426 
seeds across seawater. Further, its distribution 
throughout Asia is thought to have occurred 
during radiation through Malesia where 
opportunities for overland seed dispersal 
coincided with times of low sea levels (Wonn 
& Renner 2006). 
Torres Strait was formed by rising sea 
levels in the Holocene ( c . 8000-6500 years 
before present) that inundated the Arafura 
Plain, a low-lying land bridge that connected 
Australia and New Guinea for much of 
recent geological history (Jennings 1972; 
Woodroffe et ah 2000). Given the occurrence 
of G. gnemon in neighboring areas of central- 
southern New Guinea, it is likely the Torres 
Strait records are refugial populations that 
reflect its biogeographic distribution across 
the Malesian region. 
However, the potential for the taxon to 
have been introduced into Torres Strait by 
human vectors should not be discounted. The 
species is widely cultivated across its range, 
including in New Guinea, and hence it is 
possible that it was translocated to the islands. 
Movements of human populations and trade 
between New Guinea and Torres Strait have 
greatly influenced the distribution patterns 
of a number of important tropical crop plants 
and has influenced cultivation practices 
in the region (Haddon 1935; Barrau 1963; 
Harris 1977; Barham 2000; Denham 2008; 
Denham et ah 2009; McNiven et al. 2006; 
McNiven 2008). Furthermore, the impact of 
Torres Strait islanders upon their pre-contact 
surroundings included the introduction of 
new plant species from other islands (Shnukal 
2004; McNiven 2008), a practice that is 
ongoing in contemporary culture. The fact 
that local people do not have a local name or a 
use for the plant does not mean that it was not 
used in the past. 
Conservation Status 
Across the majority of its range Gnetum 
gnemon is a common tree species in the wild 
that is also widely cultivated throughout 
Malesia. In Torres Strait, a conservative 
estimate of its population size on Badu is 500- 
1000 individuals within an area of available 
habitat of < 200 ha. Surveys carried out by 
Austrobaileya 9(3): 421-430 (2015) 
the authors in 2007,2009,2011,2014 and 2015 
assessed the condition of the habitat as good, 
being free of weeds although diggings by feral 
pigs ( Sus scrofa) were observed throughout 
the habitat. The even age of the canopy 
and the species composition together with 
evidence of old charred stumps indicate that 
the habitat is transitional and subject to past 
burning. Invasive weeds such as Singapore 
daisy ( Sphagneticola trilobata (L.) Pruski), 
praxelis ( Praxelis clematidea R.M.King & 
H.Rob.), annual mission grass ( Pennisetum 
pedicellatum Trin. subsp. pedicellatum ) 
and leucaena ( Leucaena leucocephala 
(Lam.) de Wit) occur on the islands, but are 
mostly associated with habitation and along 
roadsides. Singapore daisy has successfully 
invaded degraded swamp forests within and 
on the margins of the Badu community and 
is considered a serious threat to these habitats 
across the island. 
Resilience to fire of Gnetum gnemon is 
not documented; however, its mesic habitat is 
likely to be sensitive to fire. Fire has been an 
ongoing influence on the island’s vegetation, 
and fire management is an increasing focus 
of the Land and Sea Ranger program (3D 
Environmental 2012a, 2012b). Given the 
small population size and highly localised 
occurrence, there is a risk of stochastic 
extinction of the species on this island. 
The upland rainforest habitat of the 
Mua population is similarly remote and 
inaccessible, and no known direct threats 
are evident. Population size is not known; 
however, the spatial extent of the forest 
type is mapped as < 477 ha (Stanton et ah 
2009). While numerous weeds occur on the 
island they are limited to the margins of the 
island communities Kubin and St Pauls and 
along some major tracks and roads. The 
undisturbed and remote nature of the upland 
habitat suggests that there would appear to 
be a very low risk of stochastic extinction 
of the population. Its lowland occurrence on 
Mua occupies approximately 20 ha within 
a linear band of riparian rainforest located 
three kilometres from the coast. The ecotone 
to adjacent Corymbia and Melaleuca grassy 
woodland vegetation is sharp and controlled 
