Lijndenia udzungwarum R.D. Stone & Q. Luke, 2015

Stone, Robert Douglas & Luke, Quentin, 2015, Lijndenia udzungwarum (Melastomataceae-Olisbeoideae): a new, endemic species from the Udzungwa Mountains of southern Tanzania, Phytotaxa 226 (2), pp. 169-176 : 170-173

Lijndenia udzungwarum R.D. Stone & Q. Luke , sp. nov. ( Fig. 1 )

Type:— TANZANIA. Morogoro region, Kilombero district, Mwanihana Forest Reserve above Sanje village, elev. 1400 − 1700 m, 10 Oct 1984, D. W. Thomas 3773 (holotype P [ P 00257930]!, isotypes K!, MO [3298576]!).

Evergreen shrub or small tree 2–3 m high; internodes (0.6–) 1.9–3.3 (–3.8) cm long; young branchlets terete in cross section. Leaves thinly coriaceous, dark green above, somewhat paler below, granular on both surfaces in dried material; petioles c. 1 mm long (rarely obsolete or up to 2 mm); blades ovate, (2.4–) 3.2–5.2 (–5.9) cm long, (0.9–) 1.8–2.8 (–3.2) cm long, rounded at base and broadly cordate, acuminate at apex; acumen c. 1 cm long, obtuse; midnerve impressed on the upper surface, prominent on the lower but becoming progressively narrower toward the leaf apex; lateral nerves much thinner than the midnerve, those of the principal pair curvilinear in the basal half of the blade but becoming weak and intramarginal in the apical half; secondary pair of lateral nerves faintly visible in the basal portion of the blade, intramarginal; transverse veins ± obscure. Inflorescences condensed to 3-flowered heads 5–8 mm in diameter, borne on filiform peduncles 10–20 (–27) mm long in the leaf axils; paired bracts at base of head distinct, ovate-lanceolate, c. 1 mm long; bracteoles suborbicular, cucullate, fused in pairs to form a cupule immediately subtending each of the flowers; pedicels 0; hypantho-calyx obconic, 2 mm long × 2.5 mm wide, the lobes broadly triangular, 0.5 mm long, obtuse-rounded to acute; corolla well exposed in bud, the petals white, broadly ovate-deltate, 2 mm long × 1.5 mm wide, rounded and abruptly acute at apex, truncate at base above the claw 0.5 mm long; anthers c. 1 mm long, ± keeled dorsally and lacking an oil-gland, the pollen sacs fronto-ventral; style 3.5 mm long; top of ovary smooth (interstaminal partitions absent). Berries blue-purple, globose, c. 7 mm in diameter, lacking a persistent calycinal crown.

Additional specimens examined (paratypes): — TANZANIA. Udzungwa Mountains National Park , Sonjo– Mwanihana Route, lat. 7°49’S, long. 36°51’E, elev. 1360 m, 8 Nov 1997, Luke 5079 ( EA!, K!) ; Udzungwa Mountains , Nyumbanitu, lat. 7°52’S, long. 36°22’E, elev. 1460 m, 28 Nov 1999, Price & Mhoro WK 329 ( K!, NHT) ; Udzungwa Mountains National Park , Mt. Luhombero, lat. 7°47’S, long. 36°32’E, elev. 1350 m, 27 Sep 2000, Luke et al. 6700 ( BR, CAS!, EA!, K!, NHT) ; Udzungwa Mountains National Park , lat. 7°48’S, long. 36°49’E, elev. 1600 m, 26 Sep 2001, Luke et al. 7839 ( CAS!, EA!, K!) .

Distribution and habitat: — Lijndenia udzungwarum is endemic to the northern part of the Udzungwa Mountains in southern Tanzania ( Fig. 2 ). According to data provided on specimen labels, the habitat of this species is in montane forest at 1350–1700 m elevation.

Of the five collections cited for L. udzungwarum , four are from within the boundaries of the Udzungwa Mountains National Park. This protected area, gazetted in 1992, covers almost 2000 km 2 in the northern Udzungwas and encompasses all of the Mwanihana forest as well as large parts of the Luhombero and Matundu forests.

