Dippenaar microstigmatidae.qxd Habitat preferences and seasonal activity of the Microstigmatidae from Ngome State Forest, South Africa (Arachnida: Araneae) A.S. DIPPENAAR-SCHOEMAN, M. VAN DER MERWE and A.M. VAN DEN BERG Dippenaar-Schoeman, A.S., M. van der Merwe and A.M. van den Berg. 2006. Habitat preferences and seasonal activity of the Microstigmatidae from Ngome State Forest, South Africa (Arachnida: Araneae). Koedoe 49(1): 85–89. Pretoria. ISSN 0075-6458. As part of the South African National Survey of Arachnida (SANSA) inventories are underway to determine the arachnid biodiversity of various biomes. A survey of ground- living spiders was conducted over a year period (1992-1993) at Ngome State Forest, KwaZulu-Natal, South Africa. Spiders were collected with 180 pitfall traps from five different habitat types ranging from indigenous forest to a pine plantation and grassland. A total of 186 specimens of the rare Mygalomorphae family Microstigmatidae were sampled, representing 2 % of the total spider fauna collected during the study. Two species, Microstigmata longipes (Lawrence) and M. zuluensis (Lawrence), occur sym- patrically. Both species were more active in the indigenous forest, and were absent or present in low numbers in the open grass and pine plantation. Microstigmata zuluensis was slightly more abundant (59 % of total) and was recorded from three of the five habi- tats, while M. longipes (41 %) was found in four of the habitat types. Both species were active throughout the year with the lowest numbers recorded in winter (June to August). The males of M. longipes peaked in November while those of M. zuluensis peaked in April. Key words: Afromontane forest, Araneae, biodiversity, Microstigmatidae, Microstig- mata, spiders, South Africa National Survey of Arachnida. A.S. Dippenaar-Schoeman, ARC-Plant Protection Research Institute, Private Bag X134, Queenswood 0121, Republic of South Africa / Department of Zoology and Ento- mology, University of Pretoria, 0002 Pretoria, Republic of South Africa; A.M. van den Berg, ARC-Plant Protection Research Institute, Private Bag X134, Queenswood 0121, Republic of South Africa; M. van der Merwe, Department of Zoology and Entomology, University of Pretoria, 0002 Pretoria, Republic of South Africa (Present address: The Joint Science Department of the Claremont Colleges, W.M. Keck Science Centre, 925 N. Mills Ave, Claremont, CA 91711-5916, USA). ISSN 0075-6458 85 Koedoe 49/1 (2006) Introduction The Microstigmatidae is a small family of spiders represented by seven genera and 13 species known from Africa, Central and South America (Platnick 2005). In Africa it is represented by a single genus Microstigmata, which is known only from South Africa (Dippenaar-Schoeman 2002; Griswold 1985). In a revision of the genus, Griswold (1985) recognised six species with their dis- tribution restricted mainly to the forest regions of the eastern parts of South Africa. The Microstigmata are small (4–13 mm), free-living mygalomorph spiders. They are the only members of the Mygalomorphae in the Afrotropical Region that do not live in silk-lined burrows or retreats. They are wan- derers and found when turning stones and logs or sifting leaf litter and humus. Speci- mens are usually encrusted with earth due to sand particles adhering to their clavate body setae. Although widely distributed through- out the eastern parts of South Africa, they are shy animals and are rarely collected. Little is known about their behaviour and natural his- tory (Griswold 1985). During a 12-month survey of the cryptofauna at Ngome State Forest in KwaZulu-Natal, South Africa, 186 microstigmatids were sam- Dippenaar microstigmatidae.qxd 2006/04/17 10:51 PM Page 85 pled with pitfall traps. This represented about 2 % of the total number of spiders col- lected during the study (Van der Merwe et al. 1996). As very little information is available on the ecology of most mygalomorph spi- ders, data on the habitat preferences and sea- sonal activity of the two Microstigmata species collected are presented here. This is the third paper on the ground-living spider fauna of the Ngome State Forest (Van der Merwe 1994; Van der Merwe et al. 1996) and the first quantitative survey of microstig- matids in South Africa. This survey forms part of the South African National Survey of Arachnida (SANSA) that was initiated in 1997. The main aim of this umbrella project is to make an inventory of the arachnid fauna of South Africa (Dippenaar-Schoeman & Craemer 2000). Thrusts within SANSA are focused on inventories of the arachnid fauna of the different floral biomes (here the Forest Biome), provinces, conserved areas and agro-ecosystems. Study area Ngome State Forest (27º49'S; 31º26'E) is sit- uated on the escarpment of northern Kwa- Zulu-Natal, South Africa, at