The harvestman fauna of the Western Soutpansberg was investigated during two collecting trips. Comments are made on the variability, ecology and remarkable morphological features of the collected material. Characters are displayed and differences to type series are highlighted. Monomontia neglecta sp. n. is described from material housed at the Natal Museum. Metabiantes leighi Pocock, 1902 is recorded for the first time for the Soutpansberg area. A species list is provided, listing all known records and the state of endemism. The relative species richness of the eastern Soutpansberg is discussed in comparison with the western area.
In autumn 2002, a study trip brought the author to the farm Lajuma in the Western Soutpansberg, Limpopo Province, South Africa. The owners of the farm are investigating the fauna and flora of the area to underline its importance for biodiversity protection and to propose it as a Biosphere Reserve. Within this scope, harvestmen were collected, and additional material collected by Dr Peter Schwendinger (Geneva, Switzerland) was included. During the investigation it became evident that a revaluation of the type material of several species was necessary to identify the new material correctly. A list of species recorded at Lajuma was prepared, and the results also pointed to differences to the type material, gave evidence of remarkable intraspecific variation and prompted the description of one new species from material in the Natal Museum. Comments are made on the ecology and biogeography of the species. Reasons for differences in species richness within the Soutpansberg, and distribution of taxa, are discussed.
MATERIAL AND METHODS
The study area (Fig. 1) was the farm Lajuma, which is named after the nearby peak Lajuma (23°01′S:29°25′E; 1747 m) and is situated between Makhado (Louis Trichardt) and Vivo in the Western Soutpansberg Mountain Range, Limpopo Province. In this paper, the collection sites at Makhado and Entabeni are regarded as the Eastern Soutpansberg, which is separated from the western part by the dry valley of the Sand River. Lajuma has been declared a Natural Heritage Site and is part of the Thavha Ya Muno Private Nature Reserve and the Soutpansberg Conservancy. The geological setting of the study area is rather complex. The Soutpansberg is composed mainly of sandstone dipping at approximately 30° north-northwesterly (Barker et al. 2006). The resulting cliffs force the uplift of clouds and a frequent release of precipitation. Constant ground-water seepage at the foot of the cliffs creates stable patches of constant humidity, which are small-scale within the mountain area. Other habitats are open savannah and cloud forest characterised by poikilohydric cryptogams.
All accessible habitats were sampled for opilionids, which were collected by sieving leaf litter, turning over stones and logs in daylight, and making a few hand collections by night. Specimens are deposited in the following institutions: NMSA — Natal Museum, Pietermaritzburg, RSA (Debbie Jennings, Juthika Baijoo); MHNG — Museum d'Histoire Naturelle, Geneva, Switzerland (Dr Peter Schwendinger); CJM — Collection of Prof. Jochen Martens, University of Mainz, Germany.
Drawings were performed with a stereomicroscope and a camera lucida. Photographs were taken with a Nikon D80, using the same microscope. Terms for genital morphological features follow Kauri (1961: 13).
Prior to Lawrence's (1963) comprehensive study on harvestmen of the Transvaal, only one species was known from the Soutpansberg (Lawrence 1931). Intensive collecting by R.F. Lawrence and N. Leleup increased this number to ten (Lawrence 1963). Starga (1992) added a further species to this list. Surprisingly, Starga (1992) lists Metabiantes perustus for Makhado (NMSA, 7606), Entabeni (NMSA, 7609) and Hanglip forest (NMSA, 7600). Why Lawrence (1963), who must have seen these specimens, did not include them in the original description of M. perustus cannot be explained. A re-examination of the type material and Starga's new records should be done in the future.
Within this report, one species is recorded as new for the Soutpansberg and one as new to science, so that the total number of species for the area is now 13.
The number of species is much smaller in the Western Soutpansberg (Lajuma, 5; Makhado, 12) and the proportion of Soutpansberg endemics is smaller (Lajuma, 40 %; Makhado, 64 %), with 45 % found only near Makhado and recorded from none of the other localities. A list of all recorded species follows, with endemic species of the Soutpansberg indicated and asterisks indicating species discussed in this account.
