''Stylosanthes'' is a genus of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s in the

legume Legumes are plants in the pea family Fabaceae (or Leguminosae), or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also called pulses. Legumes are grown agriculturally, primarily for human consum ...

family

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

and contains numerous highly important

pasture Pasture (from the Latin ''pastus'', past participle of ''pascere'', "to feed") is land used for grazing. Types of pasture Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, c ...

and

forage Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used m ...

species. It was recently assigned to the informal

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

''Pterocarpus''

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

of the Dalbergieae. The common name pencilflower is sometimes used for plants in this genus.

Description

The genus is characterised by trifoliate leaves and small yellow flowers Species may be annual or

perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...

and morphology varies between species as well as within species in response to grazing pressure. Some species such as '' S. scabra'' grow as a low woody shrub to 1.5 m, while others such as '' S. humilis'' will grow as a herbaceous shrub but can adopt a prostrate growth form and thrive under high grazing pressure.

Taxonomy and range

Taxonomy of the genus remains unsettled and controversial, with various authors favouring between 25 and 42 species, with at least 40 additional synonyms. The taxonomy is complicated by the existence of numerous natural

tetraploid Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one fro ...

and hybrid populations. Species within the genus fall within two subgenera: ''Styposanthes'' and ''Stylosanthes''. ''Styposanthes'' possess a small rudimentary secondary floral axis, which is absent from ''Stylosanthes''. ''Stylosanthes'' is closely related to the peanut genus ''

Arachis ''Arachis'' is a genus of about 70 species of annual and perennial flowering plants in the family (Fabaceae), native to South America, and was recently assigned to the informal monophyly, monophyletic ''Pterocarpus'' clade of the Dalbergieae. At ...

''. All except two species of the genus are native to the Americas. '' S. fruticosa'' has a native range that extends from

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...

, across

Arabian Peninsula The Arabian Peninsula (, , or , , ) or Arabia, is a peninsula in West Asia, situated north-east of Africa on the Arabian plate. At , comparable in size to India, the Arabian Peninsula is the largest peninsula in the world. Geographically, the ...

Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

and

Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

and '' S. erecta'' is endemic to Tropical Africa, from

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

Senegal Senegal, officially the Republic of Senegal, is the westernmost country in West Africa, situated on the Atlantic Ocean coastline. It borders Mauritania to Mauritania–Senegal border, the north, Mali to Mali–Senegal border, the east, Guinea t ...

. The putative species '' S. sundaica'', has a range that encompasses

Malesia Malesia is a biogeographical region straddling the Equator and the boundaries of the Indomalayan and Australasian realms. It is a phytogeographical floristic region in the Paleotropical kingdom. It was first recognized as a distinct region ...

but is considered by most authors to be an adventive polypoliod variety of ''S. humilis''. Ecological range extends from savanna and thorn scrub to tropical forest and montane forests.

Species

The following species are accepted: *'' Stylosanthes angustifolia'' Vogel *'' Stylosanthes biflora'' (L.) Britton, Sterns & Poggenb. *'' Stylosanthes bracteata'' Vogel *'' Stylosanthes calcicola'' Small *'' Stylosanthes campestris'' M.B.Ferreira & Sousa Costa *'' Stylosanthes capitata'' Vogel *'' Stylosanthes erecta'' P.Beauv. *'' Stylosanthes falconensis'' Calles & Schultze-Kr. *'' Stylosanthes fruticosa'' (Retz.) Alston *'' Stylosanthes guianensis'' (Aubl.) Sw. *'' Stylosanthes hamata'' (L.) Taub. *'' Stylosanthes hippocampoides'' Mohlenbr. *'' Stylosanthes hispida'' Rich. *'' Stylosanthes humilis'' Kunth *'' Stylosanthes ingrata'' S.F.Blake *'' Stylosanthes leiocarpa'' Vogel *'' Stylosanthes linearifolia'' M.B.Ferreira & Sousa Costa *'' Stylosanthes longicarpa'' Brandão & Sousa Costa *'' Stylosanthes longiseta'' Micheli *'' Stylosanthes macrocarpa'' S.F.Blake *'' Stylosanthes macrocephala'' M.B.Ferreira & Sousa Costa *'' Stylosanthes macrosoma'' S.F.Blake *'' Stylosanthes maracajuensis'' Sousa Costa & Van den Berg *'' Stylosanthes mexicana'' Taub. *'' Stylosanthes montevidensis'' Vogel *'' Stylosanthes nervosa'' J.F.Macbr. *'' Stylosanthes quintanarooensis'' Gama & Dávila *'' Stylosanthes recta'' Vanni *'' Stylosanthes rostrata'' (Burkart) Vanni *'' Stylosanthes ruellioides'' Mart. ex Benth. *'' Stylosanthes salina'' Sousa Costa & Van den Berg *'' Stylosanthes scabra'' Vogel *'' Stylosanthes seabrana'' B.L.Maass & 't Mannetje *'' Stylosanthes sericeiceps'' S.F.Blake *'' Stylosanthes suffruticosa'' Mohlenbr. *'' Stylosanthes sympodialis'' Taub. *'' Stylosanthes tuberculata'' S.F.Blake *'' Stylosanthes vallsii'' Sousa Costa & Van den Berg *'' Stylosanthes venezuelensis'' Calles & Schultze-Kr. *'' Stylosanthes viscosa'' (L.) Sw.

