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New and little-known Psychotria (Rubiaceae) from West Africa, and notes on litter-gathering angiosperms

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Abstract

Background - Five new species of Psychotria (Rubiaceae) from West Africa are described and illustrated, in the framework of a regional revision of the genus. Methods - Normal practices of herbarium taxonomy have been applied. Key results - Three of the new species, Psychotria baldwinii, P. tetragonopus and P. voorhoevei, are endemic to Liberia, while the other two, P. blydeniae and P. rubriceps, also occur in adjacent southwestern Cote d'Ivoire. The Ivorian endemic Psychotria copeensis, previously included in the synonymy of P. subobliqua, is separated as a distinct species. Psychotria blydeniae and P. tetragonopus are litterbin plants; we discuss this remarkable adaptation and its occurrence in various Angiosperm families in the African rainforests.

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... Shortly thereafter, the phenomenon was described by Ng (1980) in plants from Malaysia. Despite de Granville's and Ng's insights, many field workers still view trapped litter masses as annoying detritus that has to be cleared away before a plant (Bernal & Balslev, 1996; Humilectic plants (Dressler, 1981) Humus-collecting plants (Copeland, 1907;Hennipman, Veldhoen & Kramer, 1990;Janssen & Schneider, 2005;Hübner, 2013) Litter-collecting plants (Weissenhofer et al., 2008;Lachenaud & Jongkind, 2013) Litter-gathering plants (Cheek, Horwath & Haynes, 2008;Lachenaud & Jongkind, 2013) Litter-trapping plants (Ng, 1980; 2008) Litterbin plants (Hawthorne, 2013;Lachenaud & Jongkind, 2013) Nest-epiphytes* (Schimper, 1903) Tank-epiphytes* (Schimper, 1903) Trash-basket plants (Dressler, 1981;de Nevers, 1995;Freiberg, 1999;Gibernau et al., 2007) *Applied only to epiphytic plants. 556 S. ZONA and M. J. M. CHRISTENHUSZ specimen can be collected or photographed. ...
... Shortly thereafter, the phenomenon was described by Ng (1980) in plants from Malaysia. Despite de Granville's and Ng's insights, many field workers still view trapped litter masses as annoying detritus that has to be cleared away before a plant (Bernal & Balslev, 1996; Humilectic plants (Dressler, 1981) Humus-collecting plants (Copeland, 1907;Hennipman, Veldhoen & Kramer, 1990;Janssen & Schneider, 2005;Hübner, 2013) Litter-collecting plants (Weissenhofer et al., 2008;Lachenaud & Jongkind, 2013) Litter-gathering plants (Cheek, Horwath & Haynes, 2008;Lachenaud & Jongkind, 2013) Litter-trapping plants (Ng, 1980; 2008) Litterbin plants (Hawthorne, 2013;Lachenaud & Jongkind, 2013) Nest-epiphytes* (Schimper, 1903) Tank-epiphytes* (Schimper, 1903) Trash-basket plants (Dressler, 1981;de Nevers, 1995;Freiberg, 1999;Gibernau et al., 2007) *Applied only to epiphytic plants. 556 S. ZONA and M. J. M. CHRISTENHUSZ specimen can be collected or photographed. ...
... Shortly thereafter, the phenomenon was described by Ng (1980) in plants from Malaysia. Despite de Granville's and Ng's insights, many field workers still view trapped litter masses as annoying detritus that has to be cleared away before a plant (Bernal & Balslev, 1996; Humilectic plants (Dressler, 1981) Humus-collecting plants (Copeland, 1907;Hennipman, Veldhoen & Kramer, 1990;Janssen & Schneider, 2005;Hübner, 2013) Litter-collecting plants (Weissenhofer et al., 2008;Lachenaud & Jongkind, 2013) Litter-gathering plants (Cheek, Horwath & Haynes, 2008;Lachenaud & Jongkind, 2013) Litter-trapping plants (Ng, 1980; 2008) Litterbin plants (Hawthorne, 2013;Lachenaud & Jongkind, 2013) Nest-epiphytes* (Schimper, 1903) Tank-epiphytes* (Schimper, 1903) Trash-basket plants (Dressler, 1981;de Nevers, 1995;Freiberg, 1999;Gibernau et al., 2007) *Applied only to epiphytic plants. 556 S. ZONA and M. J. M. CHRISTENHUSZ specimen can be collected or photographed. ...
