184 S.-Afr. Tydskr. Dierk. 1988,23(3) Ant species richness of fynbos and forest ecosystems in the southern Cape J.H. Koen* and W. Breytenbach South African Forestry Research Institute, Saasveld Forestry Research Centre, Private Bag X6515. George. 6530 Republic of South . Africa Received 26 June 1987; accepted 16 March 1988 The ant fauna in fynbos and forest habitats in the southern Cape are compared. There is no significant difference in ant species richness between the two undisturbed habitat types. and the only two species common to both are Acantholepis capensis and Camponotus maculatus. The degree of Hakea sericea infestation in the fynbos negatively affected ant species richness. Ant species richness in the Afromontane forest decreased from the drier to the wetter sites. The aggressive alien ant species. lridomynnex humilis, has not invaded natural areas to any great extent. Die mierfauna in fynbos- en inheemse woud-habitatte in die Suid-Kaap is vergelyk. Daar is geen beduidende verskille in mierspesieverskeidenheid tussen die twee onversteurde habitat-tipes nie. Slags twee spesies, Acantholepis capensis en Camponotus maculatus is in albei habitatte aangetref. Die mate van Hakea sericea besmetting in die fynbos verminder mierspesieverskeidenheid. Mierspesieverskeidenheid in die Afrikaanse berQwoud het 'n afname getoon van die droeer na die natter persele. Daar is nag geen beduidende indringing van die aggresiewe uitheemse mierspesie. lridomynnex humilis, in natuurlike habitatte nie. ·To whom correspondence should be addressed The ant fauna of the western Cape, South Africa, is fairly 2 = 35% and Site 3 = 100% H. sericea cover infestation) well known (Slingsby & Bond 1981; de Kock 1984; at 570 and 577 m a.s.1. respectively. Rainfall in the area is Donnelly & Giliomee 1985a, b). No information is, non-seasonal with a mean of 800 mm per annum. Climatic however, available on the species composition of the ants extremes are experienced in the area with periods of hot, of natural and disturbed ecosystems of the southern Cape. dry berg winds or gale force winds, rain and very low Various research projects are in progress in the fynbos and temperatures with snow on the higher peaks. The soils in . ) forest habitats of the southern Cape which aim to the Waboomskraal Valley are derived from Table Moun­ 0 1 determine and evaluate management practices, and to tain sandstone and are generally shallow to moderately 0 2 determine the relationship between faunal communities deep (G. Schafer, pers. comm.). d (vertebrate and invertebrate) and environmental factors. The forest study area is in evergreen high forest (Afro­ e t a Infestation by alien vegetation (mainly Hakea sericea, an montane), 30 km to the north of Knysna, generally known d ( Australian Proteaceae) in the fynbos of the Outeniqua as the Knysna Forest (Acocks 1953). In general, the r e Mountain range is causing serious concern and the impact canopy is 20-25 m high with the following common h s i of H. sericea on the species composition (fauna and flora) species: Podocarpus falcatus, P. lalifolius, Pterocelastrus l b of the natural communities is under investigation. The tricuspidatus, Ocotea bullata, Olea capensis macrocarpa, u P presence of alien plants (e.g. Pinus radiata) have been Rapanea melanophloeos, Apodytes dimidiata, Gonioma e h reported to affect species diversity of ants in the western kamossi and Nuxia floribunda. Rainfall is alSo non­ t Cape (Donnelly & Giliomee 1985b). y seasonal with a mean of 1100 mm. Climatic conditions b Data on the ant communities have been gathered similar to Waboomskraal prevail in the forest but without d e during general arthropod surveys and are presented here t cold periods associated with snow. The soils in the area n to supply information on the distribution of ants in the a are variable and the underlying geology is Table Mountain r g coastal mountain range and in the evergreen high forests sandstone (G. Schafer, pers. comm.). e c on the plateau to the south of this range. All identified ant Three study sites were selected along a soil moisture n e specimens are lodged in the Saasveld Forestry Museum. c gradient to represent the spectrum of forest types in the i l area. Although not directly measured, soil moisture r e Study area d content affects the species composition of the associated n The fynbos study area IS to the Waboomskraal Valley vegetation (Koen & Crowe 1987). Sites 1 and 2 were in the u y (33°51'S I 22°lO'E) on the north-facing slopes of the Lily Vlei Nature Reserve of the Gouna State Forest a w Outeniqua Mountains, 30 km north-west of George. (33°56'S/23002'E), and Site 3 was on