J Insect Conserv (2006) 10:323–333 DOI 10.1007/s10841-006-9006-0 ORIGINAL PAPER The importance of monkey beetle (Scarabaeidae: Hopliini) pollination for Aizoaceae and Asteraceae in grazed and ungrazed areas at Paulshoek, Succulent Karoo, South Africa Carolin Mayer Æ Geoffrey Soka Æ Mike Picker Received: 7 October 2005 / Accepted: 21 March 2006 / Published online: 17 October 2006 Ó Springer Science+Business Media, Inc. 2006 Abstract The relative importance of monkey bee- Keywords Hopliini Æ Beetle pollination Æ Pollen load Æ tles (Hopliini, Scarabeidae) as pollinators of Aster- Livestock grazing Æ Colour preferences aceae and Aizoaceae in the Succulent Karoo as well as the influence of livestock grazing on their abun- dance and diversity was investigated. Hopliine bee- Introduction tles proved to be the, or among the, most abundant flower visitors of 12 investigated plant species. In the semi-arid Succulent Karoo and Fynbos biomes However, during single flower observations at three of the Western and Northern Cape Provinces of South Aizoaceae species, bees (Apoidea), bee flies Africa, monkey beetles (Scarabaeidae, Hopliini) are (Bombyliidae) and pollen wasps (Masaridae) were one of the most important pollinator guilds (White- the most frequent flower visitors. However, monkey head et al. 1987; Picker and Midgley 1996; Goldblatt beetles carried the highest Asteraceae and Aizoa- et al. 1998; Colville et al. 2002) pollinating a diverse ceae pollen loads, and are therefore considered to number of unrelated annuals and perennials. These play a vital role in the pollination of these two biomes contain the majority of the world’s monkey families. Abundance, species richness and diversity beetle species, having more than 700 described species of Hopliini did not appear to be heavily affected by (2/3 of the world fauna—(Steiner 1998; Vernon 1999; livestock grazing. Annual variation in the composi- Colville et al. 2002). In these biomes, the Hopliini are tion of monkey beetle populations was more dra- typically associated with the very speciose Aizoaceae matic. Still, some species showed higher abundances and Asteraceae, but relatively little is known about this on heavily grazed rangeland while others only oc- relationship (Picker and Midgley 1996). In addition to curred under low grazing pressure. It is presumed feeding on flowers, the beetles use the flowers as that changes in the composition of the vegetation, mating rendezvous sites which reinforces their role as especially the observed decrease of perennial plants pollinators (Goldblatt et al. 1998; Steiner 1998; John- in favour of annuals and geophytes (Todd and son and Midgley 2001). Unlike beetle pollinators in the Hoffman 1999) could in turn affect the composition tropics that generally rely on odour to locate flowers of monkey beetle assemblages. (Armstrong and Irvine 1990), hopliine beetles use vi- sual cues exclusively (Picker and Midgley 1996), and are attracted to bright colours even in the absence of food or odour (Steiner et al. 1994). The beetles are C. Mayer (&) Biocentre Klein Flottbek Botanical Garden, University of covered with hairs and scales, which are very effective Hamburg, Ohnhorststrasse 18, Hamburg 22609, Germany in trapping pollen grains (Goldblatt et al. 1998). e-mail: [email protected] However, in contrast to the fairly good host record data, little information is available on the pollen load G. Soka Æ M. Picker Department of Zoology, University of Cape Town, Cape capacity of monkey beetles and their relative impor- Town, South Africa tance as pollinators. The few studies that have 123 324 J Insect Conserv (2006) 10:323–333 examined pollination ecology of Aizoaceae and (heavily and continuously grazed), the second on Asteraceae in the Succulent Karoo suggest that the commercial rangeland. Since 1950, when the privately system is generalised (Struck 1992, 1994; Ihlenfeldt owned land was fenced (Rohde et al. 2003), it has only 1994) as one would expect, given the convergent floral been lightly grazed and the vegetation has recovered structure of many of the constituent flowers (especially well. The continuously high stocking rate on the com- the Asteraceae and Aizoaceae). Struck (1994) found munal rangeland had a clear impact on the vegetation, that Hymenoptera were the most frequent visitors on with a marked fence-line contrast evident. Aizoaceae and Asteraceae, followed by Diptera (bee The vegetation, typical of that of the Succulent flies) and Coleoptera (monkey beetles). Karoo, is dominated by dwarf shrub succulents, bulbs Within the greater context of global biodiversity, and annuals, with perennial grasses being rare (Struck habitat loss and fragmentation are the biggest prob- 1992). The study area receives 150–250 mm of rain lems for pollinators (Webb 1989; Donaldson et al. annually, most of which falls in winter (June– 2002; Nash et al. 2004). In the Succulent Karoo, over- August). The coefficient of variation in mean annual stocking of rangelands with resultant overgrazing of rainfall is 33% (Todd and Hoffman 1999). Studies