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Volume 92, Number 2 2005 Potgieter & Edwards 255 Stenobasipteron wiedemanni Pollination Guild Figure 1. Map of South Africa showing provinces and study sites. Note that Northern Province is now called Limpopo Province. —Nk. Nkandla Forest. —Ng. Ongoye Forest. —K. Karkloof (Leopards Bush Nature Reserve). —H. Hlabeni Forest (Creighton). —O. Oribi Gorge Nature Reserve. —U. Umtamvuna Nature Reserve. —P. Port St. Johns. —S. Stutterheim (Kologha Forest). The Prosoeca ganglbaueri Guild sensu Goldblatt and Manning (2000) included four nemestrinid fly species: Prosoeca ganglbaueri Lichtwardt, Prosoeca longipennis Loew, Prosoeca robusta Bezzi, and Stenobasipteron wiedemanni Lichtwardt. Of these species, the floral Guilds pollinated by the first three show considerable overlap, but no overlap has been shown with the Guild pollinated by S. wiedemanni. Flowers pollinated by the first three fly species are pink with dark pink markings, but some species are cream or white or deep blue. The fourth fly species, S. wiedemanni, visits flowers in shades of pink, pale blue, or mauve (Goldblatt & Manning, 2000). Goldblatt and Manning (2000) indicated that further research may show this latter species to constitute a separate Guild of pollinating flies, and in this paper we confirm the existence of this separate S. wiedemanni pollination Guild. Stenobasipteron wiedemanni (cited as Stenobasipteron sp. in Potgieter et al., 1999) is a brown nemestrinid fly species with a proboscis length of 19– 30 mm. The species is largely limited to subtropical and temperate forests along the eastern seaboard of southern Africa (Potgieter & Edwards, 2001), and adults have been collected from December to June, with activity in each locality restricted to a few months during summer (see Appendix 1). By contrast, the nemestrinid genera Moegistorhynchus and Prosoeca occur in temperate fynbos, montane grasslands, and other habitats without a closed canopy. We proposed (Potgieter & Edwards, 2001) that there are a number of long-tubed species in genera of Lamiaceae in South Africa that are pollinated by either Stenobasipteron or Prosoeca, depending on habitat. Comparative plant and long-proboscid fly pollinator distributions are presented in Potgieter and Edwards (2001). These species are distributed over the eastern part of the country and include long-tubed members of Plectranthus (Potgieter et al., 1999), Hemizygia, Salvia, Stachys, Orthosiphon Chapter 5/ 57
256 Annals of the Missouri Botanical Garden (Goldblatt & Manning, 1999, 2000), and Thorncroftia. Goldblatt and Manning (2000) included species of Thorncroftia as inferred members of their Prosoeca ganglbaueri Guild. In forests of the eastern seaboard of southern Africa a number of plant families have evolved long, narrow corolla tubes, spurs, or hypanthia (ca. 20– 35 mm), and in our study area we suggest that Stenobasipteron wiedemanni may be the primary pollinator of such species. Most of these plant species are unscented and have flowers of mauve, pink, purple, pale blue, or white. MATERIALS AND METHODS Fieldwork was conducted during the main flowering season of Plectranthus, between December and May, from 1995 to 2002. Study sites for pollinator observations are shown in Figure 1. We avoided over-collecting fly specimens, since the species occurs at low densities and we did not want to impact on the pollination service it renders. Where appropriate, observations of insect visits were followed by capture of voucher specimens that were killed in separate ethyl-acetate-containing vials and pinned with proboscides extending forward for easy measurement. Areas of pollen deposition were identified under a dissecting microscope, and samples of pollen were collected using blocks of Fuchsin Jelly and mounted. Slides were studied with a compound light microscope, and pollen samples were identified by comparison with reference slides of pollen from plants flowering in the area. Stenobasipteron wiedemanni is not easily confused with other insects in the study area, and thus only one (or rarely a few) vouchers were collected per plant species to ascertain areas of pollen deposition on the insect. After the first voucher per plant species was captured, careful observations of flies during subsequent flower visits allowed the observer to judge whether pollen would be deposited on certain areas of the insect. In cases where observations were not made by the authors of this paper, we relied on personal communication with other field workers that obtained photographic records or insect vouchers where possible. Insect vouchers for this study are lodged with the Natal Museum in Pietermaritzburg, South Africa, and plant vouchers are housed at NU, Natal University Herbarium (see Appendices 1 & 2). Distributions of the fly species were compiled from field observation and by using data from the Natal Museum (Pietermaritzburg), Albany Museum (Grahamstown), and the South African Museum (Cape Town). Distributions of Guild constituents were compiled from NU and PRECIS (National Herbarium, Pretoria (PRE) Computerised Information System), as well as published information (Codd, 1985; Pooley, 1998; Linder, 1981; Hilliard & Burtt, 1986; Edwards, 1988) and observations made during the course of this study. Distribution maps for shortertubed species of Plectranthus are available in Potgieter et al. (1999). Distribution maps were generated using ArcGIS, combining data from MS Access. Data were collected at quarter-degree-grid level, and hence the forest land cover was re-sampled to quarter-degreegrid resolution. Floral and other characters of plants shown to be effectively visited by Stenobasipteron wiedemanni were compared, and these data were used to suggest other possible members of the Guild. Nectar volume measurements were made during mornings from cultivated plants in a greenhouse, and these represent the maximum amount of nectar available to insect visitors. Nectar concentrations (as percentage of sucrose equivalents) were measured using a Bellingham & Stanley Eclipse (0– 50%) hand-held refractometer. Nectar samples were dried on Whatmans no. 1 filter paper and analyzed using a modified Gas Chromatographic