Literature review: Impact of Chilean needle grass ... - Weeds Australia
Literature review: Impact of Chilean needle grass ... - Weeds Australia
Literature review: Impact of Chilean needle grass ... - Weeds Australia
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was once widespread in south- eastern <strong>Australia</strong> but in 1993 there were only three known populations recorded since 1950, one<br />
in the ACT and two in Victoria (Edwards 1994). Edwards (1994) investigated eight additional likely sites in Canberra and one in<br />
NSW and found populations at all except one in central Canberra. Recent surveys have found it at 43 sites in NSW and 12 in the<br />
ACT (Endersby and Koehler 2006). The South <strong>Australia</strong>n distribution is based on a single individual from Bordertown (Edwards<br />
1994) and it has not been found recently in that State (O’Dwyer 2004). Endersby and Koehler (2006 citing C. O’Dwyer pers.<br />
comm.) stated that: “Prior to 2003, the species had been reported from just six areas in Victoria – Broadford, Tallarook,<br />
Flowerdale, Dunkeld, Hamilton and near Nhill-Salisbury”. However that is a highly misleading statement that should have been<br />
qualified, perhaps as ‘probably extant populations’. Edwards’ (1994 pp. 32-33) map and list <strong>of</strong> historical records showed many<br />
more localities with much wider distribution. The map provided by O’Dwyer(1999) apparently leaves out historical records<br />
noted by Edwards (1994) including Ararat, Bendigo, Castlemaine, Gisbourne, Maryborough, Monbulk, Nagambie and Woodend.<br />
The map provided by O’Dwyer (2004) is more complete, showing c. 24 distribution localities prior to 1970 and c. 7 sites after<br />
that time. Gilmore et al. (2008) stated that there were only four records in the Melbourne area prior to 2003, near Keilor,<br />
Broadmeadows and Laverton. Recent records in Victoria include <strong>grass</strong>lands in the Deer Park, Craigieburn and Epping areas<br />
(Endersby and Koehler 2006, Gilmore et al. 2008), at Greenvale and Woodlands Historic Park (personal observations, Gilmore<br />
et al. 2008) and Moyhu (personal observations).<br />
Edwards (1994) considered S. plana to be restricted to Austrodanthonia patches in native <strong>grass</strong>lands, mostly on low hills or rises,<br />
sometimes in grazed and mown areas. He stated (p.34): “The foodplant is known to be Danthonia”. Driscoll (1994) stated that<br />
the moth requires Austrodanthonia carphoides and A. auriculata <strong>grass</strong>land for survival. According to O’Dwyer (1999) and<br />
O’Dwyer and Attiwill (1999) S. plana inhabits native <strong>grass</strong>lands and <strong>grass</strong>y woodlands with >40% Austrodanthonia cover with<br />
some sites having up to 75% cover, on soils ranging from sands, through loams to clays, with available P below 14μg/g.<br />
O’Dwyer (2004) states that its habitat is native <strong>grass</strong>lands dominated by Austrodanthonia spp. particularly including also A.<br />
eriantha and A. setacea. She noted that oviposition by S. plana has not been observed. At Craigieburn and Epping, Victoria, it<br />
has recently been found in habitat previously considered atypical, dominated by T. triandra (Endersby and Koehler 2006).<br />
The flight period <strong>of</strong> S. plana is variable from place to place and year to year (Driscoll 1994), possibly late October peaking in<br />
mid November and early December and through to at least the end <strong>of</strong> January in ACT (Edwards 1994), mainly 11 am – 2 pm<br />
(Edwards 1994). According to Driscoll (1994) the likely duration <strong>of</strong> the larval stage is 21-22 months. O’Dwyer (2004 p. 3)<br />
suggests “about 11 months”. Edwards (1994) mentioned the absence <strong>of</strong> parasite records, and recorded some bird predators <strong>of</strong><br />
adults. O’Dwyer (2004) mentioned Willie Wagtail Rhipidura leucophrys and robber fly (Asilidae) predation <strong>of</strong> adults.<br />
Much <strong>of</strong> the literature on S. plana repeats unproved suppositions or speculation as facts, usually including Austrodanthonia spp.<br />
being food plants and native <strong>grass</strong>land habitat specificity, and fails even to provide full lists <strong>of</strong> known sites <strong>of</strong> occurrence. A<br />
large number <strong>of</strong> research projects on the species have failed to establish its most basic life history, including hosts plants and the<br />
duration <strong>of</strong> the larval stage. The most recent information (e.g. Braby and Dunford 2006, Endersby and Koehler 2006, Gilmore et<br />
