Plant Syst Evol (2008) 274:243–253 DOI 10.1007/s00606-008-0032-0 ORIGINAL ARTICLE A taxonomic and ecological analysis of two forest Chlorophytum taxa (Anthericaceae) on Mount Kilimanjaro, Tanzania Charlotte S. Bjorå Æ Andreas Hemp Æ Gry Hoell Æ Inger Nordal Received: 20 June 2007 / Accepted: 13 February 2008 / Published online: 16 July 2008 Ó Springer-Verlag 2008 Abstract On Kilimanjaro, Tanzania two rather different forms of Chlorophytum comosum were observed. One form occurred on higher altitudes, the other on lower altitudes. Morphological, molecular and ecological studies conclude that the two forms both are entitled to species recognition. The high altitude form must still be referred to C. comosum s.l., while the low altitude form is a new species and it is described as C. rhizopendulum Bjorå & Hemp sp. nov. The two species inhabit mutually completely exclusive habitats on Kilimanjaro. Whereas C. comosum has a wide ecological potential, C. rhizopendulum has narrow ecological demands as a highly adapted specialist. The two species are easily distinguished morphologically. Molecular studies show that C. comosum is of polyphyletic origin, and the species complex needs revision. Keywords Anthericaceae
Chlorophytum comosum
Chlorophytum rhizopendulum
Kilimanjaro
Morphology
Phylogeny
Species delimitation
Spider plant C. S. Bjorå (&)
G. Hoell Natural History Museum, University of Oslo, P.O. Box 1172, Blindern, 0318 Oslo, Norway e-mail: charlotte.bjora@nhm.uio.no A. Hemp Ecological Botanic Garden, University of Bayreuth, Universitätsstr. 30, 95445 Bayreuth, Germany I. Nordal Department of Biology, University of Oslo, P.O. Box 1066, Blindern, 0316 Oslo, Norway Introduction During several years of ecological field work by one of the authors (AH) on Mount Kilimanjaro, two rather different forms of Chlorophytum were observed, both keying out as C. comosum (Thunb.) Jacques according to the flora of tropical East Africa (FTEA, Nordal et al. 1997). One form was observed in areas lower than 1,250 m, the other in areas above 1,450 m. From 2004 to 2006 more material of the two forms was collected and analysed. Anthericum comosum was described on material from the Cape Province of South Africa by Thunberg (1794). It was transferred to the genus Chlorophytum by Jacques (1862). In the FTEA C. comosum was regarded as a widespread, heterogeneous taxon, and several formerly accepted taxa were reduced to synonymy. It was further stated that ‘‘some of the mentioned forms deserve separate taxonomic rank, but until more detailed analyses are undertaken, it is better to treat them as geographical variants or ecotypes without formal taxonomic recognition. More studies are greatly needed’’. Poulsen and Nordal (2005) revised the Guineo-Congolean taxa of Chlorophytum and concluded that C. comosum occurs in the area, with three forms, which were given varietal rank: C. comosum var. bipindense (Engl. & K. Krause) A.D. Poulsen & Nordal and C. comosum var. sparsiflorum (Baker) A.D. Poulsen & Nordal belong to the core lowland forested areas, whereas C. comosum var. comosum occurs in transitional areas, towards Sudano-Zambesian woodlands. Poulsen & Nordal were, however, aware that their morphologically based taxa might reflect parallel evolution rather than homologous evolution and stated: ‘‘If molecular analyses were to be undertaken, the resulting [...] tree may show that our 123 244 morphologically based taxa may be polyphyletic as the rain forest taxa may have evolved independently several times’’. The aim of this paper is to study representatives of the Chlorophytum comosum complex occurring on Mount Kilimanjaro, including morphological, molecular and ecological analyses, and to discuss species delimitation