Literature review: Impact of Chilean needle grass ... - Weeds Australia

Figure 3. Recorded distribution of N. neesiana in Australia, September 2006. Source: J. Backholer, Department of Primary
Industries Victoria; data from the Integrated Pest Management System (used in Snell et al. 2007). This map fails to include some
significant outliers in South Australia including Lucindale in the South East, and the Bundaleer area in the Northern Lofty
region.
N.neesiana has a very wide latitudinal range. In South America from approximately the equator (Columbia) to c. 40º S, in
Europe from c. 28-51º N, and in Australia approximately 28-43º S.
There may have been more than one introduction of N. neesiana to Australia (Hocking 2002). Wide separation of initial
populations in each State suggest that this is likely. The geographical origin of Australian populations is unknown (but see
discussion of this question in the section, below).
N. neesiana has a syanthropic distribution (New 1994), strongly associated with towns and cities and within the web of major
roads around Melbourne (Hocking 2007). It is currently most frequent in urban and urban fringe areas (in public open spaces,
vacant land etc.), roadsides, agricultural pastures, and the cultural steppe, and its range expansion in Australia appears to be
dependent to a large extent on human dispersal (Snell et al. 2007). Like many other weeds, its dispersal can be characteristed as
stratified diffusion (Shigesada and Kawasaki 1997), with long distance propagule movement giving rise to isolated new
populations and expansion at the edges of existing populations The extent to which it intrudes into natural habitats without
facilitation by humans is one of the main focuses of this investigation.
History of dispersal in Australia
Identification failures and lack of recognition
The history of dispersal of N. neesiana in Australia is poorly documented because of a widespread lack of recognition of its
presence and failure to accurately identify it. This appears to be a generalised problem with invasive grasses in native grasslands
on a world basis, at least for members of the general public (Witt and McConnachie 2004). In southern Europe N. neesiana has
been widely confused until recently with the closely related N. mucronata (Kunth) R.W. Pohl (Verloove 2005). In New Zealand,
an infestation established at Hawkes Bay in the 1950s was not identified until 1982 (Slay 2001). In Australia, an infestation
discovered at Tamworth, NSW, in 1996 had an estimated age of 30 years (Cook 1999). In discussing whether or not N. neesiana
was spreading in the ACT, the ACT Weeds Working Group (2002 p. 2) suggested that “an increase in ability to identify the
species” may have been the reason for its “presence/abundance ... now being noted”: until awareness campaigns were
implemented, few rural landholders were aware of its existence and even fewer could identify it.
According to Walsh (1998) N. neesiana has probably often been mistaken for native spear grasses Austrostipa spp. Such
mistakes have been made “even by herbarium botanists” (McLaren et al. 1998). The first known Australian collection, made in
October 1934 at Northcote (Melbourne) was originally mis-determined as the native Stipa elatior (Benth.) Hughes (a synonym
of S. scabra var. elatior Benth., now Austrostipa flavescens (Labill.) S.W.L. Jacobs and J. Everett) (McLaren et al. 1998,
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