Family Biantidae Thorell, 1889
Genus Metabiantes Roewer, 1915
Metabiantes leighi (Pocock, 1902)
Figs 2, 3A, 3B
Hinzuanius leighi: Pocock 1902: 412.
Biantes leighi (Pocock): Roewer 1912: 177.
Comments on morphology: Sexual dimorphism is poorly developed. Chelicerae of males are more massive and therefore the carapace in the eye region is wider. The scutum is more triangular in males (Fig, 3B), whereas the opisthosoma in females is more rounded. Differences like shape of the body and intensity of coloration are strongly influenced by the age of the individual after final moult. Juveniles have larger spines on the dorsal scute than adults. This might be of interest because Kauri (1961: 62) pointed to a juvenile Metabiantes being distinct due to its strong spination, although he had no assignable juveniles of spined species for comparison.
Material examined: SOUTH AFRICA: Limpopo: 18♂ 22♀ 6 juv. Lajuma, evergreen montane forest, alt. 1300–1400 m, 1–4.iv.2001, P. Schwendinger (MHNG): 4♂ 1♀ 23°02′30.0″S:29°26′48.5″E, alt. 1325 m, 24.x.2002, A.L. Schönhofer (CJM, 4093).
Ecology: M. leighi inhabits the medium layer of leaf litter in subtropical evergreen forest. The species seems to require lower humidity than, for example, Monomontia aquilonaris. It was also absent from wet forest soils near streams and springs.
Comments: As Lawrence (1963) recorded a considerable number of cryptic and difficult-to-access species of the genera Monomontia and Purcellia near Makhado, we can assume that Metabiantes leighi was not present there. At Lajuma, M. leighi was quite common to abundant, and is a new record for Limpopo Province.
Most species of the genus Metabiantes have a limited distribution, whereas the scattered records of M. leighi encompass a range of more than 1000 km along the eastern coast of South Africa (Lawrence 1931, 1933). A closer investigation of different geographic populations of M. leighi enabled Kauri (1961) to separate Metabiantes cataracticus Kauri, 1961 and M. hanstroemi Kauri, 1961 from the M. leighi area. All three species are close relatives by the shape of the glans penis (Lawrence 1933; Kauri 1961). Martens (1978a) showed allopatric speciation by geographic isolation in Biantidae from the Himalayas. This isolation forced minor morphological changes, whereas sympatric species differ strongly with respect to body size and shape of chelicerae and palps. Consequently, the syntopic M. cataracticus and M. hanstroemi should differ in the proportion of palps, body size and chelicerae, but these characters were not thoroughly investigated by Kauri (1961). Comparing body size (2.7 mm; 2.4 mm), length of the enlarged part of chelicerae (0.35 mm; 0.28 mm), spination and coloration of the two species, there is agreement with the evolutionary concept proposed by Martens (1978a) and parallels within the African Biantidae seem to hold true. A revision of the different populations of M. leighi might reveal cryptic species. For further investigation we document characters of M. leighi from Lajuma (Fig. 2), as recommended by Martens (1978a).
Family Triaenonychidae Sørensen, 1886
Genus Graemontia Lawrence, 1931
Graemontia bicornigera Lawrence, 1963
Figs 3C, 3D, 4
Graemontia bicornigera: Lawrence 1963: 295, fig. 10.
Diagnosis: The species is easily distinguished in both sexes by the armature of leg I (Fig. 4E).
Material examined: SOUTH AFRICA: Limpopo: 2♀ Lajuma, evergreen montane forest, alt. 1300–1400 m, 1–4.iv.2001, P. Schwendinger (MHNG); 1♂ (holotype) 1♀ (paratype), Mariepskop, alt. 2440 m, iii.1960, R.F. Lawrence (NMSA, 7622), penis and genital operculum of male on microscope slide; 1♀ Makhado, alt. 1370 m, ii.1960, R.F. Lawrence (NMSA, 7602).
