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Trema
	Flowers & leaves of Trema orientale at Kolkata, West Bengal, India
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Rosales
Family:	Cannabaceae
Genus:	Trema; Lour. 1790
Species
	About 15 species; see text
Synonyms
	Parasponia Miq. 1851; Sponia Comm. ex Decne. 1834;

Trema is a genus of about 15 species of evergreen trees closely related to the hackberries (Celtis), occurring in subtropical and tropical regions of southern Asia, northern Australasia, Africa, South and Central America, and parts of North America.^[1] They are generally small trees, reaching 10–20 m (33–66 ft) tall.

Taxonomy

Previously included either in the elm family, Ulmaceae, or with Celtis in the Celtidaceae, genetic analysis has shown the Celtidaceae are best placed in the hemp family, Cannabaceae.^[2]

Description

The leaves are alternate, simple, 7–15 cm (2.8–5.9 in) long, ovate-acuminate to lanceolate with a long pointed tip, and evenly serrated margins. The fruit is a small drupe 3–5 mm (0.12–0.20 in) in diameter.

Species associations

Trema species are sometimes used as food plants by the larvae of hepialid moths of the genera Aenetus, including A. splendens, which burrow horizontally into the trunk then vertically down, and Endoclita, including E. malabaricus.

Some Trema species unusually able to live in symbiosis with rhizobia for nitrogen fixation as a non-legume. In this case it is customary to mention these species as a separate genus Parasponia.^[3]

Uses

Trema orientale is widely planted for land reclamation in southern Asia, valued for its tolerance of poor soils due to its ability to fix nitrogen. It is also an invasive species on some Pacific Ocean islands.^[4]

Bark of T. orientalis at Kolkata, West Bengal, India
Flowers of T. orientale in Goa, India.
Leaves of T. orientale in Goa, India.
Flowers of T. orientale in Goa, India.
Branches of T. orientale at Kolkata, West Bengal, India

Species

Trema comprises the following species:^[5]

Trema andersonii (Planch.) Byng & Christenh.
Trema angustifolium (Planch.) Blume
Trema cannabina Lour. – type species - Lesser trema (many synonyms including T. vieillardii (Planch.) Schltr.)
Trema cubense Urb.
Trema discolor (Brongniart) Blume
Trema domingense Urb.
Trema eurhynchum (Miq.) Byng & Christenh.
Trema humbertii J.-F.Leroy
Trema lamarckianum (Roem. & Schult.) Blume – West Indian trema, Lamarck's trema
Trema levigatum Hand.-Mazz.
Trema melastomatifolium (J.J.Sm.) Byng & Christenh.
Trema micranthum (L.) Blume – Jamaican nettle tree
Trema nitidum C.J. Chen
Trema orientale (L.) Blume – Pigeon wood (synonym T. affinis (Planch.) Blume, T. orientalis)
Trema parviflorum (Miq.) Byng & Christenh.
Trema politoria (Planch.) Blume
Trema simulans (Merr. & L.M.Perry) Byng & Christenh.
Trema tomentosum (Roxb.) H.Hara – Poison peach
1. var. tomentosum (Roxb.) H.Hara
2. var. viride (Planch.) Hewson – eastern Australia (synonym T. asperum (Brongn.) Blume)

Species names with uncertain taxonomic status

The status of the following species is unresolved:^[6]

Trema acuminatissima Boerl.
Trema argentea Blume
Trema blancoi Blume
Trema bracteolata Blume
Trema burmanni Blume
Trema carinata Blume
Trema crassifolia Liebm.
Trema glabrescens Blume
Trema glomerata Blume
Trema griffithii Blume
Trema guinensis Priemer
Trema imbricata Blume
Trema lancifolia Ridl.
Trema malaccensis Gand.
Trema morifolia Blume
Trema pallida Blume
Trema philippinensis Elmer
Trema pubigera Blume
Trema rigida Blume
Trema rugosa Blume
Trema scaberrima Blume
Trema sieberi Blume
Trema strigilosa Lundell
Trema strigosa Blume
Trema viridis Blume
Trema vulcanica Merr.

References

^ "Trema micrantha (L.) Blume Jamaican nettletree". The PLANTS Database. United States Department of Agriculture. Retrieved 2009-10-06.
^ Sytsma, Kenneth J.; Morawetz, Jeffery; Pires, J. Chris; Nepokroeff, Molly; Conti, Elena; Zjhra, Michelle; Hall, Jocelyn C. & Chase, Mark W. (2002), "Urticalean rosids: Circumscription, rosid ancestry, and phylogenetics based on rbcL, trnL-F, and ndhF sequences", American Journal of Botany, 89 (9): 1531–1546, doi:10.3732/ajb.89.9.1531, PMID 21665755, S2CID 207690258
^ Op den Camp, R; Streng, A; De Mita, S; Cao, Q; Polone, E; Liu, W; Ammiraju, JS; Kudrna, D; Wing, R; Untergasser, A; Bisseling, T; Geurts, R (18 February 2011). "LysM-type mycorrhizal receptor recruited for rhizobium symbiosis in nonlegume Parasponia". Science. 331 (6019): 909–12. doi:10.1126/science.1198181. PMID 21205637.
^ Hanum, Faridah; van der Maeson, L.J.G (1997). "Plant Resources of South East Asia" (PDF). Core. p. 25. Retrieved 2022-11-14.
^ Govaerts R. "Trema Lour". Plants of the World Online. Board of Trustees of the Royal Botanic Gardens, Kew. Retrieved 22 March 2023.
^ "The Plant List entry for Trema". The Plant List, v.1.1. Royal Botanic Gardens, Kew and the Missouri Botanical Garden. September 2013. Retrieved 14 December 2020.