Document ID: chunk:federal_register_of_legislation:F2007B00384:body:0:p9
Version: federal_register_of_legislation:F2007B00384
Segment Type: other
Provision Reference: 
Character Range: 21805–24692

occurrences - reflecting uncertainty regarding reasons for the extremely limited distribution of the species and potential threats to survival; and
    * taller vegetation structures on the inland side of cliff-top sites and relatively open exposure to the coast (refer C.1 below)

The environs of any additional populations that are either newly confirmed or newly located or more precisely defined within the term of this plan need to be similarly regarded.

Due to the uncertainty of current location information and limited knowledge on the ecology and specific habitat requirements, the habitat critical to the survival of the species cannot be mapped accurately at this time.

To protect the species the precise locations of all populations should remain confidential in any listing or public record.  As an aid to confidentiality, a buffer of at least 1 kilometre around all known populations should be applied in publicly available mapping for EPBC referral and enquiry purposes.

PART C: THREATS

C.1 Biology and Ecology relevant to threatening processes

Asplenium listeri is a small terrestrial fern with shortly creeping rhizomes and fronds up to 9cm long held in a crown.  The species is described (DuPuy 1993b) as an occasional (rare) component of the sparse vegetation community characteristic of inland cliffs which rise above marginal rainforest on the terraces.  It is not recorded from the other vegetation zones (being primary rainforest; marginal terrace rainforest; open, scrubby and vine forests; coastal fringe; shorecliffs/spray zone; and mined areas).

Asplenium listeri appears to be quite specialised in its habitat of limestone rock crevices in otherwise dry and exposed sites, where few other species are found.  These sites tend to be rocky and narrow cliff-top strips up to 15 metres wide, between a very open aspect on the seaward side and a forest structure increasing up to 40 metres high on the inland side (Reddell pers. comm.).  Such situations are well placed to interrupt and capture moist flow from south-easterly trade winds (Tranter pers. comm.).  Some sites may be partly shaded, beneath or near Ficus microcarpa (Holmes & Holmes 2002).

It is highly likely that distribution and propagation of the species are related to moisture retention.  While the island experiences generally high rainfall, the limestone outcrops are highly porous due to joints and solution.  As a result, surface water is rare, being restricted to perennial springs.  These are effluxes associated with the junction of limestone with underlying basalt, and surface flow continues where they flow over volcanic rock.  Most effluxes lie at elevations below the occurrences of Asplenium listeri (which are >100 metres elevation).

It is interesting to note that the first collection of the species by Lister took place at the peak of the dry season and probably on the