Comments: Sexual dimorphism is displayed by the prominent apophysis of the first article of the male chelicerae (Lawrence 1963: fig. 10d). The penis of the holotype is permanently mounted on a microscope slide and was slightly squeezed, so that no specific structures are detectable (Fig. 4F). For further investigation of genital morphology, additional collection is required. Comparison of the female paratype with the Lajuma material revealed no differences.
Genus Monomontia Lawrence, 1931
Characters used for species definition within the genus, such as armature of the femur of the palp, do not show much morphological variation within the genus or in the related genera Ceratomontia Roewer, 1914 and Austromontia Lawrence, 1931. This is most probably because of morphological stasis to maintain functionality. Other characters, like the shape of the ocularium and body size, exhibit some variability within the single species. At present it is difficult to judge the species status of single specimens or certain populations because the genital morphology for South African Opiliones was generally ignored by Lawrence. Many characters were inconsistently investigated and now are lacking for comparison. Unfortunately, it is very likely that important structures of the penis are revealed only in the expanded state, what was never studied. Nevertheless, a thorough revision of the genus by genital morphological characters is needed.
Material examined: SOUTH AFRICA: Limpopo: 1♀ (holotype) 2♀ (paratypes) Hanglip forest, Makhado, alt. 1370 m, ii.1960, R.F. Lawrence (NMSA, 7604), ovipositor and 2 opercula genitalia mounted on microscope slide; 37♂ 18♀ Lajuma, in evergreen montane forest, alt. 1300–1400 m, 1–4.iv.2001, P. Schwendinger (MHNG); 1♂ 1♀ 23°02′30″S:29°26′48.5″E, alt. 1325 m, sieved from deep litter, 6.x & 6.xi.2002, A.L. Schönhofer (CJM. 4821).
Ecology: In deep leaf litter of evergreen montane forest.
Comments: The type series comprises three females, one indicated as the holotype by separation of chelicerae and palps to carry out drawings. The ovipositor was turned inside out, and another ovipositor is mounted on a microscope slide (paratype). In the absence of males from the type locality, specimens from Lajuma had to be assigned to M. aquilonaris on external characters only. This might be legitimate, as no sexual dimorphism was observed within the Lajuma material and specimens are indistinguishable from the type material from only 50 km away. Further collection and redescription of males from the type locality are necessary to confirm species recognition upon genital morphological characters. For this purpose, drawings of the penis from the Lajuma material are included, as well as those of leg I, chelicerae and palp.
The ventral armature of the palps, chelicerae and leg I are constant within the Lajuma material. The shape of the ocularium (Figs 6E–H), as well as the dorsal spination of the palp femur, vary, as does the number of granules on the front of the carapace (2 or 3). Additionally, the size of the males varies remarkably, as do the size and proportions of the palps, especially the length and shape of tibia and femur. The species shows similarity with Monomontia lawrencei Kauri, 1950 (similar in size, shape of ocularium and armature of palps; different in body shape and penis morphology, Kauri 1950), M. corticola Lawrence, 1938 (similar in size and armature of palps and leg I, but body and legs coloured black, Lawrence 1938a) and M. brincki Kauri, 1961 (similar in size, shape of ocularium and armature of palps; different in penis morphology, Kauri 1961). The relationships of these species should be investigated.
Material examined (all NMSA material collected by R.F. Lawrence): SOUTH AFRICA: Limpopo: 3♂ 1♀ 1 juv. (instead of 3♂ 2♀; 1♂ holotype of M. versicolor, the reminder paratypes) Mariepskop, alt. 2010 m, iii.1960 (NMSA, 7615); 1♂ Lajuma, in evergreen montane forest, alt. 1300–1400 m, 1–4.iv.2001, P. Schwendinger (MHNG); 1♂ Entabeni forest, Makhado, ii.1960 (NMSA, 7610); 1♂ Makhado, alt. 1370 m, ii.1960 (NMSA, 7601).
