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into the vegetation structure, often having high host specificity, and often then 
displaying visual resemblance to the preferred hosts (Barlow and Wiens 1977). Amyenia 
is found everywhere in Australia where mistletoes occur. This group clearly has had 
a long history in Australia, consistent with in situ development as part of the 
Gondwanan floristic element. 
The remaining Australian genera of Loranthaceae are Decaisnina, Amylotheca, Lysiana, 
Dendrophthoe and Benthmnina. They contrast strongly with the group described above 
in morphology, karyology and usually in geography. Decaisnina, Amylotheca and 
Lysiana have a genome of x = 12, with large chromosomes, and differ significantly in 
ovary structure and germination pattern from the Amyema group. Dendrophthoe and 
Benthamina have x = 9, with relatively small chromosomes, and differ from the 
Amyema group in features of inflorescence and floral structure. These five genera 
belong to two groups with major centres of speciation and diversity in the southeast 
Asian region, and strong links with African Loranthaceae. In the Malesian region 
their species richness attenuates towards the east, and in Australia they are mostly 
represented by a few species in the tropics and along the east coast. In Australia 
these genera can be clearly identified with the Intrusive Element of the flora, which 
entered the region following middle/late Tertiary contact between the Australian 
and Sunda plates. Their preferred hosts are primarily members of the Intrusive 
Element occurring in rain forests and monsoon woodlands, although eucalypts are 
occasionally parasitized. 
Even within the family Loranthaceae in Australia, then, there is integration between 
a Gondwanan component of long standing in the region, and an Intrusive component 
which has arrived more recently from Malesia (Barlow 1990). A possible explanation, 
which conforms with the phyletic relationships of Asian and African Loranthaceae, 
is that Loranthaceae endured the passage northwards on the Indian fragment 
following the breakup of Gondwana. This fragment presumably carried stocks which 
had already differentiated morphologically and genomically from other Gondwanan 
Loranthaceae (Barlow 1990). 
The most interesting genus in this scenario is Lysiana, endemic to Australia, with 
eight species together covering most of the mainland. If Lysiana is indeed derived 
from an Intrusive stock, it is a good illustration of the extent to which this floristic 
element has adapted to and colonized even temperate habitats in Australia (Barlow 
1990,1993). Even here, however, the host preferences are a key to the origin, because 
few of the preferred hosts are old Gondwanan genera. Although Acacia and Casuarina 
are commonly parasitized. Eucalyptus is not among recorded hosts. 
Viscaceae — a Laurasian family? 
In contrast, the Viscaceae do not clearly exhibit Gondwanan links like the 
Loranthaceae. At least four of the seven genera (Ginaltoa, Korthalsella, Notothixos, 
Viscum) appear to be centred in the southeast Asian/Malesian region (Barlow 1983b). 
A fifth genus, Arceuthobium, whilst species-rich in North America, is probably Asian 
in origin (Hawksworth and Wiens 1972). An eastern Asian origin for Viscaceae has 
therefore been postulated (Barlow 1983b), with Arceuthobium, Dendrophthora and 
Phoradendron reaching the New World via the Tertiary Beringian land connection. 
The family may ultimately be of Gondwanan origin (Barlow 1990), but its major 
diversification was probably a Tertiary palaeotropic Laurasian event. 
All four genera of Viscaceae in Malesia are centred there or in southeast Asia, and 
show some attenuation across Charles's Line to Papuasia, Australia and the Pacific. 