an altitude of 405–1365 m above sea level. Rainfall aver- ages 1507 mm/year, with January the wettest (227 mm) and June the driest (26 mm). The mean maximum temperatures are 26.6 ºC (January/February) and 18.6 ºC (June/July). The five different habitat types sampled were: ‘open grass’ consisting of grass sur- rounded by indigenous forest; ‘open forest’ comprising closed canopy indigenous forest characterised by the absence of significant undergrowth; ‘dense forest’ consisting of closed canopy indigenous forest with dense undergrowth; ‘ecotone pine’ with mature pine plantation surrounded and penetrated by indigenous forest vegetation, and a pine plantation not directly surrounded by indige- nous forest. For more detail on the habitat types see Van der Merwe et al. (1996). Methods Pitfall traps (n = 180) consisting of a plastic contain- er (10 cm diameter) sunk to ground level with a fun- nel leading to a honey jar, and filled with 70 % alcohol–5 % glycerol mixture, was used. The traps were spaced 5 m apart in a 3x3 grid pattern with four grids (36 pitfall traps) placed in each of the five habi- tats. Traps were continuously open and emptied in the middle of each month, from January 1992 to Jan- uary 1993. Voucher specimens are deposited in the National Collection of Arachnida at the ARC-Plant Protection Research Institute, Pretoria. Statistical analysis were conducted using the statisti- cal program GenStat (2000) to determine if signifi- cant differences existed in the abundance of the two species in the different habitat types, as well as dur- ing different seasons, using 2x3, 2x4 and one sample Chi-squared tests. Results Species numbers A total of 9 369 spiders were collected dur- ing the survey, of which 186 belonged to the Microstigmatidae. Two species, M. longipes (Lawrence) and M. zuluensis (Lawrence), occur sympatrically. A total of 110 individu- als of M. zuluensis were collected, represent- ing 59 % of all microstigmatids collected, while 76 specimens of M. longipes were col- lected, representing 41 % of the total (Table 1). Habitat preferences Microstigmata zuluensis was collected from three of the five habitats (Table 1). They were absent from the open grass and pine plantation, and more active (n = 45) in the open forest. They represented 41 % of the total, followed by the dense forest (n = 42) with 38 %, and ecotone pine (n = 23) with 21 %. Microstigmata longipes was active in four of the five habitats, being absent only from the open grass (Table 1). They were more active in the dense forest (n = 37) representing 49 % of the total, followed by the open Koedoe 49/1 (2006) 86 ISSN 0075-6458 Dippenaar microstigmatidae.qxd 2006/04/17 10:51 PM Page 86 forest (n = 32) with 42 % and 9 % in the eco- tone pine and pine plantations. Both species prefer closed canopy indige- nous forest. A total of 79 % of microstig- matids were collected from the two indige- nous forest habitats compared to the 21 % from the ecotone pine and pine plantation. The cover of the forest floor plays a less important role; 41 % in total were active in the forest habitat characterised by the absence of significant undergrowth, com- pared to the 43 % collected from forest with dense undergrowth. The Chi-squared tests indicated that the relative activity of the two Microstigmata spp. differed significantly in open forest, dense forest and ecotone pine at the 0.05 test level (χ² = 5.991, p <0.05), and that the distribution of the two species dif- fered significantly between the dense forest and ecotone pine (χ² = 5.737, p <0.05). Seasonal activity Microstigmata zuluensis was active through- out the year (except in July), but their num- bers fluctuated to show an increase in sur- face activity during autumn and early winter (April to June) when 42 % were collected, ISSN 0075-6458 87 Koedoe 49/1 (2006) Table 1 Microstigmata spp. collected from 180 pitfall traps from five habitat types at the Ngome State Forest, KwaZulu-Natal, South Africa during 1992-1993 Species Open grass Pine plantation Ecotone Dense forest Open forest Total % M. zuluensis 0 0 23 42 45 110 59 M. longipes 0 2 5 37 32 76 41 Total 0 2 28 79 77 186 100 Fig. 1. Seasonal activity of Microstigmata zuluensis collected from 180 pitfall traps at Ngome State Forest, KwaZulu-Natal, South Africa during 1992-1993. Dippenaar microstigmatidae.qxd 2006/04/17 10:51 PM Page 87 with a peak in April (n = 28). Their numbers declined to a low of 11 % during the winter months (July-August) and increased again in the spring and summer to 26 %. Microstig- mata longipes was active throughout the year with peaks in February (n = 15) and November (n = 20). Their activity fluctuated from autumn when 16 % were recorded, to a low (8 %) in winter. Activity increased again to reach a high of 40 % in the spring and 37 % in summer. As