nectar sugar analysis method based on Tanowitz and Smith (1984). Samples of 10 to 30 flowers were pooled to obtain sufficient nectar for analysis. RESULTS THE POLLINATOR Stenobasipteron wiedemanni is a day-flying dipteran that visits flowers from about 9 A.M. to4P.M., extracting nectar as a reward. Specimens have been collected between December and July, but we found that in the Eastern Cape and KwaZulu-Natal activity continued to about May (depending on the year). The behavior of these flies makes them ideal pollinators of long-tubed flower species. During flight the proboscis is folded underneath the body, but as a flower is approached the proboscis is brought forward to extend in front of the body (Fig. 2A). Flies hover in front of flowers while probing for nectar, but occasionally grasp protruding filaments or styles (in the case of Lamiaceae) or rest on landing platforms (e.g., in Isoglossa hypoestiflora Lindau, Acanthaceae). Visits to individual flowers last between one and four seconds, and a number of flowers on the same inflorescence or plant may be Chapter 5/ 58
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Pollination of Plectranthus L’Hé
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STUDENT DECLARATION 1 Pollination o
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DECLARATION BY SUPERVISOR We hereby
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ACKNOWLEDGEMENTS Financial support
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CONTENTS Abstract ……………
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apparent neo-endemics with strong a
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enhance the understanding of floral
Page 15 and 16: three species of Xylocopa Latreille
Page 17 and 18: Chapter 2: Pollination of Straight-
Page 19 and 20: References Abdel-Mogib, M., Albar,
Page 21 and 22: Plectranthus vestitus (Lamiaceae) b
Page 23 and 24: CHAPTER 2: POLLINATION OF STRAIGHT-
Page 25 and 26: 100 C.J. Potgieter et al.: Pollinat
Page 27 and 28: 102 2 14 ° I .j. / 2 .e- ¢..,~ }e
Page 29 and 30: 104 a C d Stenobasipteron sp. (N, D
Page 39 and 40: Pollination of Plectranthus spp. (L
Page 41 and 42: 648 C.J. Potgieter et al. / South A
Page 53 and 54: CHAPTER 4: CONVERGENT POLLINATION I
Page 55 and 56: Syst. Geogr. PI. 71 XVIth Ss.Gg.l.1
Page 57 and 58: Syst. Geogr. Pl. 71 Syst. Geogr. P1
Page 59 and 60: Syst. Geogr. Pl. 71 Figure 2. Distr
Page 61 and 62: Syst. Svst. Geogr. Pl. P1. 71 XVIth
Page 63 and 64: Syst. Geogr. Pl. 71 P1.71 XVIth AET
Page 65: THE STENOBASIPTERON WIEDEMANNI (DIP
Page 69 and 70: 258 Annals of the Missouri Botanica
Page 79 and 80: CHAPTER 6: NATURAL HYBRIDS Viljoen,
Page 81 and 82: 100 A.M. Viljoen et al. / South Afr
Page 83 and 84: 102 Table 1 (continued) RRI : Relat
Page 85 and 86: 104 Buchbauer, G., Jirovetz, L., Wa
Page 87 and 88: contrast, shallow flowers with rela
Page 89 and 90: [=Syncolostemon albiflorus (N.E.Br.
Page 91 and 92: Nectar volumes were measured by usi
Page 93 and 94: Table 1: Nectar sugar properties of
Page 95 and 96: To test whether these results could
Page 97 and 98: Nectar sugar concentration results
Page 99 and 100: Discussion A. Nectar Sugars Very fe
Page 101 and 102: differences in sucrose concentratio
Page 103 and 104: is that the shortest-tubed P. sacca
Page 105 and 106: Nectar volume and concentration dat
Page 107 and 108: Complete rewardlessness is rarely r
Page 109 and 110: Goldblatt, P., Bernhardt, P., Manni
Page 111 and 112: CHAPTER 8: DISCUSSION AND CONCLUSIO
Page 113 and 114: medium-proboscid nemestrinid flies
Page 115 and 116: Plectranthus (see Appendix). Anecdo
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were seen on older inflorescences),
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(Potgieter et al. 2009), developing
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Paton, A.J., Springate, D., Suddee,
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The following abbreviations are use
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1. Plectranthus ambiguus (H.Bol.) C
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2. Plectranthus hilliardiae Codd Ha
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3. Plectranthus reflexus Van Jaarsv
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4. Plectranthus saccatus Benth. Hab
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P. saccatus (12 - 14 mm) in cultiva
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Nemestrinid flies hovered while pro
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6. Plectranthus zuluensis T. Cooke
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7. Plectranthus ciliatus E.Mey ex B
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Plectranthus ciliatus is a relative
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8. Plectranthus ernstii Codd Habit,
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As discussed for P. ernstii, a tent
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acrocerid flies of the genus Psilod
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This fly species also pollinates wh
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syrphid fly, a hesperid butterfly a
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Study sites and observations Observ
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Potgieter 147 OG, 3-4-98 Prosoeca u
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14. Plectranthus petiolaris E.Mey.
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Episyrphus sp. (Syrphidae) Potgiete
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Dargle Valley in late March. On a o
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Bombyliidae (Diptera) Potgieter 38
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Insect vouchers Prosoeca umbrosa (N
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Insect vouchers Chalicodoma sp. A (
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19. Pycnostachys urticifolia Hook.
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20. Aeollanthus parvifolius Benth.
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References Brothers, D.J., 1999. Ph
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