Journal articles on the topic 'Rare plants – Western Australia – Southwestern'
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1
Catling, Paul M., and Gisèle Mitrow. "The Recent Spread and Potential Distribution of Phragmites australis subsp. australis in Canada." Canadian Field-Naturalist 125, no. 2 (April 1, 2011): 95. http://dx.doi.org/10.22621/cfn.v125i2.1187.
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To provide information on geographic occurrence, rate of spread, and potential distribution of European Common Reed, Phragmites australis subsp. australis, in Canada, we measured 1740 herbarium specimens from 21 collections across Canada, entered the information into a database, and mapped and analyzed these records. The European subspecies australis was first documented in Canada 100 years before it was recognized as an alien invader. It was not until the invading plants had entered a phase of rapid local increase after 1990 that they attracted sufficient attention that a comparison of the invasive and non-invasive plants was made. By 2001, two different races had been distinguished, and soon after they were separated as different subspecies. The first Canadian collection of the alien subsp. australis was made in southwestern Nova Scotia in 1910. By the 1920s, it occurred in southern Nova Scotia, along the St. Lawrence River near Quebec City and at Montreal. The first southwestern Ontario specimen was collected in 1948. Thus by 1950 subsp. australis was known from only four relatively small areas of Canada based on 22 collections. At this same time, the native race, subsp. americanus, had a widespread distribution in Canada represented by 325 collections. This strongly supported the comparable and limited distribution of subsp. australis at the time. By 1970, subsp. australis had spread locally but was still found only in southwestern Nova Scotia, in the St. Lawrence River valley, and in southwestern Ontario. By 1990, subsp. australis had become much more frequent in the St. Lawrence River valley and in southwestern Ontario, and it had extended westward into eastern Ontario. By 2010, it had spread throughout much of southern Ontario and southern Quebec, and it had a more extensive distribution in Atlantic Canada, but the biggest change was its spread into western Canada. It appeared in northern Ontario, northwestern Ontario, southern Manitoba, and interior southern British Columbia. The rate of spread is increasing and within a decade or two, based on the extent of appropriate plant hardiness zones currently occupied, it is expected to become abundant in the prairie provinces and across most of southern Canada.
2
Crombie, DS, JT Tippett, and TC Hill. "Dawn Water Potential and Root Depth of Trees and Understorey Species in Southwestern Australia." Australian Journal of Botany 36, no. 6 (1988): 621. http://dx.doi.org/10.1071/bt9880621.
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Water relations of selected tree and understorey species in the jarrah forest of south-western Australia were studied during summer drought and the results related to root morphology. Seasonal patterns of predawn water potential (Ψp) differed between species according to root depth and between sites according to average annual rainfall. Dawn water potentials fell most rapidly and by the greatest amount in plants with the shallowest roots. Dawn water potentials of medium and deep rooted species were not consistently different. Separation of Ψp between sites of different annual rainfall was less marked than was separation by root depth. Changes in Ψp, were consistent with a top-to-bottom drying of the soil profiles. We suggest that measurements of Ψp of plants of appropriate root depth can be used to monitor the drying of soils as an alternative to more expensive mechanical and electrical methods.
3
W. Arnold, G., M. Abensperg-Traun, R. J. Hobbs, D. E. Steven, L. Atkins, J. J. Viveen, and D. M. Gutter. "Recovery of shrubland communities on abandoned farmland in southwestern Australia: soils, plants, birds and arthropods." Pacific Conservation Biology 5, no. 3 (1999): 163. http://dx.doi.org/10.1071/pc990163.
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Passive recovery of land formerly used for agricultural production may be an inexpensive and rapid method of ecosystem recovery, and may provide an alternative method to active revegetation. Passive recovery may also contribute to sustainable agriculture (soil salinity). For undisturbed and disturbed areas of the central wheatbelt of Western Australia, this paper reports the effects of farming history (clearing only, cultivation, duration of farming, and time since farming ceased) on the soil nutrient content, plant floristics (richness and composition) and structure, and the abundance, species richness and species composition of birds and arthropods. Only one site was cultivated for >6 years. We summarize as follows: (1) Previous clearing and cultivation has left no residual effects on the nitrogen or phosphorus content in the sandy soils. (2) There were no significant differences in terms of plant species richness but some differences in cover of woody plants, grass cover and plant species composition for farming history or time since farming ceased. (3) There were no significant differences in bird species richness but differences in species composition for time since farming ceased. (4) Arthropods showed few (and low) significant differences in their abundance, richness or species composition across different farming histories and time periods since farming ceased. Farming of these shrublands has left only minor changes in the composition and structure of the vegetation, and in the abundance, species richness and species composition of the passerine bird and arthropod assemblages. Abandoned parcels of land on the sandy soils which support shrubland may yield useful conservation benefits with relatively little input.
4
Kirby, GC, BA Barlow, and S. Habel. "Sex-Ratios in a Gynodioecious Plant Ptilotus obovatus (Gaudich) F-Muell (Amaranthaceae)." Australian Journal of Botany 35, no. 6 (1987): 679. http://dx.doi.org/10.1071/bt9870679.
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Ptilotus obovatus is a gynodioecious perennial shrub with diploid and tetraploid cytotypes and is widespread in arid Australia. This study involved sex ratio counts in colonies of both cytotypes across much of the species range. Samples from diploid colonies had high frequencies of females (>55%) in Western Australia, low frequencies (<41%) in South Australia, and variable frequencies (36-77%) in southwestern Queensland. Tetraploid colonies had the opposite trend with low frequencies of females (<47%) in Western Australia and high frequencies (>54%) in the Northern Territory, South Australia and New South Wales. Ptilotus obovatus appears to be subdivided into at least five biotypes with distinct ploidy levels and sex ratios. We suggest that tetraploidy arose at least twice from diploid ancestors with different sex ratios and that the present distribution of cytotypes may reflect dispersal from refugia after recent arid maxima. The study of the genetics of male sterility in this species was impeded by the remarkably low seed set of plants in glasshouse crosses and in the field.
5
Downes, P. J., and A. W. R. Bevan. "Chrysoberyl, beryl and zincian spinel mineralization in granulite-facies Archaean rocks at Dowerin, Western Australia." Mineralogical Magazine 66, no. 6 (December 2002): 985–1002. http://dx.doi.org/10.1180/0026461026660072.
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Abstract A deposit of chrysoberyl (BeAl2O4), including the variety alexandrite, occurs near Dowerin, in the southwestern region of the Archaean Yilgarn Craton, Western Australia. The deposit is situated in the northern part of the Lake Grace Terrain, a crustal component of the southwestern Yilgarn Craton, in granulite-facies gneisses (2640–2649 Ma; T = 700°C, P <6 kbar) adjacent to the margin of the Kellerberrin Batholith (2587±25 Ma). Beryllium mineralization at Dowerin occurs in plagioclase-quartz-biotite-garnet gneiss and cross-cutting tourmaline-plagioclase veins situated adjacent to lenses of actinolite-cummingtonite-phlogopite schist. Crystals of chrysoberyl (0.15–1.74 wt.% Cr2O3; 2.25–3.23 wt.% FeO; trace–0.13 wt.% ZnO; SiO2 <0.05 wt.%) are found embedded in almandine or plagioclase, and closely intergrown with biotite and/or zincian hercynite in the host-rock gneiss. Minor Cr and Fe in the alexandrite variety of chrysoberyl were possibly derived from associated zincian hercynite and/or almandine. Trace beryl (0.04–0.20 wt.% Cr2O3; 0.54–0.71 wt.% FeO; trace– 0.22 wt.% Na2O; 0.1–0.71 wt.% MgO) occurs as anhedral interstital grains between crystals of chrysoberyl, plagioclase and biotite, and as rare inclusions in chrysoberyl. Textural and mineral chemical evidence suggests that chrysoberyl and zincian spinels (chromite to hercynite containing from 2–8 wt.% ZnO) formed during granulite-facies regional metamorphism and probably pre-dated the formation of metamorphic tourmaline-plagioclase veins during the same metamorphic episode. The Be, B and Zn required to form chrysoberyl, beryl, tourmaline and zincian spinels may have been released by metamorphic reactions in host-rock metapelites during prograde granulite-facies metamorphism.
