Thursday, July 13, 2017

[Botany • 2016] Barleria mirabilis • A Remarkable New Tree Species (Acanthaceae) from west Tanzania


Barleria mirabilis  I. Darbysh. & Q. Luke


Summary
A new species of Barleria (Acanthaceae), discovered in 2014 on the Uzondo Plateau of West Tanzania, is described and illustrated and its affinities are discussed. This is the first documented tree species in the genus Barleria. Its conservation status is assessed using the categories and criteria of IUCN; it is considered to be globally Vulnerable.

Key Words: conservation, IUCN Red List assessment, Mpanda, taxonomy, Uzondo 


Barleria mirabilis, Uzondo Plateau, Tanzania. (photo:I. Darbyshire). 

Barleria mirabilis, Uzondo Plateau, Tanzania, with M. Vorontsova providing scale
 (photo: Q. Luke).

RECOGNITION: Barleria mirabilis is most similar to B. crassa C. B. Clarke and B. nyasensis C. B. Clarke but differs markedly from both in being a tree to 4 – 6 m tall at maturity (vs a perennial herb or shrub 0.3 – 2.5 m tall); in having broader, elliptic or oblanceolate bracteoles 3 – 5 mm wide and lacking a spine tip (vs bracteoles linear-lanceolate with a spine tip or reduced to a simple spine, 0.5 – 3 mm wide); in the bracteoles and posterior and anterior calyx lobes having numerous conspicuous capitate “mushroom” glands externally (these absent in B. crassa and B. nyasensis which only have scattered small glandular hairs on the calyx); in the anterior and posterior calyx lobes being more convex and with markedly involute, entire margins (vs calyx lobes with margin not or hardly involute; denticulate to spinulose-dentate or rarely almost entire); and in the anthers being larger (6.3 – 6.6 mm vs 3 – 5 mm long).

DISTRIBUTION: Known only from the Uzondo Plateau of West Tanzania.

ETYMOLOGY: The species epithet “mirabilis” (miraculous, astonishing) refers both to the fact that this is a truly remarkable species, being the only tree Barleria recorded to date, and to the fact that such a striking and locally frequent species has not been found previously despite considerable past botanical exploration at the collecting locality.


Iain Darbyshire and Quentin Luke. 2016. Barleria mirabilis (Acanthaceae): A Remarkable New Tree Species from west Tanzania.
 Kew Bulletin. 71; 13. DOI:  10.1007/s12225-016-9622-0


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