Three of the collections cited are from the Mwanihana forest, situated along the steep, east-facing escarpment of the northern Udzungwas. This area of approx. 180 km 2, first gazetted as a Forest Reserve in 1958, includes an estimated 59 km 2 of forest spanning a wide elevational range (from 300 to 2080 m) and subdivided into lowland, transitional (submontane), montane and upper montane forest types ( Rodgers & Homewood 1982b, Lovett et al. 1988, Lovett & Pócs 1993a). The label of the type collection (Thomas 3773) clearly states the locality as being in the Mwanihana forest at 1400 − 1700 m elevation, but the geographic coordinates given (lat. 7°50’S, long. 36°55’E) are incorrect as they would place it at c. 290 m elevation in the Msolwa River valley, east of the Mikumi − Ifakara road. In the Tropicos (2015) specimens database, the coordinates of Thomas 3773 have been revised to lat. 7°47’S, long. 36°52’E.

The fourth collection of L. udzungwarum (i.e. Luke et al. 6700) is from the Luhombero massif, a remote highland plateau that includes the highest peak in the Udzungwas (elev. 2576 m). This area was previously included in the West Kilombero Scarp Forest Reserve, first gazetted in 1957 and comprising 1953 km 2 until the northern portion (910 km 2 including Luhombero) was excised into the Udzungwa Mountains National Park. Vegetation in the area has been generally described as “moist and dry montane and upper montane forest with extensive areas of bamboo and upland grassland with forest patches” ( Lovett & Pócs 1993b). The area of natural forest was reported by Rodgers & Homewood (1982b) as 25 km 2, but this would seem to be an underestimate.

The fifth collection of L. udzungwarum (i.e. Price & Mhoro WK329) is from the Nyumbanitu forest, situated in the remaining part of the West Kilombero Scarp Forest Reserve (area 1043 km 2) bordering the Udzungwa Mountains National Park on the west. The total forest cover within this reserve is reportedly 305 km 2, of which 135 km 2 is found at elevations of 1040 − 2480 m ( Frontier Tanzania 2001). Additional localities for L. udzungwarum may yet be found in the Ndundulu and Ukami forests, representing the other two large fragments of montane forest in the reserve.

Phenology: —Flowers in late September to early October. Fruits in October.

Conservation status: —Despite the evident restriction of L. udzungwarum to three fragments of montane forest in the northern Udzungwas, the IUCN (2013) has assessed it (as Lijndenia sp. nov.) as being of “Least Concern,” citing an absence of documented or observed threats. It was noted however that this assessment is contingent on the continued effectiveness of conservation measures (safeguarding of the Udzungwa Mountains National Park). No new status is proposed in the present work, i.e. the IUCN (2013) assessment of “Least Concern” for L. udzungwarum is confirmed.

Etymology: —The species epithet udzungwarum is a feminine, plural noun (Declension I) in the genitive case. It is used to indicate geographical origin, i.e. to emphasize that the new species is a local endemic of Tanzania’s Udzungwa Mountains.

Discussion: —From its congeners, L. udzungwarum is immediately distinguished by its cordate leaves (vs. leaf-bases cuneate to attenuate or rounded in other Lijndenia spp. ). The new species further differs from the East African L. brenanii and L. procteri by its 3-flowered, capitellate inflorescences borne on slender peduncles 10–20 (–27) mm long (vs. inflorescences with up to 11 or more distinctly pedicellate flowers borne on thicker, quadrangular peduncles to 11 mm long and with secondary inflorescence axes to 9 mm long). The inflorescence features of L. udzungwarum are most similar to those of the Sri Lankan species, L. capitellata ( Arnott 1836: 17) K. Bremer (1982: 123) , although this would seem to represent a case of morphological convergence as these two species are not believed to be sisters in a phylogenetic sense or even very closely related.

When L. brenanii and L. procteri were first described under Memecylon sensu lato ( Fernandes & Fernandes 1960), each species was known from a single collection, the former from Sangarawe in Tanzania’s East Usambara Mountains (Greenway 3680, holotype EA!, isotype K!, fragment P!), the latter from the Shagayu forest in the West Usambaras (Procter 208, holotype EA!, isotypes K!, TFD!). In his key to the species of Memecylon sensu lato for the Flora of Tropical East Africa, Wickens (1975) contrasted the characters of the inflorescence between these two species (i.e. inflorescence compound in L. brenanii vs. simple in L. procteri ), but the original diagnoses ( Fernandes & Fernandes 1960) also noted differences in habit and leaf size, i.e. L. brenanii a tree to 18 m high with larger leaves to 7.5 cm long × 4 cm wide, vs. L. procteri a shrub to 1.2 m high with smaller leaves to 4.5 cm long × 3 cm wide. Wickens (1975) has suggested that L. procteri might only be a shrubby form of L. brenanii , but this does not seem to be the case as the two taxa occupy distinct geographic ranges and are diagnosably different (see below for a key to the currently recognized Tanzanian species of Lijndenia ).

