Metrosideros
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{{Taxobox | color = lightgreen | name = Metrosideros | image = Metrosideros_polymorpha.jpg | image_width = 220px | image_caption = Flowers and foliage of M. polymorpha | regnum = Plantae | divisio = Magnoliophyta | classis = Magnoliopsida | ordo = Myrtales | familia = Myrtaceae | genus = Metrosideros | genus_authority = Banks ex Gaertn. | subdivision_ranks = Species | subdivision = see list }}
Metrosideros is a genus of trees native to the islands of the Pacific Ocean, from the Philippines to New Zealand and including the Bonin Islands, Polynesia, and Melanesia. The name derives from the Greek metra or "heartwood" and sideron or "iron". There are approximately fifty species of Metrosideros, in two subgenera: Mearnsia (24 species) and Metrosideros (26 species). Perhaps the best-known species are the Pohutukawa (Metrosideros excelsa), Northern Rata (M. robustus) and Southern rata (M. umbellatus) of New Zealand, and M. polymorpha or ‘Ōhi‘a lehua from the Hawaiian Islands. New Caledonia has seventeen endemic species of Metrosideros, New Zealand has eleven, and New Guinea and Hawai‘i each have five. The remainder are scattered across small islands of the Pacific, with one outlier described from South Africa.
Metrosideros seeds can disperse on the wind, which accounts for their wide distribution from a presumed origin in New Zealand. How the genus reached Hawai‘i appears puzzling because the prevailing Trade Winds blow from the East. However high altitude wind patterns may have brought seeds north from the Marquesas Islands, which molecular evidence suggests as the origin of the Hawaiian species from a single colonizing event (the Hawaiian M. polymorpha is similar to the widespread M. collina found in the Marquesas, and was long classified as a subspecies of it). Considering that the group likely spread north and east from New Zealand, counter to prevailing ground-level winds, this is not surprising.
Metrosideros are often cultivated for their showy red flowers. Some names listed in horticultural catalogs and other publications, such as M. villosa and M. vitiencensis, are actually the names of varieties or cultivars (usually of M. collina) rather than valid scientific species.
Metrosideros species
subgenus Metrosideros
- M. bartlettii (New Zealand)
- M. boninensis (Bonin Islands)
- M. cherrieri (New Caledonia)
- M. collina (from Vanuatu in the southwest to French Polynesia in the east)
- M. engleriana (New Caledonia)
- M. excelsa - Pohutukawa (New Zealand)
- M. gregoryi (Samoa)
- M. humboldtiana (New Caledonia)
- M. kermadecensis (Kermadec Islands)
- M. macropus (Hawaii)
- M. microphylla (New Caledonia)
- M. nervulosa (Lord Howe Island)
- M. nitida (New Caledonia)
- M. ochrantha (Fiji)
- M. oreomyrtus (New Caledonia)
- M. polymorpha - ‘ohi‘a lehua (Hawaii)
- M. punctata (New Caledonia)
- M. robusta - Northern Rata (New Zealand)
- M. rugosa (Hawaii)
- M. sclerocarpa (Lord Howe Island)
- M. tremuloides (Hawaii)
- M. umbellata - Southern Rata (New Zealand)
- M. waialeaiae (Hawaii)
subgenus Mearnsia
- M. albiflora (New Zealand)
- M. angustifolia (South Africa)
- M. brevistylis (New Caledonia)
- M. cacuminum (New Caledonia)
- M. carminea (New Zealand)
- M. colensoi (New Zealand)
- M. cordata (New Guinea)
- M. diffusa (New Zealand)
- M. dolichandra (New Caledonia)
- M. fulgens (New Zealand)
- M. halconensis (Philippines)
- M. longipetiolata (New Caledonia)
- M. operculata (New Caledonia)
- M. ovata (New Guinea)
- M. paniensis (New Caledonia)
- M. parkinsonii (New Zealand)
- M. patens (New Caledonia)
- M. perforata (New Zealand)
- M. porphyrea (New Caledonia)
- M. ramiflora (New Guinea)
- M. rotundifolia (New Caledonia)
- M. salomonensis (Solomon Islands; this species has been variously placed in both subgenera)
- M. scandens (New Guinea)
- M. whitakeri (New Caledonia)
- M. whiteana (New Guinea)
References
- Wagner, W.L., D. R. Herbst, and S.H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. Revised edition. University of Hawai‘i Press and Bishop Museum Press, Honolulu. 1919 pp.
- Wright, S. D., C. G. Yong, S. R. Wichman, J. W. Dawson, and R. C. Gardner. (2001). Stepping stones to Hawaii: a trans-equatorial dispersal pathway for Metrosideros (Myrtaceae) inferred from nrDNA (ITS+ETS). J. Biogeography, 28(6): 769-774.
- Wright, S. D., R. D. Gray, and R. C. Gardner. (2003). Energy and the rate of evolution: inferences from plant rDNA substitution rates in the Western Pacific. Evolution, 57(12): 2893–2898.pt:Metrosideros