annales Musée Royal de l'Afrique Centrale (Zoologique) 110: 9-89.

Leleup, N. 1965. La fauna entomologique cryptique de l'Afrique intertropicale. Annales du Musée Royal de l'Afrique Centrale (Zoologique) 141: 1-186.

Leleup, N. 1976. Coleoptera. Pselaphidae. Pp. 769-836 in Berger, L., N. Leleup and J. Debecker (eds.). Mission entomologique du Musée Royal de l'Afrique Centrale aux Monts Uluguru, Tanzanie. Revue de Zoologie Africaine 90 (4).

Mauriès, J.-P. 1989. Révision des Stemmiulides: espèces nouvelles et peu connues d'Afrique (Myriapoda, Diplopoda). Bulletin du Museum National d'Histoire Naturelle. Section A. Zoologie, biologie et écologie animales 11: 605-637.

Rodgers, W.A., J.B. Hall, L.B. Mwasumbi, C.J. Griffiths and K. Vollesen 1983. The conservation values and status of Kimboza Forest Reserve, Tanzania. Unpublished report from The Forest Conservation Working Group, University of Dar es Salaam.

Scharff, N. 1992. The linyphiid fauna of eastern Africa (Araneae: Linyphiidae) - distribution patterns, diversity and endemism. Biological Journal of the Linnean Society 45: 117-154.

Scharff, N. 1993. The Linyphiid spider fauna (Araneae: Linyphiidae) of mountain forests in the Eastern Arc mountains. Pp. 115-132 in Lovett, J. and S.K. Wasser (eds.). Biogeography & ecology of the rain forests of Eastern Africa. Cambridge, UK: Cambridge University Press.

Scharff, N., M. Stoltze and F.P. Jensen 1982. The Uluguru Mts., Tanzania. Report of a study-tour 1981. Unpublished report, Zoological Museum of Copenhagen.

Go to: Top of page, Contents of Part A, or Next Section on Botany.

---

^[1] Reading Table 7.1 it is clear that at least 36 species occur in the Ulugurus. The reason for including only 28 of them (those marked with asterisks plus Epibolus pulchripes) in the calculation of the percentage of endemism is that it is not possible to say whether some of the last eight taxa (those marked with a) may actually be endemic as well.