Lijndenia brenanii is evidently an extremely rare species that has been recollected only twice in the Kwamkoro forest near the type locality (Mgaza 437, EA!, K!, TFD!; Ruffo & Mmari 2213, TFD!). In January 2002, the first author could not relocate L. brenanii in spite of several days searching in the East Usambaras, although in the Shume forest (West Usambaras) he did succeed in finding a new Lijndenia population currently determined as L. aff. brenanii (Stone et al. 2438, CAS!, DSM, K!, MO!, NU!, TFD, UPS). These are trees to 15 m high.

Lijndenia procteri has been recollected several times in the Shagayu forest, its only known locality in the West Usambaras (Mgaza 616, BR!, EA!, K!, TFD!; Borhidi et al. 84-850, MO!, UPS! & 86-040, UPS!; Iversen 85-767, UPS!; Stone et al. 2440, BR, CAS!, DSM, EA, G, K!, MO!, NU!, P!, PRE, TFD, UC, UPS, US). These are shrubs to 5 m high. In addition, a new population of L. procteri has been discovered in the nearby South Pare Mountains (Chome Forest Reserve, Mwangoka et al. 1868, CAS!, MO!).

Lijndenia udzungwarum is not the only Lijndenia species that has been found in the mountains of southern Tanzania. Several collections from this region have cuneate leaf-bases and relatively large leaves matching those of L. brenanii (e.g. Rodgers 390, DSM, K!; Thomas 3760 & 3916, MO!; Luke 5077, K!; Luke et al. 9200, EA!, K!; Ndangalasi 405, K!; Abeid et al. 2438, EA!; Luke 12793, EA!, K!; Marshall et al. 2072, K!). Other material has smaller leaves resembling those of L. procteri (Kisena & Mmari 1715, K!; Luke et al. 7938, CAS!, EA!, K!; Luke 10474, DSM, EA!, K!, MO, NHT; Luke et al. 11345, EA!, K!, MO, NHT). The first author has obtained nrDNA spacer sequences from some of these southern Tanzanian populations indicating they represent a distinct evolutionary lineage in comparison to the populations further north in the Usambaras (R.D. Stone, unpublished data). Additional collections and further study are needed to discover any morphological differences that might be used to diagnose the southern populations in comparison with typical L. brenanii or L. procteri , and also to determine if the larger-leaved and smaller-leaved plants all belong to the same species. There is an indication that the larger-leaved plants in the Udzungwas are found in the understory of submontane or montane forest (700 − 1800 m elevation) while the smaller-leaved plants occupy ridgetop sites at 1750 − 1900 m.

Memecylon cogniauxii Gilg (1898: 44) is another Eastern Arc endemic that superficially resembles L. udzungwarum in having cordate leaves and axillary inflorescences on long slender peduncles. However, M. cogniauxii has apparently uninervate (not trinervate) leaves and clearly belongs in Memecylon sensu stricto (see Stone 2014). Furthermore, M. cogniauxii is known only from the East Usambara, West Usambara, South Pare, Nguru, and Uluguru mountains; it is not known to occur in or near the Udzungwas.

Figures

FIGURE 1. Lijndenia udzungwarum. A. Flowering branch. B–C. Leaves. D. Detail of lower leaf surface. E. Inflorescence. F. Open flower (top view). G. Fruit, side & top views (A, C from Luke et al. 6700, CAS; B, D−G from Thomas 3773, K, MO, P). Drawing by Sandie Burrows.

FIGURE 2. Map of the northern Udzungwa Mountains showing known localities for Lijndenia udzungwarum. Major forests are named. The inset at upper left shows the location of the Udzungwa Mountains within the Eastern Arc Mountains (in grey, with forest patches shown in black) of Tanzania and Kenya. The Udzungwa Mountains National Park boundary is from the World Database on Protected Areas (IUCN & UNEP-WCMC 2015). Limits of forested areas in the northern Udzungwas are according to a land-use classification by the GIS Services branch of the International Livestock Research Institute (2002). Limits of the Eastern Arc Mountains (inset) are from Platts et al. (2011a, 2011b).