Comments: The penis of the holotype is deformed by mounting it on a microscope slide. We therefore investigated a paratype from Mariepskop to compare genitalia with material from Makhado and Lajuma. Although very similar in body shape and coloration, the males from the type locality differ from the Soutpansberg material by larger size, more elongated ocularium, lack of fine granulation on femur of the palps, smaller straight mediolateral spine on the palpal femur, and, to a lesser degree, shape of the penis. Characters such as dorsal spination on palps and basal article of chelicerae are variable within specimens from both localities. A validation of these clearly different forms should be a subject of the revision of the genus.
Monomontia aquilonaris: Lawrence 1963: 299 (partim).
Monomontia versicolor: Lawrence 1963: 302 (partim).
Etymology: From Latin neglecta (neglected, disregarded). This clearly distinguishable species was overlooked by Lawrence (1963). He first separated smaller specimens from his material but later included them in M. aquilonaris and M. versicolor.
Diagnosis: Conspicuously small, yellow and short-legged Monomontia. Ocularium flat, extended over the front margin of prosoma, rounded at tip (Fig. 6I).
Small body size (Figs 5H, 5I); light yellow-brown, dorsal scute densely granulated with two large granules on front margin of carapace; no markings dorsally. Legs short, leg I (Fig. 7K): calcaneus of metatarsus more than half the length of astragalus; tarsus longer than metatarsus; femur ventrally with 4 spined tubercles, the second basal one largest, the third smallest. Ocularium (Fig. 6I) small, smooth and rounded; only faintly elevated dorsally; drawn out over the front margin of the carapace, eyes small, surrounded by a much larger background of black pigmentation. Chelicera (Figs 7L, 7M) with a few ventral granules on segment I, dorsally inflated and ending in a spine; small spines and a large triangular on segment II dorsally; a riffled area is present on ventral article I distal, possibly a stridulatory organ. Palps (Figs 8I–K): trochanter with 1 large spine dorsal and ventral; femur dorsal with 3 prominent equally-sized spines and one smaller distal one, ventrally basal spine with three teeth, the middle one largest, medial with 1 spine distally, from this 4 spines distally alternating in size; femur, tibia and tarsus ventrally covered with rounded granules, dorsal smooth. Penis (Figs 9I–K, 10I–K) short and stout; almost parallel sided in dorsal view; in lateral view constricted below glans and above the base of truncus; muto bent dorsally (lateral view), forming two circular lamellae diverging disto-laterally, hind wall of muto above these lamellae gradually tapering to a blunt apex (dorsal view); lamellae cinctiform at base broad, forming small medial lobes and large lateral ones, these are long and slightly curved, bent dorsally, apex folded inwards, confined by three large lateral spines and a small one dorsally. Females similar to males but can be distinguished by shorter palps and metatarsus of leg I. Tibia of leg I variable, sometimes with one tubercle ventrally.
Measurements (mm): ♂ (n=10),♀ (n=4), data for ♀ in parentheses: body size: 1.35–1.53 (1.37–1.45); leg I: femur: 0.5–0.52 (0.45–0.47), patella: 0.26–0.28 (0.25–0.26), tibia: 0.29–0.31 (0.29–0.3), metatarsus: 0.35–0.37 (0.31–0.32), tarsus: 0.4–0.42 (0.37–0.4); palpus: femur: 0.53–0.64 (0.49–0.51), patella: 0.33–0.35 (0.28–0.29), tibia: 0.46–0.62 (0.36–0.37), tarsus: 0.5–0.52 (0.43–0.45)
Holotype: ♂ SOUTH AFRICA: Limpopo: Makhado [= Louis Trichardt, 23°02′S:29°54′E], ii.1960, R.F. Lawrence (NMSA, 7645); identified in 1963 as M. versicolor.
Paratypes: ♀ same data as holotype; 9♂ 3 ♀ SOUTH AFRICA: Limpopo: Hanglip forest north of Makhado, vi. 1961, N. Leleup (NMSA, 19204). R.F. Lawrence identified these specimens in 1963 as M. aquilonaris.
