Barlow, Advances in systennatic knowledge Loranthaceae and Viscaceae 
859 
The change in perception of endemism among Australian mistletoes is largely an 
outcome of exploration since 1960, both in the field and in herbaria. Australian 
species have been discovered in New Guinea, and new records of New Guinean 
species have been made in Australia, mostly in Cape York Peninsula. Australian 
species have been revealed in the flora of the Lesser Sunda Islands. Critical studies 
have shown that the mistletoes of New Caledonia are all conspecific with species of 
Australia, New Guinea or New Zealand. The result of these discoveries is that 
mistletoes, especially Loranthaceae, now appear to conform in their species endemism 
levels with the general patterns of angiosperm families in Australia. 
Tlie only slightly doubtful case of endemism involves Mudkrina celastroides. There 
are two old collections from New Zealand, both by collectors who also visited 
Australia, and Barlow (1966) suggested that confusion of labels may have occurred. 
However Norton and Reid (1995) have argued that M. celastroides was present as a 
vagrant in New Zealand, from Australia, and that it became extinct in New Zealand 
some time ago. 
These changes in perception of endemism in Australian mistletoes do not necessarily 
mean that the assumptions on dispersibility are incorrect. Exchanges between 
Sundaland, New Guinea, Australia and probably New Caledonia, as reflected in 
present species distributions, have probably occurred in latest Tertiary or Quaternary 
times. They have probably coincided with the several sea level minima which occurred 
during these times. They are supported by the very common occurrence of mistletoe 
species on more than one of the major islands of the Malesian archipelago. When 
allowances are made for intermittent water barriers, most of the species concerned 
have relatively continuous distributions. They have probably been dispersed over 
continuous land or narrow water barriers by their usual dispersal agents. 
A good example of the limits of such dispersibility involves the Australian species 
Deudrophthoe glabrescens and D. odontocalyx. Both are widespread in open forests of 
northern Australia, but are now also known from the Lesser Sunda Islands, one 
species reaching dry habitats in eastern Java. They have probably reached the region, 
across a narrow water gap, from northwestern Australia, and their distribution in 
Malesia is limited by habitat requirements. 
This example contrasts with the absence of mistletoes (and mistletoe birds) from 
Tasmania, although the fossil record shows that they were present throughout the 
Tertiary period (Macphail et al. 1993). Although habitat requirements in Tasmania 
may be met at the present time, the present water barrier between Tasmania and the 
Australian mainland is apparently too broad for normal dispersal to occur. 
The constraints on mistletoe dispersal imposed by the dispersal agent are best 
illustrated by the few notable exceptions to the common distribution patterns. A few 
loranth species have attained wide distributions in the Pacific, reaching oceanic 
islands. Most striking is Decaisnim forsteriana, whicli ranges from the Solomon Islands 
to Tahiti and the Marquesas. Amyema artensis reaches Samoa and the Caroline Islands. 
Ileostyliis micranthiis, a relatively unspecialized New Zealand species, apparently 
reached Norfolk Island about a century ago. It is significant that these dispersal 
events have all occurred beyond the range of the specialized bird dispersal agents of 
the genus Dicacum, which only reach as far eastwards as the Solomon Islands. 
Strangely, exceptional dispersal events in loranths probably involve disruption of 
the symbiosis between mistletoe and specialized bird dispersal agent (Barlow and 
Schodde 1993). When mistletoe fruits become available to more generalist feeders, 
dispersal may be less efficient but extend over longer distances. 