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Lee, J. G. H., H. C. Finn, and M. C. Calver. "Ecology of black cockatoos at a mine-site in the eastern jarrah-marri forest, western Australia." Pacific Conservation Biology 19, no. 1 (2013): 76. http://dx.doi.org/10.1071/pc130076.
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Three threatened black cockatoos inhabit the Jarrah Eucalyptus marginata-Marri Corymbia calophylla forest of southwestern Australia: Baudin’s Cockatoo Calyptorhynchus baudinii, Carnaby’s Cockatoo C. latirostris, and Forest Redtailed Black Cockatoo C. banksii naso [FRTBC]. Their local ecology in relation to anthropogenic disturbance is poorly known, hampering effective conservation management. Therefore we studied their group size, site occupancy patterns, habitat use, and food plants at a mine-site and its surrounds in the eastern forest over three years. FRTBC showed similar group sizes and occupancy across seasons, suggesting year-round residency and no marked seasonality in movements and grouping patterns. In contrast, Carnaby’s Cockatoos were up to twice as abundant in spring and summer, indicating migrating or transient flocks and some year-round residents. Few Baudin’s Cockatoos were present in summer, but their abundance increased at other times. All three cockatoos were observed in modified or humanmade habitats such as mine-site rehabilitation, farm paddocks, and pine plantations. Carnaby’s Cockatoos used the broadest habitat range. We documented feeding on 16 plant species, with Carnaby’s Cockatoos eating at least 10. Examination of feeding residues as well as observations of behaviour were essential to obtain a complete picture of feeding. Current mine-site rehabilitation protocols provide food for all three black cockatoos within a decade and should continue to do so long-term if Marri is maintained in the seed mix. However, because climate change scenarios predict declining rainfall over much of southwestern Australia, the plant species used to revegetate mine-sites and other landscapes may need to be reconsidered. For areas that do not specify restoring a jarrah forest landscape, the selective use of exotic or non-endemic flora better adapted to lower rainfall conditions may be an option.
7
Kennedy, J., and G. Weste. "Vegetation Changes Associated With Invasion by Phytophthora cinnamomi on Monitored Sites in the Grampians, Western Australia." Australian Journal of Botany 34, no. 3 (1986): 251. http://dx.doi.org/10.1071/bt9860251.
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The effects of invasion by Phytophthora cinnamomi were measured on sites representing the larger forest regions of the Grampians. Changes were obvious at first, with the death of more than 50% of the species including large plants such as Xanthorrhoea australis, but soon became dificult to detect as susceptible species were replaced by field-resistant graminoids. Reductions were assessed in species heterogeneity and plant density during 1976, at the onset of disease and from 1977 to 1984. Susceptible species disappeared from infested forest and no re-emergence was observed. Less-susceptible plants such as some Euca/yptus spp. declined in number, regeneration and size, due to deaths or dieback of the branches. Reductions in tree canopy and the loss of structural dominants of the understorey caused changes in the flora which are likely to persist. The survival of rare, susceptible endemic species may be endangered. On dry, steep slopes the dead plants were not replaced and the amount of bare ground increased causing erosion of the soil surface. Some graminoid species increased in abundance on level, infested sites, resulting in a different species composition but with both species heterogeneity and plant density numerically similar to the previous flora.
8
Touchell, DH, KW Dixon, and B. Tan. "Cryopreservation of Shoot-Tips of Grevillea scapigera (Proteaceae): a Rare and Endangered Plant From Western Australia." Australian Journal of Botany 40, no. 3 (1992): 305. http://dx.doi.org/10.1071/bt9920305.
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Cryopreservation of leaf, petiole, stem pieces and shoot-tips was investigated as a means for long-term maintenance of germplasm of the rare and endangered species, Grevillea scapigera A.S. George. Crypreservation was only achieved using shoot-tips or axillary buds and a slow-cooling regime with the aid of an improvised freezing device. The highest survival of thawed explants (20%) was obtained with 4-week-old in vitro shoot-tips cultured for 48 h in a prefreezing liquid culture medium supplemented with 5% dimethylsulfoxide. The pretreated shoot-tips were frozen in a liquid medium containing 10% dimethylsulfoxide cooled at a rate of 0.5°C/min to -40°C and held at this temperature for 30 min before being plunged into liquid nitrogen. Shoot-tips that survived the freeze-thaw cycle produced callus followed by shoot production 22 weeks after thawing. All shoots regenerated from thawed tissues and transferred to soil appeared phenotypically identical to untreated control shoots and plants. Rapid methods for assessing post-thaw tissue viability and explant recovery using triphenyltetrazolium chloride were tried but these methods were inadequate for determining the capacity of thawed tissues to recover from freeze damage.
9
Cox, Brad. "Granite Outcrops Symposium." Pacific Conservation Biology 4, no. 3 (1998): 271. http://dx.doi.org/10.1071/pc98271a.
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Western Australia is a flat landscape. Granite outcrops are one of the few features that rise above the terrain. This makes them unique landmarks for people, and islands for plants and animals. They are highly significant in terms of their geological, biological and cultural values. They contain some of the world's oldest rocks, are an important source of water, often contain aboriginal heritage sites and are refuges for many rare and endangered flora and fauna.
10
Pierce, Nuri B., and Michael G. Simpson. "Polyaperturate pollen types and ratios of heteromorphism in the monocot genus Conostylis (Haemodoraceae)." Australian Systematic Botany 22, no. 1 (2009): 16. http://dx.doi.org/10.1071/sb08040.
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Pollen aperture heteromorphism (variation of aperture number in pollen grains within each flower and in all plants of a taxon) is described in the diverse monocot genus Conostylis R.Br. (Haemodoraceae) and that of related genera, all endemic to Western Australia. We report results of pollen observations from 153 specimens. In Conostylis, aperture number varies greatly, with biporate, triporate, tetraporate and polyporate pollen present, features considered rare and possibly developmentally significant for monocots. Pollen aperture types and their ratios in this genus are stable and consistent within species and subspecies groupings and phylogenetically informative.
11
Miller, Ben P., David R. Symons, and Matthew D. Barrett. "Persistence of rare species depends on rare events: demography, fire response and phenology of two plant species endemic to a semiarid Banded Iron Formation range." Australian Journal of Botany 67, no. 3 (2019): 268. http://dx.doi.org/10.1071/bt18214.
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The association of rare plant species and Banded Iron Formation (BIF) ranges in semiarid Western Australia is a noted phenomenon. These ranges are also a focus of iron ore exploration and mining. Decisions and planning required for development, conservation and management resulting from this interest, often consider translocation of these threatened species. Nonetheless, little is known about the ecology of BIF-endemic species to support any such decisions. We assessed population structure, patterns of growth, mortality, recruitment, reproduction and in situ seedbank persistence for two declared rare flora species. The shrub Darwinia masonii, and sedge Lepidosperma gibsonii are endemic to an area <40 km2 on the south-western boundary of the Australian arid zone. Both species were found to be long lived and slow growing, with evidence for reliance on rare events such as fire, and high rainfall years, including, for some processes, consecutive high rainfall years for growth, reproduction and recruitment. Retrieval and germination of seed batches shows that both species’ seedbanks are long-lived, with seasonal dormancy cycling. This, together with the ability of mature plants to survive through years not supporting growth, and, for L. gibsonii, to resprout after fire, are key mechanism for persistence in this unpredictable and low rainfall environment.
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Ladd, P. G., C. J. Yates, R. Dillon, and R. Palmer. "Pollination ecology of Tetratheca species from isolated, arid habitats (Banded Iron Formations) in Western Australia." Australian Journal of Botany 67, no. 3 (2019): 248. http://dx.doi.org/10.1071/bt18249.
