Eucalypt is a descriptive name for woody plants with capsule fruiting bodies belonging to seven closely related genera found across Australasia: Eucalyptus, Corymbia, Angophora, Stockwellia, Allosyncarpia, Eucalyptopsis and Arillastrum.
Evolution and distribution
For an example of changing historical perspectives, in 1991, largely genetic evidence indicated that some prominent Eucalyptus species were actually more closely related to Angophora than to other eucalypts; they were accordingly split off into the new genus Corymbia.
Although separate, all of these genera and their species are allied and it remains the standard to refer to the members of all seven genera Angophora, Corymbia, Eucalyptus, Stockwellia, Allosyncarpia, Eucalyptopsis and Arillastrum as "eucalypts" or as the eucalypt group.
The extant genera Stockwellia, Allosyncarpia, Eucalyptopsis and Arillastrum are recognized as having evolved from ancient lineages of the Myrtaceae family. According to genetic, fossil and morphological evidence, it is hypothesised that they evolved into separate taxa before the evolution of the well known Eucalyptus genus, the related Corymbia, Angophora genera, and all of their many species. These four genera of ancient origins, consisting of six known species, continue today naturally, successfully reproducing and growing in monsoon forests and rainforests, in north-eastern Australia, Arnhem Land plateau, New Guinea, the Moluccas and New Caledonia. However, across the Australian continent since its climatic drying, these humid habitats have become relatively restricted areas compared to present day New Guinea and to ancient times when Australia was part of the Gondwana continent.
Eucalyptus deglupta has naturally spread the furthest from its Eucalyptus genus Australian geographic origins, as the only species known growing naturally in the nearby northern hemisphere, from New Guinea to New Britain, Sulawesi, Seram Island to Mindanao, Philippines. Eucalyptus urophylla also grows naturally as far west as the Flores and Timor islands.
Eucalypts from fire prone habitats are attuned to withstand fire in several ways:
Their seeds are often held in an insulated capsule, which opens only in response to and after the devastation of a bushfire. Once cooled down, the land becomes a freshly fertilised seed bed. Oils in the leaves tend to make the fire more severe and therefore more damaging to less attuned species, giving an evolutionary advantage to the eucalypts. Epicormic buds under the often thick bark of the trunk and branches are ready to sprout new stems and leaves after a fire.
These advantages work well in areas affected by long dry spells.
There are over 700 eucalypt species that dominates landscapes all over Australia, but diversity is reduced in rainforests and arid environments.
- Plant Guide: Eucalyptus, Corymbia and Angophora at Australian Native Plants Society
- Eucalypt Research at Currency Creek Arboretum
- Ladiges, Pauline Y.; Udovicic, Frank; Nelson, Gareth (2003). "Australian biogeographical connections and the phylogeny of large genera in the plant family Myrtaceae". Journal of Biogeography 30 (7): 989–998. doi:10.1046/j.1365-2699.2003.00881.x. ISSN 1365-2699. Retrieved 22 Mar 2013.
- Lyne, A. 1996 "An Introduction to the Eucalypts The Genera Eucalyptus, Corymbia and Angophora" Centre for Plant Biodiversity Research and Australian National Herbarium. Canberra
- Carr, Denis J.; Carr, S.G.M.; Hyland, Bernie P.M.; Wilson, Paul G.; Ladiges, Pauline Y. (2002). "Stockwellia quadrifida (Myrtaceae), a new Australian genus and species in the eucalypt group". Botanical Journal of the Linnean Society 139: 415–421. doi:10.1046/j.1095-8339.2002.00062.x.
- Costermans, L. 2006 "Trees of Victoria and adjoining areas".6th ed. ISBN 0-9599105-4-9