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Litter-trapping plants have specialized growth habits and morphologies that enable them to capture falling leaf litter and other debris, which the plants use for nutrition after the litter has decayed. Litter is trapped via rosettes of leaves, specially modified leaves and/or upward-growing roots (so-called ‘root baskets’). Litter-trappers, both epiphytic and terrestrial, are found throughout the tropics, with only a few extra-tropical species, and they have evolved in many plant families. The trapped litter mass is a source of nutrients for litter-trapping plants, as well as food and housing for commensal organisms. Despite their unique mode of life, litter-trapping plants are not well documented, and many questions remain about their distribution, physiology and evolution.–© 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, ●●, ●●–●●.
... The large leaves are tightly clasped around the stem and, due to the short internodes towards the stem apices, the opposite-decussate pairs form together a pseudo-rosette which creates a basket-like effect that collects humus and leaf litter from the forest. This habit appears to be unique in Acanthaceae though it has evolved in many different families (Zona & Christenhusz 2015;Lachenaud & Jongkind 2013) and may represent a remarkable case of convergence. The precise role of this adaptation remains unclear for J. gigantophylla, though in other litter-gathering plants commensal organisms are believed to utilise the caught debris as food and/or housing, whilst the host plant benefits from nutrients as this debris is broken down (Zona & Christenhusz 2015). ...
... Litter-gathering plants such as this are surprisingly understudied, especially as far as Africa is concerned. It appears that they are often gregarious, with a strong tendency for several litter-gathering species to grow together (Lachenaud & Jongkind 2013). The reasons for this are unclear, but the litter-gathering habit may represent an adaptation to nutrient-poor soils. ...
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Background and aims – The taxonomic status of Duvernoia gigantophylla Lindau from southern Cameroon is considered in relation to the wider Justicia extensa-laxa complex of tropical Africa. Its unusual litter-gathering habit (currently unique in Acanthaceae) is also discussed.Methods – This study was based on normal practices of herbarium taxonomy and morphological analysis. All relevant protocols were followed in the production of the conservation assessment and selection of the lectotype. Key results – A new combination Justicia gigantophylla (Lindau) H.J.Sm. & C.Moran is proposed for this narrowly endemic and endangered species, which is re-instated, with a new description and conservation assessment. A basic key to the wider J. extensa-laxa complex is presented. Justicia gigantophylla is assessed as Endangered (EN B1ab(iii)+2ab(iii)) according to the 2012 criteria of IUCN and a new lectotype is also designated.
... (as in Q. antonensis) architecture, consisting of rosettes or crowns of leaves borne on a single stem or at the ends of sparse branches (Zona & Christenhusz 2015). Schopfbaum trees and shrubs account for more than 40 genera of litter trappers, and have evolved independently multiple times within a few species-rich genera (e.g., Psychotria; Lachenaud & Jongkind, 2013). ...
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Quadrella antonensis and its congener, Q. dressleri, are striking examples of shrubs and small trees the architecture and morphology of which appear to be adapted to trap leaf litter falling from the forest canopy. Endemic to a few highland locations in Panama, Q. antonensis apparently trades‐off light‐capture efficiency for aboveground nutrient capture. Leaves are arranged in spirals around branch tips into basket‐like structures. These “trash baskets” collect and retain litter and produce adventitious fine roots that proliferate in the rich humus that develops inside them. Concerted efforts are needed to better understand the adaptive significance of litter‐trapping morphologies, the conditions that favor their evolution, and to protect the dwindling habitats of these botanical oddities.
... The impressive Ecological Atlas of Woody Plant Species by Poorter et al. (2004), shows the profiles of the rare and endemic species of the Upper Guinean forests. The number of new endemic species discovered since the appearance of the second edition of the Flora of West Tropical Africa is considerable and the botanical exploration of the Upper Guinean forests, especially of Liberia, continues to yield new species (Lachenaud & Jongkind 2013;Jongkind 2012Jongkind , 2015Jongkind , 2016Jongkind , 2017Jongkind , 2019. A specimen of an undescribed species of Antidesma L. (Phyllanthaceae) was recently collected in Liberia by C.C.H. Jongkind, who is still actively exploring the botanical diversity of this country. ...
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Background and aims – The botanical exploration of Liberia, notably by C.C.H. Jongkind, has yielded several new species. One of his recent collections proved to contain a new species of Antidesma.Methods – Normal practices of herbarium taxonomy were applied to study the relevant herbarium material available at BR, K, and WAG. The relevant collecting data are stored at the Naturalis Biodiversity Center, Leiden, Section Botany. Map Maker was used to produce the distribution map.Key results – Antidesma jongkindii Breteler is described as a new species and illustrated. Its distinction from the other three species present in Liberia is presented in a key. The species is proposed to be listed as Critically Endangered [CR B2ab (ii)] following IUCN criteria.