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Pollination and reproductive ecology of arid zone species in Australia are neglected topics. This is particularly true of rare species, some of which are threatened by mining operations. The bee community at Windarling Range in southern Western Australia and the pollination ecology of four rare Tetratheca taxa with distributions restricted to Banded Iron Formation inselbergs in the arid south-west were examined in winter and spring to understand if pollination rate was affecting the reproductive ecology of the plants. The bee fauna on the Windarling Range was sampled using coloured pan traps at three landscape positions of ridge (where Tetratheca paynterae subsp. paynterae occurs), slope and flats and the insect visitors to T. paynterae subsp. paynterae were quantified by direct observation. The bee fauna varied over the two years with average richness higher in 2010 than 2011 and was higher on the ridge compared with the slope and flats below the inselberg. The Tetratheca species are buzz pollinated and T. paynterae subsp. paynterae is only visited by a subsection of the bee fauna, mainly Lasioglossum species, which were shown to be relatively faithful to the species in terms of the pollen they carried. Flowering mainly occurs after the winter wet season, but may occur at other times when there has been substantial rain. This may not coincide with bee activity. In the winter flowers may be poorly serviced if maximum daytime temperatures are below 20°C. However, in spring when temperatures are higher the majority of flowers were pollinated and there was no significant difference in proportion of pollinated flowers between the four taxa examined. As T. paynterae is outcrossing the propensity for bees to attend few flowers on a visit to each plant, often on the outer part of the plant canopy, will likely ensure a high success rate for seed formation. High seed set in such an arid environment with few suitable sites for seedling establishment is essential so some propagules can find safe sites for establishment to maintain population numbers.
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Watson, EM. "Cytoevolutionary Studies in the Genus Bulbine Wolf (Liliaceae) .II. The Australian Annual Taxa (Bulbine semibarbata s.1.)." Australian Journal of Botany 34, no. 5 (1986): 505. http://dx.doi.org/10.1071/bt9860505.
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A cytological survey, using root tip mitotic cells and supplemented by some crosses and pollen fertility studies, was carried out on plants of 55 populations of the Australian annual Bulbine sernibarbata s.1. (Liliaceae). There are 4x, 8x and 12.x populations.The 4x forms are almost completely confined to eastern Australia and comprise populations of two kinds: (1) 28-chromosome types, corresponding in morphology to B. alata Baijnath, which to date has had limited taxonomic acceptance; (2) 26-chromosome types with the morphology of B. sernibarbata s. str. The alata form occurs in arid, the sernibarbata in more mesic, areas. The eastern 8x populations are mainly 2n = 54 and are intermediate between the other two taxa in both range and morphology. This suggests an allopolyploid origin based on hybridisation between the alata and sernibarbata types. The western 8x populations are nearly all 2n = 52, with much interpopulation variation in karyotype and a mesic distribution similar to that of the eastern 26-chromosome types. The karyotypic diversity parallels the species richness of other genera in southwestern Australia and indicates that the complex may be older than the corresponding polyploid complex within the perennial B. bulbosa s.1. The 12x (2n =78) populations are confined to arid and transitional rainfall areas of Western Australia. The identification of a distinctive 28-chromosome karyotype for the alata group gives support to the recognition of B. alata Baijnath, and, by providing a logical euploid bridge between the chromosome numbers of the African (2n = 14) and Australian species, strengthens the arguments for treating the two groups as congeneric.
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BAASANMUNKH, SHUKHERDORJ, BATLAI OYUNTSETSEG, CHULUUNKHUYAG OYUNDARI, KHURELPUREV OYUNDELGER, MAGSAR URGAMAL, DAVAAJAV DARIKHAND, NERGUI SONINKHISHIG, et al. "The vascular plant diversity of Dzungarian Gobi in western Mongolia, with an annotated checklist." Phytotaxa 501, no. 1 (May 19, 2021): 1–55. http://dx.doi.org/10.11646/phytotaxa.501.1.1.
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The Dzungarian Gobi (DzG), one of 16 phytogeographical regions in the country, is located in the southwestern part of Khovd province in western Mongolia. It comprises some of Mongolia’s largest reserves, namely the Great Gobi B Strictly Protected Area and the National Park Bulgan gol-Ikh Ongog. We conducted a comprehensive survey of the area’s floristic diversity between 2009 and 2019 by collecting vascular plants from different vegetation types in various seasons. In addition, we critically checked relevant published literature and material from the herbaria ALTB, GLM, GWF, HAL, KHU, LE, MW, NS, OSBU, UBA, and UBU to determine the occurrence of vascular plant species in the DzG region. Based on our collection data, a comprehensive checklist of DzG’s flora was compiled, representing 913 vascular plant taxa (including 34 subspecies and one variety) belonging to 329 genera and 70 families. Twenty-one taxa were newly found in the DzG region. We also investigated the conservation status of all species noted, and 19 endemic plants and 96 threatened species, including six critically endangered, 26 endangered, 57 vulnerable, and seven near threatened plants were recognized in this region. Eight rare species were newly assessed according to regional conservation status based on GeoCat and IUCN. The richest plant families found were Asteraceae (153 species), Fabaceae (77 species), Amaranthaceae (69 species), and Poaceae (68 species). Several uncertain endemic and non-endemic plants remain still discussion, such as Papaver baitagense and Rosa baitagensis; thus, further studies are needed on their taxonomic and conservation status. For each taxon, we provide its distribution in the region, elevation range, voucher number, and additional references. Finally, we analyzed species hotspots of DzG, based on three different plant species richness criteria: i. all recorded species, ii. endemic species, and iii. threatened species using our georeferenced records. The most diverse hotspot area in DzG is the Baitag Bogd Mountain area, which comprises the highest species number of all three richness criteria.
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Bunn, Eric, and Kingsley W. Dixon. "In Vitro Propagation of the Rare and Endangered Grevillea scapigera (Proteaceae)." HortScience 27, no. 3 (March 1992): 261–62. http://dx.doi.org/10.21273/hortsci.27.3.261.
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Micropropagation, including adventitious shoot growth from leaf sections, was achieved for Grevillea scapigera (Proteaceae), a rare and endangered species from Western Australia. Shoot tips were initiated on filter paper supports with liquid WPM (Woody Plant Medium) and supplemented with 20 μm zeatin riboside and 2 μm GA3. Shoots were then incubated on WPM solidified with agar and supplemented with 5 μm kinetin and 0.5 μm BA, which produced an approximate 6-fold multiplication rate per month. Up to three adventitious shoots were induced from 0.7-cm2 leaf sections after 6 to 7 weeks on solid 1/2 MS (Murashige and Skoog) medium supplemented with 10 μm BA and 0.5 μm IBA. Shoots, 30 to 50 mm long, were rooted in vivo in a fogged glasshouse under 70% shade using a commerical rooting powder [IBA, 0.1% (w/w)] applied to the base of the shoots. Most (67%) of the shoots treated in this way rooted after 5 weeks. Established, rooted plants have been grown on under glasshouse conditions. Chemical names used: N6-[2-isopentenyl] adenine riboside (zeatin riboside); gibberellic acid (GA3); 6-furfurylaminopurine (kinetin); N-(phenylmethyl)-1H-purine-6-amine (BA); 1-H-indole-3-butyric acid (IBA).
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McDougall, K. L., R. J. Hobbs, and G. E. St Hardy. "Vegetation of Phytophthora cinnamomi-infested and adjoining uninfested sites in the northern jarrah (Eucalyptus marginata) forest of Western Australia." Australian Journal of Botany 50, no. 3 (2002): 277. http://dx.doi.org/10.1071/bt01096.