Usage

Species within the genus have many properties that make them valuable forage species. They are capable of

nitrogen fixation Nitrogen fixation is a chemical process by which molecular dinitrogen () is converted into ammonia (). It occurs both biologically and abiological nitrogen fixation, abiologically in chemical industry, chemical industries. Biological nitrogen ...

and are capable of improving soil fertility in addition to providing high protein stock feed. The genus is also noted for its ability to extract phosphorus from soils where it is not available to other species. Seeds are hard and long lived leading to high soil seed banks and rapid recovery following fire or heavy grazing. Seed survives passage through the gut of grazing animals and is dispersed widely in this manner allowing for rapid dispersal. Many species are adapted to hot, dry climates and are drought resistant. These traits have made the genus the world’s most widely used tropical pasture legume. ''Stylosanthes'' has been introduced across the tropical world as a pasture species. Its most important use has been in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

where over a million hectares of primarily native pasture have been oversown with ''Stylosanthes'' species; primarily '' S. hamata'', ''S. scabra'' and ''S. humilis'' This can lead to a ten-fold increase in productivity, though 2–3 fold increases are normal. ''Stylosanthes'' are the most important forage legumes in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

and the most important pasture legumes of tropical

. ''Stylosanthes'' are also important forage species in tropical Africa. ''Stylosanthes'' are important green manure species in

West West is one of the four cardinal directions or points of the compass. It is the opposite direction from east and is the direction in which the Sun sets on the Earth. Etymology The word "west" is a Germanic word passed into some Romance langu ...

and

Central Africa Central Africa (French language, French: ''Afrique centrale''; Spanish language, Spanish: ''África central''; Portuguese language, Portuguese: ''África Central'') is a subregion of the African continent comprising various countries accordin ...

, primarily '' S. guianensis'' and ''S. hamata'', and species are planted and harvested for commercial leaf meal production for poultry and pig feed in

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

and

. The genus has also been used as a nitrogen input into low input or organic cropping systems. Species are used as fallow species in

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

and

. S. hamata used for intercropping with grain crops in India and Africa with yield increases up to 25%. ''Stylosanthes'' species have been used for land reclamation, soil stabilization and soil regeneration work because of their drought resistance, ability to restore soil fertility, improve soil physical properties and provide permanent vegetation cover. Despite their ability to dramatically improve productivity in grazing lands, ''Stylosanthes'' can also cause problems. ''Stylosanthes'' can dominate pasture at the expense of grass which can lead to problems because the plants provides less protection from

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

than grass. ''Stylosanthes'' dominance can also lead to soil acidification, as soil nitrate levels build up and are then leached down the soil profile. ''Stylosanthes'' species are considered invasive species and environmental weeds in

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

, the

Pacific Islands The Pacific islands are a group of islands in the Pacific Ocean. They are further categorized into three major island groups: Melanesia, Micronesia, and Polynesia. Depending on the context, the term ''Pacific Islands'' may refer to one of several ...

and

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

. Many ''Stylosanthes'' species are susceptible to anthracnose fungus ('' Colletotrichum gloeosporioides'') which retards growth and seed development, and this had led to numerous commercial cultivars being abandoned.

Notes

:Some sources treat ''Stylosanthes acuminata'', ''Stylosanthes aurea'', ''Stylosanthes campestris'', ''Stylosanthes gracilis'', ''Stylosanthes grandifolia'', and/or ''Stylosanthes hippocampoides'' as synonyms of ''Stylosanthes guianensis''. :Some sources treat ''Stylosanthes bahiensis'' as a synonym of ''Stylosanthes pilosa''. :Some sources treat ''Stylosanthes cayennensis'' as a synonym of ''Stylosanthes hispida''. :Some sources treat ''Stylosanthes figueroae'' and/or ''Stylosanthes sundaica'' as synonyms of ''Stylosanthes humilis''. :Some sources treat ''Stylosanthes guineensis'' as a synonym of ''Stylosanthes erecta''. :Some sources treat ''Stylosanthes macrosoma'' as a synonym of ''Stylosanthes montevidensis''. :Some sources treat ''Stylosanthes nervosa'', ''Stylosanthes suffruticosa'', and/or ''Stylosanthes tuberculata'' as synonyms of ''Stylosanthes scabra''. :Some sources treat ''Stylosanthes subsericea'' as a synonym of ''Stylosanthes macrocarpa''.

References

{{Authority control Fabaceae genera Forages Taxa named by Olof Swartz