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

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Insect diversity in diverse central European meadows is approximately 1500 species (Tscharntke and Greiler 1995). Comparable data is not available for Australia. Yen (1999) found what appeared to be lower invertebrate diversity at ordinal (Order) or higher levels in the fauna of Derrimut Grassland compared to other, non-grassland regions of Victoria, but cautioned that a range of methodological factors might be the cause. Farrow (1999) found 328 morphospecies by sweep net sampling of 11 native grasslands in the ACT, considered to be a good representation of the canopy fauna, but excluding Lepidoptera, almost all Diptera and some minor orders. Similarly, Farrow (2006) found an estimated 383 species at 15 grasslands sites. Yen, Horne, Kay and Kobelt (1994a) found a total of 210 spp. in Victorian Basalt Plains grasslands remnants, but surveyed only three orders as a whole (Coleoptera, Hemiptera and Orthoptera) and just a small part (Formicidae) of another (Hymenoptera). The rest of the Hymenoptera along with the unsurveyed orders Lepidoptera and Diptera are all highly speciose, with micro-Hymenoptera in particular being highly diverse (Farrow 1999 2006). Increased insect diversity and biomass is generally correlated with increased floristic diversity, structural complexity (including vertical stratification) of the vegetation and plant biomass (Tscharntke and Greiler 1995, Ens 2002a). However if increased biomass results in reduced floristic diversity, invertebrate diversity is likely to decline (e.g. Hadden and Westbrooke 1999, McQuillan 1999, Ens 2002a) and increased biomass in temperate south-eastern Australian grasslands is generally associated with overdominance by a limited number of grasses which suppress smaller inter-tussock species. Impact of invasive grasses Data on the impact of invasive grasses on insects is very limited. Chown and Block (1997 cited by Samways 2005) found that the beetle Hydromedion sparsutum was smaller in areas of South Georgia Island where alien grasses were dominant. New (2000) found that ant diversity in grasslands dominated by native or exotic grasses was similar and species composition of the grasses was probably less influential than structural diversity in the vegetation. However Gibson and New (2007) pointed out that disturbance effects were confounded. Hagiwara et al. (2009) demonstrated the potential benefits to the endangered butterfly Lycaeides argyrognmon praeterinsularis of removing Eragrostis curvula, which increased flowering and seed production of the butterfly’s host plant. Melbourne (1993) and Melbourne et al. (1997) investigated the variation in numbers of a range of invertebrate taxa in grasslands of the ACT dominated by exotic or native species. Miller and New (1997) compared the ant faunas of areas dominated by an exotic grass and by native grasses. Grassland insects Pasture pests have generally been the main focus of invertebrate research in Australian grasslands (e.g. Gregg 1997). The great majority are native species subject to occasional outbreaks and are valuable components of biodiversity in natural areas. Losses from insect attack in grasslands on a global basis are estimated to amount to 9-32% of plant biomass (Tscharntke and Greiler 1995). Insect herbivory can have significant impacts on rare and endangered plants. Archer (1984) recorded the depradations of unidentified grasshoppers on colonies of Thesium australe, a plant once widespread in temperate native grasslands, attributed to severe depletion of other vegetation by mammalian grazers (Archer 1984 1987). Important agricultural grassland pest taxa in Australia include grasshoppers and locusts (Acrididae), Teleogryllus commodus (Walker) (Orthoptera: Gryllidae), Therioaphis trifolii (Monell) and Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), weevils (Coleoptera: Curculionidae), larvae of Elateridae, Tenebrionidae and Scarabaeidae (particularly Melolonthinae, Aphodius tasmaniae (Hope) (Aphodiinae) and Adoryphorus couloni (Burmeister) (Dynastinae)(Coleoptera), underground grass grubs (Lepidoptera: Hepialidae), larvae of Noctuidae and Pyralidae (particularly Hednota spp.) (Lepidoptera) and ant seed predators (Hymenoptera: Formicidae) (Gregg 1997). Mites including Balaustium and Penthaleus spp. are important cereal pests (Anon. 2008b). Many adult Melolonthinae species feed on trees, particularly Eucalyptus spp., or use them for mating, while others do not feed in the adult stage (Roberts et al. 1982). Larvae live in the soil, eating roots, probably often of grasses, and other organic matter. In pastures on the New England tablelands (NSW), smaller species in the tree-feeding group were significantly more abundant in areas with low tree densities than larger species (Roberts et al. 1982). Highest densities of the non-tree-feeding group, which included the largest species (e.g. Rhopaea spp.), occurred in areas with 0-10% tree cover. Ridsdill-Smith (1975) noted that several of the Northern Tablelands species were known to eat living grass roots and found that Sericesthis nigrolineata (Boisduval) preferred grass roots to dead organic matter. Hardy (1976b) found that Scitala sericans Erichson predominantly inhabits grasslands and dry sclerophyll forests, the native grasslands inhabited being dominated byPoa spp. and also the exotic Agrostis capillaris L. in some areas. Larvae of Antitrogus Burmeister (Melolonthini) “feed on the roots of grasses and other similar plants” (Allsopp 2003 p. 159). Various Dynastinae are also common in pastures and lawns in south-eastern Australia, where many feed on grass roots. Cyclocephala signaticollis Burmeister, introduced to Australia from South America has larvae that damage pasture and turf in Australia (Carne 1956) and is now common in the ACT (Robin Bedding CSIRO pers. comm. via M. Malipatil). This species inhabits the core range of N. neesiana in Argentina and likely damages it. According to A. Martinez (reported in Carne 1956 p. 220) it is found in “the provinces of Buenos Aires, the eastern part of Córdoba, southern Santa Fé, in Entre Rios and the northeast of the Pampa territory [and] Uruguay ... the roots of native grasses are the natural food .. while they also attack ... wheat, maize ... and barley”. The well-studied pasture pest Adoryphorus couloni was the most abundant beetle collected in pitfall traps at Craigieburn grassland by Gibson and New (2007). Dramatic fluctuations of native insect populations in pastures are commonplace (e.g. Davidson 1982), as they are in natural grasslands (Yen 1999). Population irruptions of phytophagous species may play a role in the patch dynamics of the lowland grasslands. For example, the underground feeding damage to Poa snow grass by the Alpine Grassgrub Oncopera alpina Tindale in the Australian Alps, described as “extensive patch death” by McDougall and Walsh (2007) is “part of an important ecological cycle opening up overgrown grass swards to invasion by the numerous flowering herbs for which the Kosciuszko area is famous” (Edwards 2002 p. 61). Similarly Green and Osborne (1994) reported that the Poa snow grass feeding larvae of the casemoth ‘Plutorectis’ caespitosae Oke (Psychidae, Lomera caespitosae in Common 1990) cause severe patch damage to large areas in the subalpine zone, especially below the treeline, when in large numbers, but recovery after winter is rapid. 152
Nematodes are mostly minute animals that can be extremely abundant in soils and on plants, particularly on the roots. Numerous species are associated with grasses in Australia and several have been recorded from native Stipeae. These are discussed in an Appendix to this literature review. Exotic invertebrates are often widespread and common in native grasslands, particularly in urban fringe areas (personal observations). Collembola is one group with a substantial proportion of exotics, however many higher taxa including various Coleoptera families and Formicidae are largely or almost entirely dominated by native species (New 2000). Common exotics present in grasslands include molluscs (slugs and snails), red legged earth mites Halotydeus destructor (Tucker), insects such as the aforementioned aphids, the African black beetle Heteronychus arator (Scarabeidae: Dynastinae), the weevils Graphognathus leucoloma (Boheman) and Sitona discoideus (Gyllenhal) (Gregg 1997, Hill et al. 1997),the European honeybee Apis mellifera, and possibly earthworms (Annelida: Haplotaxida). Morgan (1995b) found that H. destructor grazed seedlings of the endangered Rudidosis leptorrhynchoides but did not significantly affect their survival, and that grazing by unidentified slugs occurred mostly on very young seedlings and caused little damage. Exotic Chriothrips spp. (Thysanoptera: Thripidae) are found on grasses in south-eastern Australia (Mound and Palmer 1972). The grassland daisy Senecio macrocarupus is subject to attack by red-legged earthmites Halotydeus destructor (Tucker) and aphids (Hills and Boekel 2003). H. destructor and blue oat mites Penthaleus major (Dugès) attack a wide range of native grassland forbs including species of Craspedia, Podolepis and Senecio (Robinson 2005). The Portuguese Black Millipede Ommatoiulus moreletti (Lucas) (Julidae) has spread into Victorian basalt plains grasslands, and although there is no evidence of competition with native millipedes, it may influence litter decay rates (Yen 1995). Many of the invasive insect species probably have significant effects on grassland plants and the ecological functioning of the system, but there appear to be no studies that have directly addressed particular impacts. The agricultural literature, although restricted to few species, contains some valuable data about invertebrate impact on ecosystem processes, particularly effects on plant biomass production (Gregg 1997) and soils. A range of exotic molluscs are considered pests of pastures (Smith and Kershaw 1979, Kershaw 1991) and have been suggested to be important predators of sensitive native plants such as orchids (Sydes 1994, Daniell 1994). Exotic slugs “appear to be highly invasive of native grasslands” and were found to be equally abundant in grasslands dominated by exotic and native grasses in the ACT (Melbourne et al. 1997 p. 366). Daniell (1994) recorded no or few species of native molluscs at four Melbourne grasslands, and observed that exotic slugs can occur at very high densities in native grasslands. Holland et al. (2007) found only exotic molluscs, three snail and five slug species, in extensive surveys in the Victorian volcanic plains. A few mollusc species have been identified as threats to particular native taxa, e.g. unidentified slugs and snails are considered a threat to Diuris fragrantissima (Webster et al. 2004), the Black-keeled Slug Milax gagates (Draparnaud) defoliates Rutidosis leptorrhynchoides (Daniell 1994), slug predation has caused the