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264 Annals of the
Missouri Botanical Garden
these may allow exploitation by bees. Other species
in the Guild (with shorter corolla tubes) are not
solely visited by S. wiedemanni, but still need to
be included since the fly provides an efficient pollination
service (Potgieter et al., 1999).
DISCUSSION BY FAMILY
LAMIACEAE
Pollination of Plectranthus hilliardiae, P. reflexus,
P. ambiguus, and long-tubed forms of P. saccatus
has previously been discussed in Potgieter et
al. (1999) and Potgieter and Edwards (2001). In
most areas where Stenobasipteron wiedemanni has
been observed, Plectranthus species (long- or shorttubed)
tend to form a major component of the forest
understory. Orthosiphon tubiformis occurs in different
habitat to forest understory Plectranthus species
and has been discussed by Goldblatt and Manning
(2000).
ACANTHACEAE
Honeybees collect pollen from Isoglossa hypoestiflora,
but the long, narrow corolla tube prohibits
nectar access. Honeybees would not contribute to
significant pollen carryover over large distances,
since pollen is groomed into the scopae before the
worker bees return to their hives. Isoglossa cooperi
closely resembles I. hypoestiflora in floral shape
and size, differing only in the presence of glandular
hairs on the calyx and bracts. The species are often
sympatric (Fig. 4A). From a pollination perspective,
these two species are very similar and fit the Stenobasipteron
wiedemanni pollination Guild. They occur
in afromontane and scarp forest and are generically
anomalous with respect to flower color and
corolla morphology. Most Isoglossa Oerst. species
in South Africa are hymenophilous (pers. obs.),
with creamy white flowers and short corolla tubes
(mostly less than 10 mm in length). These creamy
white species are common in savanna and tropical
and subtropical forests.
The observation of visits to Hypoestes aristata
shows that Stenobasipteron wiedemanni may form
part of a more generalized suite of pollinators in
species with shorter floral tubes. As in shortertubed
Plectranthus species, the fly still contributes
to pollen carryover, since the elongate anther filaments
deposit pollen on the body of the fly and the
elongate style is able to remove pollen from this
position. A similar situation exists in Barleria obtusa,
where long-proboscid bees can also access
nectar by crawling into the widened distal part of
the corolla tube.
ORCHIDACEAE
The record for long-proboscid fly pollination in
Brownleea Harv. ex Lindl. (Goldblatt & Manning,
2000) highlights the disjunction between grasslandand
forest-growing species. Brownleea macroceras
Sond. is pollinated by Prosoeca ganglbaueri (Johnson
& Steiner, 1995), which occurs in montane
grassland at high altitudes. By contrast, B. coerulea
is a forest margin species of lower altitudes and is
pollinated by Stenobasipteron wiedemanni. Brownleea
coerulea is a widespread species (Fig. 3C) that
also occurs in Madagascar, where its pollination has
not been studied.
BALSAMINACEAE
The floral visits by Stenobasipteron wiedemanni
to Impatiens hochstetteri subsp. hochstetteri are the
first published records of nemestrinid fly pollination
in the Balsaminaceae. This plant species is
widespread across Africa, but the distribution of S.
wiedemanni elsewhere in Africa is not known.
Grey-Wilson (1980) recorded butterflies as pollinators
of the ‘‘flat type’’ flowers in the section to
which I. hochstetteri subsp. hochstetteri belongs, yet
little information is available on the pollination of
specific Impatiens L. (Grey-Wilson, 1980). We have
observed papilionoid butterfly visits to I. hochstetteri
subsp. hochstetteri at Ferncliffe Nature Reserve
in Pietermaritzburg (KZN) confirming the above.
The distribution of Impatiens hochstetteri subsp.
hochstetteri in southern Africa (Fig. 3D) shows a
number of plots outside forested areas. This species
relies on moist forest habitats and may occur in
scrub forest patches that are below the resolution
of our Geographic Information System that was
used for mapping.
GESNERIACEAE
Very little is known about pollination in Streptocarpus
(Hilliard & Burtt, 1971), and it is likely
that Stenobasipteron wiedemanni is the pollinator of
a number of Streptocarpus species that conform to
the floral morphology of S. formosus.
IRIDACEAE
The genus Hesperantha comprises many scented,
pale species with crepuscular anthesis that are
thought to be pollinated by moths (Goldblatt, 1984).
Contrary to this pattern, H. huttonii is odorless, has
diurnal anthesis and colored flowers—attributes
suited to nemestrinid fly pollination. Long-proboscid
fly pollination of day-flowering species of Hesperantha
is not uncommon. Hesperantha latifolia
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