The sharp eye and inquisitive nature of an amateur botanist has led to the discovery of a semi-parasitic plant species in the Songimvelo Nature Reserve in Barberton. After photographing mistletoe from the genus Viscum and collecting samples for the Mountainlands Nature Reserve Herbarium. Delia Oosthuizen realised something about her specimen was “not quite right.”
Although it was not the first time they were collected in the reserve. previous collections were identified as
other species. “I had difficulty identifying the specimen and asked Prof Kevin Balkwill from Wits University for assistance.” Delia says. “After sending him photos he decided it was worth a closer look and we visited the forest together.”
This is when they realised the differences. The Viscum species with flattened stems and no leaves found in the reserve was definitely different from the two recorded in literature. When compared to the Combretum mistletoe ( Viscum combreticola), not only are the habitats different. the mature stem segments of the specimen are much shorter. In addition. the immature berries of the Songimvelo specimens are different. The other species in this group. Viscum anceps. has shorter stem segments and the berries are smooth and glossy.
Once Oosthuizen and Balkwill determined the plant was not the same. they immediately realised the importance of the discovery. “We were excited and knew there was a lot of work ahead to verify it.” says Oosthuizen. This included looking at numerous photos. more site visits. and many collections.
The reserve falls within the Barberton Centre of Plant Endemism. which is an area with a significant number of endemic and rare plant species. explains Oosthuizen. The variety of habitats. elevations and different microclimates between the mountains can cause existing species to evolve. she adds.
To date, Viscum songimveloensis has only been found on a single host plant – the green witch-hazel
(Trichocladus grandiflorus) and at two localities in the reserve. Due to its limited numbers. it is classified as vulnerable on the Red List of South African Plants. Southern Africa is home to 20 species of Viscum. with 70 of them found in Mpumalanga.
Written by René de Klerk
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