and speciation based on these data. C. S. Bjorå denaturation (96°C), 5 s annealing (50°C), and 4 min elongation (60°C) for 25 cycles altogether, in a Perkin Elmer 9700 thermocycler. Cyclic sequencing reaction products of rps16 intron were purified with ExoSAP-ITÒ (USB Corporation, Cleveland, OH, USA) while ITS1 products and trnL-F spacer were purified using Princeton Separations Centri Sep Spin Columns according to their manual. Finally the samples were applied to a microamp reaction plate with 10 ll HiDi per sample and run on an ABI PRISM 3100 automated sequencer. Materials and methods Plant materials Morphological information was extracted from Nordal et al. (1997) and Poulsen and Nordal (2005). The sources of plant material and voucher/accessions used in this study are listed in Table 1, along with GenBank accession numbers for the sequences. Nomenclature follows FTEA (1952) and Beentje (1994). Cytology Root tips were pretreated on 0.02 M 8-hydroxyquinoline, fixed in 100% acetic acid : 100% ethanol = 1:3, hydrolysed in 1 M HCl at 60°C for 12 min, washed in cold water and stained in Feulgen solution. DNA extraction, gene amplification, and sequencing Total genomic DNA was extracted from herbarium specimens or silica dried leaf tissue samples using the Qiagen’s DNeasy kit for DNA extraction following the manufacturer’s instructions. The trnL-F spacer and rps16 intron were amplified using the primers of Taberlet et al. (1991) and Oxelman et al. (1997), respectively. Amplification of the ITS1 region was accomplished using modified primers after White et al. (1990) (‘‘ITS5mod’’: GGAAGTAAAAG TCGTAACAAGG and ‘‘ITS2mod’’: GCTACGTTCTTC ATCGATGC). For all regions the following PCR profile was run in a Perkin Elmer 9700 thermocycler: 94°C for 2.5 min, then 32 cycles of 94°C for 30 s, 53°C for 30 s, 72°C for 50 s, followed by a final extension at 72°C for 4 min. PCR products of rps16 were not purified before cyclic sequencing while the ITS1 products and trnL-F spacer were purified using QIAquick PCR purification columns (Qiagen, Valencia, California), following the manufacturer’s protocol. Cycle sequencing of the amplified product was conducted with the BigDye Terminator Sequencing Kit (PE Applied Biosystems) using 2.5 ng of primer in a 5 ll reaction volume. Sequencing conditions were the following: 10 s 123 Sequence alignment and phylogenetic analyses The electropherograms were inspected visually and the sequences edited in Sequencher TM(Version 4.0.5 Ó Gene Codes Corporation), and aligned manually using BioEdit Sequence Alignment Editor (Version 4.0.5 Hall 1999). All molecular characters were assessed as independent, unordered and equally weighted (Fitch parsimony, Fitch 1971). The maximum parsimony analyses were performed using Nona (Version 2.0 Ó P. A. Goloboff 1999/http://www. cladistics.com) via Winclada (Nixon 1999) using the heuristic search algorithm with branch swapping and 1,000 random replications. To estimate support for internal branches, parsimony jackknifing was performed; the number of replications was set to 1,000, and the number of search replications to 20 and 5,000 max trees. Species selected for molecular analyses are mainly species that belongs in the monophyletic x = 7 clade of Chlorophytum (Nordal et al. 1990; Bjorå et al. unpubl. data.). Based on earlier studies (Hoell 2005) Anthericum corymbosum Baker was chosen as an outgroup. The aligned sequences are available from the corresponding author. Ecology Ecological data were collected since 1996 along 30 transects disposed across wide changes in elevation (Hemp 2006a, b). The altitudinal range of the transects extended from 760 m (Rau forest near Moshi) to 5,895 m (Kibo peak). In all important vegetation types