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Sclerosperma pro fi ziana. A habit; B detail of trunk; C , D , E leaves; F basal part of petiole with leaf sheath; G various developmental stages of immature in fl orescence; H in fl orescence with prophyll removed; J detail of in fl orescence with very young fruits; K detail of proximal part of in fl orescence, peduncular bract partly removed, at staminate anthesis; L staminate fl ower from distal part of in fl orescence at staminate anthesis; M infructescence with immature fruits, peduncular bract opened; N seedling. A from photo Hall & Enti GC 36150, B from photo Moore 9883, C – E , from Pro fi zi 840, F , K , L , N from Gillet 279a (BR), G , M from Laurent 1054, H , J from Gillet 279a (WAG). DRAWN BY HANS DE VRIES .
Source publication
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 specie...
Context in source publication
Context 1
... a 3-lobed, glabrous cupule or margins of two sepals distinct and imbricate, some- what angled by mutual pressure; petals 3, distinct, asymmetrical. Rachis of infructescence 6 -10 cm long, bearing up to 30 fruits. Fruit globose to obovoid, 3 - 3.5 × 3.8 -4 cm to 4 -4.5 × 2.5 -3 cm (not yet mature). Seed globose to obovoid 3 × 3.5 cm to 3.5 × 3 cm (Fig. 2). Sclerosperma profiziana is found on relatively dry patches in swampy areas, in valley bottom forest, in forest that is often waterlogged or along streams. CONSERVATION STATUS. Although this species is geo- graphically locally common, it is highly localised with many geographical disjunctions. As such we suggest that, while the species ...
Citations
... Sclerosperma profizianum occurs only sporadically in Ghana, Gabon, the Republic of the Congo, the Democratic Republic of the Congo, and Angola. Sclerosperma walkeri has a similar distribution as S. profizianum but does not occur in Ghana (Dransfield et al., 2008;Van Valkenburg et al., 2008b). Living Sclerosperma are pleonanthic and monoecious plants; they are small, usually between 2 to 6 m high, and often form groups as part of the forest understory. ...
... and compiled from literature (Supplementary Material 1). Each dataset was checked for natural distribution outliers (e.g., specimens from botanical gardens) using published chorological data (Van Valkenburg et al., 2008b;Bourobou Bourobou et al., 2016). Additionally, multiple occurrences with identical coordinates were merged, resulting in a dataset including 81 georeferenced occurrence data for the three extant Sclerosperma species. ...
... Consistent with this pattern and in agreement with highly diverse pollen records from West Africa (Salard-Cheboldaeff and Dejax 1991; Morley 2011; and a summary of these in Couvreur 2015), Pan et al. (2006) reported palms as an important and speciose component of the Chilga floras and noted the extreme paucity of palm fossil occurrences (pollen or otherwise) from the Neogene of Africa. The only record of palms at Mush is pollen and phytoliths of Sclerosperma, a genus that is today restricted to swampy habitats in Central and West Africa (Van Valkenburg et al. 2008;Grímsson et al. 2019;Currano et al. 2020). Today, there are~800 palm species in the Neotropics,~1200 in Southeast Asia, and just 65 on the African continent (Dransfield et al. 2008). ...
... Although no palm macrofossils were identified in the census collections, Sclerosperma pollen ( Fig. 4I-K), which is morphologically distinct from other palm genera (Grímsson et al., 2019), was recovered from four stratigraphic levels. Today, Sclerosperma most commonly occurs in swampy areas of West Africa (Van Valkenburg et al., 2008). ...
Miocene paleoecology of East Africa has implications for human origins and understanding the vicariant legacy forests found today on either side of the East African Rift. Fossil leaves preserved in 21.73 million year old lacustrine sediments from the Mush Valley, Ethiopia, provide a unique opportunity to investigate forest composition and dominance-diversity patterns at an ecological scale. We classified and analyzed 2427 leaves in total from two to three quarries within each of six stratigraphic levels, spanning 7 m of section; we estimate each quarry census represents one to three centuries, and 50–60 kyrs separate the oldest and youngest levels. Pollen, phytolith, and compound-specific organic geochemical data were also collected in a detailed stratigraphic context to provide independent, integrated lines of evidence for landscape evolution and lacustrine paleoecology of the system that preserves the macrofossils. Forty-nine leaf morphotypes were documented, and Legume 1 dominated all samples. Nonmetric multidimensional scaling, Jaccard similarity analyses, and diversity and evenness indices demonstrate a degree of change comparable to community ecology dynamics, likely illustrating a dynamic stable state in forest vegetation surrounding the lake. Taxonomic assessments of leaves, phytoliths, and pollen are consistent with a closed canopy forest with limited palm diversity. A high abundance of des-A ring triterpenoid molecules (diagenetic products formed by microbial degradation under anoxic conditions) and very negative δ¹³C values (<−45‰) of several hopanoid compounds point to anoxic conditions at the lake bottom, consistent with exquisite fossil preservation. The proportion of mid-chain n-alkanes is low, signifying relatively few submerged plants, but increases up-section, which signals shallowing of the paleolake. The Mush Valley locality is unique in Africa with regard to its very early Miocene age and the abundance and quality of organic remains. This densely forested landscape in an upland volcanic region of the Ethiopian Plateau showed resilience amid volcanic eruptions and had botanical affinities with species found today in West, Central, and eastern Africa.