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The vegetation of seven sites in the northern jarrah forest of Western Australia infested with Phytophthora cinnamomi was recorded and compared with adjoining vegetation. The number of species per quadrat was found to be the same in vegetation affected by P. cinnamomi as in healthy vegetation, although there were more species overall in affected vegetation. Vegetation of uninfested sites had a higher cover and more species per quadrat of trees and shrubs and lower cover and fewer species per quadrat of annual plants than vegetation of infested sites. Although many species that are known to be highly susceptible to infection by P. cinnamomi were rare at infested sites, only two (Banksia grandis and Tetratheca hirsuta) were absent from all of the 50-year-old infested parts of sites. Several species that are known to be highly susceptible to infection by P. cinnamomi were as common at infested as at healthy sites. The presence of such species at infested sites and the capacity of P. cinnamomi to infect species it does not kill suggest that this pathogen will persist and continue to influence future vegetation in the jarrah forest.
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Macphail, Michael K., and Robert S. Hill. "What was the vegetation in northwest Australia during the Paleogene, 66–23million years ago?" Australian Journal of Botany 66, no. 7 (2018): 556. http://dx.doi.org/10.1071/bt18143.
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Fossil pollen and spores preserved in drillcore from both the upper South Alligator River (SARV) in the Kakadu National Park, Northern Territory and the North-West Shelf, Western Australia provide the first record of plants and plant communities occupying the coast and adjacent hinterland in north-west Australia during the Paleogene 66 to 23million years ago. The palynologically-dominant woody taxon is Casuarinaceae, a family now comprising four genera of evergreen scleromorphic shrubs and trees native to Australia, New Guinea, South-east Asia and Pacific Islands. Rare taxa include genera now mostly restricted to temperate rainforest in New Guinea, New Caledonia, New Zealand, South-East Asia and/or Tasmania, e.g. Dacrydium, Phyllocladus and the Nothofagus subgenera Brassospora and Fuscospora. These appear to have existed in moist gorges on the Arnhem Land Plateau, Kakadu National Park. No evidence for Laurasian rainforest elements was found. The few taxa that have modern tropical affinities occur in Eocene or older sediments in Australia, e.g. Lygodium, Anacolosa, Elaeagnus, Malpighiaceae and Strasburgeriaceae. We conclude the wind-pollinated Oligocene to possibly Early Miocene vegetation in the upper SARV was Casuarinaceae sclerophyll forest or woodland growing under seasonally dry conditions and related to modern Allocasuarina/Casuarina formations. There are, however, strong floristic links to coastal communities growing under warm to hot, and seasonally to uniformly wet climates in north-west Australia during the Paleocene-Eocene.
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Rossiter, RC, and WJ Collins. "Genetic diversity in Old Subterranean Clover (Trifolium subterraneum L.) Populations in Western Australia. I. Pastures sown initially to the Dwalganup strain." Australian Journal of Agricultural Research 39, no. 6 (1988): 1051. http://dx.doi.org/10.1071/ar9881051.
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Subterranean clover burrs were collected during summer from 28 sites, 10 of which were in the <500 mm annual rainfall zone. All sites had been sown to the Dwalganup strain, 30-50 years ago. Spaced plants were grown from seed from burr subsamples of each population. Several morphological characters, flowering dates, and oestrogenic isoflavones in late spring leaf samples were determined. At maturity, burr samples were collected from each plant, and the isozyme patterns in seeds were determined for eight enzyme systems using starch gel electrophoresis. Populations from the lower rainfall (< 500 mm) sites usually consisted of one or two strains - Dwalganup with or without Geraldton - and variant (or 'unknown') genotypes were very rare or absent. Populations from the higher rainfall (> 500 mm) sites, on the other hand, comprised about 50% of a few known strains - mostly Dwalganup and/or Dinninup - the remaining 50% consisting of numerous variant genotypes. Infrequent outcrossing between the Dwalganup and Mt Barker strains is the likely major source of this variation. Possible explanations for the lack of variant genotypes in the lower rainfall zone are discussed.
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Krauss, Siegfried L., and Janet Anthony. "Genetic impacts of habitat loss on the rare Banded Ironstone Formation endemic Ricinocarpos brevis (Euphorbiaceae)." Australian Journal of Botany 67, no. 3 (2019): 183. http://dx.doi.org/10.1071/bt18131.
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Ricinocarpos brevis (Euphorbiaceae) is a declared rare species currently known from only three Banded Ironstone Formation (BIF) ranges (Perrinvale, Johnston and Windarling Ranges) in the Yilgarn region of Western Australia. The present study assessed the potential impact of proposed mining on genetic diversity within R. brevis. Approximately 30 plants were sampled from each of 14 sites across the known distribution of R. brevis. Genetic variation and its spatial structure was assessed with 144 polymorphic AFLP markers that were generated by two independent primer pairs: M-CTG/P-AC (81 markers) and M-CTA/P-AC (63 markers). Hierarchical spatial genetic structure was assessed by an analysis of molecular variance (AMOVA), Mantel tests of association between genetic- and geographic-distance and ordination. Specific attention was given to the extent of genetic differentiation of the three populations on the Windarling Range W4 deposit, which was proposed for mining operations. Strong genetic differentiation (ΦPT=0.186–0.298) among the three ranges was found. Genetic differentiation of the Johnston Range populations from Windarling and Perrinvale was greater than expected under isolation by distance predictions, suggesting adaptive genetic differentiation driven by site environmental differences, reflected by differences in plant community, substrate and landscape features. In contrast, genetic differentiation among the three Windarling Range regions (W2, W3, W4) was weaker (ΦPT=0.055–0.096). Mean pairwise ΦPT=0.078 for the 10 Windarling sites, which was unchanged with the removal of the W4 populations. In addition, none of the markers scored were unique to the W4 populations. Thus, for this set of markers, the removal of plants on the Windarling Range W4 deposit had little impact on genetic diversity within R. brevis. Strong concordance in results from the independent datasets generated by the two AFLP primer pairs provides overall support for the conclusions drawn.
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Brundrett, Mark C. "A Comprehensive Study of Orchid Seed Production Relative to Pollination Traits, Plant Density and Climate in an Urban Reserve in Western Australia." Diversity 11, no. 8 (July 26, 2019): 123. http://dx.doi.org/10.3390/d11080123.
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The pollination of 20 common terrestrial orchids was studied in a 60-ha urban banksia and eucalypt dominated woodland in Western Australia. Five years of data (24,000 flowers, 6800 plants) measured fruit set relative to floral areas, capsule volumes, climate, phenology, pollination mechanisms, disturbance tolerance and demography. Pollination varied from 0–95% of flowers, floral displays from 90–3300 mm2 and capsules from 15–1300 mm3 per spike. Pollination traits strongly influenced outcomes, with self-pollination highest (59—95%), followed by sexually deceptive autumn or winter-flowering (18–39%), visual deception (0–48%) and sexually deceptive spring-flowering (13–16%). Pollination was limited by drought in autumn or spring and cool winter temperatures. Some orchids were resilient to drought and one formed seed after the leaves withered. Plant density had the greatest impact on fruit set for orchids forming large groups, especially for sexually deceptive pollination. Consequently, small group average (SGA) pollination was up to 4× greater than overall averages and peak seed production occurred in the best locations for genetic exchange and dispersal. SGA rates and seedpod volumes were strongly linked to clonality, but not to demographic trends. Resource competition limited flowering at higher plant densities and competition within spikes resulted in smaller, later-forming seedpods. Pollination data from co-occurring common orchids identified five evolutionary trade-offs linked to pollination, provided baseline data for rare species and revealed impacts of changing climate.
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Sinclair, Elizabeth, Belinda Cheetham, Siegfried Krauss, and Richard Hobbs. "Morphological and molecular variation in Conospermum triplinervium (Proteaceae), the tree smokebush: implications for bushland restoration." Australian Journal of Botany 56, no. 5 (2008): 451. http://dx.doi.org/10.1071/bt07137.
