Ledermanniella aloides (Engl.) C.Cusset (Cusset 1974: 273)

Bidault, Ehoarn, Boupoya, Archange, Ikabanga, Davy U., Nguimbit, Igor, Texier, Nicolas, Rutishauser, Rolf, Mesterhazy, Attila & Stevart, Tariq, 2023, Novitates Gabonenses 93: a fresh look at Podostemaceae in Gabon following recent inventories, with a new combination for Ledermanniella nicolasii, Plant Ecology and Evolution 156 (1), pp. 59-84 : 59

Ledermanniella aloides (Engl.) C.Cusset (Cusset 1974: 273)

Figs 4D , 6C

Inversodicraea aloides Engl. ( Engler 1915: 271, 273, plate 175)

Type.

CAMEROON • Adamaoua, Pass Tchape ; 27 Feb. 1909; [7°23 ’00” N, 11°55 ’00” E]; 1500 m; fl.; Ledermann 2785; holotype: B; isotype: BM [BM000910397] .

Distribution.

Sierra Leone, Nigeria, Cameroon, Central African Republic, Gabon, Angola. This species was first collected in Gabon in 1993 by Lee White at Lopé, probably not in the Ogooué river, but in a small tributary. We have not been able to retrieve this collection and confirm the identification made by Sosef in 2017. In 2007, another collection, Kato et al. GB-10, was made in the Lenké river near Booué (erroneously labelled as Ledermanniella bifurcata by Koi et al. 2012, see Notes). Since 2017, it has been collected 47 times by the authors and colleagues, including 13 collections from the Louétsi river, 11 from the Komo river, and 23 from the Ogooué or its tributaries. Ledermanniella aloides is the second most commonly found Podostemaceae species in Gabon.

Habitat and ecology.

In Gabon, rapids in rivers from ca 10 to 450 m wide, 85-550 m in elevation (up to 1,500 m in Cameroon). It appears to be very abundant where encountered, forming dense, monospecific mats. In Gabon, flowers and fruits were collected in March, July, August, and September, elsewhere also in May, November, and December. In Gabon, it appears to share the same micro-habitat as I. thollonii , L. pusilla , Tristicha trifaria , and was once found near Saxicolella nana . Ledermanniella aloides is often found in relatively slow-running currents.

Notes.

Ledermanniella aloides , unlike I. thollonii or L. pusilla , never shows developed stems. Nevertheless, some characters used by Cusset (1984) to distinguish it from morphologically close species seem to be more variable than suspected. We observed that the distichous arrangement of leaves and the absence of ramification of the blade are constant throughout the recently collected material, but the presence and shape of stipules, the presence and size of the sheath, and the length and overall shape of the blade can vary. We have noticed three morphogroups occurring in Gabon: one characterized by having all leaves of reproductive rosettes without stipules, with sheaths enlarged but folded and imbricate, and with ensiform (laterally flattened) leaf blade; another group characterized by most leaves with 1-2 stipules at base, with sheaths enlarged but less folded, and leaf blades less obviously ensiform; and a third group with enlarged sheaths bearing obscure (rounded) stipules, and with leaf blade widening on their apical portion, most of them showing a conspicuous midrib. Nevertheless, we are reluctant to name and describe these morphogroups as separate entities, as all characters mentioned here show continua, including in collections from West Africa. Morphological continua between these character states can sometimes even be observed on single shoots, with strong polymorphism of leaves depending on their position relatively to the spathellae. Most of the Gabonese collections studied could be assigned to either one of the three morphogroups based on the observation of the numerous individual shoots they each comprise (usually several dozens or even hundreds of shoots), but all of them also comprise a significant portion of shoots displaying intermediate character states. We believe it is best for now to consider L. aloides as a morphologically variable species, occurring from Sierra Leone to Central African Republic and to Angola. Ledermanniella aloides remains recognizable from any other Ledermanniella species mainly by the combination of always stemless shoots, leaves arranged distichously, blade always entire, the presence of two stamens, and pollen as monads, among other minor differences. In light of the new information on the morphological variability of sheath, stipules, and leaf blade, the validity of L. sanagaensis may be questioned. The description provided by Cusset (1984), as well as the only collection of this species we could study (Kato et al. CMR134 from the type locality at Nachtigal on the Sanaga river, Cameroon), are both included within the morphological range of variation observed on the Gabonese material. Nevertheless, we consider it premature to stop considering L. sanagaensis as a valid and different species until more material from Cameroon is made available and allows for better comparison. In addition, we believe a phylogenetic analysis should be conducted on this group of species, to help untangle this complex and to confirm the hypothesis of L. aloides as a widespread, variable species.

Figures

Figure 4. Distribution maps of Podostemaceae in Gabon. A. Inversodicraea annithomae (grey circles), I. boumiensis (red diamonds). B. Inversodicraea nicolasii (red diamonds), I. paulsitae (grey circles), I. tenax (orange triangles). C. Inversodicraea thollonii (red diamonds), Ledermanniella bifurcata (grey circles). D. Ledermanniella aloides (grey circles), L. schlechteri (red diamonds).

Figure 6. Photographs illustrating a selection of species treated in this paper. A, B. Inversodicraea thollonii (A: Boupoya et al. 1948; B: Boupoya et al. 1943). C. Ledermanniella aloides (Boupoya et al. 1749). D, E. Ledermanniella bifurcata (D: Boupoya et al. 1954; E: Boupoya et al. 1958). F, G. Ledermanniella pusilla (F: Boupoya et al. 1733; G: Boupoya et al. 1735). H. Ledermanniella pygmaea (H: Boupoya et al. 1764). Photographs: Archange Boupoya.