... and S. walkeri A. Chev. (van Valkenburg et al. 2008). The genus was first described by Gustav Mann and Hermann Wendland in 1864 based on material belonging to S. mannii collected by Mann in an inundated forest near the Gaboon (now the Ogooué) River upstream from Point Clara (Mann & Wendland 1864). ...
... The genus was first described by Gustav Mann and Hermann Wendland in 1864 based on material belonging to S. mannii collected by Mann in an inundated forest near the Gaboon (now the Ogooué) River upstream from Point Clara (Mann & Wendland 1864). But, Sclerosperma remained rather enigmatic over time, and although new species were described, they were so rarely collected that the circumscription of these taxa was clarified only recently (van Valkenburg et al. 2008). All three species of Sclerosperma are small, clustering understorey palms, ranging in height from 2 to 6 (to 12) m. ...
... The fruits are readily sought by animals (e.g. gorillas), so in faunal-rich regions intact infructescences are rarely found (van Valkenburg et al. 2008). The unique pollen morphology of Sclerosperma (triangular, triporate, reticulate) within the Arecaceae was first noted by Erdtman and Sing (1957) and often discussed by M.M. Harley and collaborators in the years 1991 to 2008 during their comprehensive work on the pollen morphology of this family (Harley & Hall 1991;Harley 1996Harley , 1999Harley , 2004Harley & Baker 2001;Harley & Dransfield 2003;Dransfield et al. 2008). ...
The palm family, Arecaceae, is notoriously depauperate in Africa today, and its evolutionary, paleobiogeographic, and
extinction history there are not well documented by fossils. In this article we report the pollen of two new extinct species of
the small genus, Sclerosperma (Arecoideae), from a late Oligocene (27–28 Ma) stratum exposed along the Guang River in
Chilga Wereda of north-western Ethiopia. The pollen are triporate, and the two taxa can be distinguished from each other
and from modern species using a combination of light and scanning electron microscopy, which reveals variations in the
finer details of their reticulate to perforate exine sculpture. We also report a palm leaf fragment from a stratum higher in the
same section that is in the Arecoideae subfamily, and most likely belongs to Sclerosperma. The implications of these
discoveries for the evolutionary history of this clade of African arecoid palms is that their diversification was well underway
by the middle to late Oligocene, and they were much more widespread in Africa at that time than they are now, limited to
West and Central Africa. Sclerosperma exhibits ecological conservatism, as today it occurs primarily in swamps and flooded
forests, and the sedimentology of the Guang River deposits at Chilga indicate a heterogeneous landscape with a high water
table. The matrix containing the fossil pollen is lignite, which itself indicates standing water, and a variety of plant
macrofossils from higher in the section have been interpreted as representing moist tropical forest or seasonally inundated
forest communities.
... and S. walkeri A. Chev. (van Valkenburg et al. 2008). The genus was first described by Gustav Mann and Hermann Wendland in 1864 based on material belonging to S. mannii collected by Mann in an inundated forest near the Gaboon (now the Ogooué) River upstream from Point Clara (Mann & Wendland 1864). ...
... The genus was first described by Gustav Mann and Hermann Wendland in 1864 based on material belonging to S. mannii collected by Mann in an inundated forest near the Gaboon (now the Ogooué) River upstream from Point Clara (Mann & Wendland 1864). But, Sclerosperma remained rather enigmatic over time, and although new species were described, they were so rarely collected that the circumscription of these taxa was clarified only recently (van Valkenburg et al. 2008). All three species of Sclerosperma are small, clustering understorey palms, ranging in height from 2 to 6 (to 12) m. ...
... The fruits are readily sought by animals (e.g. gorillas), so in faunal-rich regions intact infructescences are rarely found (van Valkenburg et al. 2008). The unique pollen morphology of Sclerosperma (triangular, triporate, reticulate) within the Arecaceae was first noted by Erdtman and Sing (1957) and often discussed by M.M. Harley and collaborators in the years 1991 to 2008 during their comprehensive work on the pollen morphology of this family (Harley & Hall 1991;Harley 1996Harley , 1999Harley , 2004Harley & Baker 2001;Harley & Dransfield 2003;Dransfield et al. 2008). ...