Full textAbstract:
Ecological restoration benefits from information on population genetic structure and variation within a species to make informed decisions on where to source material of the local genetic provenance. Conospermum triplinervium is extremely rare in Bold Park, a large bushland remnant currently undergoing restoration in Perth, Western Australia. We sampled plants from Bold Park and six other native populations across the northern half of the species’ range to assess patterns of morphological and genetic variation. There was considerable variation across six leaf measures with significant differentiation among some populations. The molecular data showed a high level of population structure (ΘB = 0.4974), with varying degrees of spatial overlap among populations in an ordination plot. Significant differentiation was observed among all pairs of populations, except for Bold Park and its geographically closest populations at Kings Park and Neerabup. These two populations had greater genetic variation (50.9% and 54.5% polymorphic markers, respectively) than did that at Bold Park (20.2%). The small Bold Park population would benefit from augmentation (via cuttings) from local plants. However, in the longer term, should the Bold Park population show evidence of declining viability, then material should be sourced from the genetically similar Kings Park population to increase genetic variation whilst also maintaining genetic integrity.
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Yates, Colin J., Philip G. Ladd, David J. Coates, and Shelley McArthur. "Hierarchies of cause: understanding rarity in an endemic shrub Verticordia staminosa (Myrtaceae) with a highly restricted distribution." Australian Journal of Botany 55, no. 3 (2007): 194. http://dx.doi.org/10.1071/bt06032.
Full textAbstract:
Verticordia staminosa C.Gardner & A.C.George subsp. staminosa is an extremely rare shrub occurring as an isolated population of ~1200 plants on a granite outcrop in the semi-arid agricultural region of Western Australia, separated from its closest relative V. staminosa subsp. cylindracea by 400 km. We aimed to determine a hierarchy of causes for explaining the extremely restricted distribution of subsp. staminosa, and to determine the genetic relationships among populations within both subspecies. We measured allozyme variation in all known populations of the two subspecies. There were exceptionally high levels of genetic divergence between subsp. staminosa and subsp. cylindracea, including an apparent duplication of the gene encoding phosphoglucomutase, leading to an additional gene in subsp. cylindracea. These findings combined with UPGMA analysis indicate a very long period of historical separation, perhaps originating in the early Pleistocene. Genetic variation was partitioned mostly between rather than within populations, with very low levels of genetic variation within populations of both subspecies. For subsp. staminosa we quantified seed production for three consecutive years and demography for five consecutive years. We used transition matrix models to describe the shrub’s population dynamics and stochastic simulations to explicitly compare the effects of low rainfall and disturbance on population viability. Verticordia staminosa subsp. staminosa produces large numbers of seeds each year and has flower to fruit ratios greater than reported for related rare and common congeners. Seedling recruitment occurs in most years, with pulses in the wettest years. The mean finite population growth rate was 1.031. Elasticity analyses showed that population growth rate was more sensitive to stasis of established plants than to seedling recruitment. Population viability declined with lower rainfall and increased fire-related mortality of adult plants. Rarity in subsp. staminosa is best explained by evolutionary history and the interaction of climate change and disturbances such as fire that kill plants. Climatic fluctuations since the late Pliocene might have led to stochastic extinction episodes of populations on other granite outcrops, resulting in the currently restricted distribution. We discuss the implications of our findings for management of the species.
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Tremblay, Raymond L., Maria-Eglée Perez, Matthew Larcombe, Andrew Brown, Joe Quarmby, Doug Bickerton, Garry French, and Andrew Bould. "Dormancy in Caladenia: a Bayesian approach to evaluating latency." Australian Journal of Botany 57, no. 4 (2009): 340. http://dx.doi.org/10.1071/bt08163.
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Dormancy is common in many terrestrial orchids in southern Australia and other temperate environments. The difficulty for conservation and management when considering dormancy is ascertaining whether non-emergent plants are dormant or dead. Here we use a multi-state capture–recapture method, undertaken over several seasons, to determine the likelihood of a plant becoming dormant or dying following its annual emergent period and evaluate the frequency of the length of dormancy. We assess the transition probabilities from time series of varying lengths for the following nine terrestrial orchids in the genus Caladenia: C. amoena, C. argocalla, C. clavigera, C. elegans, C. graniticola, C. macroclavia, C. oenochila, C. rosella and C. valida from Victoria, South Australia and Western Australia. We used a Bayesian approach for estimating survivorship, dormancy and the likelihood of death from capture–recapture data. Considering all species together, the probability of surviving from one year to the next was ~86%, whereas the likelihood of observing an individual above ground in two consecutive years was ~74%. All species showed dormancy of predominantly 1 year, whereas dormancy of three or more years was extremely rare (<2%). The results have practical implications for conservation, in that (1) population sizes of Caladenia species are more easily estimated by being able to distinguish the likelihood of an unseen individual being dormant or dead, (2) population dynamics of individuals can be evaluated by using a 1–3-year dormancy period and (3) survey effort is not wasted on monitoring individuals that have not emerged for many years.
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Ohlsen, Daniel J., Leon R. Perrie, Lara D. Shepherd, and Michael J. Bayly. "Taxonomic status and distribution of the critically endangered Christmas Island spleenwort (Asplenium listeri, Aspleniaceae): it is not as rare as we thought." Australian Systematic Botany 27, no. 6 (2014): 372. http://dx.doi.org/10.1071/sb14047.
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Asplenium listeri C.Chr. has been considered endemic to Christmas Island and is one of only two fern species listed as Critically Endangered under Australia’s Environment Protection and Biodiversity Conservation Act. Its status as a distinct species has been questioned because of morphological similarity to the widespread A. polyodon G.Forst., which also occurs on Christmas Island. Molecular analyses revealed that A. listeri and plants attributed to A. polyodon from coastal limestone in New Caledonia and Vanuatu share the same rbcL, trnL–trnF and rps4–trnS haplotype and that other samples of A. polyodon in Australia and the south-western Pacific belong to three separate molecular lineages. One of these lineages is formed by epiphytic A. polyodon from Christmas Island and has a chloroplast haplotype closely related to that of A. listeri, differing by four mutations. The A. listeri haplotype and each of the three A. polyodon lineages are associated with morphological characters and are all worthy of recognition as separate species. Asplenium listeri is here expanded to include limestone dwelling populations in the Pacific previously assigned to A. polyodon. This greatly extends the geographic range of A. listeri, and its conservation status should be revised accordingly. Application of correct names to all species in the A. polyodon complex requires further molecular sampling throughout its geographic range and clarification of how type material relates to each of the molecular groups.
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Vincent, Brian J., Sarah Barrett, Anne Cochrane, and Michael Renton. "Germination characteristics and the relationship between population structure, soil seed bank density and fire response in the rare endemic Stachystemon vinosus (Halford & R.J.F.Hend.) (Euphorbiaceae) from southern Western Australia." Seed Science Research 29, no. 2 (June 2019): 124–34. http://dx.doi.org/10.1017/s0960258519000126.
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AbstractThe regeneration niche defines the specific environmental requirements of the early phases of a plant's life cycle. It is critical for the long-term persistence of plant populations, particularly for obligate seeders that are highly vulnerable to stochastic events in fire-prone ecosystems. Here, we assessed germination characteristics and the relationship between population structure, soil seed bank density and fire response in Stachystemon vinosus (Euphorbiaceae), a rare endemic shrub from Western Australia, from burnt and long unburnt habitats. Many plants in long unburnt habitat were similar in size to those in recently burnt habitat. Soil seed bank density was related to plant abundance and fire history with density lower in burnt than unburnt sites. Thus, inter-fire recruitment may play a critical role in the requirements of the study species. To assess the dormancy status and germination requirements we used a ‘move-along’ experiment with temperatures from six seasonal phases of the year. Seeds were incubated under light and dark conditions, with and without smoked water, and with and without dry after-ripening. Germination was most effective when seeds were treated with smoked water and incubated in the dark at temperatures resembling autumn/winter conditions. After-ripening increased germination in light and dark incubated seeds in the absence of smoked water but was unnecessary for optimal germination in smoked water treated seeds. Irrespective of treatment, seeds showed a requirement for cooler temperatures for germination. These results suggest that rising temperatures and changes in fire regime associated with global warming may alter future germination responses of Stachystemon vinosus.
