The genus is characterised by trifoliate leaves and small yellow flowers [4] Species may be
annual or
perennial 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.[5]
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.[6] The taxonomy is complicated by the existence of numerous natural
tetraploid and
hybrid populations.[7] Species within the genus fall within two subgenera: Styposanthes and Stylosanthes. Styposanthes possess a small rudimentary secondary
floral axis, which is absent from Stylosanthes.[8]Stylosanthes is closely related to the peanut genus Arachis.[6]
All except two species of the genus are native to the Americas. S. fruticosa has a native range that extends from
South Africa to
Ethiopia, across
Arabian Peninsula to
Pakistan,
India and
Sri Lanka[9] and S. erecta is endemic to Tropical Africa, from
Tanzania to
Senegal.[10] The putative species S. sundaica, has a range that encompasses
Malesia but is considered by most authors to be an adventive polypoliod variety of S. humilis.[9] Ecological range extends from savanna and thorn scrub to tropical forest and montane forests.[6]
Species within the genus have many properties that make them valuable forage species. They are capable of
nitrogen fixation and are capable of improving soil fertility in addition to providing high protein stock feed.[12] The genus is also noted for its ability to extract phosphorus from soils where it is not available to other species.[13] 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.[5] Many species are adapted to hot, dry climates and are drought resistant.[14]
These traits have made the genus the world’s most widely used tropical pasture legume.[14]Stylosanthes has been introduced across the tropical world as a pasture species. Its most important use has been in
Australia where over a million hectares of primarily native pasture have been oversown with Stylosanthes species; primarily S. hamata, S. scabra and S. humilis[15] This can lead to a ten-fold increase in productivity, though 2–3 fold increases are normal.[5]Stylosanthes are the most important forage legumes in
South America[16] and the most important pasture legumes of tropical
India.[17]Stylosanthes are also important forage species in tropical Africa.[5]
Stylosanthes are important green manure species in
West and
Central Africa, primarily S. guianensis and S. hamata, and species are planted and harvested for commercial leaf meal production for poultry and pig feed in
China and
India. 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,
Africa and
Australia. S. hamata used for intercropping with grain crops in India and Africa with yield increases up to 25%.[5]
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.[17][18][19][20]
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 than grass.[5]Stylosanthes dominance can also lead to
soil acidification, as soil nitrate levels build up and are then leached down the soil profile.[21]Stylosanthes species are considered invasive species and environmental weeds in
Australia,
Taiwan, the
Pacific Islands and
Hawaii.[6] Many Stylosanthes species are susceptible to
anthracnose fungus (Colletotrichum gloeosporioides) which retards growth and seed development,[5] and this had led to numerous commercial cultivars being abandoned.
Notes
1247810 Some sources treat Stylosanthes acuminata, Stylosanthes aurea, Stylosanthes campestris, Stylosanthes gracilis, Stylosanthes grandifolia, and/or Stylosanthes hippocampoides as synonyms of Stylosanthes guianensis.
3 Some sources treat Stylosanthes bahiensis as a synonym of Stylosanthes pilosa.
5 Some sources treat Stylosanthes cayennensis as a synonym of Stylosanthes hispida.
615 Some sources treat Stylosanthes figueroae and/or Stylosanthes sundaica as synonyms of Stylosanthes humilis.
9 Some sources treat Stylosanthes guineensis as a synonym of Stylosanthes erecta.
11 Some sources treat Stylosanthes macrosoma as a synonym of Stylosanthes montevidensis.
121416 Some sources treat Stylosanthes nervosa, Stylosanthes suffruticosa, and/or Stylosanthes tuberculata as synonyms of Stylosanthes scabra.
13 Some sources treat Stylosanthes subsericea as a synonym of Stylosanthes macrocarpa.
References
^Lavin M, Pennington RT, Klitgaard BB, Sprent JI, de Lima HC, Gasson PE (2001). "The dalbergioid legumes (Fabaceae): delimitation of a pantropical monophyletic clade". Am J Bot. 88 (3): 503–33.
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10.2307/2657116.
JSTOR2657116.
PMID11250829.
^USDA, NRCS (n.d.).
"Stylosanthes". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 4 December 2015.
^Sa R (萨仁); Salinas AD (2010).
"笔花豆属" [61. Stylosanthes Swartz, Prodr. 7, 108. 1788.]. In Wu ZY (吴征镒); Raven PH; Hong DY (洪德元) (eds.).
Flora Republicae Popularis Sinicae [Flora of China]. Vol. 10 (Fabaceae). Missouri Botanical Garden Press, St. Louis, and Science Press, Beijing. pp. 135–136.
ISBN9781930723917. Retrieved 12 February 2014.
^Gillies ACM, Abbott RJ (1996). "Phylogenetic relationships in the genus Stylosanthes (Leguminosae) based upon chloroplast DNA variation". Plant Syst Evol. 200 (3–4): 193–211.
doi:
10.1007/BF00984935.
S2CID28591537.
^
abCook B, Pengelly B, Brown S, Donnelly J, Eagles D, Franco A, Hanson J, Mullen B, Partridge I, Peters M, Schultze-Kraft R (2005).
"Tropical Forages entry for Stylosanthes". Tropical Forages. CSIRO Sustainable Ecosystems (CSIRO), the Department of Primary Industries and Fisheries (DPI&F Queensland), el Centro Internacional de Agricultura Tropical (CIAT), and the International Livestock Research Institute (ILRI). Retrieved 12 February 2014.
^Hall T, Glatzle A (2004).
"Cattle production from Stylosanthes pastures"(PDF). In Chakraborty S (ed.). High-Yielding Anthracnose-Resistant Stylosanthes for Agricultural Systems. Australian Centre for International Agricultural Research (ACIAR). pp. 51–64.
ISBN978-1-86320-442-2.
^Noble AD, Cannon M, Muller D (1997). "Evidence of accelerated soil acidification under Stylosanthes-dominated pastures". Aust J Soil Res. 35 (6): 1309–1322.
doi:
10.1071/S97053.