Abstract:
Background: The African violets are endangered plant species restricted mainly
to the Eastern Arc Mountains biodiversity hotspots in Kenya and Tanzania. These
plants grow well in shaded environments with high humidity. Given their restricted
geographical range and published evidence of dependance on insect vectors to
facilitate sexual reproduction, understanding their pollination biology is vital for
their survival.
Methods: We conducted an empirical study using flower visitor observations, pan
trapping and bagging experiments to establish the role of flower visitors in the fruit
set of a locally endemic and critically endangered species of African violet in Taita
Hills, Kenya, Streptocarpus teitensis.
Results: The study found that fruit set is increased by 47.8% in S. teitensis when
flowers are visited by insects. However, it is important to note the presence of
putative autogamy suggesting S. teitensis could have a mixed breeding system
involving self-pollination and cross-pollination since bagged flowers produced 26.9%
fruit set.
Conclusions: Insects appear to be essential flower visitors necessary for increased
fruit set in S. teitensis. However, there is evidence of a mixed breeding system
involving putative self-pollination and cross-pollination suggesting that S. teitensis
is somewhat shielded from the negative effects of pollinator losses. Consequently,
S. teitensis appears to be protected to a degree from the risks such as reproduction
failure associated with pollinator losses by the presence of a safety net in putative
self-pollination.
