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Gladiolus longicollis (Honey flower)
Aandblom [Afrikaans]; khahla-e-nyenyane, khukhu-rupa [South
Sotho]; sidvwana [Swazi]; umbejo [Zulu] Life
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> Spermatophyta (seed plants) > Angiospermae (flowering
plants) > Monocotyledons > Order: Asparagales
> Family: Iridaceae > Genus:
Gladiolus
Description
Distribution and habitat
Widely distributed in southern Africa, from the southern
Cape to Limpopo Province and Swaziland. Occurs in low, open grassland.
Life cycle
- Flowers in spring and early summer but usually only after fire in the
preceding winter.
- The flower is closed for most of the day, starting to open only from
about 17h00, earlier if it is cloudy. In the evening it produces a strong,
sweet frangrance, attractive to hawk moth pollinators (Johnson and
Alexandersson 2002).
Ecological interactions
Pollinators
Johnson and Alexandersson (2002) studied pollination of
this species by hawkmoths (Lepidoptera:
Sphingidae) at a site near Pietermaritzburg. The following hawk moth
species, captured at a light trap, had Gladiolus longicollis pollen on
them:
Of these species, only Agrius convolvuli has a
proboscis long enough to reach the nectar of flowers in this study area. The
other species would have tried to reach it unsuccessfully but in the process
would have picked up some pollen and affected pollination of a few flowers.
However, it was clear that Agrius convolvuli was the main pollinator at
this site. They found that flowers with longer tubes were more likely to produce
fruit than flowers with shorter tubes. If the tube is longer than the moth's
proboscis, then the moth has to press its head into the flower to get to the
nectar and in so doing presses it against the anthers and the stigma where
pollen transfer then takes place. If the tube is shorter than the proboscis then
the moth can reach the nectar without having to press its head into the flower
and hence does not pick up pollen.
There is extensive variation in flower length over the
distribution of Gladiolus longicollis and one would expect that in areas
where the dominant hawk moths have shorter probosces, flower length would be
shorter as well.
Publications
Text by Hamish Robertson |
