''Otholobium'' is a genus of flowering plants in the

pea family The Fabaceae or Leguminosae,International Code of Nomenc ...

with over 50 named species, but several also remain undescribed sofar. Species may be herbaceous perennials, subshrubs, shrubs or small trees. The alternately set leaves are accompanied by stipules and mostly consist of three leaflets, sometimes just one. The inflorescences are on short or long stalks in the axils of the leaves. Within the inflorescences, the pea-like flowers occur in groups of three, rarely of two, subtended by a bract, and each individual flower also is subtended by a narrow bract. The petals may be white, pink, purple or blue, often with a differently colored nectar guide, that may sometimes even be yellow. The seedpods contain just one, black, dark or light brown seed. Most species are restricted to the Cape provinces of South Africa, but some occur at higher elevations in eastern Africa. Charles Stirton erected the genus in 1981. The species in South America will probably be segregated, because these are not sufficiently related to the African species.

Description

As far as known, the species currently assigned to the genus ''Otholobium'' are

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

s with 20

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

s (2n=20). They are

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...

subshrub A subshrub (Latin ''suffrutex'') or dwarf shrub is a short shrub, and is a woody plant. Prostrate shrub is a related term. "Subshrub" is often used interchangeably with "bush".Jackson, Benjamin, Daydon; A Glossary of Botanic Terms with their Der ...

s or sometimes spreading

herbs In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal ...

with alternately set leaves, each consisting of one or three entire leaflets carrying black or transparent

glands In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure De ...

, which have a wedge-shaped base and a pointed or blunt tip that is often hooked, with the main vein extended beyond the tip. Left and right of the base of the leafstalk, are two softly hairy

stipule In botany, a stipule is an outgrowth typically borne on both sides (sometimes on just one side) of the base of a leafstalk (the petiole). Stipules are considered part of the anatomy of the leaf of a typical flowering plant, although in many speci ...

s that may be partly merged with the stalk or entirely free, and are oval with a pointy tip or awl-shaped, while several veins create a striped appearance. Otholobium obliquum Dupreez 5

The flowers are seated or on a very short stalk, growing in

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

s consisting of 1 or 5-18 groups of 3 or rarely 2, set in the

leaf axil A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

s or at the tip of the stems. Every individual flower is subtended by a

bract In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...

and every triplet is subtended by an oval bract. The 5 sepals are merged at the base to form a bell-shaped calyx and 5 unequal lobes at the top. The lowest lobe may or may not be much longer or broader than the rest, while the upper 2 or 4 lobes may be merged further toward the tip. The inside of the calyx is sometimes covered in black, stubby hairs. As in most

Faboideae The Faboideae are a subfamily of the flowering plant family Fabaceae or Leguminosae. An acceptable alternative name for the subfamily is Papilionoideae, or Papilionaceae when this group of plants is treated as a family. This subfamily is wide ...

, the corolla is zygomorph, forms a specialized structure and consists of 5 free petals. These may be white, yellow or pale blue in color. The upper petal, called the banner or standard, is large and envelops the other petals in the bud. It is

oblong An oblong is a non-square rectangle. Oblong may also refer to: Places * Oblong, Illinois, a village in the United States * Oblong Township, Crawford County, Illinois, United States * A strip of land on the New York-Connecticut border in the Unit ...

or oval in shape, with weakly developed

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...

and auricles and no appendages. The 2 adjacent petals called wings have long claws, are tinged purple at the blunt tip, are adorned by ridges, and enclose the 2 bottom petals. The two bottom petals have long claws and are tinged purple at the blunt tip, are free at the base but fused together at their tip and they form a boat-like structure called the keel. In ''Otholobium'', the keel is much shorter than the wings. The keel contains 10 identically shaped filaments, 9 are fused while 1 is partially free. The

anther The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...

s are alternately fixed to their filament at the base and at midlength. The seated

ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. ...

is either covered in hairs or in glands and contains 1

ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the fe ...