over 1,500 sampling plots (relevés) were established using the method of Braun-Blanquet (1964). Plot size was chosen with respect to the minimum areas of the different vegetation types. The relevés were clustered according to floristic similarity and the resulting plant communities are presented in percentage degree tables showing the relative frequency (constancy) of the species (Hemp 2001). pH was measured in the main root horizon of selected plots using a WTW pH-meter (pH 330). Two parallel samples were taken and measured in distilled water and a 0.01 M CaCl2 solution, respectively. Species Voucher/accession no. Locality GPS-coordinates and altitude GenBank accession number rps16 trnL-F ITS 1 Anthericum corymbosum Baker Nordal 4601 (ETH) Kenya, K6: Mua Hills, SW of Nairobi S01°270 E 37°120 EU128959 EU128939 EU128949 Chlorophytum africanum Engl. A. Bjørnstad 2054 (O) Tanzania, T7: Mbeya D., Magangwe S07°450 E 34°120 – EU000020 EF999986 C. andongense Baker Nordal & Bjorå 5013 (O) Tanzania, T3: Pare D., SW of N Pare, near Lembeni S03°470 2200 E37°150 0700 , 1,120 m EU128960 EU128940 EU128950 C. blepharophyllum Schweinf. ex Baker Hoell & Nordal 24 (O) Zambia, B: Lukulu road S14°380 0800 E24°260 0900 , 1,140 m EU128961 EU000023 EF999989 C. comosum (Thunb.) Jacques Nordal 3803 (O) South Africa: Cape, Grootvatersbosch EU128962 EU000026 EF999992 C. comosum (Thunb.) Jacques Poulsen BI98-271 (AAU) Uganda, U2: Budongo Forest Reserve N01°430 E31° 310 EU128963 EU128941 EU128951 C. comosum (Thunb.) Jacques Nordal 3162 (O) Zimbabwe, Cult. in Harare EU000027 EF999993 C. comosum (Thunb.) Jacques high alt. form Hemp 3690 (O) Tanzania, T2: Kilimanjaro, forest above Old Moshi S03°150 0700 E37°260 3000 , 2,200 m EU128964 EU128942 EU128952 C. comosum (Thunb.) Jacques, low alt. form Nordal, Bjorå & Hemp 5006 (O-holo, B, EAH, NTH -iso) Tanzania, T2: Rombo D., Holili Area, rd. Himo to Lake Chala S03°210 1000 E37°370 3800 EU128965 EU128943 EU128953 C. comosum (Thunb.) Jacques, low alt. form Bjorå & Hemp 847 (O) Tanzania, T2: Rombo D S03°200 4700 E37°360 3900 ,820 m EU128966 EU280157 EU128954 C. comosum (Thunb.) Jacques, low alt. form Bjorå & Hemp 848 (O) Tanzania, T2: Rombo D S03°190 6000 E 37°380 1800 ,1,071 m EU128967 EU280158 EU128955 C. filipendulum Baker Poulsen 956 (O) Uganda, U2: Masindi D. Nkuutu & H. Dumba. Budongo Forest Reserve. N01°560 E 31°440 , 950 m EU128968 EU000028 EF999994 C. filipendulum Baker Nordal 3219 (O) Zimbabwe, E: Chipinge D., Kiledo lodge S20°120 E 32°380 EU128969 EU128944 EU128956 C. floribundum Baker Hoell & Nordal 14 (O) Zambia, B: Sesheke S17° 210 5300 E 24° 090 0400 , 980 m EU128970 EU000029 EF999995 0 00 0 00 C. gallabatense Schweinf. ex Baker Hoell & Nordal 25 (O) Zambia, B: Lukulu road S14°38 08 E 24°26 09 , 1,140 m EU128971 EU000030 EF999996 C. geophilum Peter ex Poelln. Hoell & Nordal 26 (O) Zambia, B: Lukulu road S14° 310 0700 E 24°150 4300 , 1,090 m EU128972 EU000032 EU000098 C. lancifolium Welw. ex Baker Nordal 4576 (O) Zambia, N: Kundabwika Falls S09°130 0400 E29°180 1600 , 1,040 m EU128973 EU128945 EU128957 Nordal 1033 (O) Ethiopia: 51 km E of Nekemte EU128974 EU000035 EU000002 Nordal & Bjorå 5011 (O) Tanzania, T2: Moshi-Arusha Rd., Kwa Sadala S03°180 1000 E 37° 12’ 3000 EU128975 EU128946 EU128958 C. macrorrhizum Poelln. Nordal & Bjorå 4521 (O) Malawi, N: Nyika, near Zambian border S10°230 0200 E33°470 2000 EU128976 EU000036 EU000003 245 123 C. macrophyllum Asch. C. macrophyllum Asch. A taxonomical and ecological analysis of Chlorophytum on Mount Kilimanjaro Table 1 Species included in morphological and molecular analyses of Chlorophytum, with voucher information and GenBank sequence accession numbers indicated. Geographical divisions following the regional