National recovery plan for the Nightcap Oak (Eidothea hardeniana)

Threatened Species Unit, Western
New South Wales Department of Environment and Conservation, 2004
ISBN: 0 7313 6781 2

4. Threats and Management Issues

4.1 Current Threats

Lack of knowledge

As the Nightcap Oak has only recently become known to science, there is little information available about the species biology and ecology. Basic information such as habitat requirements is needed in order to adequately manage the species.

Small population size

Small population size makes the Nightcap Oak vulnerable to inbreeding depression (Ellstrand & Elam 1993) and stochastic events.

Fire

There is no information on the response of the Nightcap Oak to fire. As the species occurs in rainforest, it is presumed that fire is not needed for germination and reproduction. As fire would change the habitat conditions of the site, it is likely that fire would adversely impact upon the Nightcap Oak.

Weeds

Exotic plant species are not currently considered to be a threat in the habitat of the Nightcap Oak.

Tourism and site visitation

Commercial and recreational activities such as bushwalking, mountain biking and other outdoor activities are becoming increasingly popular in the Nightcap Range area. These activities may have an impact on the Nightcap Oak from direct impacts such as trampling and potential indirect impacts such as the introduction of pathogens or weed propagules.

Visitation and potential collection by enthusiasts may also constitute a significant threat to the species through those impacts listed above as well as a potential reduction in the recruitment of the species by the removal of propagules.

Breeding system

A potentially limiting factor is the breeding system of the Nightcap Oak. It is not known whether the Nightcap Oak is self-compatible or self-incompatible (section 3.5). Self-incompatibility requiring obligate cross-pollination between plants is common in other members of the Proteaceae including some species of Persoonia (Krauss 1994), Telopea (Whelan & Goldingay 1989) and Banksia (Goldingay et al. 1991) and this could present special problems for a reduced population of trees like the Nightcap Oak.

Natural rates of fecundity drop when parents cross with offspring or siblings exchange pollen (Richards 1986).

If the Nightcap Oak is pollinated by beetles, katydids and hover flies, natural rates of pollen flow between individual trees will be limited as these insects do not show the long-range foraging patterns associated with organisms such as large-bodied bees, sphinx moths, honeyeaters or flying foxes (Bernhardt pers comm).

If the Nightcap Oak is pollinated by only one, or a small number of insect species, then conservation of these species must also be ensured in managing the Nightcap Oak.