Shorea is a genus of about 196 species of mainly rainforest trees in the family Dipterocarpaceae. The timber of trees of the genus is sold under the common names lauan, luan, lawaan, meranti, seraya, balau, bangkirai, and Philippine mahogany.[2]
The majority of Shorea spp. are general flowering species, which is an event occurring at irregular intervals of 3–10 years, in which nearly all dipterocarp species together with species of other families bloom heavily.[5] General flowering is thought to have evolved to satiate seed predators[6] and/or to facilitate pollination.[5] Both explanations apparently hold merit.[7] Flowering is thought to be triggered by droughts that occur during transition periods from La Niña to El Niño.[8] The magnitude of a flowering event is suggested to be dependent on the timing of the droughts associated with the El Niño southern oscillation cycle, with the largest events occurring after an interval of several years with no flowering.[8]
Shorea spp. are insect pollinated. A variety of insects have been identified as pollinators, with species within the sections of Shorea sharing the same insect pollinators. Flowering within a section is sequential within one habitat and species association to prevent competition for pollinators.[9]
Seed predation and mortality have an impact on the reproduction process of dipterocarps such as Shorea. In Singapore, crab-eating macaque and moth larvae are known seed predators.[10]
Taxonomy
Shorea fossils (linked with the modern sal, S. robusta, which is still a dominant tree species in Indian forests) are known from as early as the Eocene of Gujarat, India. They are identifiable by the amber fossils formed by their dammar resin.[11] Other fossils include a Miocene-aged fossilized fruit from the same region; this fruit most closely resembles the extant S. macroptera of the Malay Peninsula.[12]
Of the 148 species of Shorea currently listed on the IUCN Redlist, most are listed as being critically endangered.[13] Some concerns exist regarding the IUCN's listing of dipterocarps, as the criteria used to assess the level of threat are based mainly on animal population characteristics. This is thought to overstate the threat assessment, when applied to long-lived, habitat-specific organisms such as trees.[4]
Many economically important timber trees belong to Shorea. They are sold under various trade names including "lauan", "lawaan", "meranti", "seraya", "balau", "bangkirai", and "Philippine mahogany". The "Philippine mahogany" sold in North America is not a true mahogany at all, but a mixture of woods from the genus Shorea.
Other products from Shorea spp. include dammar and illipe. Dammar is a resin collected from a variety of species. It varies in colour among the different taxonomic groups. Shorea wiesneri is listed in many websites as an important source of dammar;[14] however, this appears to be either a trade name or a synonym.[15][16]
^ abAshton, P. S. "Dipterocarpaceae". In Tree Flora of Sabah and Sarawak, Volume 5, 2004. Soepadmo, E.; Saw, L. G. and Chung, R. C. K. eds. Government of Malaysia, Kuala Lumpur, Malaysia. ISBN983-2181-59-3
^ abSakai, Shoko; K Momose; T Yumoto; T Nagamitsu; H Nagamasu; A A Hamid; T Nakashizuka (1999). "Plant reproductive phenology over four years including an episode of general flowering in a lowland dipterocarp forest, Sarawak, Malaysia". American Journal of Botany. 86 (10): 1414–36. doi:10.2307/2656924. JSTOR2656924. PMID10523283.
^Maycock, Colin R.; R. N. Thewlis; J. Ghazoul; R. Nilus; David F. R. P. Burslem (2005). "Reproduction of dipterocarps during low intensity masting events in a Bornean rain forest". Journal of Vegetation Science. 16 (6): 635–46. doi:10.1658/1100-9233(2005)016[0635:RODDLI]2.0.CO;2.
^ abSakai, Shoko; Rhett D. Harrison; Kuniyasu Momose; Koichiro Kuraji; Hidetoshi Nagamasu; Tetsuzo Yasunari; Lucy Chong; Tohru Nakashizuka (2006). "Irregular droughts trigger mass flowering in aseasonal tropical forests in Asia". American Journal of Botany. 93 (8): 1134–39. doi:10.3732/ajb.93.8.1134. PMID21642179.
^Chong, Kwek Yan; Chong, Rie; Tan, Lorraine W.A.; Yee, Alex T.K.; Chua, Marcus A.H.; Wong, Khoon Meng; Tan, Hugh T.W. (1 November 2016). "Seed production and survival of four dipterocarp species in degraded forests in Singapore". Plant Ecology & Diversity. 9 (5–6): 483–490. Bibcode:2016PlEcD...9..483C. doi:10.1080/17550874.2016.1266404. S2CID89849984.
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