Plant Ecology and Evolution 148 (3): 409–419, 2015 http://dx.doi.org/10.5091/plecevo.2015.1040 REGULAR PAPER A synopsis of Soyauxia (Peridiscaceae, formerly Medusandraceae) with a new species from Liberia Frans J. Breteler1,*, Freek T. Bakker2 & Carel C.H. Jongkind3 1Grintweg 303, NL-6704 AR Wageningen, The Netherlands (previously Herbarium Vadense, Wageningen) 2Biosystematics Group, Wageningen University, P.O. Box 647, NL-6700 AP, Wageningen, The Netherlands 3Botanic Garden Meise, Nieuwelaan 38, BE-1860 Meise, Belgium *Author for correspondence: [email protected] Background – Botanical exploration of the Sapo National Park in Liberia resulted in the discovery of a new species, which, after DNA investigation, was identified as belonging to Soyauxia of the small family Peridiscaceae. Methods – Normal practices of herbarium taxonomy and DNA sequence analysis have been applied. All the relevant herbarium material has been studied, mainly at BR, K, P, and WAG. The presented phylogenetic relationships of the new Soyauxia species is based on rbcL gene sequence comparison, inferred by a RAxML analysis including 100 replicates fast bootstrapping. The distribution maps have been produced using Map Maker Pro. Relevant collection data are stored in the NHN (Nationaal Herbarium Nederland) database. Key results − The new species Soyauxia kwewonii and an imperfectly known species are treated in the framework of a synopsis with the six other species of the genus. rbcL sequence comparison followed by RAxML analyses yielded a well-supported match of S. kwewonii with the Soyauxia clade. Its conservation status according to the IUCN red list criteria is assessed as Endangered. Its distribution as well as the distribution areas of the genus and of the remaining species are mapped. Soyauxia ledermannii is neotypified and the most common species in Gabon, S. glabrescens, is also illustrated. Key words – Peridiscaceae, Medusandraceae, Soyauxia, taxonomic synopsis, new species, tropical Africa, Liberia. INTRODUCTION research on relationships of Peridiscaceae, Medusandra was not sampled, nor even mentioned. On the other hand, Whit- The genus Soyauxia was described by Oliver in 1882, based tonia was mentioned but not included in their analysis. on S. gabonensis Oliv. He classified it in the Passifloraceae. Soyauxia shows some distinct morphological features in Later on Gilg (1925) placed it in the Flacourtiaceae. Hutch- which it differs from Peridiscus, such as the pinnate (also inson & Dalziel (1927) treated it as a member of, again, the Passifloraceae. It remained there till Brenan (1954) rec- in Whittonia) instead of palmate leaf venation, the presence ognised it as a member of his then recently described fam- of petals, the quadrilocular anthers, the superior ovary, and ily Medusandraceae, based on Medusandra Brenan (Brenan the long styles. These elements are not mentioned in table 1952). Hutchinson (1959) still kept Soyauxia in the Passiflo- 1 of Soltis et al. (2007), which was based on characters of raceae and opposed Brenan’s view that it belonged to Me- Peri discus only. A recent DNA-based analysis (Wurdack dusandraceae. Metcalfe (1962), when commenting upon the & Davis 2009) placed also Medusandra in Peridiscaceae, anatomical features of the new genus Whittonia (Sandwith which now comprises four genera. Two of these, Peridiscus 1962), took also Soyauxia into account and, despite some and Whittonia, are both monotypic, and natives of tropical distinct elements pointing to Peridiscaceae, suggested that it South America, whereas Medusandra with two species and was best placed in Flacourtiaceae rather than in Passiflorace- Soyauxia with seven or eight species, occur in tropical Af- ae. He also considered Medusandra not to be closely allied rica. to Soyauxia. Cronquist (1981) followed Metcalfe (1962) in Recent botanical exploration of the Sapo National Park placing Soyauxia in the Flacourtiaceae and Takhtajan (1997) in Liberia resulted in the discovery of a new species of placed it in the Passifloraceae. Soltis et al. (2007) placed Soyauxia. Based on fruiting material, it was at first classified Soyauxia in the Peridiscaceae. However, in their DNA-based as a new species of, possibly, Apodiscus (Phyllanthaceae). Its All rights reserved. © 2015 Botanic Garden Meise and Royal Botanical Society of Belgium – ISSN 2032-3921 Pl. Ecol. Evol. 148 (3), 2015 sterile and fruiting material is indeed very difficult to distin- have discovered several new species in and around the park, guish from this genus and, to a lesser extent, from Amanoa, most of them endemic to the south-east of Liberia. Example also of Phyllanthaceae. DNA investigation by the second au- of these endemics are Eugenia sapoensis Jongkind (Jong- thor, however, revealed that it