African Floras are indicated after country EU000008 EU000012 EU000041 S03°030 3700 E 37°020 3100 Tanzania, T2: Moshi-Arusha Rd. EU000045 EU128980 EU128981 S00°310 3100 E 36°200 1900 Kenya, K3: Near Gilgil EU280155 EU000007 EU128948 S09° 050 3400 E29°110 0000 , 1,000 m Zambia, N: E of Mununga Bridge EU000040 EU128978 EU128979 S14°020 0100 E 23°390 2700 , 1,060 m Zambia, B: N of Lukulu EU280154 EU128947 EU128977 N01°470 E 31°350 Uganda, U2: Bunyoro D, Budongo Forest Reserve ITS 1 Voucher/accession no. Poulsen 975 (AAU) Hoell & Nordal 31 (O) Nordal & Bjorå 4567 (O) Nordal & Bjorå 4621 (O) Nordal & Bjorå 5012 (O) C. occultum A.D. Poulsen & Nordal C. pauper Poelln. C. pusillum Schweinf. ex Baker C. silvaticum Dammer C. viridescens Engl. rps16 GPS-coordinates and altitude The somatic chromosome number of the low altitude form of C. comosum is 2n = 14 (Fig. 1). Locality Results Species Table 1 continued trnL-F C. S. Bjorå GenBank accession number 246 123 Cytology Morphological analyses The rhizome of the low altitude Chlorophytum comosum is much more prominent than that of the high altitude C. comosum (Fig. 2c). It can be up to 1 m long and is covered with old leaf bases. The low altitude form also has aerial roots with chlorenchyma, which is never found in the high altitude form. The roots of the high altitude form are provided with distal tubers, lacking in the low altitude form. The high altitude form often has more than one peduncle per plant in contrast to the low altitude form. The low altitude form typically has two flowers per node, while the high altitude form has 3–6 flowers per node. The low altitude form has greenish, urceolate flowers; the high altitude form has whitish, stellate flowers (Fig. 2e). The outer tepals are five-veined in the high altitude form and three-veined in the low altitude form. Pseudovivipary, otherwise common in C. comosum, is not observed in any of the Mount Kilimanjaro plants. Molecular analyses The maximum parsimony analysis based on the rps16 data set resulted in more than 25,000 most-parsimonious trees (MPTs) of 89 steps each, with consistency index (CI) of 0.84 and retention index (RI) of 0.81. Twenty-four out of 747 characters were parsimony informative. Similar, the analysis of the trnL-F data set resulted in 1,211 MPTs of 45 Fig. 1 Mitotic metaphase of a root tip cell in low altitude C. comosum (Nordal, Bjorå & Hemp 5006 Holotype) A taxonomical and ecological analysis of Chlorophytum on Mount Kilimanjaro 247 Fig. 2 Low altitude Chlorophytum comosum. A, habitat, C, habit, E, left flower. High altitude C. comosum B, habitat, D, habit, E right flower steps each (CI = 0.97, RI = 0.96). Out of 296 characters, eight were parsimony informative. Lastly, the analyses of the ITS1 data set resulted in 21 MPTs of 233 steps each (CI = 0.67, RI = 0.58). Of 296 characters, 45 were parsimony informative. The combination of the three data sets resulted in a data matrix of 1,338 characters of which 78 were parsimony informative. The parsimony analysis resulted in 8 MPTs of 384 steps each (CI = 0.72, RI = 0.62). The separate analyses of the three molecular data sets resulted in less-resolved trees than the combined analysis. There were no hard incongruencies in the separate analyses compared to the combined analysis, except that in the rps16 tree Chlorophytum macrophyllum Asch. and C. pusillum Schweinf. ex Baker formed a clade (JK = 50), and in the ITS1 tree C. pauper Poelln. and C. pusillum formed a clade (JK = 77). In the strict consensus tree of the combined analysis (Fig. 3), C. andongense Baker and C. viridescens Engl., both from Tanzania, form a well-supported clade (A, Jackknife support, JK = 100), sister to the rest of the ingroup taxa (clade B, JK = 