Myrtaceae

Encyclopedia : M : MY : MYR : Myrtaceae

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The Myrtaceae or Myrtle family are a family of dicotyledon plants, placed within the order Myrtales. Myrtle, clove, guava, feijoa, allspice, and eucalyptus belong here. All species are woody, with essential oils, and flower parts in multiples of four or five. One notable character of the family is that the phloem is located on both sides of the xylem, not just outside as in most other plants. The leaves are evergreen, alternate to mostly opposite, simple, and usually with an entire (not toothed) margin. The flowers have a base number of five petals, though in several genera the petals are minute or absent. The stamens are usually very conspicuous, brightly coloured and numerous.

The family Myrtaceae has at least 3000 species distributed in 130-150 genera. They have a wide distribution in tropical and warm-temperate regions of the world, and are typically common in many of the world's biodiversity hotspots. Genera with capsular fruits such as Eucalyptus, Corymbia, Angophora, Leptospermum, Melaleuca, Metrosideros are restricted to the Old World, apart from the monotypic genus Tepualia in Chile. Genera with fleshy fruits have their greatest concentrations in eastern Australia and Malesia (the Australasia ecozone) and the Neotropics. Eucalyptus is a dominant, nearly ubiquitous genus in the more mesic parts of Australia and extends north sporadically to the Philippines. Eucalyptus regnans is the tallest flowering plant in the world. Other important Australian genera are Callistemon (bottlebrushes), Syzygium, and Melaleuca (paperbarks). The genus Osbornia, native to Australasia, are mangroves. Eugenia, Myrcia, and Calyptranthes are among the larger genera in the neotropics.

Historically, the Myrtaceae were divided into two subfamilies.

• Subfamily Myrtoideae have fleshy fruits and opposite, entire leaves. Most genera in this subfamily have one of three easily recognized types of embryos. The genera of Myrtoideae can be very difficult to distinguish in the absence of mature fruits. The Myrtoideae are found worldwide in subtropical and tropical regions, with centres of diversity in the Neotropics, northeastern Australia, and Malesia.
• Subfamily Leptospermoideae has dry, indehiscent fruits (capsules) and leaves arranged spirally or alternate. The Leptospermoideae are found mostly in Australasia, with a centre of diversity in Australia. Many genera in Western Australia have greatly reduced leaves and flowers typical of more xeric habitats.

The division of the Myrtaceae into the Leptospermoideae and Myrtoideae was challenged by a number of authors, including Johnson and Briggs (1984), who identified 14 tribes or clades within the Myrtaceae, and found the Myrtoideae to be polyphyletic. A molecular analysis by Wilson, O'Brien et. al. (2001) found eleven strong groupings within the family, including many of the groupings identified by Johnson and Briggs. Further molecular analysis by Sytsma and Litt (2002) found that the Neotropic Myrtoideae grouping fit within the paraphyletic Leptopermoideae.

The genera Heteropyxis and Psiloxylon, which some authorities include in Myrtaceae, are here placed as separate families by most authors, based on evidence of their divergence before the origin of the common ancestor of the Myrtaceae.

Genera

Accara Acmena Acmenosperma Actinodium Agonis Allosyncarpia Amomyrtella Amomyrtus Angasomyrtus Angophora Archirhodomyrtus Arillastrum Astartea Asteromyrtus Austromyrtus Backhousia Baeckea Balaustion Barongia Basisperma Beaufortia Blepharocalyx Callistemon Calothamnus Calycolpus Calycorectes Calyptranthes Calyptrogenia Calythropsis Calytrix Campomanesia Carpolepis Chamelaucium Chamguava Choricarpia Cleistocalyx Cloezia Conothamnus Corymbia Corynanthera Cupheanthus Darwinia Decaspermum Eremaiea

Eucalyptopsis Eucalyptus Eugenia Feijoa (syn. Acca) Gomidesia Gossia Hexachlamys Homalocalyx Homalospermum Homoranthus Hottea Hypocalymma Kania Kjellbergiodendron Kunzea Lamarchea Legrandia Lenwebbia Leptospermum Lindsayomyrtus Lithomyrtus Lophomyrtus Lophostemon Luma Lysicarpus Mallostemon Marlierea Melaleuca Meteoromyrtus Metrosideros Micromyrtus Mitranthes Mitrantia Monimiastrum Mosiera Myrceugenia Myrcia Myrcianthes Myrciaria Myrrhinium Myrtastrum Myrtella Myrteola

Myrtus Neofabricia Neomitranthes Neomyrtus Ochrosperma Octamyrtus Osbornia Paramyrciaria Pericalymma Phymatocarpus Pileanthus Pilidiostigma Piliocalyx Pimenta Pleurocalyptus Plinia Pseudanamomis Psidium Purpureostemon Regelia Rhodamnia Rhodomyrtus Rinzia Ristantia Scholtzia Siphoneugena Sphaerantia Stereocaryum Stockwellia Syncarpia Syzygium Tepualia Thryptomene Tristania Tristaniopsis Ugni Uromyrtus Verticordia Waterhousea Welchiodendron Whiteodendron Xanthomyrtus Xanthostemon

References

• Johnson, L.A.S. and Briggs, B.G. 1984. Myrtales and Myrtaceae – a phylogenetic analysis. Annals of the Missouri Botanic Garden 71: 700-756.
• Wilson, Peter G., O'Brien, Marcelle M., Gadek, Paul A., and Quinn, Christopher J. 2001. "Myrtaceae Revisited: A Reassessment of Infrafamilial Groups". American Journal of Botany 88 (11): 2013–2025. Available [online] (pdf file).
• Sytsma, Kenneth J. and Amy Litt. 2002. Tropical disjunctions in and among the Myrtaceae clade (Myrtaceae, Heteropyxidaceae, Psiloxylaceae, Vochysiaceae): Gondwanan vicariance or dispersal? (Abstract). Botany 2002 Conference, University of Wisconsin, Madison, Wisconsin, August 4-7 2002.

 

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