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E. Twigg, Laurie, Tim J. Lowe, and Gary R. Martin. "The presence and implications of viable seed in the faeces of invasive free-ranging European Rabbits and Red Foxes." Pacific Conservation Biology 15, no. 3 (2009): 158. http://dx.doi.org/10.1071/pc090158.
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Invasion by weeds and other undesirable plants threatens global biodiversity. However, the role of mammals in maintaining and spreading weeds is often overlooked. Here we confirm that two widely distributed and abundant Australian mammalian pests, the European Rabbit (Oryctolagus cuniculus) and the Red Fox (Vulpes vulpes), can spread viable seed. Our assessment mainly involved determining the number and viability of seeds recovered from faeces of free-ranging individuals inhabiting several areas within the Mediterranean region of south-western Australia, an internationally recognized biodiversity hotspot. In summer, viable seeds were recovered from 3?4% of the rabbit faecal pellets (n = 190) compared to 21?40% of pellets in autumn (n = 235). Ten (77%) of the 13 species of seed identified were weeds. Of the 1,136 seeds recovered, 16% germinated. In all, 13-30% of rabbits passed viable seeds in summer, increasing to 44?73% of rabbits in autumn. In captive wild rabbits, mean passage time of marked seed through the intestinal tract ranged from 4?7 h. This, together with the small home ranges of Australian European rabbits, suggests that they may generally disperse seeds over 1?2 km. Nine to 27% of foxes passed viable seed. Although 48% of scats (n = 62) contained whole seed, only 12.9% of all scats contained viable seed (range 9.1%?19.0%). Viable seeds (4/8) were also recovered from the hides of some shot foxes. In all, 63% (12/19) of seed species identified in the scats and pelts of foxes were weeds. Rabbits (primary dispersal) and foxes (primary, and secondary dispersal via seeds ingested with prey) may be important dispersers of viable seed, and may be essential for less common, but important, long-distance plant dispersal, particularly by some invasive species. Thus, suppression of weeds can be added to the benefits of reducing the abundance of rabbits and foxes to protect the unique biota and agricultural production in southwestern Australia.
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Dugas, Daniel P., and Gregory J. Retallack. "Middle Miocene fossil grasses from Fort Ternan, Kenya." Journal of Paleontology 67, no. 1 (January 1993): 113–28. http://dx.doi.org/10.1017/s0022336000021223.
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At the well-known fossil mammal locality of Fort Ternan in southwestern Kenya, radiometrically dated at about 14 million years old (middle Miocene), fossil grasses have been preserved by nephelinitic sandstone in place of growth above a brown paleosol (type Onuria clay). Large portions of grass plants as well as fragments of leaves have revealed details of silica bodies, stomates, and other taxonomically important features under the scanning electron microscope. The computer database for grass identification compiled by Leslie Watson and colleagues was used to determine the most similar living grass genera to the five distinct kinds of fossil found. Two of the fossil species are assigned to Cleistochloa kabuyis sp. nov. and C. shipmanae sp. nov. This genus includes one species from low fertility dry woodland soils of New South Wales and Queensland and a second species from “raw clay soils” in western New Guinea. A third fossil species, represented by a large portion of a branching culm, is assigned to Stereochlaena miocenica sp. nov. This genus includes five species of low-fertility woodland soils in southeastern Africa. Both Cleistochloa and Stereochlaena are in the supertribe Panicanae of the subfamily Panicoideae. A fourth species is assigned to Distichlis africana sp. nov. and provides a biogeographic link between the single species of this genus now living in coastal grasslands in southeastern Australia and the 12 species of dunes and deserts found throughout the Americas from Patagonia and the West Indies to the United States and Canada. A fifth species is, like D. africana, in the subfamily Chloridoideae, but its stomata were not seen and it could belong to Cyclostachya, Pogoneura, or Polevansia. This earliest known wooded grassland flora in Africa is taxonomically unlike the modern grass flora of fertile volcanic African landscapes, and may have been recruited from an archaic grass flora of Gondwanan desert and lateritic soils.
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Jones, BA, RA How, and DJ Kitchener. "A field study of Pseudocheirus occidentalis (Marsupialia : Petauridae) I. Distribution and Habitat." Wildlife Research 21, no. 2 (1994): 175. http://dx.doi.org/10.1071/wr9940175.
Full textAbstract:
Surveys aimed at determining the distribution and habitat of the rare and endangered western ringtail possum (Pseudocheirus occidentalis) were undertaken in south-western Australia during 1990-92. Surveys relied on sightings of animals, or their characteristic faecal pellets or dreys. Habitat descriptions were collected in areas occupied by P. occidentalis to describe the vegetation and topography. Additional information about habitat was collected at subsets of sites to reflect leaf nutrient levels (nitrogen, phosphorus and potassium) of the major food plants, and to reflect the relative senescence of vegetation communities, and their fire and fox-baiting history. The species has a patchy occurrence from the Collie River to Two Peoples Bay, occurring most commonly in coastal or near-coastal forest that includes Agonis flexuosa as a major component. The most inland population occurs at Perup and this is the only known population living in forest without A. flexuosa. Local extinction has been extensive in the inland and northern parts of the original range (as it was known about 1900) and local decline has been patchy and occurred in most decades (1900-89) in different parts of the original range. Analysis of a matrix of relative abundance and habitat variables identified two habitat parameters associated with higher abundance of P. occidentalis: higher levels of nitrogen in foliage of the major food plant and a higher degree of canopy continuity. Hollow abundance was also implicated as a covariate of relative abundance. Assessment of levels of nitrogen, potassium and phosphorus in A. flexuosa leaves indicated that occupied sites tended to have relatively high nutrient levels. The pattern of decline and persistence of populations in different habitats is discussed with respect to environmental factors considered to have changed over the last century.
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Krauss, Siegfried L., and Janet M. Anthony. "The potential impact of mining on population genetic variation in the Banded Ironstone Formation endemic Tetratheca erubescens (Elaeocarpaceae)." Australian Journal of Botany 67, no. 3 (2019): 172. http://dx.doi.org/10.1071/bt18054.
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Tetratheca erubescens is a narrowly endemic species including ~6300 plants restricted to a 2-km2 distribution on the south Koolyanobbing Range Banded Ironstone Formation (BIF) in Western Australia. A key objective of the present study was to characterise population genetic variation, and its spatial structuring across the entire distribution of T. erubescens, to enable a quantification of genetic variation that may be affected by proposed mining of the BIF. In total, 436 plants (~30 at each of 14 sites) from across the entire distribution were sampled, genotyped and scored for allelic variation at 11 polymorphic microsatellite loci. Fifty-nine alleles were detected (mean alleles per locus=5.36, range 2–10), and observed heterozygosity was low to moderate and typically lower than expected heterozygosity across all loci (mean observed heterozygosity (Ho)=0.41, mean expected heterozygosity (He)=0.48). Given the restricted distribution of T. erubescens, overall genetic structuring was surprisingly strong (overall FST=0.098). A range-wide spatial autocorrelation analysis indicated a significant positive genetic correlation at distances up to 450m, largely corresponding to the scale of more-or-less continuous distribution within each of two geographic clusters. In support, a STRUCTURE analysis identified an optimal number of genetic clusters as K=2, with assignment of individuals to one of two genetic clusters corresponding with the main geographic clusters. The genetic impact of proposed mining on T. erubescens was assessed on the basis of identifying plants within the proposed mine footprint (all plants from 4 of 14 sites). Repeating analyses of genetic variation after removal of these samples, and comparing to the complete dataset adjusted for sample size, resulted in the loss of one (very rare: overall frequency=0.001) allele (i.e. 58 of 59 alleles (98.3%) were recovered). All other parameters of genetic variation (mean Na, Ne, I, Ho, He, F) were unaffected. Consequently, although up to 22% of all plants fall within the mine footprint and, therefore, may be lost, <2% of alleles detected will be lost, and other genetic parameters remained unaffected. Although these results suggest that the proposed mining will result in a negligible impact on the assessed genetic variation and its spatial structuring in T. erubescens, further research on impacts to, and management of, quantitative genetic variation and key population genetic processes is required.
