Commiphora kaokoensis ( Burseraceae ) , a new species from Namibia , with notes on C

Commipora kaokoensis W.Swanepoel. here described as a new species, is known only from the Kaokoveld Centre of Endemism, an arid region in northwestern Namibia. Illustrations of the plant and a distribution map are provided. Diagnostic characters include the petiolate or subsessile. all-simple and relatively large leaves with the lamina obovate or elliptic. New information is provided on the leaf morphology and geographical distribution of C. namaensis Schinz and C. dinteri Engl., species with which the new species shares some similarities. When without leaves or fruit, the three species can easily be con­ fused. A comprehensive table with diagnostic morphological features to distinguish between the three species is presented.


INTRODUCTION
A new species, Commiphora kaokoensis W.Swane poel. is described.Apart from one specimen (Giess 9427 in WIND) collected in 1966, the new species remained uncollected until recently.This can be attributed to its limited range in remote parts of the Kaokoveld.north western Namibia.In addition, when without leaves or fruit, the plants are virtually indistinguishable from C. namaensis Schinz (Van der Walt 1973) and C. dinteri Engl.(Van der Walt 1974), species for which it could have been mistaken in the past.
New information is provided on the leaf characteris tics of C. namaensis and C. dinteri.Diagnostic morpho logical features to differentiate between these two species and C. kaokoensis are presented.Previous misidentifications of C. dinteri are corrected and apparently wrongly indicated localities, including quarter-degree grids, of two herbarium specimens are rectified.
Apart from examining the herbarium collections of C. kaokoensis, C. dinteri and C. namaensis in WIND and PRE, numerous populations of the three species were studied all over their respective ranges in Namibia dur ing two years of extensive field work.Morphological characters were all determined from fresh material.
Inflorescence: flowers borne in clusters or solitary, axillary.Flowers sessile or subsessile, unisexual, perigynous, appearing before or with leaves or occasionally flowering continuously until leaves have been shed.Bracteoles ovate, apex acute, glandular, up to 1.2 mm long.Calyx green to maroon or cherry, continuous with hypanthium, usually sparsely glandular otherwise glabrous; lobes ovate to triangular, apex acute.Petals greenish yellow to yellow, glabrous, narrowly elliptic to oblanceolate, recurved towards apex, but minute tip inflexed, inserted on hypanthium.Disk cylindrical with 4 fleshy lobes, adnate to hypanthium but distal part of lobes free.Male flowers 2.8-4.9 mm long; calyx 1.6-3.4mm long, lobes 0.8-1.4mm long; petals 2.4-4.0 mm long; disk lobes distinctly bifid at apex; stamens 8, 4 long sta mens with filaments 1.6-2.8mm long, inserted on margin of disk lobes, 4 short stamens with filaments 0.8-2.1 mm long, inserted on margin of disk between lobes; anthers 0.7-1.0mm long, equal in length on short and long sta mens; filaments subterete, rarely flattened and broadened over lower part; gynoecium rudimentary (Figure 4A-C).
C. dinteri usually has predominantly trifoliolate leaves with a few additional simple leaves.Only rarely, in a few restricted localities, does it either have only simple leaves, or predominantly simple leaves with a few additional trifoliolate leaves, or simple and trifoli olate leaves together in equal numbers on the same plant.Simple leaves in C. dinteri are variable in shape, and on individual plants may vary between obovate, elliptic, ovate, cordate, oblate or slightly oblong.Un like C. kaokoensis, the simple leaves of C. dinteri are always petiolate, with the lamina usually much small er, about half the size, (3-)7-18(-27) x (3-)6-15 (-25) mm; the midrib is inconspicuous and not, or only slightly raised, ab-and adaxially towards the lamina base; the petiole in t/s differs from C. kaokoensis by being triangular, pentagonal or reniform in shape, usu ally smaller, 0.7-0.8x 0.6-0.7 mm, and with only 3-7 vascular bundles.For comparable lamina size, the peti oles of both C. namaensis and C. dinteri are slender when compared to those of C. kaokoensis.Petioles of C. kaokoensis with t/s dimensions similar to those of C. namaensis and C. dinteri, are only found on excep tionally small leaves, occasionally present amongst the usually larger leaves.Additional differences between these three taxa are provided by fruit morphology: the suture of the putamen in C. kaokoensis is convex towards the fertile locule and the angle between locules at the apex is 42°-91°.In C. namaensis the suture is rectilinear and the apical angle between locules is 80°-150°, whereas in C. dinteri the suture is rectilinear but curved towards the sterile locule at the apex and the apical angle is 51°-120°.Through examination of herbarium specimens and plants in the field, a comprehensive comparative table of diagnostic characters to differentiate between the three taxa was compiled (Table 1).
Etymology: the specific epithet refers to the Kaoko veld of northwestern Namibia.The distribution of C. Habitat and ecology: habitat requirements of C. kaokoensis are quite specific.It occurs in the Namib Desert and pro-Namib, 45-130 km from the coast at alti tudes of 200-1 100 m, where the annual rainfall is 75-150 mm.It grows in rocky areas preferring terraces of calcrete and outcrops consisting of metasedimentary and metamorphic rocks of the Damara Supergroup, including marble, marble-conglomerate, quartzite, gneiss and inclined strata of schist (Mendelsohn et al. 2002).It is restricted to calcrete formations, wherever it occurs with in the extensive areas of Etendeka Group basalt, e.g. at Palm near Palmwag.In spite of extensive searching, nowhere could it be found on formations from the Karoo Supergroup and associated lavas of the Etendeka Group, not even in areas where these occur within only a few metres of C. kaokoensis specimens growing on rocks of the Damara Supergroup.