the DiepwaHe e t Fynbos communities were dominated by Proteaceae, State Forest (33°56'S I 23009' E). Site 1 (dry forest) a G Ericaceae, Restionaceae and Cyperaceae. The most has fairly dense vegetation with an understorey of tree t e common species include Protea repens, P. lorifolia, regeneration and thorny shrubs. Site 2 (moist forest) has a n i b Leucadendron salignum, L. eucalyplifolium and dense understorey of 2-5 m high Trichocladus crinitus and a S Hypodiscus striatus. Three sites were chosen on a H. trees with rounded crowns. Site 3 (wet forest) consists of y sericea infestation gradient. The uninfested, mature (18- straight-stemmed and slender-crowned trees with an b d year-old) fynbos (Site 1) is at a slightly higher elevation understorey of ferns, especially Cyathea capensis (Koen & e c (645 m a.s.l.) than the two H. sericea infested sites (Site Crowe 1987). u d o r p e R S. Afr. J. Zoo!. 1988, 23(3) 185 Methods Table 2 Formicidae collected in two areas in the Data on arthropod communities were gathered during two southern Cape with presence (+) and absence (-) indi­ separate studies: one on the effects of H. sericea on the cated community structure of plants and insects, and the other Fynbos on the changes in the community structure of birds and Forest insects between different forest types. Although different 51 52 53 collection methods were employed, the data is sufficient 0%· 35%· 100%· 51 52 53 to make gross comparisons between the ant communities in the two habitats. Dotichoderinae Arthropods were sampled nine times during the period lridomyrmex humi/is + May 1983 to March 1984 (fynbos) and monthly from April Technomyrmex a/bipes + 1983 to March 1984 (forest) using 150 mm wide pitfall Fonnldnae traps with vehicle anti-freeze as preservative. Although Anop/o/epis custodiens + + + Marsh (1984) found pitfall trapping to be an unreliable Acantho/epis capensis + + + + way of determining relative abundances of ant species in Camponotus macu/atus + + + + + the Namib Desert, Samways (1983), de Kock (1984), Camponotus niveosetosus + Andersen (1986a, b) and Marsh (1986) found it a reliable Camponotus rufog/aucus + + method to determine species richness in various habitats. Camponotus (sp. nova) + We used 12 traps in each of the fynbos sites, set 10 m apart Camponotus sp. 2 + Plagio/epis decora + + on a contour running through the length of the study area. Myrmldnae Crematogaster Jiengmei + + 22r---------------------------------------, Crematogaster peringueyi + + + Me1'8nopJus peringueyi + + + N o Monomorium de/agoensis + + + o 17 Monomorium austra/e + F Monomorium S P springvaJense + E C 12 Monomorium sp. 1 + I Monomorium sp. 2 + . E ) S 0 Monomorium sp. 3 + 1 0 7 Ocymyrmex barbiger + 2 Pheidole capensis + d e t Pheidole fore/i + a 2L-----~----~----~-----L----~----~--~ Pheido/e sp. 2 d + + ( o 2 4 6 B 10 12 So/enopsis punctaticeps + r OBSERVATION PERIOD e Strumigenys havi/andi h --a-- rOREST -+ IT/mos + + s i l SyJ/aphopsis arno/di + b Figure I Cumulative species diverSity curves for fynbos and SyJ/aphopsis sp. 1 u + forest habitats in the southern Cape. P Tetramorium ackermani + e h Tetramorium de/agoensis + t y Tetramorium grassii + + + b Table 1 Number of ant species caught per bait type for Tetramorium sp. 1 + d e a one-year period in the fynbos study site 2 t Tetramorium sp. + n Tetramorium sp. 3 + a Banana! r g Tetramorium sp. 4 + + rum Mean! e Gen. nov. (near Pheido/e) + c Date Meat Faeces mixture Unbaited trap n e Ponerinae c i l 05/1983 5 6 4 3,75 o Discothyrea poweri -' + + r e 0611983 5 7 7 1 5 Hypopoilera nata/ensis + d n 0811983 3 10 9 8 7,5 Hypoponera u 09/1983 3 10 4 3 5 punctatissima y + a 1011983 12 12 9 3 9 Leptogenys attenuata + w e t 11/1983 9 6 10 8 8,25 Leptogenys nitida + a 01/1984 8 7 10 13 9,5 Trachymesopus G t wroughtoni + + + e 0211984 13 8 10 7 9,5 n i 0311984 8 4 11 13 9 Pseudomyrmldnae b a Tetraponera emeryi + S Mean 7,3 7,7 7,7 6,6 7,3 y b Total 21 13 6 13 11 4 d 5td dev. of mean no. species 1 bait type = O,5J. e c 5td dev. of mean no. species 1 month = 2,2. ·Percentage Hakes present. u d o r p e R 186 S.-Afr. Tydskr. Dierk. 1988,23(3) The traps remained in situ for a 3O-day period/month. Table 4 Ant species richness in various 'natural' and Twenty-five traps were used in each of the forest sites on a disturbed habitats. - = 'natural' sites, * = disturbed sites 25 x 25 m grid and the trapping continued for a 4-7-day period per month. Although more days trapping was done Habitat and Locality Richness Source in the fynbos, we feel confident that most species were Heathland·· 22 Andersen 1986a sampled in the forest as no additional species were added S.E.