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Jones, BA, RA How, and DJ Kitchener. "A field study of Pseudocheirus occidentalis (Marsupialia : Petauridae) II. Population studies." Wildlife Research 21, no. 2 (1994): 189. http://dx.doi.org/10.1071/wr9940189.
Full textAbstract:
Field studies of the rare and endangered western ringtail possum (Pseudocheirus occidentalis) were undertaken at five main sites in south-western Australia. Population studies employing capture-markrelease and telemetry methods were concentrated at Abba River and Locke Estate, near Busselton, and supplementary telemetry records were obtained for three females at Yendicup, Perup, near Manjimup. The location of dreys and sightings were mapped at Geographe Bay (near Busselton) and Emu Point (Albany). Mature adults of both sexes weighed about 1000 g and attained maturity at 830-900 g. Young were estimated to spend about 104 days in the pouch and emerge at 130-150 g. Lactation ceased when young weighed 550-650 g. Most births were of single young, but at Locke 16.7% of females with pouch young carried twins. In the Busselton area some births occurred in all months, but there were few between December and March. Most births occurred during April-July, but a secondary peak occurred during September-November, especially at Locke. At Locke 69% of animals were females and this ratio was similar in all age classes, but at Abba the sex ratio was parity. At Locke hollows were rare and animals usually rested in dreys; at Abba hollows in Eucalyptus gomphocephala were the usual rest sites and dreys were rare, occurred only near the watercourse and were used only by males; at Yendicup no dreys were observed and hollows in eucalypts were the usual rest sites. Animals used 2-7 rest sites each. Home ranges of females at Yendicup averaged about 2.5 ha; in the Busselton area home ranges averaged less than 1 ha. Less than 1% of both day and night sightings were of animals at ground level. Plots of the location of dreys and sightings at three sites showed that possums were not evenly dispersed, and at two sites there were areas of apparently suitable habitat that were rarely used. Density was estimated for four sites: Abba River 3.7-4.3 ha-1, Locke Estate 2.4-4.5 ha-1, Geographe Bay 0.3-0.6 ha-1 and Emu Point 0.1-0.4 ha-1. Evidence of predation by foxes was found at Abba, Locke and Geographe Bay. Microscopic inspection of faecal pellets showed that, where Agonis flexuosa grew, its leaves accounted for 79-100% of diet. Small amounts of several other plants were also taken. At Perup A. flexuosa was absent and the diet consisted predominantly of leaves of the two common eucalypts (Eucalyptus calophylla and E. marginata).
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Brundrett, Mark C. "Scientific approaches to Australian temperate terrestrial orchid conservation." Australian Journal of Botany 55, no. 3 (2007): 293. http://dx.doi.org/10.1071/bt06131.
Full textAbstract:
This review summarises scientific knowledge concerning the mycorrhizal associations, pollination, demographics, genetics and evolution of Australian terrestrial orchids relevant to conservation. The orchid family is highly diverse in Western Australia (WA), with over 400 recognised taxa of which 76 are Declared Rare or Priority Flora. Major threats to rare orchids in WA include habitat loss, salinity, feral animals and drought. These threats require science-based recovery actions resulting from collaborations between universities, government agencies and community groups. Fungal identification by DNA-based methods in combination with compatibility testing by germination assays has revealed a complex picture of orchid–fungus diversity and specificity. The majority of rare and common WA orchids studied have highly specific mycorrhizal associations with fungi in the Rhizoctonia alliance, but some associate with a wider diversity of fungi. These fungi may be a key factor influencing the distribution of orchids and their presence can be tested by orchid seed bait bioassays. These bioassays show that mycorrhizal fungi are concentrated in coarse organic matter that may be depleted in some habitats (e.g. by frequent fire). Mycorrhizal fungi also allow efficient propagation of terrestrial orchids for reintroduction into natural habitats and for bioassays to test habitat quality. Four categories of WA orchids are defined by the following pollination strategies: (i) nectar-producing flowers with diverse pollinators, (ii) non-rewarding flowers that mimic other plants, (iii) winter-flowering orchids that attract fungus-feeding insects and (iv) sexually deceptive orchids with relatively specific pollinators. An exceptionally high proportion of WA orchids have specific insect pollinators. Bioassays testing orchid-pollinator specificity can define habitats and separate closely related species. Other research has revealed the chemical basis for insect attraction to orchids and the ecological consequences of deceptive pollination. Genetic studies have revealed that the structure of orchid populations is influenced by pollination, seed dispersal, reproductive isolation and hybridisation. Long-term demographic studies determine the viability of orchid populations, estimate rates of transition between seedling, flowering, non-flowering and dormant states and reveal factors, such as grazing and competition, that result in declining populations. It is difficult to define potential new habitats for rare orchids because of their specific relationships with fungi and insects. An understanding of all three dimensions of orchid habitat requirements can be provided by bioassays with seed baits for fungi, flowers for insects and transplanted seedlings for orchid demography. The majority of both rare and common WA orchids have highly specific associations with pollinating insects and mycorrhizal fungi, suggesting that evolution has favoured increasing specificity in these relationships in the ancient landscapes of WA.
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Lamont, Byron B., Neal J. Enright, E. T. F. Witkowski, and J. Groeneveld. "Conservation biology of banksias: insights from natural history to simulation modelling." Australian Journal of Botany 55, no. 3 (2007): 280. http://dx.doi.org/10.1071/bt06024.
Full textAbstract:
We have studied the ecology and conservation requirements of Banksia species in the species-rich sandplains of south-western Australia for 25 years. Loss of habitat through land-clearing has had the greatest impact on their conservation status over the last 50 years. Ascertaining optimal conditions for conservation management in bushland requires detailed knowledge of the species under consideration, including demographic attributes, fire regime, growing conditions and interactions with other species. Where populations have been fragmented, seed production per plant has also fallen. The group most vulnerable to the vagaries of fire, disease, pests, weeds and climate change are the non-sprouters, rather than the resprouters, with population extinction so far confined to non-sprouting species. Recent short-interval fires (<8 years) appear to have had little impact at the landscape scale, possibly because they are rare and patchy. Fire intervals exceeding 25–50 years can also lead to local extinction. Up to 200 viable seeds are required for parent replacement in Banksia hookeriana when growing conditions are poor (low post-fire rainfall, commercial flower harvesting) and seed banks of this size can take up to 12 years to be reached. Seed production is rarely limited by pollinators, but interannual seasonal effects and resource availability are important. Genetic diversity of the seed store is quickly restored to the level of the parents in B. hookeriana. Florivores and granivores generally reduce seed stores, although this varies markedly among species. In Banksia tricuspis, black cockatoos actually increase seed set by selectively destroying borers. Potential loss of populations through the root pathogen Phytophthora cinnamomi also challenges management, especially in the southern sandplains. Prefire dead plants are a poor source of seeds for the next generation when fire does occur. Harvesting seeds and sowing post-fire have much to commend them for critically endangered species. Bare areas caused by humans can result in ideal conditions for plant growth and seed set. However, in the case of B. hookeriana/B. prionotes, disturbance by humans has fostered hybridisation, threatening the genetic integrity of both species, whereas fine-textured soils are unsuitable for colonisation or rehabilitation. Few viable seeds become seedlings after fire, owing to post-release granivory and herbivory and unsuitable germination conditions. Seedling-competitive effects ensure that season/intensity of fire is not critical to recruitment levels, except in the presence of weeds. Water availability during summer–autumn is critical and poses a problem for conservation management if the trend for declining rainfall in the region continues. Our simulation modelling for three banksias shows that the probability of co-occurrence is maximal when fire is stochastic around a mean of 13 years, and where fire-proneness and post-fire recruitment success vary in the landscape. Modelling results suggest that non-sprouting banksias could not survive the pre-European frequent-fire scenario suggested by the new grasstree technique for south-western Australia. However, we have yet to fully explore the conservation significance of long-distance dispersal of seeds, recently shown to exceed 2.5 km in B. hookeriana.
