Herbarium specimens document habitat change

Botanists studying Solanum have used herbarium specimens to document vegetation change in Kenya, and have also described three new species.

View on map: Kenya,

26 Oct 2011

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A map showing all known collection sites of Solanum polhillii

All known collection sites of Solanum polhillii Voronts. in Kenya and Tanzania. Sites not visited are marked as black triangles, sites visited where the species was not found are marked as red circles, and sites visited where the species was successfully recollected are marked as green squares. (Image: P. Ficinski)

Herbarium specimens are not just for taxonomists. Herbarium collections are a treasure trove of data on historic plant distributions, often recording the ecological environment and vegetation type seen at the time of the collection.

The newly described Solanum polhillii Voronts. is restricted to partly shaded limestone savanna habitats sheltered from herbivory (Image: M.S. Vorontsova).

In May 2009, Maria Vorontsova and a team from the National Museums of Kenya, the Natural History Museum (London) and RBG Kew were in Kenya hunting for rare species of wild spiny aubergines (Solanum subgenus Leptostemonum). They revisited 17 localities recorded in 40 collections made between 1922-1985. Direct comparisons between specimen notes and the current environment were combined with the personal knowledge of local people to decide whether significant environmental changes had occurred. The plants were successfully recollected in only four of the sites, and clear evidence of vegetation change was seen at 24% of the sites.

Many localities no longer constitute suitable habitat for these species. Vegetation clearance and increased grazing are commonplace across East Africa but such land use changes are not recorded and nobody knows how much vegetation is being lost. Dedicated studies of vegetation change should consider using herbarium collections as a source of information on past vegetation cover.

As a result of studies of herbarium collections and visits to the collection localities, the team identified three new species of Solanum: S. polhillii from the Acacia-Commiphora savanna, S. phoxocarpum from the Kenyan highlands, and S. malindiense from the coastal vegetation.

Item from Dr Maria Vorontsova (Grass Taxonomist, RBG Kew)
Originally published in Kew Scientist 39

Article reference:

Vorontsova, M.S., Christenhusz, M.J.M., Kirika, P., Muthoka, P. (2010). Three new species of Solanum from Kenya: using herbarium specimens to document environmental change. Systematic Botany 35: 894-906.

More on this story

Kew Plant Profile - Solanum phoxocarpum (osigawai)

NHM Blog - The spiny wild aubergine hunt

Background

Solanaceae Source: an online monograph of the genus Solanum

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