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

pea family Fabaceae () or Leguminosae,International Code of Nomen ...

with over 50 named species, but several also remain undescribed so far. 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. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

s with 20

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

s (2n=20). They are

shrub A shrub or 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 by their multiple ...

subshrub A subshrub (Latin ''suffrutex'') or undershrub is either a small shrub (e.g. prostrate shrubs) or a perennial that is largely herbaceous but slightly woody at the base (e.g. garden pink and florist's chrysanthemum). The term is often interch ...

s or sometimes spreading

herbs Herbs are a widely distributed and widespread group of plants, excluding vegetables, with savory or aromatic properties that are used for flavoring and garnish (food), garnishing food, for medicinal purposes, or for fragrances. Culinary use typi ...

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

glands A gland is a Cell (biology), cell or an Organ (biology), organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also funct ...

, 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 (botany), petiole). They are primarily found among dicots and rare among monocots. Stipules are considered part ...

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 In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

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

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

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, associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves in size, color, shape or texture. They also lo ...

and every triplet is subtended by an oval bract. The 5 sepals are merged at the base to form a bell-shaped

calyx CALYX, Inc. is a non-profit publisher of art and literature by women founded in 1976 based in Corvallis, Oregon. CALYX publishes both '' CALYX, A Journal of Art and Literature by Women'' twice a year and CALYX Books, which publishes one to three ...

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 widely ...

, the corolla is

zygomorph Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''coroll ...

, 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 an object longer than it is wide, especially 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 ...

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 Arthro ...

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 (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

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

ovary The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...

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 sporangium, megasporangium), ...

. It carries the swollen

style Style, or styles may refer to: Film and television * ''Style'' (2001 film), a Hindi film starring Sharman Joshi, Riya Sen, Sahil Khan and Shilpi Mudgal * ''Style'' (2002 film), a Tamil drama film * ''Style'' (2004 film), a Burmese film * '' ...

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 111 species of shrubs, trees, and herbs native to southern and eastern Africa, ranging from Kenya to South Africa. In South Africa they are commonly referred to as fountainbush (English ...

'' 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 ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

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 genus, genera. It is the first work to consistently apply binomial nomenclature ...

in 1753, the first work to consistently apply

binomial names In taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, altho ...

. 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 botani ...

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-Quentin, Aisne, Saint-Quentin7 April 1834 in Paris) was a French clergyman, Botany, botanist, and Exploration, explorer. From 1785 to 1786, he was sent by Louis XVI of France, Louis XVI to Algeri ...

who added ''P. acuminata'', ''P. ononoides'' and ''P. sericea'', which are currently named ''O. acuminatum'', ''O. virgatum'' and ''O. sericeum'' respectively. When Carl Thunberg, 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 the Electorate of Hanover, he lectured in Göttingen and in 1826 became a professor of botany at the University of Königsb ...

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, Holy Roman Empire – 13 December 1858 Cape Town), was a botanical and insect collector who collected extensively in Cape Colony. He was the author, with Christian Friedrich Ecklon, of ...

, 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 organism ...

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, 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 John Gilbert Baker (13 January 1834 – 16 August 1920) was an England, English botanist. His son was the botanist Edmund G ...

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. afrum'').

Henry Georges Fourcade Henry Georges Fourcade (1865-1948), 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 Cape floristic region, Southern ...

described ''P. heterosepalum'' (= ''O. heterosepalum'') in 1932. The genus ''Otholobium'' was erected in 1981 by the British/South African botanist

Charles Stirton Charles is a masculine given name predominantly found in English and French speaking countries. It is from the French form ''Charles'' of the Proto-Germanic name (in runic alphabet) or ''*karilaz'' (in Latin alphabet), whose meaning was ...

. He chose ''Psoralea afra'' as

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

. 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. 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 evaluated and categorized by the International Union for Conservation of Nature (IUCN) as not being a focus of wildlife conservation because the specific species is still plentiful in the wil ...

: '' O. acuminatum'', '' O. arborescens'', '' O. bracteolatum'', '' O. afrum'', '' 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 Conservation status, categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature (IUCN) as that may be vulnerable to Endangered species, endangerment in the ne ...

: '' 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, inv ...

: '' O. bowieanum'', '' O. curtisiae'', '' O. incanum'', '' O. pungens'', '' O. saxosum'' and '' O. thomii''. Two are thought to be

critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

: '' 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

{{Authority control

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

Flora of Africa Fabaceae genera