... The area in south-east Liberia, where the new species is found is a biodiversity hotspot known to be home to several other local endemic species, most of them discovered only recently, including Napoleonaea sapoensis Jongkind (Prance & Jongkind 2015), Pauridiantha liberiensis Ntore (Ntore 2008), Pavetta sapoensis Hawthorne (Hawthorne 2013), Psychotria tetragonopus O. Lachenaud & Jongkind (Lachenaud & Jongkind 2013) and Soyauxia kwewonii Breteler & Jongkind (Breteler, Bakker & Jongkind 2015). At the moment, an important part of the forest in this area being replaced by oil palm plantations. ...
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BACKGROUND: Fieldwork in Liberia in recent years has improved our knowledge of the local endemic species. OBJECTIVES: To describe a new species in Bertiera to accommodate material from the south-east of Liberia that cannot be included in any known species. METHODS: Existing herbarium collections were studied, the new species was studied in the field and the relevant published literature was consulted. RESULTS: The new species Bertiera sinoensis is described and illustrated here based on six specimens. CONCLUSIONS: The new species adds one more species to the botanical hotspot in south-east Liberia. It is assigned a preliminary conservation status of 'Endangered' (IUCN).
... The tropical African flora, particularly in Lower Guinea (LG, a phytogeographical area of Central Africa, which extends from southwest Nigeria to north Angola and separated from the Congo Basin by the Sangha River; White 1979), is no exception to the rule as illustrated by several taxonomic revisions resulting in splitting species previously grouped in a single taxon, or in lumping previously recognized species (e.g. Breteler 2011, Walters et al. 2011, Hyam et al. 2012, Lachenaud & Jongkind 2013, Van der Burgt et al. 2015. Several population genetic studies conducted on different species in tropical Africa demonstrated the existence of sympatric genetic groups, sometimes highly differentiated, suggesting that cryptic species could be common and thus that taxonomy based on morphological markers alone may overlook many species (Dauby et al. 2010, Koffi 2010, Heuertz et al. 2014. ...
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Taxonomic classification based on morphology alone can prove difficult. This is the case of the polymorphic forest tree species Santiria trimera in Africa, whose classification has remained controversial for over a century. Studies combining chloroplast and nuclear DNA sequences show the existence of several phylogenetic clades in this taxon, with some occurring in sympatry in western Central Africa suggesting the existence of at least two species. By combining genetic and morphological markers, we aim to assess the species delimitation in the Santiria species complex. Morphological trait (trunk, leaflet, flower and fruit characteristics) analysis using 223 standing individuals and 103 herbarium samples were combined with genetic analyses using 479 individuals genotyped at eight microsatellite markers. Genetic clusters were identified using Bayesian assignment in order to delimit species following the Biological Species Concept and to identify distinctive characters from morphometric analyses in retrospect. Three genetic clusters were identified and found to occur in sympatry. The type of inflorescence and the colour of unripe fruit were the most discriminant morphological traits among those genetic clusters, while many quantitative traits showed overlapping distributions between genetic clusters and explain the difficulty encountered by previous botanists to resolve the taxonomy of Santiria. The combination of genetic and morphological data suggests the presence of three species within the taxon Santiria trimera from western Central Africa. This work should guide a taxonomic revision within the genus Santiria in Africa.
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Background: Secondary foundation species (FS) are organisms that inhabit ecosystems structurally defined by a primary foundation species, providing additional structure to habitats and communities. Trash-basket epiphytes (TBE) are secondary FS that enhance arboreal soil accumulation, providing shelter to animals, and rooting sites for plants. While their importance may vary across biomes, TBE have been overlooked as drivers of biodiversity and ecosystem functions. Here, we discuss the prevalence of TBE across biomes, their effects on biodiversity and ecosystem functions, and future research directions. Methods: We performed a systematic literature review of articles, books and theses and collated and synthesised information about the taxonomic distribution of TBE, their effects on ecosystem functions, and reports of plant-animal and plant-plant interactions. Then, we analysed the global distribution of TBE using a generalized linear model and summarised two studies to assess their effects on soil invertebrates. Results: We identified 120 publications describing 209 species of TBE. Most TBE belong to Araceae (43%), Polypodiaceae (23%), and Orchidaceae (14%) and occur in all tropical and southern temperate forests. TBE richness peaks in the South-American Pacific mangroves, Eastern Cordillera Real, and the Napo moist forests. TBE effects on ecosystem functions include arboreal soil accumulation, water retention and temperature regulation in the canopy, and nutrient leaching through stem-flow. TBE provide shelter to species in more than 97 animal families, including from invertebrates to mammals, while 72 vascular plants have been reported to root in arboreal soil of TBE. Conclusions: TBE are a compelling group of model organisms that can be used to study ecological processes such as facilitation cascades, niche construction, extended phenotypes, or the effects of secondary FS on biodiversity and ecosystem functioning. TBE should also be included in forest management plans to enhance the availability of microhabitats in the canopy supporting its associated flora and fauna.
