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 comprise six known species, restricted to monsoon forests and rainforests in north-eastern Australia, the
Arnhem Land plateau,
New Guinea, the
Moluccas and
New Caledonia. These genera are recognised as having evolved from ancient lineages of the family
Myrtaceae. According to genetic, fossil and morphological evidence, it is hypothesised that they evolved into separate taxa before the evolution of the more widespread and well-known genera
Eucalyptus,
Corymbia and
Angophora, and all of their many species.
Eucalyptus deglupta has naturally spread the furthest from the Australian geographic origin of the genus
Eucalyptus, being 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. == Adaptations ==