C. dinteri Engl.
Hitherto C. dinteri was regarded as having trifoliolate leaves only, with no mention of simple leaves (Van der Walt 1986).However, thorough investigation revealed that many herbarium specimens of C. dinteri in PRE and WIND have in addition to trifoliolate leaves, a small per centage of simple leaves, variable in shape, including ovate, obovate, elliptic, cordate, oblate, slightly oblong, or orbicular.During field work throughout the range of C. dinteri, both simple and trifoliolate leaves were found to a varying extent on virtually all individual plants examined.The presence of the occasional simple leaf on plants was probably overlooked (or at least not sampled) when sever al specimens were collected.For example, Van der Walt 201, 207 in WIND and PRE respectively, have trifoliolate leaves only, whereas the duplicates in PRE and WIND respectively, each have a few additional simple leaves.Moving north, between the Khan and Omaruru Rivers in central-western Namibia, a gradual increase in the percent age of simple leaves on specimens of C. dinteri was observed.Specimens from the south of this area (Stingbank and Ebony areas, 2215AB), have a small percentage of simple leaves, similar to those observed further afield in south-central Namibia at Maltahohe (2416DD) and in the Tsaris Mountains (2416CD).To the east of the Schwarze Kuppen (2115CA; -CB), the percentage simple versus tri foliolate leaves is ± equal, whereas in the vicinity of the Omaruru River (Nai-nais & Okombahe areas, 2115AC; -AD), the majority of leaves are simple with only a few tri foliolate leaves, both on dwarf lateral branches and on long shoots.This is likewise the case with plants from the Uis area (2114BD), which were previously considered as an isolated population of C. namaensis (Van der Walt 1986), probably on account of the simple leaves, which resemble those of C. namaensis to a certain extent.In addition to both the simple and trifoliolate leaves resembling those of C. dinteri.the floral structure and fruit of the plants in the Uis area resemble those of C. dinteri as well (Table 1).Therefore, it is concluded that all these specimens belong to C. dinteri and that all specimens from the Uis area (pre dominantly simple-leaved) were previously misidentified as being C. namaensis.
In the Purros area of the Kaokoveld (1812DA), pre dominantly simple-leaved plants (Swanepoel 26 & 27) were found alongside plants with predominantly trifolio late leaves (Swanepoel 28,29 & 30).The leaves were relatively large, especially on the predominantly simple leaved plants and the petioles were long and slender, similar to those in some C. dinteri specimens from the Okombahe area (2115AD) in central-western Namibia.In the Flora o f southern Africa (Van der Walt 1986), C. dinteri specimens with large leaves are also mentioned for plants from the Orupembe area, 60 km to the north.A specimen with predominantly trifoliolate leaves, Jacobsen & Moss K154, displays the same characteris tics typical of C. dinteri from the Orupembe area.A speci men with simple leaves.Moss & Jacobsen K/95 and from the same locality as Jacobsen & Moss K154, was previously identified as C. cf.namaensis, probably on account of the simple leaves, which resemble those of C. namaensis superficially.This specimen displays the same characteristics as Swanepoel 26.27 with leaves large and petioles relatively slender.It lacks, however.the presence of a few typical C. dinteri trifoliolate leaves as found on Swanepoel 26, 27 (only discovered on these plants upon thorough examination).The presence of the occasional trifoliolate leaf on plants was probably over looked (or at least not sampled) when Moss & Jacobsen K195 was collected.Therefore, it is concluded that both Swanepoel 26, 27 and Moss & Jacobsen K195 belong to C. dinteri, and are similar to specimens from the Uis area.In all the examples mentioned above, simple and trifoliolate leaves occur on both short lateral branchlets and on long shoots.Lateral leaflets are smaller than ter minal leaflets to a variable extent.Hence C. dinteri is considered a heterophyllous species as it usually devel ops both simple and trifoliolate leaves on the same plant.

