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An exceptional case of a different nature is Korthalsella (Viscaceae), which is 
widespread in the Pacific and also reaches remote Indian Ocean islands. In this 
genus the seeds are very small, and are probably dispersed by external attachment 
to birds rather than by ingestion. This presumably allows the seeds to remain with 
the bird dispersal agent for a longer time (Barlow 1983a). 
Advances in knowledge of Australian mistletoes thus show them to be a very typical 
component of the Malesian/ Australasian flora. Although normally of low dispersibility, 
they have migrated through the region, in several directions, as geophysical and biotic 
circumstances have allowed. Their distributions in the region are probably more a 
function of ecological requirements, and of time, than strictly of geography. 
Mistletoes and conservation issues 
Much current research interest in Australian mistletoes is concerned with questions of 
environmental impact. In New Zealand, mistletoes are under serious threat, largely 
through predation by the introduced Australian brush-tailed possum (Norton and 
Reid 1995). In Australia, in contrast, mistletoes are perceived to be increasing in 
abundance, and in some situations to be a threat to their host populations (Reid 1995). 
Mistletoes are recognized as a problem primarily in situations where the forest habitat 
has been substantially altered. Heavy infestations, and host tree death, are commonly 
reported along roadsides, in parks and reserves, and in remnant vegetation in rural 
areas. Scattered or isolated trees are presumably targets for higher levels of visitation 
by mistletoe birds, and provide good conditions for mistletoe establishment. 
There is increasing awareness that a long liistory of habitat disturbance in Australia has 
brought major changes in the structure of biotic communities, even in the absence of 
introductions of exotic species (Flannery 1994). Mistletoes have clearly become part of 
this process in this century. They have intricate symbiotic relationships with their hosts, 
their dispersal agents, and with their predators (Barlow and Wiens 1977). Changes in 
these interactions have altered mistletoe balance in both directions. In Australia, even 
though they are native plants, mistletoes are emerging as serious environmental weeds. 
Some current research, especially by N. Reid and colleagues at the University of New 
England, is aimed at better understanding these interactions, and at appropriate 
environmental management. Implications for forestry and reforestation, both in Australia 
and beyond, are serious, and there is need to increase research capacity in this area. 
Conclusion 
Loranthaceae and Viscaceae have become model groups for study of plant evolution and 
adaptation, biogeography, physiology, genetics and conservation management. Knowledge 
derived from Australian studies has made a major contribution in aU of these fields. 
Advances in knowledge have been very significant in the last 40 years, and have been 
driven by progress in understanding the systematics and relationships of the species. 
References 
Agardh, J.G. (1858) Theoria Systematis Plantarmn. (Gleerup: Lund). 
Barlow, B.A. (1962) Studies in Australian Loranthaceae. 1. Nomenclature and new additions. Proc. 
Linn. Soc. New S. Wales 87: 51-61. 
Barlow, B.A. (1963) Studies in Australian Loranthaceae. IV. Chromosome numbers and their 
relationships. Proc. Linn. Soc. Neiv S. Wales 88; 151-160. 