The palm family, Arecaceae, is notoriously depauperate in Africa today, and its evolutionary, paleobiogeographic, and
extinction history there are not well documented by fossils. In this article we report the pollen of two new extinct species of
the small genus, Sclerosperma (Arecoideae), from a late Oligocene (27–28 Ma) stratum exposed along the Guang River in
Chilga Wereda of north-western Ethiopia. The pollen are triporate, and the two taxa can be distinguished from each other
and from modern species using a combination of light and scanning electron microscopy, which reveals variations in the
finer details of their reticulate to perforate exine sculpture. We also report a palm leaf fragment from a stratum higher in the
same section that is in the Arecoideae subfamily, and most likely belongs to Sclerosperma. The implications of these
discoveries for the evolutionary history of this clade of African arecoid palms is that their diversification was well underway
by the middle to late Oligocene, and they were much more widespread in Africa at that time than they are now, limited to
West and Central Africa. Sclerosperma exhibits ecological conservatism, as today it occurs primarily in swamps and flooded
forests, and the sedimentology of the Guang River deposits at Chilga indicate a heterogeneous landscape with a high water
table. The matrix containing the fossil pollen is lignite, which itself indicates standing water, and a variety of plant
macrofossils from higher in the section have been interpreted as representing moist tropical forest or seasonally inundated
forest communities.
... ; Van Valkenburg et al. 2008). The first account of Sclerosperma pollen by Erdtman and Sing (1957) documented its unique morphology within the palm family (triangular, triporate, reticulate), features often discussed by M.M. Harley in the years 1991 to 2008 through her extensive work with colleagues on the pollen morphology of Arecaceae (Harley & Hall 1991;Harley 1996Harley , 1999Harley , 2004Harley & Baker 2001;Harley & Dransfield 2003;Dransfield et al. 2008). ...
... Despite the number of publications containing pollen descriptions and micrographs of the extant genus, Sclerosperma, a detailed characterisation of the pollen morphology of the three species was needed. Also, the taxonomy of this genus was only recently revised (Van Valkenburg et al. 2008), and showed that previously published pollen material often originated in misidentified specimens. SEM). ...
... Classification above genus level follows Dransfield et al. (2008) and APG IV (2016). Herbarium materials were assigned to extant species according to Van Valkenburg et al. (2008). Pollen grains of each taxon are described individually. ...
Three currently accepted Sclerosperma species appear to produce four different pollen morphologies. Sclerosperma mannii and S. walkeri pollen share the same distinct reticulate sculpture, but S. profizianum produces three different pollen types (microreticulate, fossulate, and perforate). The pollen morphology suggests that S. mannii and S. walkeri are sister taxa of the same intrageneric lineage. The pollen diversity observed in S. profizianum suggests (a) this taxon is unique regarding its pollen diversity despite being a non-heterostylous plant or (b) that circumscription of S. profizianum as a species may well be in the need of redefinition.
... Distribution data for all studied species were extracted from the high quality expert-derived RAINBIO database (Dauby et al., 2016;Sosef et al., 2017). Distribution information for palms is particularly well documented as RAINBIO contains all data from Blach-Overgaard et al. (2010), a comprehensive dataset of all African palm occurrences derived from herbarium records and identified via expert knowledge (Bayton, 2007;Sunderland, 2012;van Valkenburg et al., 2008;van Valkenburg and Sunderland, 2008). For one specimen, the RAINBIO identification was incorrect, and we thus re-identified it. ...
... Distribution data for all studied species were extracted from the high quality expert-derived RAINBIO database (Dauby et al., 2016;Sosef et al., 2017). Distribution information for palms is particularly well documented as RAINBIO contains all data from Blach-Overgaard et al. (2010), a comprehensive dataset of all African palm occurrences derived from herbarium records and identified via expert knowledge (Bayton, 2007;Sunderland, 2012;van Valkenburg et al., 2008;van Valkenburg and Sunderland, 2008). For one specimen, the RAINBIO identification was incorrect, and we thus re-identified it. ...
... Data about the known uses of each species were gathered from a wide range of different literature sources (Adu-Anning, 2004;Amwatta, 2004;Arbonnier, 2009;Barrow, 1998;Burkill, 1997;Cunningham and Milton, 1987;Defo, 2004;Dijkman, 1999;Dransfield, 1986;Dransfield and Beentje, 1995 Table 1 The conservation status and associated parameters of the 61 continental African palm species assessed in this study. and Konda ku Mbuta, 2014;Nzuki Bakwaye et al., 2013;Otedoh, 1976;Ouattara et al., 2015;Peltier et al., 2008;Sola et al., 2006;Stave et al., 2007;Sunderland, 2001Sunderland, , 2007Sunderland, , 2012Sunderland et al., 2001Sunderland et al., , 2004Sunderland and Obama, 1999;van Valkenburg et al., 2008;van Valkenburg and Dransfield, 2004;van Valkenburg and Sunderland, 2008;Welch and Welch, 1999;Yembi, 1999;Zoro Bi and Kouakou, 2004) and the internet database PROTA4U (https://www.prota4u.org/ ). ...
