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| Isoglossa pareensis I.Darbysh. & Hemp, in Darbyshire et Hemp, 2023. |
Summary
Isoglossa pareensis I.Darbysh. & Hemp (Acanthaceae), from submontane moist forest at Mwala in the South Pare Mountains of northeastern Tanzania, is described and illustrated. This species is considered to be related to I. gregorii (S.Moore) Lindau and I. punctata (Vahl) Brummitt & J.R.I.Wood, which are widespread in the montane forests of eastern Africa, but it clearly differs from these species in inflorescence structure and indumentum and in anther morphology. Notes on the habitat requirements and extinction risk of this new species are provided; it is considered to be Vulnerable under IUCN criterion D2 because of its extremely limited range and a plausible future threat from wildfires. The recent discovery of the Critically Endangered acanthaceous herb Asystasia masaiensis Lindau at lower, drier elevations at the same site is also reported and the first known photograph of that species is reproduced
Key Words: Conservation, extinction risk, Isoglossinae, IUCN Red List, taxonomy.
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| Isoglossa pareensis I.Darbysh. & Hemp sp. nov. A habit, flowering branch; B flower in situ; C face view of corolla with stamens and stigma visible at mouth; D dissected corolla with stamens; E partial infructescence with mature capsules; F indumentum of calyx lobe, side view, external face to left; G indumentum of peduncle; H capsule with seeds, and dorsal view of capsule valve; J mature seed, with detail of sculpturing. A & D from Hemp 8165; B & C from photographs of plants in the field; E – J from Hemp 6953. DRAWN BY ANDREW BROWN. |
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| Isoglossa pareensis I.Darbysh. & Hemp sp. nov. A – C in situ at Mwala, Tanzania, collected as A. Hemp 7355; D & E in cultivation at UBT. PHOTOS: A – C a. Hemp; D, E U. Meve. |
Isoglossa pareensis I.Darbysh. & Hemp sp. nov.
RECOGNITION. Isoglossa pareensis is similar to I. gregorii in foliage and to both I. gregorii and I. punctata in corolla form and in having seeds with elongate, minutely glochidiate tubercles, but differs from both in the inflorescence being a panicle-like thyrse with pedunculate dichasial or monochasial cyme units (vs inflorescence a simple spike or, if branched, the branches being spiciform with (sub)sessile cyme units); in the anther thecae overlapping for c. half their length (vs thecae fully superposed to widely separated); in the capsule being puberulous with eglandular and occasional glandular hairs (vs capsule glabrous or occasionally with few eglandular hairs towards apex and/or with scattered glandular and/or long eglandular hairs); and in the inflorescence axes and calyces having a more dense indumentum including more numerous glandular hairs. It additionally differs from I. gregorii in having linear-lanceolate bracts, 1.3 – 3.6 × 0.3 – 0.5 mm (vs bracts elliptic, somewhat obovate or basal pairs ovate, (3.5 –) 4.5 – 14 × 0.7 – 6 mm) (Fig. 5; Table 1).
ETYMOLOGY. The species epithet “pareensis” denotes that this species is, so far as is known, endemic to the Pare Mountains of Tanzania.
Iain Darbyshire and Andreas Hemp. 2023. A further New Species of Isoglossa (Acanthaceae) from the Eastern Arc Mountains of Tanzania. Kew Bulletin. DOI: 10.1007/s12225-023-10103-1