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Book
Robbrecht E, De Block P., Dessein S & Lachenaud O. (2020) Rubiaceae, Introduction, 199 pp. In : Sosef M. (ed.) Flore d’afrique centrale (République démocratique du Congo − Rwanda − Burundi), Nouvelle série, Spermatophyta. Meise Botanic Garden This first part of the treatment of the Rubiaceae occurring in the Democratic Republic of the Congo, Rwanda and Burundi provides an introduction to the family. The classification of Robbrecht & Manen (2006) in two subfamilies and four supertribes, adapted according to a number of recent findings, is followed and outlined. This fourth largest family of Angiosperms is represented in the Flora area by about 750 species classified in some 120 genera and 27 tribes. Its position, delimitation, classification and phylogeny are briefly discussed. A survey of uses is given. Coffee is the most important commodity from this family, and the second most economic coffee species (robusta) has a central African origin. A survey of morphological diversity and chromosome number variation is provided. It is richly illustrated with 27 plates, most in colours, covering features of habit, inflorescences, flowers, fruits and seeds. To identify material to tribal level, two tables, one for each subfamily, with distinctive characters and a synoptic key to the tribes are provided. Material can be identified to genus level using three keys, one for flowering material, one for fruiting material and a third one for complete material (flowers and fruits). The latter arranges the genera in six artificial groups. Additionally, a list of spot characters is provided to assist identification. In French.
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Six new species of Pavetta L. are described from the Wet Evergreen forests of Ghana, Ivory Coast and Liberia: Pavetta sonjae, P. bomiensis, P. abujuamii, P. ankasensis, P. quasidigita and P. sapoensis, the first of these with ornamental potential. The last three are considered ‘litter-bin’ species, a morphological syndrome whereby forest understorey plants accumulate litter in their leaf axils. Certain venation patterns are defined precisely and used to delimit species. The six new species are illustrated, compared with similar species and their conservation status is evaluated.
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A taxonomic revision of the palm genus Sclerosperma (Arecaceae) is presented. Three species are recognised: S. mannii H. Wendl., which is relatively widespread from Liberia to the Democratic Republic of Congo; S. walkeri A. Chev., which is apparently confined to the interior of Gabon and a band along the Congo River; and S. profiziana, a new species previously considered conspecific to S. mannii that is found in southwest Ghana, Congo, the Democratic Republic of Congo and Angola. The taxonomic history, morphology, distribution and conservation status of the genus and each species are discussed.
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A new species of Psychotria (Rubiaceae) from southern CameroonBackground - A novelty is described in the framework of an ongoing revision of Psychotria in West and Central Africa.Methods - Normal practises of herbarium taxonomy have been applied.Key results - Psychotria sonkeana O.Lachenaud & Séné, a new species endemic to southern Cameroon, is described and illustrated. Belonging to section Confertiflorae, it is related to P. subobliqua Hiern and P. globiceps Hiern, but differs from both in having fistulose branches, puberulent peduncles and green-and-white-striped immature fruits. The species is assessed to be Endangered according to the IUCN criteria. French Contexte - Une nouvelle espèce est décrite dans le cadre d'une révision en cours des Psychotria en Afrique occidentale et centrale. Méthodes - Les méthodes usuelles de taxonomie d'herbier ont été appliquées. Résultats-clés - Psychotria sonkeana O.Lachenaud & Séné, espèce nouvelle endémique du sud Cameroun, est décrit et illustré. Appartenant à la section Confertiflorae, il est voisin de P. subobliqua Hiern et P. globiceps Hiern, dont il diffère notamment par les rameaux fistuleux, les pédoncules pubérulents et les fruits striés de vert et de blanc à l'état immature. L'espèce est évaluée comme « En danger » selon les critères de l'UICN.