Although the palm flora of continental Africa totals just 66 species, they are amongst the most useful plants across the continent, providing many important resources for human populations. Studies have shown that African palms will likely be negatively affected by global change, leading to increased threats to their survival. Here we conduct the first full global conservation assessment for 61 continental African palm species following IUCN Red List Categories and Criteria. Our study revealed that fewer than 10% of the evaluated species were assessed as Threatened. Within the Threatened category, one species was assessed as Critically Endangered, three as Endangered and two as Vulnerable. These results underline an overall low extinction risk for African palms in the immediate future, which is substantially lower than the global estimate of 21% for all plants. These results could be linked to the generally large distribution patterns of African palm species, the broad ecological amplitudes of most species and their good representation inside the African protected areas network. However, a non-negligible number of species (~15%) lack sufficient data to be properly assessed. This highlights the importance of further studies to improve our basic understanding of their distribution and threats. Our study
provides a rather optimistic view of this highly important African plant resource yet, some widespread species are becoming locally rare due to over-harvesting for human use. At a local level, palm resources are generally non-sustainably exploited, which, coupled with climate change, could lead to a rapid increase in threat status over time.
... Identification of all palms sampled was based on specialized literature, in particular for rattans (Sunderland 2003(Sunderland , 2012, Sclerosperma (van Valkenburg et al. 2008), Borassus (Bayton 2007), and Phoenix (Barrow 1998), whereas the identification of other taxa made use of the general treatments by Tuley (1995) and Hawthorne and Jongkind (2006). We completed our identifications with the study of specimens deposited in the major herbaria from Ghana (GC, KUM and CCG), as well as in the European herbaria containing the most important collections of West African palms (BM, BR, BRU, FI, G, K, P and WAG). ...
... This African palm genus has a disjunct distribution and only one of the three species currently recognized by van Valkenburg et al. (2008) is naturally distributed in Ghana. ...
Gruca et al. 2014) highlights the critical importance of these plants for local populations. In tropical Africa, from Senegal in the west to Somalia in the east, palms provide a wide array of food, drink and medicines and are usually regarded as a reliable yet inexpensive resource for building, weaving, clothing or fuel. Nevertheless, apart from the well-known oil palm, Elaeis guineensis Jacq., and to a lesser extent Borassus aethiopum Mart., a large majority of African palms is mostly harvested from wild populations. PALMS 59(2): 85–103
A review is given of pollination systems in the palm family (Arecaceae). Pollination studies of 149 species (6% of the total number) in 60 genera (33% of the total number) are reviewed. The majority of these studies (75%) are of Neotropical palms. In the sample of 149 species, approximately 52% are beetle-pollinated, 27% bee-pollinated, 7% fly-pollinated, 5% thrips pollinated, 5% wind pollinated, 3% moth-pollinated, and 1% mammal-pollinated. A few other species may be bird-pollinated. Adaptations of inflorescences and flowers to pollinators are not readily apparent except for a general tendency for bee-/fly-pollinated species to have longer, open inflorescences and beetle-pollinated species to have shorter, condensed inflorescences. Classical pollination syndromes are not useful in describing, classifying, or predicting palm pollination systems because of numerous exceptions. The degree to which palm pollination systems may be considered specialized or generalized is unclear. There appear to have been numerous, bidirectional shifts in palms between beetle pollination and bee/fly pollination, and less often shifts to other pollinators. Beetle-pollinated inflorescences are usually visited by bees, and bee-pollinated inflorescences are usually visited by beetles. It seems likely that many species of palm, irrespective of pollinator, have their inflorescences used as brood-sites by beetles.
Vegetative branching is common in the palms (Arecaceae). However, current terms to describe vegetative branching diversity are not consistent and do not cover the full range of branching types. In this study vegetative branching types in the palms were reviewed and defined, and the phylogenetic distribution of palm branching types was described. Branching types were described from a literature review and field observations; 1903 species representing all 181 genera were included. Five branching types were found: lateral axillary branching, shoot apical division, false vivipary, abaxial branching, and leaf-opposed branching. Most species (55%) exhibited no vegetative branching. Lateral axillary was the most common branching type. Lateral axillary branching and shoot apical division were predicted to be the earliest-evolved branching types. The present study suggests that branching types have different evolutionary histories, and it is likely that the solitary habit is more common now than when palms initially diverged from commelinid relatives.