Comments: Specimens of this species were included in the descriptions of M. aquilonaris and M. versicolor by Lawrence (1963) but represent no type material of the latter two species. The new species differs markedly from M. versicolor by its much smaller size and from both species by its small, rounded and flat ocularium with intense pigmentation around the eyes. The ocularium closely resembles that of M. krausi Kauri, 1961, but M. neglecta differs in the tarsal formula 3-3-4-4 of the legs and the strong dorsal spination of the palp femur. The penis is different from other investigated or described Monomontia species, but shows a close resemblance to Ceratomontia minor Lawrence, 1931 (Kauri 1961).
Family Phalangiidae Latreille, 1802
Genus Rhampsinitus Simon, 1879
Rhampsinitus transvaalicus Lawrence, 1931
Figs 11, 12A–L
Diagnosis: Although highly variable, males of this species are easily distinguished by a row of large retrolateral curved spines on the femur of chelicerae (Figs 12E, G, I–K). The closely related R. leighi Pocock, 1902 has smaller spines irregularly scattered on the chelicerae (Fig. 12M). The penis of R. transvaalicus is bulbous at the base, whereas that of R. leighi is slender in lateral view (Figs 12A–D, 12N, 12O).
Material examined: SOUTH AFRICA: Limpopo: 7♂ Hanglip Forest, north of Makhado, alt. 1370 m, ii. 1960, R.F. Lawrence (NMSA, 7597); 4♂ 4♀ (NMSA, 7598); 2♀ (NMSA 7603); 1♀ 1♀ Makhado, alt. 915 m (NMSA, 7605); 1♂ 1♀ Entabeni forest, 48 km east of Makhado (NMSA, 7607); 5♂ 2♀ 316 juv. Lajuma, alt. 1350 m, evergreen montane forest, 22.x–19.xi.2002, A.L. Schönhofer (CJM, 4812–4820).
Other material examined: R. leighi: SOUTH AFRICA: KwaZulu-Natal: 1♂ Hluhluwe Game Reserve (28°S:32°E), higher altitude forest with Celtis africana, Harpephyllum caffrum, 1982, W. Wickler (CJM, 2142) (Fig. 12M–O).
Biology/Ecology: Most animals were caught walking on a road in subtropical evergreen forest at night. They were most abundant near a small permanent stream. Pitfall trapping was successful only for small juveniles. Traps recorded specimens only in forest habitats with permanent water a few hundred metres away. Two males were found sitting at the side of stones near the ground, face looking down ready to catch prey. Adults' bodies were often infested by red mites. Only seven adults were caught, but 316 juveniles in predominantly early stages of development. On one occasion a juvenile was seen carrying a cockroach double its body size; whether it was caught or just picked up dead was not observed. Adults are recorded from October to December and in February. The presence of juveniles in February suggests extension of maturity beyond that date. P. Schwendinger did not collect any specimen in April.
Comments: As the material from Lajuma contained only five adult males, which were highly variable in body size, coloration and length of chelicerae, additional material from the type locality Makhado was investigated. These specimens showed allometric growth of the male chelicerae and palps with increasing body size (Fig. 13). This phenomenon is reported from other Phalangiidae like the European Phalangium opilio Linnaeus, 1761, Zacheus crista (Brullé, 1832) (for both see Martens 1978b; Lerma 1952), the African Guruia africana (Karsch, 1878) (Starga 1984) and R. leighi (Pocock 1902; Lawrence 1931; Kauri 1961). Martens (1978b) mentioned males of European species becoming similar to females with decreasing body size and loss of external sexual characteristics. In R. transvaalicus this is nicely expressed in the toothing of the cheliceral pincer, which is radically changed to female appearance if body size falls below a certain value. Large specimens display three prominent teeth, whereas smaller males and females have only two (Figs 12H, 12F, 12L, 13). Kauri (1961) mentioned this circumstance for the closely related Rhampsinitus leighi without connecting it to allometric growth. Other characters, like length of legs, darkness of coloration or intensity of spination of chelicerae and ocularium, gradually change with body size. A convergent sexual dimorphism is exhibited in members of the Australian and New Zealand family Monoscutidae Forster, 1948. Males of the genera Pantopsalis Simon, 1879 and Spinicrus Forster, 1949 have extremely elongated palps (Forster 1949) and are polymorphic in respect to this character (Taylor 2004).