loss of a Pterostylis nutans R.Br. (Orchidaceae) colony (Sydes 1994), while unidentified slugs and possibly Common Garden Snails Helix aspersa (Müller) caused mortality of Thesium australe planted at Lake Omeo (Scarlett et al. 2003). Lenz et al. (2003 p. 30) applied molluscide in a low-diversity, weedy native grassland with a high population of the white snail Cernuella virgata da Costa and found that snail exclusion had no effect on vascular plant species composition over 9 months. The dietary preferences of introduced herbivorous molluscs in regard to native plants do not appear to have been investigated (Lenz et al. 2003) except for M. gagates which was found by Holland et al. (2007) to prefer some native plants over others, with the two native grasses tested having relatively low palatability. Grass-feeding insects Various insect groups that avoid plants with toxic metabolites are restricted to Poaceae including some Acrididae (Orthoptera) and Auchenorrhyncha (Hemiptera). Theoretical considerations suggest that the general absence of toxic principles should result in a lower ratio of endophagous to ectophagous feeders in grasses than in dicotyledons, and that appears to be the case, with external feeders being much more common than gall-makers, borers and miners. Ratios of c.30:10 and 30:1 have been recorded in six grass species (Tscharntke and Greiler 1995). Dominance of ectophages is also apparent in Sporobolus spp. (Witt and McConnachie 2004). Veldtman and McGeoch (2003) found five grass species with insect galls, caused by five gall-forming insect species, in a broad survey in South Africa. Poaceae had one of the highest number of galled species compared with other plant families. However, herbaceous plants generally have fewer gall-forming species than woody plants, possibly in part because lignified material is more long-lasting, and is thus ‘safer’ for gall formation (Veldtman and McGeoch 2003). Most of the chewing ectophages on grasses are oligophagous, whereas amongst the main ‘sucking’ groups (Hemiptera) Delphacidae are monophagous while Cicadellidae has a higher proportion of oligophages (Tscharntke and Greiler 1995). As with vertebrates, the nutritional quality of grass foliage, particularly silicate and lignin content, are important determinants of palatability for invertebrates. Juvenile foliage has a reduced content of these structural polymers but has better chemical defenses against herbivores. C 3 species have higher protein contents than C 4 species, so may be preferred by herbivores. Large abundant grasses generally have larger faunas (5-12x) than rare, small species. Two variables, shoot length and life-cycle dichotomy (annual or perennial) explain a high proportion of variance in the species richness of a particular grass. Unpredictably in the spatial and temporal distribution of annuals, rather than any difference in the number of possible niches they offer appears to explain this (Tscharntke and Greiler 1995). Data on the grass food plants of insects in Australia, as elsewhere in the world, is very fragmentory. The literature appears to be devoid of studies of whole faunas associated with Australian native grass species. According to Wapshere (1993) no arthropods had been recorded from Nassella trichotoma in Australia, despite its long presence in the country, and nothing was known of the invertebrate faunas of Austrostipa species (although this is no longer correct for these grasses). At attempt has been made to draw together some of the scattered information sources on grass invertbrates in an Appendix to this Literature Review. Taxa of Gondwanan origin such as Austrodanthonia may harbour a larger range of endemic coevolved invertebrates than species such as T. triandra which have colonised Australia more recently from the north (E.D. Edwards cited by Driscoll 1994). Lawton and Schroder (1977 p.137) compiled data on the insects associated with species of British plants but excluded Poaceae “because the insect data appeared to be particularly unreliable”, the entomological literature frequently recording “grass”, rather than particular grass species as food plants. However they found that the monocots studied had the fewest insect species associated with them compared with shrub, perennial herb, ‘weeds and annuals’, and aquatic dicot herb groups investigated. 153
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Literature review: Impact of Chilea
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Fire 49 Other disturbances 50 Shade
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Conventions and standards Botanical
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neesiana appears to be a habitat ge
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population densities of existing sp
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elated plants have similar defences
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For invasion to occur there must be
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As yet there appears to be no evide
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experimental manipulation of specie
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species tend to be those which tran
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Taxonomy and nomenclature Stipeae N
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Vernacular names ‘Needlegrass’
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to Bouchenak-Khelladi et al. 2009).