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Lamont, Byron B., Roy Wittkuhn, and Dylan Korczynskyj. "Ecology and ecophysiology of grasstrees." Australian Journal of Botany 52, no. 5 (2004): 561. http://dx.doi.org/10.1071/bt03127.
Full textAbstract:
‘Xanthorrhoea…is in habit one of the most remarkable genera of Terra Australis, and gives a peculiar character to the vegetation of that part of the country where it abounds’ Robert Brown (1814). Grasstrees (arborescent Xanthorrhoea, Dasypogon, Kingia), with their crown of long narrow leaves and blackened leafbase-covered trunk (caudex), are a characteristic growth form in the Australian flora. Xanthorrhoea is the most widespread genus, with 28 species that are prominent from heathlands to sclerophyll forests. While leaf production for X. preissii reaches a peak in spring–summer, growth never stops even in the cool winter or dry autumn seasons. Summer rain, accompanied by a rapid rise in leaf water potential, may be sufficient to stimulate leaf production, whereas root growth is confined to the usual wet season. Grasstrees are highly flammable yet rarely succumb to fire: while retained dead leaves may reach >1000°C during fire, the temperature 100 mm above the stem apex remains <60°C and the roots are insulated completely. Immediately following fire, leaf production from the intact apical meristem is up to six times greater than that at unburnt sites. For X. preissii, pre-fire biomass is restored within 40 weeks; the mass of live leaves remains uniform from thereon, whereas the mass of dead leaves increases steadily. Leaves usually survive for >2 years. In X. preissii, the post-fire growth flush corresponds to a reduction in starch storage by desmium in the caudex. Minerals, especially P, are remobilised from the caudex to the crown following a spring fire, but accumulate there following an autumn fire. At least 80% of P is withdrawn from senescing leaves, while >95% K and Na are leached from dead leaves. Most stored N and S are volatilised by fire, with 1–85% of all minerals returned as ash. Despite monthly clipping for 16 months, X. preissii plants recover, although starch reserves are depleted by 90%, indicating considerable resilience to herbivory. Analysis of colour band patterns in the leafbases of X. preissii shows that elongation of the caudex may vary more than 5–50 mm per annum, with 10–20 mm being typical. Exceptionally tall plants (>3 m) may reach an age of 250 years, with a record at 450 years (6 m). Fires, recorded as black bands on the leafbases, in south-western Australia have been decreasing in frequency but increasing in variability since 1750–1850. Some grasstrees have survived a mean fire interval of 3–4 years over the last two centuries. In more recent times, some grasstrees have not been burnt for >50 years. The band-analysis technique has been used to show a downward trend in plant δ13C of 2–5.5‰ from 1935 to the present. Grasstrees are most likely to flower in the first spring after fire. A single inflorescence is initiated from the apical meristem, elongating at up to 100 mm day–1 and reaching a length up to 3 m, with one recorded at 5.5 m. This rapid rate of elongation is achieved through leaf (and inflorescence) photosynthesis and desmium starch mobilisation. The developing spike and seeds are vulnerable to a moth larva. Leaf production recommences from axillary buds and the trade-off with reproduction is equivalent to 240 leaves in X. preissii. Flowering and seed production are affected by time of fire. Grasstrees are mainly insect-pollinated. Up to 8000 seeds per spike are produced, although pre-dispersal granivory is common. Seeds are released in autumn and persist in the soil for <2 years. Most fresh seeds germinate in the laboratory but germination is inhibited by light. At any time, seedlings and juveniles may account for most plants in the population, although there may be up to an 80% reduction within 1 year of seedling emergence, often due to kangaroo herbivory. In the absence of fire, mortality of adults may be 4% per annum. Although few grasstree species are considered rare or threatened, their conservation requirements, especially in regard to a suitable fire regime, remain unknown. Grasstrees are particularly susceptible to the exotic root pathogen, Phytophthora cinnamomi, although recruitment among some species has been observed 20–30 years after pathogen invasion. Much remains to be known about the biology of this icon of the Australian bush.
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Pretorius, Z. A., and C. M. Bender. "First Report of Virulence for the Wheat Leaf Rust (Puccinia triticina) Resistance Gene Lr32 in South Africa." Plant Disease 94, no. 3 (March 2010): 381. http://dx.doi.org/10.1094/pdis-94-3-0381a.
Full textAbstract:
The wheat leaf rust resistance gene Lr32 was transferred from Aegilops tauschii Coss. to bread wheat (Triticum aestivum L.) (1). Despite virulence for Lr32 in some isolates from Bulgaria, Israel, and Turkey, the gene has been reported to be effective in Australia, Mexico, the United States, and South Africa (1,2). A leaf rust isolate that differed in its avirulence/virulence profile from previously recorded races of Puccinia triticina Eriks. in South Africa was collected from triticale (× Triticosecale) in the Western Cape in 2005. According to the South African leaf rust differential set (3), this isolate (UVPt19) was avirulent for Lr3a, 3bg, 3ka, 10, 11, 16, 20, 26, and 30 and virulent for Lr1, 2a, 2b, 2c, 14a, 15, 17, 24, and Thatcher (Tc, control). Except for Lr20 in cv. Thew, all differentials are Tc near-isogenic lines. In comparison with known South African races (3), it differed from race 3SA132 at the Lr10 locus. Using standard rust pathology protocols (3), an expanded set of Lr gene lines (non Tc lines indicated) showed that UVPt19 is avirulent on wheat seedlings containing Lr9, 19, 21, 25, 27+31 (Gatcher), 29, 36 (ER84018), 37, 41 (KS91WGRC10), 44, 45, 47 (KS90H450), 50 (KS96WGRC36), 51 (R05), and 52, and virulent for Lr12, 22a, 23, 28, 32, 33, and 35. In the seedling stage, UVPt19 was virulent for the temperature sensitive genes Lr13, 18, and 34 at 25°C, but produced lower infection types (ITs) on Lr18 and 34 at 14 to 18°C. Seedlings of Pavon 76 (Lr46) were resistant (IT ;1=) to UVPt19. The susceptible response of lines carrying Lr32 was confirmed by high ITs (3++4) on RL5713/2*Mq, RL6086 (TcLr32), and RL5713/2*Mq//6*Palmiet. A control isolate (UVPt9) produced ITs ;1+, ;1+, and ;;1= on these lines, respectively. UVPt19 was virulent on line RL6092 (TcLr20) but avirulent on Thew. When tested on adult plants of lines RL6011 (TcLr12), CT263 (TcLr13), RL6044 (TcLr22a), RL6058 (TcLr34), RL6082 (TcLr35), RL6081 (TcLr37), and Tc (control), UVPt19 was only virulent (IT 3+) on CT263 and Tc. Flag leaves of RL6011 (IT ;1), RL6044 (IT 1), RL6058 (IT Z3-), RL6082 (IT 0;), and RL6081 (IT ;1) were resistant. UVPt19 was virulent on seedlings of 11 of 13 triticale cultivars and lines tested as opposed to UVPt9, which was virulent to only one entry. From a collection of 105 South African bread wheat cultivars and elite breeding lines, UVPt19 was virulent on 13 and five were mixed in their response to this isolate. All IT experiments were repeated. Although virulence has emerged for Lr32 in South Africa, the gene has not been used in local cultivars. Previously, McIntosh et al. (1) also reported that Lr32 has not been exploited in wheat production. On the basis of current evidence, UVPt19 appears to be potentially more damaging to triticale than bread wheat. Furthermore, the race seems rare because it was not collected in a recent wheat leaf rust survey in South Africa (3). References: (1) R. A. McIntosh et al. The Wheat Rusts: An Atlas of Resistance Genes, CSIRO-Kluwer, Dordrecht, the Netherlands, 1995. (2) Z. A. Pretorius. Phytophylactica 21:195, 1989. (3) T. Tarekegn et al. S. Afr. J. Plant Soil 26:51, 2009.