al. 2008) indicate it is a widespread and common species that thrives in degraded pastures, including areas dominated by N.<br />
neesiana. The development <strong>of</strong> knowledge <strong>of</strong> this species is instructive. It has never been, as claimed by New (2000) a species<br />
“appraised reasonably fully” and its use as a flagship taxon has been <strong>of</strong> little value even for its own preservation, since so much<br />
<strong>of</strong> its basic life cycle remains poorly understood.<br />
S. selene has been considered a particularly significant taxon because it exists in five distinct parthenogenetic forms (Douglas<br />
2000); however it has not been listed under Victoria’s Flora and Fauna Guarantee Act (Department <strong>of</strong> Sustainability and<br />
Environment 2009a) (Table 18).<br />
The Cryptic Sun Moth S. theresa Doubleday is morphologically similar to other Synemon species in the <strong>grass</strong>-feeding group and<br />
it has been suggested that it too feeds on Austrodanthonia (Douglas 2003b). No existing populations are known but locality data<br />
on old specimen labels indicate it was an inhabitant <strong>of</strong> open <strong>grass</strong>y woodland with Austrodanthonia and Austrostipa in the<br />
understorey (Douglas 2003b). It is listed as a threatened species under the Victorian Flora and Fauna Guarantee Act<br />
(Department <strong>of</strong> Sustainability and Environment 2009a).<br />
The Orange Sun Moth S. nais Klug occurs in the Mallee in Victoria and in South <strong>Australia</strong> and Western <strong>Australia</strong>. In the Mallee<br />
it is known from “a floristically diverse combination <strong>of</strong> open <strong>grass</strong>y areas interspersed with stands <strong>of</strong> trees and shrubs”, the<br />
<strong>grass</strong>y areas dominated by Austrodanthonia setacea and Austrostipa spp. (Douglas 2003b p. 7). Oviposition behaviour suggests<br />
that A. setacea and an unidentified Austrostipa sp. may be larval hosts (Douglas 2003b). It is listed as a threatened species under<br />
the Victorian Flora and Fauna Guarantee Act (Department <strong>of</strong> Sustainability and Environment 2009a).<br />
Only a single population <strong>of</strong> the Striated Sun Moth Synemon sp. aff. collecta is known in Victoria, from near Shelley. Its habitat<br />
may have originally been open <strong>grass</strong>y woodland and <strong>grass</strong>land dominated by Austrodanthonia spp. (Douglas 2003b).<br />
Edwards (1996) noted that the “<strong>grass</strong> feeding species in particular have sufferred drastic reductions in distribution from the use<br />
<strong>of</strong> <strong>grass</strong>lands for agriculture”; urban development threatens populations <strong>of</strong> some species and invasion by introduced weeds has<br />
been identified as a threat to S. plana: “Without grazing or mowing the low-growing natives can become shaded and eventually<br />
choked out by taller exotic plants” (Edwards 1993 p. 17, Edwards 1994). In western Victoria this species survives in sheepgrazed<br />
Austrodanthonia pastures in which fertilisers and pesticides are not used (Dear 1996). According to Douglas and Marriott<br />
(2003 p. 90): “Any disturbance, through ploughing and other types <strong>of</strong> cultivation and/or excessive invasion <strong>of</strong> exotic <strong>grass</strong>es and<br />
forbs” leads to the disappearance <strong>of</strong> Synemon spp. Exotic perennial and annual <strong>grass</strong>es, not including Nassella spp., are listed as<br />
threats by O’Dwyer (2004). Cultivation in Two Wells area <strong>of</strong> South <strong>Australia</strong> was blamed for the extinction <strong>of</strong> S. selene in South<br />
<strong>Australia</strong> (Douglas 2000). These opinions should be viewed with some scepticism since they are based almost solely on<br />
observational correlations. S. plana continues to exist in areas <strong>of</strong> the ACT subject to light grazing or mowing, and the<br />
underground larval stage probably confers resistance to fire (Driscoll 1994). Douglas (2000) suggested that moderate disturbance<br />
from grazing, slashing or possibly fire appears to be necessary for S. selene to flourish (Douglas 2000). Douglas and Marriott<br />
(2003) advocated weed control and regular mowing, burning or grazing to remove accumulated dead <strong>grass</strong> “that provides cover<br />
for predators and reduces the extent <strong>of</strong> acceptable sites for oviposition”.<br />
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