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Solanum ruvu

A rare, African spiny aubergine, Solanum ruvu has been collected only once and is now likely to be extinct in the wild.

Detail of Solanum ruvu specimen

Detail of Solanum ruvu specimen collected by B. Mhoro and the Frontier-Tanzania Programme in the Ruvu Forest Reserve. This is the only collection known of this species, and one of the only two herbarium specimens known.

Species information

Scientific name: 

Solanum ruvu Voronts.

Conservation status: 

The preliminary assessment is Extinct (EX, IUCN, 2001). Efforts have been made to re-collect this species but failure to find it again and documented severe habitat destruction indicates that there is a high probability that it is now extinct.

Habitat: 

Most likely wet coastal forest understorey, at about 100-300 metres above sea level.

Key Uses: 

None known.

Known hazards: 

None known.

Taxonomy

Subclass: 
Superorder: 
Asteranae
Order: 
Solanales
Family: 
Solanaceae
Genus: Solanum

About this species

This rare species has been collected only once, as part of a general survey in 2000. By the time it was identified as a new species by Kew botanist Maria Vorontsova in 2010, its native forest had already been destroyed. An expedition in 2010 tried to re-collect it but the plant was not found and is now most likely extinct.

The story of Solanum ruvu highlights the way in which the destruction of Tanzania’s coastal forests has impacted on biological diversity.

Genus: 
Solanum

Discover more

Geography and distribution

Known from only a single collection in the Ruvu Forest in the Morogoro District of Tanzania.

The area where Solanum ruvu used to grow is now cultivated to grow bananas, papaya, manihot, and rice.

Coastal forests were once widespread along the eastern African seaboard but the majority have now disappeared leaving over 250 known remnant forest patches. These patches are typically isolated from each other by a mixture of farmland and thicket areas. Many have exceptional levels of local endemism, but are small, fragmented, surrounded by populated areas and are becoming rapidly degraded.

The Ruvu Catchment Forest Reserve is poorly known and has not been explored in detail by botanists. It is situated in the eastern foothills of the Uluguru mountains and managed by the Forest Catchment project of the Morogoro Region.

Solanum ruvu is known from a single collection made by the Frontier-Tanzania Coastal Forest Research Programme in 2000, most likely in the part of Ruvu Forest now known as the Chafungo forest fragment.

Description

Overview: Solanum ruvu is a climbing herb or shrub with a dense covering of 4-6 mm long straight prickles.

Leaves: The leaves are 9-12 x 2.5-4.5 cm and are very thin, with almost no hairs.

Solanum ruvu herbarium specimen collected by B. Mhoro and the Frontier-Tanzania Programme in the Ruvu Forest Reserve.

Flowers: The unbranched inflorescences are 5-9 cm long, and bear 10-15 flowers. The inflorescence stalk is densely prickly. Only one or two flowers are open at any one time. The flowers are 1.2-1.8 cm wide, with long thin petals of 6-8 × 1.5-2 mm. The anthers are 5-6 mm long, and have openings at the tips.

The only information we have about this species comes from a single herbarium collection (two herbarium specimens) and hence other details such as plant height, flower colour, fruits and seeds are unknown.

Threats and conservation

The Chafungo forest fragment is a highly fertile area with black cotton soil over limestone, and is difficult to reach by road. The Waluguru people were moved to the area during agricultural reforms in 1974 and population growth as well as clearance of the natural vegetation for agriculture has been on the increase ever since.

The usual sequence of land cultivation starts with planting maize for the first two seasons following forest-clearance, later followed by matrix crops, including bananas, rice, sesame, tomato, and manihot (cassava). Sesame is also grown as a cash crop and provides the highest profit.

Trees in the Chafungo forest fragment are said to have been cleared in 2003. Currently, the majority of the land there is used to grow rice and sesame. Approximately 3% of the area is occupied by limestone rocks and cannot be cultivated. Forest fragments with remnant natural vegetation can still be found on these limestone outcrops.

The membranous leaves of Solanum ruvu, which almost completely lack indumentum (a covering of fine hairs or bristles), suggest that the species inhabited the dark and wet forest understorey, making it unlikely to survive clearance for agriculture.

The Chafungo thicket vegetation, the nearby Kingira and Loholole fragments, and the surrounding area, were thoroughly searched during an expedition to Tanzania in March 2010. In none of the nearby forest fragments was a full tree canopy preserved, and S. ruvu was not refound. Local people did not recognise pictures of the plant and there is a real probability that this species may already have been driven to extinction. 

Hunting for wild spiny aubergines in the Ruvu Forest

The only wild vegetation remaining in the Ruvu forest is restricted to the white limestone boulders where cultivation is not possible. Rice is seen growing in the foreground.

An international botanical expedition, involving Maria Vorontsova (while working for the Natural History Museum, London and collaborating with Kew), Eric Tepe (University of Utah) and Frank Mbago (University of Dar es Salaam) searched for Solanum ruvu in March 2010.

Searches were carried out in the Ruvu Forest and the Chafungo forest fragment at the exact latitude and longitude specified by the original collection. After two days of searching it was concluded that no intact coastal forest remained anywhere near the original collection area and that the forest fragments were not large enough to provide a forest canopy to support an understorey species such as S. ruvu.

This species at Kew

There are only two known herbarium specimens of this species: one held at Kew’s behind-the-scenes Herbarium, and one at the Missouri Botanical Garden, USA.

Botanical drawing

Botanical drawing of Solanum ruvu showing the habit and enlarged prickles, flowers, and tiny star-shaped hairs. Drawn by Lucy T. Smith.

 

Botanical drawing of Solanum ruvu (© Lucy T. Smith)

 

References and credits

Edmonds, J.E., Vorontsova, M.S. & Knapp, S. Solanaceae. In: Flora of Tropical East Africa, ed. H. Beentje, Royal Botanic Gardens, Kew. In preparation.

Hall, S.M, Fanning, E. & Howell, K.M. (eds) (2004). Ruvu South Forest Reserve: a biodiversity survey. Frontier Tanzania Environmental Research Report 111. The Society for Environmental Exploration, the University of Dar es Salaam, Ulanga District Council, Kilombero Valley, Tanzania. 

PBI Solanum Project (2010). Solanaceae Source. Available online (accessed 25 November 2010).

Vorontsova, M.S. & Mbago, F.M. New Solanum species from Tanzanian coastal forests may already be extinct. Journal of East African Natural History, in press.

Kew Science Editor: Maria Vorontsova
Copyediting: Emma Tredwell
Kew would like to thank the following contributors: Dr Sandy Knapp (Natural History Museum and the PBI Solanum Project); Frank Mbago and Dr Mkabwa LK Manoko (University of Dar es Salaam); Tanzania Commission for Science and Technology; Morogoro Region Catchment Forest Office; Mohammed Suleiman and other residents of the Ruvu Forest; Eric Tepe (University of Utah); British Airways for sponsoring expedition flights; National Science Foundation (NSF) for sponsoring the PBI Solanum project.

While every effort has been taken to ensure that the information contained in these pages is reliable and complete, the notes on hazards, edibility and suchlike included here are recorded information and do not constitute recommendations. No responsibility will be taken for readers’ own actions.

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