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Rafflesia
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Rafflesia is a genus of parasitic flowering plants. It was discovered in the Indonesian rain forest by an Indonesian guide working for Dr. Joseph Arnold in 1818, and named after Sir Thomas Stamford Raffles, the leader of the expedition. It contains approximately 26 species (including four incompletely characterized species as recognized by Meijer 1997), all found in southeastern Asia, on the Malay Peninsula, Borneo, Sumatra and Kalimantan, West Malaysia, and the Philippines. The plant has no stems, leaves or true roots. It is an endoparasite of vines in the genus Tetrastigma, spreading its root-like haustoria inside the tissue of the vine. The only part of the plant that can be seen outside the host vine is the five-petaled flower. In some species, such as Rafflesia arnoldii, the flower may be over 100 cm in diameter, and weigh up to 10 kg. Even the smallest species, R. manillana, has 20 cm diameter flowers. The flowers look and smell like rotting meat, hence its local names which translate to "corpse flower" or "meat flower" (but see below). The vile smell that the flower gives off attracts insects such as carrion flies, which transport pollen from male to female flowers. Little is known about seed dispersal. However, tree shrews and other forest mammals apparently eat the fruits and disperse the seeds. Rafflesia is an official state flower of Sabah in Malaysia, as well as for the Surat Thani Province, Thailand.
The name "corpse flower" applied to Rafflesia is confusing because this common name also refers to the Titan Arum (Amorphophallus titanum) of the family Araceae. Moreover, because Amorphophallus has the world's largest unbranched inflorescence, it is sometimes mistakenly credited as having the world's largest flower. Both Rafflesia and Amorphophallus are flowering plants, but they are still distantly related. Rafflesia arnoldii has the largest single flower of any flowering plant, at least when one judges this by weight. Amorphophallus titanum has the largest unbranched inflorescence, while the Talipot palm (Corypha umbraculifera) forms the largest branched inflorescence, containing thousands of flowers; this plant is monocarpic, meaning that individuals die after flowering.
Classification
Species
Unverified species
- Rafflesia borneensis
- Rafflesia ciliata
- Rafflesia titan
- Rafflesia witkampii
Comparison of mitochondrial DNA (mtDNA) sequences of Rafflesia with other angiosperm mtDNA indicated that this parasite evolved from photosynthetic plants of the order Malpighiales.. Another study from that same year confirmed this result using both mtDNA and nuclear DNA sequences, and showed that three other groups traditionally classified in Rafflesiaceae were unrelated. A more recent study found Rafflesia and its relatives to be embedded within the family Euphorbiaceae, which is surprising as members of that family typically have very small flowers. According to their analysis, the rate of flower size evolution was more or less constant throughout the family except at the origin of Rafflesiaceae, where the flowers rapidly evolved to become much larger before reverting to the slower rate of change.
Philippine speciesSince 2002 there has been a tremendous amount of activity by Filipino scientists who have discovered and named several new species of Rafflesia. Before this time there were two species known: R. manillana and R. schadenbergiana, the latter of which was last seen in 1882 on Mt. Apo in Davao Province on Mindanao Island, but was thought to be extinct. The following gives a chronicle of these activities:
- 2002. A Rafflesia was found in the mountains of Antique Province that differed from any previously described. It was named Rafflesia speciosa by Barcelona and Fernando (Kew Bulletin, 57: 647-651, 2002).
- 2005. Another Rafflesia was discovered in the Philippines by Drs. Fernando and Ong on remote Mt. Candalaga, Maragusan, Campostela Valley Province on Mindanao. It was named Rafflesia mira by Fernando and Ong (2005. Asia Life Sciences 14: 263-270). Another group (Madulid et al. 2005 Acta Manilana 53: 1-6) published another name (R. magnifica) later, thus R. mira stands as the nomenclaturally valid name. R. mira (29 cm in diameter), is much larger than R. speciosa (18-20 cm) of Antique Province, and definitely larger than Luzon’s R. manillana (14-20 cm in diameter).
- 2005. During his expedition to Mt. Igtuog and Mt. Sakpaw in the Central Panay mountain range in April 2005, Renee Galang discovered a previously undescribed Rafflesia. This was named R. lobata by Galang and Madulid (2006, Folia Malaysiana 7: 1-8).
- 2006. Danny Balete collected a previously undescribed species of Rafflesia in 1991 in the Bicol Region of southern Luzon. The collection was not recognized as a new species until further field work confirmed that this taxon was different than R. manillana. Several new populations have also been seen in the Camarines Sur Province [Mt. Isarog and Mt. Asog (or Mt. Iriga)] in the vicinity of Buhi and Iriga City. This was named R. baletei by Barcelona, Cajano, and Hadsall (2006. Kew Bulletin 61: 231-237). The names R. irigaense or R. irigaenses are invalid and refers to the same taxon.
- 2007. In 1994 Pascal Lays rediscovered buds of R. schadenbergiana in South Cotabato. His paper reporting this result has only recently been published. Moreover, Dr. Julie Barcelona reports on the discovery of yet another population of this rare species in Bukidnon (Flora Malesiana Bulletin, submitted; see also Parasitic Plant Connection).
- 2007. Mt. Banahaw in Luzon, a popular destination for mountaineering and religious groups seemed, until recently, an unlikely spot to find a new species of Rafflesia. But such was the case. Ironically, two papers have been published naming this Rafflesia as a new species. Apparently the first one was by Madulid et al. in 2006 (Philippine Scientist 43: 43–51) and the second by Barcelona et al. in 2007 (Blumea 52: 345–350). Thus, the correct name is R. banahawensis, not R. banahaw.
See also
External links
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