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1 m (Walsh 1994), ca. 90 cm (Verloo
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Figure 2. Anatomy of the seed of N.
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are the seeds larger/smaller, longe
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also based on a misunderstanding of
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Table 2. Modified Feekes Scale for
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Argentina, in the provinces of Chac
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Figure 3. Recorded distribution of
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1994). Only 3 of 186 exotic grasses
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According to Morfe et al. (2003) th
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populations have been found in the
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(Honaine et al. 2006). The flechill
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In Australia the altitudinal range
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Proximity to urban development appe
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In the southern Brazilian campos of
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arundinacea (Gardener et al. 2005).
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al. 2008). Cues for masting may be
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Approximately 200 alien grass speci
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Dispersal of seed in contaminated s
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In New Zealand, Hurrell et al. (199
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No emergence was observed in undist
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and high impact (“ability to caus
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also noted that despite a wide rang
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a small reduction in seedhead produ
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Slashing and mowing Slashing can re
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Themeda re-establishment McDougall
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species (Lawton and Schroder 1977 p
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y increased importance of ant grani
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BIODIVERSITY “Biodiversity ... on
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According to Woods (1997 p. 61) “
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2004, Richardson and van Wilgen 200
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negative depending on the particula
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Competition with native plants Comp
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asexual seed production, so local f
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GRASSLANDS Grasses: “... the most
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susceptible to N. neesiana invasion
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Floristic composition, vegetation s
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proportion of the flora then presen
Page 101 and 102: tussock space (Stuwe and Parsons 19
Page 103 and 104: Like vascular plant diversity, comm
Page 105 and 106: Opinions differ on the nature and i
Page 107 and 108: Species Common Name Family Aust ACT
Page 109 and 110: in shifting the distribution, exten
Page 111 and 112: of these systems is largely explain
Page 113 and 114: pasture. The least understood trans
Page 115 and 116: tend to benefit more from relaxed c
Page 117 and 118: Bovids crop their food between the
Page 119 and 120: are therefore less likely to distur
Page 121 and 122: esult in a “short-term flush” o
Page 123 and 124: Fire effects on weeds Moore (1993 p
Page 125 and 126: Table 8. Typical nutrient levels in
Page 127 and 128: grasses produced sigificantly more
Page 129 and 130: Fossorial vertebrates are or were o
Page 131 and 132: (Rosengren 1999). Approximately one
Page 133 and 134: Table 12. Areal extent and conserva
Page 135 and 136: Foreman (1997) investigated the eff
Page 137 and 138: Willis (1964) considered that the f
Page 139 and 140: Austrostipa-Enneapogon) from around
Page 141 and 142: Woodlands and New England Grassy Wo
Page 143 and 144: Thylogale billardierii), Peramelida
Page 145 and 146: Its original habitat on the mainlan
Page 147 and 148: Table 17. Endangered reptile specie
Page 149 and 150: equirement, but unlike plants and v
Page 151: e assigned the same biodiversity sc
Page 155 and 156: found in all mainland states, O. co
Page 157 and 158: Keyacris scurra, Melbourne (1993) o
Page 159 and 160: was once widespread in south- easte
Page 161 and 162: eing sluggish and wingless, and exi
Page 163 and 164: estoration and, if Australia follow
Page 165 and 166: close to the plant are able to bury
Page 167 and 168: Species *Chirothrips mexicanus Craw
Page 169 and 170: Table A2.1 (continued) Species Life
Page 171 and 172: Table A2.1 (continued) Species *Het
Page 177 and 178: Nematodes of grasses and grasslands
Page 179 and 180: REFERENCES Aceñolaza, F.G. (2004)
Page 181 and 182: Benson, D. and McDougall, L. (2005)
Page 183 and 184: Chan, C.W. (1980) Natural grassland
Page 185 and 186: DNRE (Department of Natural Resourc
Page 187 and 188: Fuhrer, B. (1993) A Field Companion
Page 189 and 190: Groves, R.H. and Whalley, R.D.B. (2
Page 191 and 192: Iaconis, L. (2004) Chilean needle g
Page 193 and 194: Levine, J.M., Adler, P.B. and Yelen
Page 195 and 196: McDougall, K.L. (1987) Sites of Bot
Page 197 and 198: Morfe, T.A., McLaren, D.A. and Weis
Page 199 and 200: Perelman, S.B., León, R.J.C. and O
Page 201 and 202: Saunders, D.A. (1999) Biodiversity
Page 203 and 204:
Thellung, A. (1912) La flore advent
Page 205 and 206:
Weiss, J. and McLaren, D. (2002) Vi
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