Trema is a genus 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. They are generally small trees, reaching 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.

Description

The leaves are alternate, simple, long, ovate-acuminate to lanceolate with a long pointed tip, and evenly serrated margins. The fruit is a small drupe 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.

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.

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Image:Bark I IMG 3300.jpg|Bark of T. orientalis at Kolkata, West Bengal, India

File:Trema orientalis (Pigeon Wood) W IMG 2236.jpg|Flowers of T. orientale in Goa, India.

File:Trema orientalis (Pigeon Wood) W2 IMG 2237.jpg|Leaves of T. orientale in Goa, India.

File:Trema orientalis (Pigeon Wood) W2 IMG 2236.jpg|Flowers of T. orientale in Goa, India.

Image:Branches I IMG 3304.jpg|Branches of T. orientale at Kolkata, West Bengal, India

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Species

Trema comprises the following species:

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

Species names with uncertain taxonomic status

The status of the following species is unresolved:

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

References

  • Pacific Island Ecosystems at Risk (PIER) page on Trema orientalis (with photos)