. It carries the swollen

style Style is a manner of doing or presenting things and may refer to: * Architectural style, the features that make a building or structure historically identifiable * Design, the process of creating something * Fashion, a prevailing mode of clothing ...

that is topped by a pin-shaped stigma, without or with a brush of hairs. From it develops a swollen, softly hairy fruit that ends in a slight beak and protrudes from the calyx when ripe. The fruit does not open. The seeds are light brown to black in colour and longer than wide.

Differences with related genera

''Otholobium'' differs from ''

Psoralea ''Psoralea'' is a genus in the legume family (Fabaceae) with over 60 closely related species native to southern Africa. In South Africa they are commonly referred to as fountainbush (English); fonteinbos, bloukeur, or penwortel (Afrikaans); and u ...

'' and '' Hallio'' by the lack of a cupulum, a small, 2- or 3-lobed bract that encircles the peduncle between its base and the calyx. It differs from '' Cullen'', which has a black glandular-warty fruit.

Taxonomy

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

was the first to describe a species now assigned to this genus, and he called it ''Trifolium fruticans''. It is now known as ''Otholobium fruticans''. This name was published in the

Species Plantarum ' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genera. It is the first work to consistently apply binomial names and was the ...

in 1753, the first work to consistently apply

binomial names In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

. Two further species were described by

Carl Linnaeus the Younger Carl Linnaeus the Younger, Carolus Linnaeus the Younger, Carl von Linné den yngre (Swedish; abbreviated Carl von Linné d. y.), or ''Linnaeus filius'' (Latin for ''Linnaeus the son''; abbreviated L.fil. (outdated) or L.f. (modern) as a botanic ...

in 1781. He named them ''Psoralea rotundifolia'' and ''P. stachydis'', and these species are now known as ''Otholobium rotundifolium'' and ''O. hirtum''. This was followed in 1794 by

Jean Louis Marie Poiret Jean Louis Marie Poiret (11 June 1755 in Saint-Quentin7 April 1834 in Paris) was a French clergyman, botanist, and explorer. From 1785 to 1786, he was sent by Louis XVI to Algeria to study the flora. After the French Revolution, he became a p ...

who added ''P. acuminata'', ''P. ononoides'' and ''P. sericea'', which are currently named ''O. acuminatum'', ''O. virgatum'' and ''O. sericeum'' respectively. When

Carl Thunberg Carl Peter Thunberg, also known as Karl Peter von Thunberg, Carl Pehr Thunberg, or Carl Per Thunberg (11 November 1743 – 8 August 1828), was a Swedish naturalist and an "apostle" of Carl Linnaeus. After studying under Linnaeus at Uppsala Un ...

, who visited the Cape from 1772 till 1775, revised ''Psoralea'' in 1823, and therein added ''P. tomentosa'', ''P. racemosa'', ''P. argentea'' and ''P. striata'' (now ''O. sericeum'', ''O. racemosum'', ''O. argenteum'' and ''O. striatum'').

Ernst Heinrich Friedrich Meyer Ernst Heinrich Friedrich Meyer (1 January 1791 – 7 August 1858) was a German botanist and botanical historian. Born in Hanover, he lectured in Göttingen and in 1826 became a professor of botany at the University of Königsberg, as well as Dire ...

described in 1832 ''Psoralea obliqua'' (now ''Otholobium obliquum''), ''P. bracteata'' var. ''bracteata'' (now ''O. fruticans'') and ''P. bracteata'' var. ''brevibracteata'' (the current ''O. bracteolatum''). In 1836, ''Psoralea'' was reviewed by

Christian Friedrich Ecklon Christian Friedrich Ecklon (17 December 1795 – 1 December 1868) was a Denmark, Danish botany, botanical collector and apothecary. Ecklon is especially known for being an avid collector and researcher of plants in South Africa. Biography Ecklon ...

and

Karl Ludwig Philipp Zeyher Karl Ludwig Philipp Zeyher (2 August 1799 Dillenburg, Hessen, Germany – 13 December 1858 Cape Town), was a botanical and insect collector who collected extensively in South Africa. He was the author, with Christian Friedrich Ecklon, of ''Enumer ...

