and native membracids in the CFR, which greatly increased the discovery of
inflorescences of the Wagon Tree, Protea nitida, by the ants. This in turn, led to
decreased visitation rates of P. nitida flowers by several native arthropods and
potential pollinators (Lach 2007).
It is well known that invasive plants can disrupt native plant-pollinator interactions (Traveset and Richardson 2014). We know that native plant-pollinator networks are highly specialised in South Africa (Pauw and Stanway 2015). Invasive
plant species can influence these networks indirectly, for example by competing with
native plants for pollinators and acting as ‘magnet species’, attracting pollinators
away from native species (Biotic Indirect Effects Hypothesis; Catford et al. 2009).
Alternatively, invasive plants may increase the “overall attraction” and increase
pollinator visitation to only certain native species. Gibson et al. (2013) asked
whether the prolific flowering of invasive Acacia saligna acts as a magnet for
pollinators in South Africa. They found a large overlap in floral visitors between
one native species, Roepera fulva, and A. saligna. Moreover, visitation rates to
R. fulva were significantly lower in invaded than in uninvaded sites. This observation
was mainly due to visits of native honeybees. Whether lower visitation rates resulted
in lower fitness of R. fulva (e.g. reduced seed set) was not tested. In contrast, no
effects on the efficiency of bird pollination of native species was caused by the
presence of the invasive Showy Banksia, Banksia speciosa (Erckie 2017). Banksia
species are known to add significant amounts of nectar to the landscape during the
peak flowering time of native CFR Proteaceae (Geerts et al. 2013). Erckie (2017)
compared visitation rates by nectar feeding-birds and subsequent seed set, between
Sugarbush, Protea compacta, populations adjacent to, and far away from, invasive
B. speciosa plants. Although B. speciosa attracted significantly more sugarbirds and
significantly fewer sunbirds than P. compacta, it did not reduce sugarbird numbers
or visitation rates in P. compacta populations, and therefore had no impact on seed
set for this species.
The Banksia speciosa example illustrates that pollination impacts on native plants
may be neutral, but that native pollinators may well benefit. Evidence for such
impacts comes from invasive eucalypts (genus Eucalyptus) and kangaroo paws
(genus Anigozanthos) in South Africa. In its Australian range, the Evergreen Kangaroo Paw (A. flavidus) is mainly pollinated by perching Western Spinebills
(Acanthorhynchus supercilliosus) and New Holland Honeyeaters (Phylidonyris
novaehollandiae) (Phillips et al. 2014). Given this eco-evolutionary experience,
and as expected, this species is pollinated by perching sunbirds and sugarbirds in
South Africa’s CFR (Le Roux et al. 2010). Anigozanthos flavidus produces rich
nectar for these birds during late summer, when nectar is generally scarce in the
CFR. This was evident when, following the mechanical removal of invasive
A. flavidus populations, sugarbird visitation dropped from 425 visits per hour
(with sometimes more than ten birds observed at any given time) to only three
sugarbirds per hour. With no overlap between the flowering times of native species
and A. flavidus, it is unlikely that this negatively effects the pollination services of
co-occurring native plants. Similar to kangaroo paws, Australian eucalypts are in
important nectar source for honeybees during summer months in the CFR. This
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inflorescences of the Wagon Tree, Protea nitida, by the ants. This in turn, led to
decreased visitation rates of P. nitida flowers by several native arthropods and
potential pollinators (Lach 2007).
It is well known that invasive plants can disrupt native plant-pollinator interactions (Traveset and Richardson 2014). We know that native plant-pollinator networks are highly specialised in South Africa (Pauw and Stanway 2015). Invasive
plant species can influence these networks indirectly, for example by competing with
native plants for pollinators and acting as ‘magnet species’, attracting pollinators
away from native species (Biotic Indirect Effects Hypothesis; Catford et al. 2009).
Alternatively, invasive plants may increase the “overall attraction” and increase
pollinator visitation to only certain native species. Gibson et al. (2013) asked
whether the prolific flowering of invasive Acacia saligna acts as a magnet for
pollinators in South Africa. They found a large overlap in floral visitors between
one native species, Roepera fulva, and A. saligna. Moreover, visitation rates to
R. fulva were significantly lower in invaded than in uninvaded sites. This observation
was mainly due to visits of native honeybees. Whether lower visitation rates resulted
in lower fitness of R. fulva (e.g. reduced seed set) was not tested. In contrast, no
effects on the efficiency of bird pollination of native species was caused by the
presence of the invasive Showy Banksia, Banksia speciosa (Erckie 2017). Banksia
species are known to add significant amounts of nectar to the landscape during the
peak flowering time of native CFR Proteaceae (Geerts et al. 2013). Erckie (2017)
compared visitation rates by nectar feeding-birds and subsequent seed set, between
Sugarbush, Protea compacta, populations adjacent to, and far away from, invasive
B. speciosa plants. Although B. speciosa attracted significantly more sugarbirds and
significantly fewer sunbirds than P. compacta, it did not reduce sugarbird numbers
or visitation rates in P. compacta populations, and therefore had no impact on seed
set for this species.
The Banksia speciosa example illustrates that pollination impacts on native plants
may be neutral, but that native pollinators may well benefit. Evidence for such
impacts comes from invasive eucalypts (genus Eucalyptus) and kangaroo paws
(genus Anigozanthos) in South Africa. In its Australian range, the Evergreen Kangaroo Paw (A. flavidus) is mainly pollinated by perching Western Spinebills
(Acanthorhynchus supercilliosus) and New Holland Honeyeaters (Phylidonyris
novaehollandiae) (Phillips et al. 2014). Given this eco-evolutionary experience,
and as expected, this species is pollinated by perching sunbirds and sugarbirds in
South Africa’s CFR (Le Roux et al. 2010). Anigozanthos flavidus produces rich
nectar for these birds during late summer, when nectar is generally scarce in the
CFR. This was evident when, following the mechanical removal of invasive
A. flavidus populations, sugarbird visitation dropped from 425 visits per hour
(with sometimes more than ten birds observed at any given time) to only three
sugarbirds per hour. With no overlap between the flowering times of native species
and A. flavidus, it is unlikely that this negatively effects the pollination services of
co-occurring native plants. Similar to kangaroo paws, Australian eucalypts are in
important nectar source for honeybees during summer months in the CFR. This
412
J. J. Le Roux et al.