Document ID: chunk:federal_register_of_legislation:F2007B00384:body:0:p13
Version: federal_register_of_legislation:F2007B00384
Segment Type: other
Provision Reference: 
Character Range: 32360–35242

the Greta Beach Road in the vicinity of Population 2; and
    * maintenance or construction for water supply infrastructure that may be potential habitat [see B.2.2 above].

C.2.3 Weeds

No Weeds of National Significance are known to affect any populations of Asplenium listeri.

Numerous species of weeds have invaded forest margins along roads and tracks and around mining fields, and sparse vegetation communities, such as those on the terraces, are also vulnerable to such invasion.

The very hardy native ferns Nephrolepis multiflora (scurfy sword fern) and Nephrolepis biserrata (broad sword fern) can spread aggressively to form dense and tangled colonies which confound access, and compete strongly with other plants (Swarbrick 1997).  N. multiflora is particularly noted as an invader of mining fields (CofA 2002) where it is often dominant in areas of poor thin soil and limestone pinnacles, while also forming dense thickets more than 2 metres tall in damper, more shaded gullies towards the margins of old mines (DuPuy 1993c).  However, there is no evidence that either species is competing with Asplenium listeri in its exposed cliff-top habitat (Reddell pers. comm.).

With the possible (and uncertain) exception of former habitat that may have been affected by weed invasion following mining, the specialised habitat now occupied by Asplenium listeri makes it unlikely that weed invasion has contributed to the restricted distribution of the species through competition, and there is no reference to weed species in records of known localities.  The most recent survey notes that the species is not subject to tangible threats from invasive weeds (Holmes & Holmes 2002).

C.2.4 Exotic fauna

There are no records indicating any specific threats from the activity of exotic fauna.

The species occasioning most concern on the island in recent times is yellow crazy ant (Anoplolepsis gracilipes), which was introduced accidentally between 1915 and 1934.  It has recently undergone a population explosion and the ants have formed multi-queened 'supercolonies'.  This has had a marked impact on other terrestrial fauna such as land crabs and in turn has changed the vegetation profile in some forest types.  Although Asplenium listeri may be vulnerable to episodic changes in canopy density or encroachment by other vegetation (Holmes & Holmes 2002), the effects brought about by the yellow crazy ant are not considered likely to affect the areas associated with Asplenium listeri (Claussen pers. comm.).

Of greater potential impact may be the giant African snail (Achatina fulica) which feeds on a wide variety of plants but may be expected to take refuge in moist locations, including those favoured by ferns.  It is not known whether this species has had, or is likely to have, any impact on Asplenium listeri.  Although the presence of land crabs appears to restrict