, who distinguished ''P. albicans'' (= ''O. argenteum''), ''P. algoensis'' and ''P. bracteolata'' (which are considered to be

conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organ ...

and are known today as ''O. bracteolatum''), ''P. candicans'' (now ''O. candicans''), ''P. cephalotes'' and ''P. stachyerum'' (both now included in ''O. stachyerum''), ''P. hilaris'' (currently ''O. racemosum''), ''P. polyphylla'' (now ''O. polyphyllum''), ''P. rupicola'' (now included in ''O. striatum''), ''P. uncinata'' (now ''O. uncinatum'') and ''P. venusta'' (now ''O. venustum''). In the same year Meyer published a revision in which he distinguished ''P. carnea'', ''P. obliqua'', ''P. parviflora'', ''P. triantha'' (now known as ''O. carneum'', ''O. obliquum'', ''O. parviflorum'' and ''O. trianthum'' respectively), ''P. cephalotes'' (= ''O. stachyerum''), ''P. densa'' (= ''O. acuminatum''), and ''P. spathulata'' (= ''O. mundianum''). In Volume II of the

Flora Capensis ''Flora Capensis'' is a book that described the flora found in colonial South Africa, encompassing the Cape Colony, Kaffraria and the Colony of Natal, as it was known during the second half of the 19th century. Creating the book was suggested by t ...

, published in 1862,

William Henry Harvey William Henry Harvey, FRS FLS (5 February 1811 – 15 May 1866) was an Irish botanist and phycologist who specialised in algae. Biography Harvey was born at Summerville near Limerick, Ireland, in 1811, the youngest of 11 children. His father ...

newly described ''P. bowieana'', ''P. hamata'', ''P. macradenia'', ''P. polysticta'' and ''P. thomii'' (now ''O. bowieanum'', ''O. hamatum'', ''O. macradenium'', ''O. polysticum'', ''O. thomii''). Daniel Oliver described ''Psoralea foliosa'' (= ''O. foliosum'') in 1885, while

Edmund Gilbert Baker Edmund Gilbert Baker (1864–1949) was a British plant collector and botanist. He was the son of John Gilbert Baker. Works * ''Synopsis of Malveae'', 1895 * ''The plants of Milanji, Nyassa-land''. Con James Britten. 1894 * ''Catalogue of the Pl ...

distinguished ''P. foliosa'' var. ''gazense'' (= ''O. '' subsp. ''gazense'') in 1911. Helena Forbes added in 1930 ''P. bolusii'' (= ''Otholobium bolusii'') and ''P. royffei'' (included in ''O. caffrum'').

Henry Georges Fourcade Henry Georges Fourcade, also known as Henri Georges Fourcade and sometimes Georges Henri Fourcade, was a surveyor, forester, pioneer of photogrammetry and as botanist, a major early collector of the Southern Cape flora. Early life Henry ...

described ''P. heterosepalum'' (= ''O. heterosepalum'') in 1932. The genus ''Otholobium'' was erected in 1981 by the British/South African botanist Charles Stirton. He chose ''Psoralea caffra'' as

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

. He reassigned many species previously included in ''Psoralea'' to his new genus and described many new species since then: ''Otholobium pungens'' in 1981, ''O. rubicundum'' and ''O. pictum'' in 1982, ''O. swartbergense'' in 1986, ''O. accrescens'', ''O. arborescens'', ''O. dreweae'', ''O. flexuosum'', ''O. fumeum'', ''O. incanum'', ''O. lanceolatum'', ''O. lucens'', ''O. nigricans'', ''O. nitens'', ''O. piliferum'', ''O. prodiens'', ''O. pustulatum'', ''O. sabulosum'', ''O. saxosum'' and ''O. spissum'' in 1989. He described ''O. fumeum'' and ''O. nigricans'' from Natal and Transvaal in 1990. Also in 1990, James Grimes proposed to include eight species that occur in the Andes mountains: '' O. brachystachyum'', '' O. glandulosum'', '' O. higuerilla'', '' O. holosericeum'', '' O. munyense'', '' O. pubescens'' (originally ''Psoralea brachystachya'', ''P. glandulosa'', ''P. higuerilla'', ''P. holosericea'', ''P. munyense'' and P. pubescens''), '' O. mexicanum'' (''Indigofera mexicana'') and the new species '' O. diffidens''. Probably, the Andean species should be removed from Otholobium. ''O. curtisiae'' was described in 2013 by Stirton together with A. Muthama Muasya. These two authors further described ''O. accrescens'', ''O. dreweae'', ''O. lanceolatum'', ''O. lucens'', ''O. nitens'', ''O. piliferum'', ''O. prodiens'', ''O. sabulosum'', and ''O. saxosum'' in 2017. The name of the genus ''Otholobium'' is a combination of the Greek words ὠθέω (ōthéō) meaning to push and λοβός (lobos) meaning pod, which Stirton selected because its fruit seems to be pushed out of the calyx.