72). Clade B is further divided in two subclades Ba and Bb. Subclade Ba is well-supported (JK = 99) and contains C. africanum Engl. and C. silvaticum Dammer collected in Tanzania and Kenya, respectively, and C. macrorrhizum Poelln. from Malawi. The species of interest in this study are included in the next clade Bb (JK = 82). Chlorophytum geophilum Peter ex Poelln. (Bb i), Chlorophytum occultum A.D. Poulsen & Nordal (Bb ii) and the high altitude C. comosum (Bb iii) form separate branches of a larger polytomy. Otherwise C. gallabatense Schweinf. ex Baker and C. floribundum Baker cluster together (Bb iv, JK = 75). Likewise, C. lancifolium Baker and C. blepharophyllum Schweinf. 123 248 Fig. 3 Strict consensus of eight MPTs found by phylogenetic analysis of combined plastid trnL-F spacer, rps16 intron and nrDNA ITS. CI = 0.72, RI = 0.62, L = 384. Jackknife values are shown above the branches C. S. Bjorå A. corymbosum Kenya C. adongense Tanzania 100 C. viridescens Tanzania A 99 100 Ba 98 i ii iii 75 vi 72 B 82 Bb C. macrorrhizum Malawi C. silvaticum Kenya C. africanum Tanzania C. geophilum Zambia C. occultum Uganda high alt. C. comosum Kilimanjaro C. gallabatense Zambia C. floribundum Zambia C. lancifolium Zambia C. blepharophyllum Zambia C. comosum Zimbabwe C. comosum South Africa 69 v 96 vi 72 vii 54 69 97 X=7 C. filipendulum Uganda C. macrophyllum Tanzania C. pauper Zambia C. macrophyllum Ethiopia C. pusillum Zambia C. comosum Uganda C. filipendulum Zimbabwe low alt. C. comosum 5006 Kilimanjaro low alt. C. comosum 847 Kilimanjaro 98 low alt. C. comosum 848 Kilimanjaro ex. Baker show a sister group relationship (Bb v, JK = 69). The two C. comosum specimens collected in Zimbabwe and South-Africa, form a clade with jacknife support of 98 (Bb vi). Within the same polytomy a larger subclade (Bb vii, JK = 72), where C. filipendulum Baker from Uganda, C. macrophyllum from Tanzania and C. pauper from Zambia constitute separate branches. Chlorophytum macrophyllum from Ethiopia and C. pusillum from Zambia form a poorly supported clade (JK = 54). Chlorophytum comosum from Uganda clusters with C. filipendulum from Zimbabwe (JK = 69), and finally, the low altitude C. comosum specimens from Kilimanjaro form a wellsupported clade (JK = 97). Ecological comparison of the low altitude form and the high altitude form Both Chlorophytum forms were found inside the forest. To determine the ecological references and phytosociological affiliation, Table 2 gives an overview (in a condensed form showing the relative frequency of the species) of forest types inhabited by both Chlorophytum forms on Mount Kilimanjaro (for the determination of the altitudinal zones see Hemp 2006a, for the description of these forest types see Hemp 2006b). The habitats of the low altitude form are 123 situated inside riverine forests (community 1 and 2, Table 2), where it hangs from rocks partly covering boulder flanks (Fig. 2a). These rocky habitats are situated in (steep and narrow) gorges within the savanna on the southern and eastern foothills of Mount Kilimanjaro (Fig. 4) in semi-shaded conditions. This intermediate light condition is displayed by, on the one hand, the occurrence of more shade tolerating species such as the co-occurring ferns Asplenium strangeanum Pic. Serm and Adiantum incisum Forssk. and on the other hand by light demanding ferns such as the typical savanna fern Actiniopteris radiata Link, which has a similar distribution on Mount Kilimanjaro as the low altitude form (Hemp 2001). The low altitude form grows vigorously in large colonies in community 1 (Table 2), which represents gallery forests with episodically running water. These forests are lighter than the riverine forests along larger streams with