One male of R. leighi (CJM, 2142) is remarkable for its large body size, extending the variability of this species to 7.05 mm. Chelicerae length of 42 mm results in chelicerae 6 times longer than body size (Fig. 12M; chelicerae 2–4 times longer than body are reported by Lawrence (1931) and Kauri (1961)).
Description: Chelicerae smooth and of normal size; palps variously coloured; apophysis on inner side of patella densely covered by hairs and by some large rounded spines hardly visible within the hairs, femur and tibia strongly covered with hairs distally; dorsal coloration with an indistinct saddle and an inconspicuous median band; ocularium white in the upper part with three long white spines on each side.
Comments: This specimen is not related to R. transvaalicus and they differ ecologically and morphologically. P. Schwendinger placed it close to R. ingae Kauri, 1961. Distinct spines on the ocularium and a prominent apophysis on the inner side on patella of the palp are more similar to R. maculatus Kauri, 1961, but the specimen differs in dorsal coloration and in spination of the ocularium. This might be a new species, but requires additional adult males to be identified.
Material: SOUTH AFRICA: Limpopo: 1 juv. Mount Lajuma, grassland alt. 1600–1740 m, 5.iv.2001, P. Schwendinger det. 2001, near R. ingae (MHNG).
DISCUSSION AND CONCLUSION
Harvestmen are cryptic soil arthropods which require habitats with constant and high humidity, and many species are restricted to forests and forest-like habitats. This dependency on habitats that are rare and scattered within South Africa has caused strong fragmentation of populations and has possibly increased speciation processes, especially in species groups with little ability to disperse. With respect to the Soutpansberg area, this hypothesis would predict different endemic species for the western and eastern parts of the mountain range, especially in groups like Pettalidae and Triaenonychidae. A different hypothesis assumes dispersal across the mountain range during more favourable climatic conditions. The dry surrounding savannahs may have had isolating effects, reducing interchange with other areas. In dry periods the suitable habitats were reduced to small fragments, and habitats may even have lost suitable conditions for several species so that population and diversity reduction occurred.
The results clearly favour the second hypothesis because only few species and no exclusive endemics were found in the western part of the Soutpansberg. As the eastern range shows higher elevation, is more humid and therefore supports more and stable forest habitats, this provides further explanation for this circumstance. Nevertheless, this investigation records one known species as new for the Western Soutpansberg and it is not unlikely that within the scattered and remote valleys of the western part some species still await discovery.
I am most grateful to all people who helped me have a successful and unforgettable field trip to the Soutpansberg: Prof. Ian Gaigher and Dr Retha Gaigher (Lajuma, RSA) for accommodation and discussions; Jabu Linden (Ottoshoek, RSA) for intensive help with the fieldwork; Stefan Foord (University of Venda, RSA) for helpful comments on sampling techniques; Mrs Debbie Jennings and Ms Juthika Baijoo (Natal Museum, RSA) for loan of type specimens; and Dr Peter Schwendinger (Musée de Histoire Naturelle Geneva, Switzerland) for loan of additional material and for helpful information. Dr Peter Jäger (Senckenberg Museum Frankfurt, Germany) provided facilities and material for this work. Dr Udo Ganslosser (Zoologisches Institut, Erlangen, Germany) helped to organize the field trip. Prof Jochen Martens revised an earlier version of this manuscript, Mikhail Mostovski (Natal Museum, RSA) and two anonymous referees made helpful comments. The German Academic Exchange Service (DAAD) provided me with a grant to travel to South Africa.