Phylogeny

Comparison of homologous DNA has increased the insight in the phylogenetic relationships. The following tree represents current insight in the relationship within the Psoraleeae.

Distribution, habitat and ecology

Almost all species assigned to the genus ''Otholobium'' are limited to the Cape provinces of South Africa, but a few can be found outside South Africa along the continent’s east coast to Kenya. ''O. foliosum'' subsp. ''gazense'' occurs in the

Chimanimani Mountains The Chimanimani Mountains are a mountain range on the border of Zimbabwe and Mozambique. The mountains are in the southern portion of the Eastern Highlands, or Manica Highlands, a belt of highlands that extend north and south along the internatio ...

along the Zimbabwe-Mozambique border, and ''O. foliosum'' subsp. ''foliosum'' in the mountains of Malawi, Tanzania and Kenya. The genus is absent from Ethiopia and Madagascar. Like in many other plant genera, species density dramatically decreases to the east and north of the West Cape province. The species assigned to the genus by Grimes occur in the Andes from Chile in the south to Colombia and Venezuela in the north.

Conservation

The conservation status of forty-eight species has been assessed for South Africa, one of which has two subspecies. One of those subspecies occurs in the mountains of eastern Africa but does not occur in South Africa. The survival of twenty-four taxa is considered to be of

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

: '' O. acuminatum'', '' O. arborescens'', '' O. bracteolatum'', '' O. caffrum'', '' O. candicans'', '' O. flexuosum'', '' O. foliosum ''subsp.'' gazense'', '' O. fumeum'', '' O. hirtum'', '' O. mundianum'', '' O. nigricans'', '' O. obliquum'', '' O. parviflorum'', '' O. pictum'', '' O. polyphyllum'', '' O. polystictum'', '' O. sericeum'', '' O. spicatum'', '' O. stachyerum'', '' O. striatum'', '' O. trianthum'', '' O. virgatum'', '' O. wilmsii'' and '' O. zeyheri''. Four species are regarded as

near threatened A near-threatened species is a species which has been categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature as that may be vulnerable to endangerment in the near future, but it does not currently qualify fo ...

: '' O. accrescens'', '' O. bolusii'', '' O. spissum'' and '' O. swartbergense''. Seven species are rare: '' O. carneum'', '' O. fruticans'', '' O. heterosepalum'', '' O. macradenium'', '' O. nitens'', '' O. pustulatum'' and '' O. racemosum''. Four species are regarded as vulnerable: '' O. dreweae'', '' O. hamatum'', '' O. lucens'' and '' O. rotundifolium''. Six have been categorised as

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

: '' O. bowieanum'', '' O. curtisiae'', '' O. incanum'', '' O. pungens'', '' O. saxosum'' and '' O. thomii''. Two are thought to be critically endangered: '' O. lanceolatum'' and '' O. rubicundum''. Finally, three taxa have not been evaluated, '' O. argenteum'' because not enough information was available to determine its conservation status, '' O. prodiens'' because there is doubt about its status as a species and '' O. foliosum ''subsp.'' foliosum'' because it does not occur in South Africa.

References

{{Taxonbar, from=Q5221384

Otholobium ''Otholobium'' is a genus of flowering plants in the pea family with over 50 named species, but several also remain undescribed sofar. Species may be herbaceous perennials, subshrubs, shrubs or small trees. The alternately set leaves are accompa ...

Flora of Africa Fabaceae genera