permanent water (community 2), which have a higher and denser tree layer. In contrast to the low altitude form, which occurs in only two vegetation types, the high altitude form was found in seven (out of a total of 21 (Hemp 2006b)) forest communities and in one of open area. These seven forest types cover a large altitudinal and ecological range from wet to drier forests. The plant community of open land is A taxonomical and ecological analysis of Chlorophytum on Mount Kilimanjaro 249 Table 2 Phytosociological affiliation of the two Chlorophytum forms at Kilimanjaro 1–9: forest communities Table 2 continued of secondary character representing vegetation of trampled ground on forest paths (Fig. 2b). A detailed description of this habitat is given by Hemp (2008). Such semi-shaded conditions on forest edges represent the main habitat of this species, where it grows more vigorously and in higher numbers than inside the forest. However, 123 250 C. S. Bjorå Fig. 4 Distribution of low altitude Chlorophytum comosum (filled circle) and high altitude C. comosum (filled square), on Mount Kilimanjaro, Tanzania Table 3 Important habitat parameters of the two forest forms of Chlorophytum Mean habitat parameters Low altitude form High altitude form Mean SD n Min Max Mean SD n Min Max Altitude (m asl) 1,028 123 8 900 1,240 2,016 212 32 1,460 2,490 Annual temperature 20.7 0.6 8 21.3 19.4 15.1 1.2 32 12.4 18 Annual minimum temperature 13.2 0.7 8 13.9 11.7 6.7 1.4 32 3.6 10 Annual preciptation 981 103 8 850 1,100 1,850 405 32 1,100 2,500 pH CaCl2 7.2 0.4 4 6.5 7.6 4.6 0.9 10 3.4 6.6 pH H2O 7.5 0.4 4 6.9 7.8 5.2 0.9 10 3.9 6.8 Slope (°) Cover tree layer (%) 80 60 5.5 8.2 6 6 70 50 85 70 21 72.4 14 7.1 32 25 0 60 50 80 Cover shrub layer (%) 53.3 11.1 6 40 70 47.7 18.8 25 20 80 Cover herb layer (%) 38 20 6 10 60 (77.1) 38 (13.1) 26.8 (7) 25 (50) 2 (95) 100 In brackets: only open habitats, in italics: only forest habitats; climatic parameters from Hemp (2006a, b) compared to the low altitude form, which is able to produce large, dominant colonies, the high altitude form was never found with high individual numbers and vegetation cover (Fig. 2b, d). 123 Important ecological habitat parameters of the two Chlorophytum forms not only differ widely in (mean) values but also in their ranges (Table 3). The high altitude form covered an altitudinal range of nearly 1,000 m, A taxonomical and ecological analysis of Chlorophytum on Mount Kilimanjaro extending from about 1,500–2,500 m (lower montane to middle montane). In contrast, the low altitude form was only found between 900 and 1,240 m (colline to submontane). Consequently, parameters related to altitude (e.g. precipitation and temperature) showed respective differences. The low altitude form grows on neutral to alkaline soils (pH 7.2 and 7.5, in H2O and CaCl2, respectively) whereas the high altitude form is mainly found on acidic soils (mean pH 4.6 and 5.2). However, the light regimes of the habitats are similar, although the high altitude form is only found under a denser tree canopy (Table 3). Therefore, both species can be regarded as forest plants, notwithstanding the fact that the low altitude form thrives on rocks (within forests) and the high altitude form partly on semi-shaded forest tracks or forest edges. Discussion Morphological analyses The two forms of C. comosum occurring on Mount Kilimanjaro fall into two distinct morphological types which are easy to distinguish. The high altitude form falls within the C. comosum complex according to FTEA (Nordal et al. 1997), while the low altitude form has some distinct characters that does not fit in the present understanding of C. comosum and needs taxonomic recognition. 