habitats is often stated as the major negative impact on were carried out in the springs (August–October) of biodiversity and associated ecological processes, such 2002–2004. as pollination, seed dispersal, seed germination and nutrient dispersion (Davis and Heywood 1994; Dean Flower visitation by pollinators et al. 1995; Todd and Hoffman 1999). The perennial vegetation component decreases in favour of annuals In 2004, the pollination of 12 species, each of the most and geophytes (Allsopp 1999; Todd and Hoffman common and flowering Asteraceae and Aizoaceae 1999), and the reduced flower display of certain plant species was examined closely to determine the relative species could make degraded land less attractive to importance of monkey beetle pollinators for these two insect pollinators (Gess and Gess 1993; Mayer 2004). families. The species chosen for study were: Astera- Changes in plant species composition would also ceae—Chrysocoma ciliata L. (n = 6), Pentzia incana reduce larval host plant availability (Kearns et al. (Thunb.) Kuntze (n =7), Senecio niveus (Thunb.) 1998). The reduced numbers of pollinators would Willd. (n = 9), Hirpicium alienatum (Thunb.) Druce result in lowered seed set, which in turn would also (n = 5), Tripteris sinuata DC. (n = 12) and Osteosper- affect recruitment and seed-eating animals, and thus mum spinescens Thunb. (n = 7), and Aizoaceae—Che- upset entire food chains (Kearns et al. 1998). Mayer iridopsis namaquensis N.E.Br. (n = 20), Cheiridopsis (2004) found significantly reduced numbers of flowers denticulata (Haw.) N.E.Br (n = 18), Ruschia goodiae and fruit set per individual plant for some Aizoaceae L. Bolus (n = 18), Conicosia elongata (Haw.) species on heavily grazed sites in the Paulshoek area of N.E.Br. (n = 9), Leipoldtia schultzei (Schltr. & Diels) central Namaqualand (the north-western part of the Friedrich (n = 16) and Lampranthus godmaniae L. Succulent Karoo). On the other hand hymenopteran Bolus (n = 6). diversity (especially that of bees and pollen wasps) was For each plant species, all flower visitors were col- not different across a gradient of grazing intensity lected directly from individual (tagged) plants at (Mayer 2005). hourly interval over a 4 day period. Insects were pre- This study examines the relative importance of served in 70% ethanol in individual Eppendorf vials to monkey beetles as pollinators of Asteraceae and prevent cross contamination of pollen grains. Aizoaceae in the Succulent Karoo. Secondly, it inves- In 2003 and 2004, 10 min flower observations at tigated whether intensive livestock grazing had a neg- single flowers of different Aizoaceae species (Cheirid- ative impact on monkey beetle species richness, opsis denticulata, Ruschia goodiae and Ruschia viridi- diversity, and abundance. folia) were conducted on both study sites, recording number and (where possible) species of visiting insects. Materials and methods Pollen analysis Study site A pollen reference library (Moore and Webb 1978) was created for the 12 selected plant species. Pollen The present study was carried out at two sites in the from flowers and insects was processed and mounted vicinity of Paulshoek, Northern Cape Province (Todd on microscope slides essentially following the proce- and Hoffman 1999), one being situated on communal dure described by MacGillivray (1987), using Kaiser’s 123 J Insect Conserv (2006) 10:323–333 325 glycerine jelly to trap pollen grains (Hall and Hawes Beetles were also the most abundant flower visitors 1991). of Asteraceae (Table 1). In particular, Senecio niveus Also in 2004, colour preferences exhibited by monkey and Osteospermum spinescens were visited almost beetles were investigated with eight sets of transparent exclusively by a single species of Hopliini (comprising plastic water traps (tubs 8 ·6 · 7 cm), each set con- 95% of all visitors for both plant species, Table 1). tained one of each tub painted blue, yellow, orange, red, Bombyliidae, and, to a lesser extend Meloidae, pink and white. Four sets of six tubs (tubs spaced 25– Halictidae and Melyridae also visited the species of 30 cm apart) were placed at 50 m intervals on both the Asteraceae. Again, there was one exception with heavily and the lightly grazed site, approximately 1 km Hirpicium alienatum being mainly visited by Phalacri- away from the fence. To examine pollinator abundance dae (50%) and no monkey beetles. and diversity at the heavily and lightly grazed sites, three sets of colour traps filled with water were set out on each Pollen loads of Aizoaceae and Asteraceae side of the fence-line, at different distances (100, 400 and 1000 m) from the fence in the springs of 2002–2004. All the flower visitors carried appreciable pollen loads Each set comprised five pans (2 · 20 cm) of each colour except for Nitidulidae sp. 1 (Table 2). Some species (white and yellow, with additional blue and pink pans for carried more pollen than others. trials in 2002 and 2003, respectively), placed about 10 m For Aizoaceae, Apidae (i.e. Apis mellifera) carried apart along a transect line.