belongs in the Peridiscaceae. kind 2015: 3), Heckeldora jongkindii J.J.de Wilde (De Wilde Its formal description has been included in the synopsis of all 2007: 182), Napoleonaea sapoensis Jongkind (Prance & Soyauxia species presented below. Jongkind 2015: 31), Pavetta sapoensis W.D.Hawth. (Haw- Sapo National Park, where the only fertile tree of the new species was found, is an area of c. 1800 km2 of protected rain thorne 2013: 573) and Psychotria tetragonopus O.Lachenaud forest in the south-east of Liberia. The flora of this national & Jongkind (Lachenaud & Jongkind 2013: 228). Several park was practically unknown until the start of this century other new species still have to be published. At the moment and is still underexplored. Since 2002 botanical expeditions Sapo National Park is more and more becoming an island Figure 1 – Phylogenetic relationships of Soyauxia kwewonii based on rbcL gene sequence comparison, inferred by RAxML analysis including 100 replicates fast bootstrapping. Numbers at nodes indicate bootstrap values and branch widths are drawn proportional to support; scale bar indicates number of substitutions per site. 410 Breteler, Bakker & Jongkind, A new species of Soyauxia (Peridiscaceae) from Liberia of protected forest surrounded by new mining activities, oil (WAG) from Liberia for S. floribunda and Cheek 10617 (K) palm plantations, roads and railways planned or in progress. from Cameroon for S. talbotii. Both voucher specimens have been seen for this publication. METHODS DISCUSSION Normal practices of herbarium taxonomy have been applied. All relevant herbarium material of the genus Soyauxia has Molecular phylogenetic analysis been studied, mainly at BR, K, P, and WAG. The distribution The phylogenetic analysis of the rbcL alignment yielded maps have been produced using Map Maker Pro. Its collect- the tree depicted in fig. 1, in which the Liberian specimen is ing data are stored in the NHN (Nationaal Herbarium Ned- firmly positioned in a trichotomy with the two Soyauxia se- erland) database accessible at http://vstbol.leidenuniv.nl/nhn/ quences, showing comparable branch lengths. We therefore Explore. conclude that it is phylogenetically very close to the two ear- DNA extraction was performed using standard CTAB- lier sampled Soyauxia species. based protocols (see Bakker et al. 1998) and included or- ganic extractions with CH3Cl. PCR amplification of rbcL Chorology followed Wurdack & Davis (2009), using primers 713f and 1460r. Resulting fragments were Sanger sequenced, depos- The genus Soyauxia is confined to the subdivisions Upper ited in GenBank under accession number KR080511, and and Lower Guinea of the Guineo-Congolian Region (White used as query in BLASTn searches in GenBank. The 100 1979). Its southeastern limit is situated in the coastal Loango most similar sequences were then combined in an alignment National Park in Gabon, from where an unidentified speci- containing mostly Saxifragales affinity sequences, and using men (number 8 in the synopsis below) has been collected. Ranunculus as outgroup. Both subdivisions contain three endemic species, Soyauxia floribunda, S. grandifolia and S. kwewonii in Upper Guin- The rbcL sequence alignment, containing 46 sequences, ea, and S. gabonensis, S. glabrescens and S. ledermannii in was then subjected to phylogenetic analysis using RAxML Lower Guinea. Soyauxia talbotii occurs in both subdivisions (Stamatakis 2014) through the Science Gateway (San Diego; (fig. 2). Miller et al. 2010) at www.phylo.org, using default settings. The ‘bipartitions.result’ tree, containing the best ML tree Morphology plus bootstrap values were then visualised in FigTree (Drum- mond et al. 2012). The data from the two earlier sampled The distinct, circular flower disc in Peridiscus, from where Soyauxia species used in the tree are based on Kpadeyeah 20 the Peridiscaceae derived their name, is dehiscent in Soyaux- Figure 2 – Distribution of the genus Soyauxia. 411 Pl. Ecol. Evol. 148 (3), 2015 ia, where it falls off with the stamens or somewhat later. with central column and 6–8 pendulous ovules. Fruit capsu- Its appearance and position looks very much like an inner, lar, dehiscent into 3–4 valves. Seed one with copious bony staminodial row of stamens and may better be conceived as endosperm. Embryo small. such. From this point of view, and looking at Keay’s key to An African genus of seven to eight species confined to the genera of Medusandraceae (Keay 1958), the two genera forests in Upper and Lower Guinea of the Guineo-Congolian become morphologically more similar: Soyauxia has now Region. staminodes and no disc just like in Medusandra. The fertile stamens of e.g. Soyauxia glabrescens (fig. 5E & H) are also more or less united into rows at the base. A true intrastami-