ENVIRONMENT
25 March 2020
EXPLORER | 7
The large white fleshy stigma can clearly be seen in this un-pollinated orchid Disperis capensis (‘Cape Witch Orchid’, or ‘Moederkappie’).
The Orchid and the Carpenter
By Dr Anina Lee Whale Coast Conservation
W
e have all read about the decline in bee populations around the world and the dire predictions for a world devoid of bees. Most of these articles refer to honey bees. However, there are hundreds more types of wild bees that perform equally critical functions in nature. How much do we know about them? Whale Coast Conservation had invited wild bee expert Jenny Cullinan from Ujubee to come and tell us more at our monthly talk in March. But alas, Covid-19 tripped us up. Jenny sent us the following teaser for her talk: As a keystone species, honey bees are fundamentally important to all terrestrial life, yet information about them is slanted to support their agricultural exploitation. By contrast, this talk looks at the ecology of all wild bees, not only honey bees. A richly illustrated talk covering the complex world of bees and their interconnectedness to everything around them. The talk will take you right into this wild world of bees living wild and free. Some solitary bees blow nectar bubbles into the wind; others mate on just one type of flower, some use leaves to line their nests, or close their entrance holes with cellophane… Disappointing – but once life is back to normal we will definitely invite Jenny again. In the meantime, I can do no better than tell you about one of Jenny’s interesting observations about the orchid and the carpenter. When we think about orchids we usually have a mental picture of large glamorous exotic flowers with romantic overtones. Yet they are very common. In fact, the orchid family (Orchidaceae) is the second largest of all the flower families in the world after the daisies (Asteracaea). So orchids are really very common. With the fabulous diversity of flowers in fynbos, one would therefore expect to find lots of orchids among the more obvious fynbos species. And we do. Some are large and bold (like the fields of pink Satyrium carneum along the R43 just outside Gansbaai) and some are very small, but systematically tracked down by a small band of orchid enthusiasts. Disperis capensis is one of the Fernkloof specials. Its common name is ‘Cape Witch Orchid’, or ‘Moederkappie’. Two very different descriptions, but both obvious, depending on how you look at it. But before we talk about pollination we should have a brief look at the structure of an orchid. A pollinated orchid with pollen stuck to the stigma. PHOTOS: Jenny Cullinan & Karin Steenberg of Ujubee
In order to attract the pollinator, the petals of an orchid are arranged as an attractive frame for the reproductive area of the plant. (There is an astounding variety of orchid ‘frames’). Pollen is contained in a pair of structures called ‘pollinaria’ (singular pollinarium), which end in sticky patches called ‘viscidia’ (singular viscidium). These are situated above a large, fleshy two-lobed stigma that leads to the ovary beneath the flower – the ovary often looking like a flower stem. The Cape Witch Orchid has no nectar or other reward for bees, so it uses deception to attract the carpenter bee to its flowers for pollination. The orchid times its flowering to coincide with that of another similarly coloured flower such as Muraltia, which does have nectar as a reward for the bee. The carpenter bee (Xylocopa rufitarsis) visits Muraltia for nectar. But sometimes he mistakenly visits the witch orchid instead. Realising that there is no nectar to be had, he immediately flies off. But too late – he has an unwelcome hitchhiker. The sticky viscidium is firmly stuck to his chest. As he flies off, the pollinarium is drawn out of the flower. The pollinarium immediately curls backwards so that the pollen grains are now facing outwards, ready to be delivered to the stigma (female part) of the next orchid mistakenly visited by our busy bee. The pollen can now fertilise the flower, which results in seeds to grow the next generation of orchids. Jenny Cullinan moved to the Cape seven years ago and has been involved with wild bee research in Cape Point Nature Reserve (TMNP) and various other biomes for the past six years. Her research is self-funded and is totally focused on the ecology of wild bees; a long and thoughtful study of the bees’ home and of all of the living world around them – and of the consequences of our actions in it. She is also an artist (sculptor), using her art to raise awareness about bees. She is the founder of Ujubee Conservation and in 2019 won a Conservation at Work 'Cape Fox' award for the Best Contribution to Biodiversity by an Individual. Source: Pollination by Deception by Jenny Cullinan and Karin Sternberg
ABOVE: A carpenter bee (Xylocopa rufitarsis) visiting Muraltia for nectar. BELOW: The pollen grains are outwardly orientated as the bee flies from flower to flower sipping nectar.