C. namaensis Schinz
According to Van der Walt (1986), C. namaensis occurs as an isolated outlier population in the Uis area of north western Namibia, in addition to being widespread in south ern Namibia and the adjacent parts of South Africa.As explained above, all the plants from the Uis area should be reclassified as C. dinteri.Trifoliolate leaves and transi tional forms of simple to trifoliolate leaves on plants under cultivation are mentioned by Van der Walt (1986)

SPECIMENS EXAMINED
The location given for the previously unidentified specimen of C. kaokoensis, Giess 9427 (WIND), namely Spaarwater 711, is from a locality underlain by Etendeka lava (basalt) associated with the Karoo Supergroup.This is in stark contrast with the geological formations at all the other known localities for this species which are sit uated on formations of the Damara Supergroup.As expected, extensive searching for C. kaokoensis on the Farm Spaarwater 711 produced no specimens, nor could any suitable habitat be found.However, on the Farm Palm 708, 20 km to the northwest of Spaarwater, a few small specimens of C. kaokoensis were found growing on an isolated formation of calcrete within the otherwise homogeneous Etendeka basalt area.Twelve kilometres to the south of Spaarwater, on the Farm Fonteine 717.also in the basalt area, C. kaokoensis was found growing on an isolated outcrop of dolomite.Further explorations on Spaarwater for any calcrete formation outcrops would in all probability produce some C. kaokoensis specimens at that locality.
The combination of distance, bearing and quarterdegree square given for Moss & Jacobsen K195 and Jacobson & Moss K154, both C. dinteri, is incorrect.Investigation revealed that a point 25 km to the northwest of Purros is situated within quarter-degree square 1812DB and not within 1812DD as given for the locality of these specimens.In addition, none of the plants in question could be found during field work in 1812DD.nor could any be found in a wide area around a point situated 25 km to the northwest of Purros.At a point, west-northwest.25 km from Purros on the Purros-Orupembe District road (D3707), situated within 1812DA.many plants were found in habitat similar to that given for the two specimens.Therefore it seems appropriate to consider the locality for both Moss & Jacobsen K195 and Jacobsen & Moss K154 to be as follows: 25 km from Purros on road D3707, in quarter-degree square 1812DA.
and were found on many C. dinteri plants during the present study, whereas only simple leaves were found on C. namaensis during extensive field work in southern Namibia.Trifolio late and intermediate leaves, however, are present on a single herbarium specimen of C. namaensis (Giess & Muller 14284) from southern Namibia (2717AC).It is con cluded that C. namaensis is confined to southern Namibia and adjacent areas in South Africa and that it only very rarely develops a few trifoliolate leaves in addition to the usually simple leaves.