251 both morphological and molecular are needed to untwine this complex. The basic chromosome number, x = 7, represents a synapomorphy for clade Bb, where the two Mount Kilimanjaro forms occur. In contrast, x = 8 represents the plesiomorphic character state of the genus (Nordal et al. 1990). Ba, the sister clade of Bb, includes the species formerly referred to the genus Dasystachys Baker, until Marais and Reilly (1978) transferred them to Chlorophytum. The two species C. adongense and C. viridescence Engl. form a sister clade to clade B, are both characterised by uniquely having branched inflorescences and thick, spongy roots. Ecological analyses The two forms of Chlorophytum comosum occurring at Mount Kilimanjaro inhabit completely exclusive habitats (Fig. 4). Whereas the high altitude form has a wide ecological potential, the low altitude form has narrow ecological demands as a highly adapted specialist. The low altitude form is rare on Mount Kilimanjaro, although it is locally abundant. Only eight localities are known up to now in this area (Fig. 4). This is due to its very specific habitat demands and the natural and anthropogenic rarity of the preferred habitat type. In contrast the high altitude form is widespread, inhabiting nearly the whole forest belt between 1,500 and 2,500 m. Taxonomical implications Molecular analyses The two forms of C. comosum do not form a monophyletic group in the strict consensus tree of the combined analysis (Fig. 3). Representatives of the three subpopulations of the low altitude form found on Mount Kilimanjaro form a well supported clade (subclade Bb vii), while the high altitude form is unresolved within subclade Bb. The molecular analysis indicates that C. macrophyllum, C. filipendulum and C. comosum have a polyphyletic origin and need to be investigated further. This is in accordance with Nordal et al. (1997) who stated that ‘‘The C. comosum complex is furthermore not very well delimited from C. filipendulum.’’ They reduced 23 species to synonymy under C. comosum, but indicating that some of them might deserve separate taxonomic rank. The low altitude form can easily be distinguished from C. comosum s.l. based on morphology, this form can therefore be given taxonomic recognition. The high altitude C. comosum from Mount Kilimanjaro and C. comosum from Uganda are not clustering with C. comosum from South Africa, but as the type of C. comosum is South African, the name ‘comosum’ will probably belong in clade Bb vi. These taxa are, however, not easy to delimitate morphologically and more studies, Based on these findings, we have no doubt that the low altitude form deserves recognition at the species level. The high altitude form must, with the morphological knowledge we have today, still be referred to C. comosum s.l. However, as the molecular analysis show, the species delimitation of C. comosum is problematic. Nordal et al. (1997) in FTEA might have included the rock-inhabiting low altitude form of Mount Kilimanjaro in their concept of C. comosum in a wide sense. Therefore, it is necessary to check their synonyms relating to plants from Mount Kilimanjaro and the Eastern Arc Mountains to find out whether this taxon might already have an appropriate name at species level. Such taxa/names are discussed below, in order of priority. Chlorophytum glaucidulum Engl. ex Poelln. was described by Poellnitz (1946) based on material from W Usambara (Engler 1220, B). The plant has roots with swollen tubers and fits with C. comosum, as defined here. Chlorophytum inopinum Poelln. (Poellnitz 1946) was described on material from Eastern Usambara (Peter 23673, B). It was reduced to C. comosum in FTEA (Nordal et al. 1997), with a note that the form tends to approach C. gallabatense Schweinf. ex