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Plectranthus (see Appendix). Anecdotal evidence, publications by Goldblatt & Manning
(1999, 2000) and confirmation by pollen collected from voucher specimens of S.
wiedemanni, extended the Guild to members of other plant families (Acanthaceae,
Orchidaceae, Balsaminaceae, Gesneriaceae and Iridaceae) that occur in forested
habitat along the Eastern seaboard of southern Africa.
A study on pollination systems in Brownleea (Larsen et al. 2008) confirmed that in a
Grahamstown population (EC, South Africa), B. coerulea is pollinated by S.
wiedemanni, with flies at this site also visiting stands of Hypoestes aristata (Vahl) Sol.
ex. Roem & Schult. (Acanthaceae) which may act as a magnet species; this species
was included in the S. wiedemanni guild by Potgieter & Edwards (2005). Interestingly,
B. coerulea at Umtamvuna was rather found to be pollinated by a tabanid fly, Ph.
aethiopica, with P. ciliatus creating a possible magnet effect at the study site which was
a forest patch situated next to grassland (Larsen et al. 2008).
This type of habitat is similar to that occupied by succulent forms of P. saccatus with
short, white flowers that have blue speckling on the corolla limbs, which superficially
resemble the speckled nectar guides of P. ciliatus (and that of B. coerulea). A few
plants of B. coerulea were seen amongst the population of P. saccatus studied at
Beacon Hill, Umtamvuna NR, but for which no pollinator data was recorded. It is
possible that Ph. aethiopica pollinates this form of P. saccatus at Umtamvuna NR,
since the average proboscis length (8.9 mm) listed in Table 2 of Larsen et al. (2008)
corresponds favourably to the 5 – 7 mm tube length of P. saccatus at this site. It is,
however, also possible for acrocerid flies or anthophorine bees to be the pollinators of
this Plectranthus species (see Appendix, P. saccatus). The month of observation of B.
coerulea at Umtamvuna NR is not given by Larsen et al. (2008), but it is likely that S.
wiedemanni had not yet emerged at that site at the time of the study, since the fly
species has been recorded from forests at that site (C. Potgieter unpubl. data). At the
Kologha Forest study site where P. ciliatus was observed for pollinators in the current
Plectranthus study (near Stutterheim, EC), B. coerulea was seen to be pollinated by S.
wiedemanni, with a voucher carrying pollinaria of the orchid (Potgieter & Edwards
2005).
Stenobasipteron wiedemanni is responsible for the evolution of specialised long-tubed
corollas in four species (or forms) of Plectranthus, three of which are endemic to the
Pondoland Centre of Endemism. The long-tubed form of P. saccatus that occurs on
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