expected of pitfall trapping, more males (55 %) were sampled in both species, fol- lowed by immature specimens (32 %) and females (13 %). Males of M. zuluensis were active during eight months of the year (Fig. 1). They were active in autumn and early winter with a peak (n = 21) in April when 19 % of the specimens were collected and second peaks in October (n = 9) and December (n = 8). Juveniles were active throughout the year (except July) with a slight peak in April (n = 7). The females were collected irregularly during five months of the year. Males of M. longipes were active five months of the year, and their numbers peaked in November (n = 19; 20 %) but were absent from samples between February and August. Juveniles were absent during four months of the year with a peak in February (n = 10). Female numbers peaked in Febru- ary and March (n = 5; 17 %) (Fig. 2). Discussion and conclusion The two species M. longipes and M. zuluen- sis are typical cryptofauna of indigenous for- est habitats (Griswold 1985; Lawrence 1952). Although the two species occurred sympatrically and both were active through- out the year their reproductive periods differ. The males of M. zuluensis peaked in April, compared to the males of M. longipes that peaked in November. Koedoe 49/1 (2006) 88 ISSN 0075-6458 Fig. 2. Seasonal activity of Microstigmata longipes collected from 180 pitfall traps at Ngome State Forest, KwaZulu-Natal, South Africa during 1992-1993. Dippenaar microstigmatidae.qxd 2006/04/17 10:51 PM Page 88 Both species preferred the indigenous forest habitats with either dense or low under- growth where 85 % of the specimens were collected above the open grass habitat or pine forest where only 15 % of the two species were found. Based on general collec- tion information and distribution records Griswold (1985) identified M. zuluensis as a more tolerant species occurring also in habi- tats outside indigenous forests. This observa- tion was confirmed in this study where 12.4 % of M. zuluensis was collected from ecotone pine compared to the 3.8 % of M. longipes found outside the indigenous forest. Conservation biologists are starting to recog- nise the importance of the invertebrate com- ponent in the functioning of healthy ecosys- tems. Of prime importance in any conserva- tion scheme is the identification of species sensitive to changing environmental factors, as found here. In many areas of Africa the planting of exotic trees has supplanted indigenous forest. This has an effect on plant structure at the ground level, which could have an effect on the community structure of the ground-living spider fauna. Since spiders are an important component of the forest floor ecosystem this could have significant effects on other invertebrate groups and plants as well. As only a fraction of South Africa’s area (0.2 %) is covered by high evergreen forest (Huntley 1984) the conser- vation of these undisturbed indigenous forests with their cryptofauna is of utmost importance and should receive high priority for conservation efforts. Acknowledgement We thank the forester Michael Peter at Ngome State Forest for his assistance as well as students who assisted with field work. Helene Muller of the ARC- Biometry Unit was responsible for the statistical analysis of data. References DIPPENAAR-SCHOEMAN, A.S. 2002. The baboon and trapdoor spiders of Southern Africa: an identifi- cation manual. Pretoria: Agricultural Research Institute. (Plant Protection Research Institute Handbook no. 130). DIPPENAAR-SCHOEMAN, A.S. & C. CRAEMER. 2000. The South African National Survey of Arachni- da (SANSA). Plant Protection News 56: 11-12. GENSTAT FOR WINDOWS. 2000. Release 4.2. Fifth Edition. Oxford: VSN International. GRISWOLD, C.E. 1985. A revision of the African spi- ders of the family Microstigmatidae (Araneae: Mygalomorphae). Annals of the Natal Museum 27: 1-37. HUNTLEY, B.J. 1984. Characteristics of South African biomes. In: BOOYSEN P. DE V & N.M. TAINTON (eds). Ecological effects of fire in South African ecosystems. Berlin: Springer. LAWRENCE, R.F. 1952. New spiders of the eastern half of South Africa. Annals of the Natal Muse- um 12: 183-226. PLATNICK, N.I. 2005. The world spider catalog, ver- sion 5.5. American Museum of Natural History, online at http://research.amnh.org/entomology/ spiders/catalog/index.html VAN DER MERWE, M. 1994. A comparative survey of cursorial spider communities in indigenous Afromontane forests and in pine plantations. M.Sc. thesis, University of Pretoria, Pretoria. VAN DER MERWE, M., A.S. DIPPENAAR-SCHOEMAN & C.H. SCHOLTZ. 1996. Diversity of ground-living spiders of Ngome state Forest, Kwazulu/Natal: a comparative survey in indigenous forest and pine plantations. African Journal of Ecology 34: 342-350. 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