Baker. It has an erect 123 252 C. S. Bjorå Fig. 5 Chlorophytum rhizopendulum Bjorå & Hemp. a Habit, b Detail of flower, c Capsule. Drawing by A. Hemp. Drawing based on Nordal, Bjorå & Hemp 5006 (Holotype) inflorescence and is totally different from the rock-inhabiting form described here. Chlorophytum rugosum Poelln. (Poellnitz 1946) was described on material from N Pare at 1,700 m (Peter 14334, B). This form has thin roots, probably with tubers and a short erect inflorescence, and appears to be a depauperate form of C. comosum. Chlorophytum usambarense Engl. ex Poelln. was described by Poellnitz (1946) on material from E Usambara (Scheffler 237, B). It has a short rhizome and corresponds to C. comosum as defined here. Accordingly, as there are no older names available for the low altitude rock-inhabiting plants, a new species name and description is required. Chlorophytum rhizopendulum Bjorå & Hemp nov.sp. Simile C. comoso (Thunb.) Jacques sed rhizomate supra solum crescente robustiore et longiore usque ad 1 m; radicibus crassis sine tuberibus; pedicellis brevioribus usque ad 4 mm; floribus viridibus; tepalis exterioribus cum quinque nervis (non cum tribus nervis). Nascitur in faucibus, rhizomatibus de rupe dependentibus, multis locis societates amplas producens. Tanzania T2, Rombo Distr., near road from Himo to Lake Chala, alt. 1,000 m, UTM Zone 37: 3/47/500 E, 96/ 29/300 S, on bare rock in narrow ravine. 23.6.04. Nordal, Bjorå and Hemp 5006 (=Hemp 3296) (O, holotype; B, EAH, NHT, isotypes). Prominent rhizomes up to 1 m long and about 1.5 cm in diameter, covered with old leaf bases, whitish when cut, turning red-brown when oxidised; thick whitish, tomentose aerial roots with chlorenchyma (Fig. 5). Leaves rosulate, sheathing, lacking petiole, whitish in lower parts, glossy green above, duller, more greyish below with distinct midrib, 30–42 cm long and 3.4–4.2 cm wide. Inflorescence 123 lax, with sterile bracts in lower part, up to 100 cm long, nodes widely scattered with mostly two flowers per node; bracts supporting flowers about 4 mm long and 2 mm wide. Pedicels 4 mm long, with a joint in the upper half. Flowers green, urceolate, petals about 8 mm long, outer 3 mm wide with five nerves, inner 2 mm wide with three nerves. Filaments scabrid, slightly fusiform, 5 mm long. Anthers 1.5 mm long. Style straight, slightly longer than the stamens. Capsules trigonous, 7–8 mm long, about 5 mm wide, with truncate base and emarginate apex. Seeds irregularly folded. Pseudovivipary not observed. IUCN red list category Chlorophytum rhizopendulum is known from eight localities in the Mount Kilimanjaro area. The type locality hosts approximately 1,000 mature individuals. The second largest population consists of approximately 500 individuals, four subpopulations contain less than 100 mature individuals each and in the two last subpopulations there are fewer than ten mature individuals. The area of occupancy (IUCN 2001) is estimated to be far less than 500 km2, severely fragmented and we have been observing a continuing decline in the subpopulations due to habitat destruction. C. rhizopendulum has very specific habitat demands, and is dependent on shade and rocky surfaces. The areas where the species is found have no governmental protection and with heavy logging, the quality of the habitat will be reduced considerably. Based on criteria B2a, b(iii) + E (IUCN 2001), C. rhizopendulum must be regarded as an Endangered Species (EN). Acknowledgments We gratefully acknowledge the financial support granted by the Norwegian Research Council (CSB, Project 151050) NUFU (IN, PRO39/02) and the Deutsche Forschungsgemeinschaft (AH). Thanks to Anne K. 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