摘要:

AbstractAn assessment of the impact of the soil‐borne pathogenic fungus,Phytophthora cinnamomi(Oomycetes, Peronosporales), on the plant communities of the Stirling Range National Park was carried out between December 1988 and April 1989. A total of 541 plant species were collected, with the Proteaceae and the Myrtaceae the two largest families in the study region. Of the 330 species assessed for susceptibility toP. cinnamomi, 118 (36%) were recorded as having at least some individuals in a population judged to have been killed by the fungus and 33 (10%) were highly sensitive to the pathogen (more than 80% of plants in a population killed). Several families had large numbers of susceptible species, while others were apparently unaffected by the pathogen. Notably, 85% of proteaceous species assessed were rated as susceptible toP. cinnamomi. Proteaceous elements had a mean projective foliage cover of 40% in healthy plant communities, but had a mean cover of only 10% at sites that had a long history of infestation with the fungus. In contrast, some species with low levels of susceptibility to the pathogen, such as some monocotyledons, were found to be more abundant at old‐infested sites than at healthy sites. Growth form may also influence susceptibility, with herbaceous perennials, annuals and geophytes assessed in this survey apparently unaffected by the fungus whereas 48% of woody perennials surveyed were susceptible.Changes in the floristic structure of plant communities may influence the composition of associated animal communities. In particular, vertebrate flower visitors may be vulnerable since 59% of the species with vertebrate‐pollinated flowers were found to be susceptible to the pathogen. This research highlights the serious ecological impact ofP. cinnamomion native plant communities and suggests that significant components of the flora and associated fauna of the southwest of Western Australia are endangered by this virulent pat

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1993.tb00439.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPollen analysis of the sediments of a small bog, supporting a stand of cool temperate rainforest in southeastern Tasmania, was undertaken in order to examine the history of the stand dominant,Nothofagus cunninghamii, presently growing outside its predicted climatic range. The pollen record covers at least the last 9000 years and reveals changes in the bog and in the surrounding vegetation, although pollen percentages ofN. cunninghamiiare sufficiently high to indicate that the species could have had a local presence throughout the recorded period. It is likely that thisN. cunninghamiistand is relictual, surviving not only Holocene climates, but also the cool dry conditions of the last glacial period. This ability to survive changing and sometimes very unfavourable climates leads to the conclusion that great caution must be exercised in using present climates alone to predict the potential distribution ofN. cunninghamii.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1993.tb00440.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractSclerolaena diacanthais a common and widespread, short‐lived chenopod of arid Australia. The diaspore contains a food mass attractive to ants and, at sites where the antRhytidoponerasp B is common, thousands of diaspores accumulate on the nest mounds. Bagged plants set seed, showing that it is self‐compatible. Population genetic variation was investigated at two levels: within and between sites, and within and between seed banks accumulated on the ant nests. Electrophoretic analysis of adult plants for 17 loci at 12 sites revealed nine polymorphic loci, but within sites only 6–18% of the loci were polymorphic. The values for mean gene diversity (He = 0.042) and total genetic diversity, (HT= 0.088) were lower than those recorded for most other plant species. The mean fixation index of 0.52 indicated a mixed mating system with about 70% selfing. Most of the genetic diversity was distributed within sites (Dst = 0.008) and the mean value of 0.094 for GST indicated low levels of genetic differentiation. Electrophoretic analysis of seeds from 12 ant mounds at two sites showed that genetic differentiation was three times greater between seed banks than between the sites. However, collectively the genetic diversity stored within ant mounds was similar to the total diversity within the sites. It appears that restricted ant‐dispersal and moderate inbreeding may create a local population structure that is undetected when sampling at a larger scale. Since investigations of genetic patterns on a very local scale are just beginning, there is much to learn about the evolutionary and genetic consequences of different seed flow p

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1993.tb00441.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe arthropod assemblages occurring in the canopies of tropical, subtropical and cool temperate sites have been sampled using a pyrethrum knockdown technique. Details of the techniques used and the climate and vegetation of the areas studied are presented together with an analysis of the distribution of individual arthropods across Orders. An approach using generalized linear modelling partitioned the variance in numbers among sites within forest types and across the three forest types. The effects of both these components were significant. The differences between the ordinal signatures of each forest type are discussed and a number of hypotheses proposed to account for these differences, based on knowledge of the biology of the groups concerned. For the tropical and subtropical sites a comparison was made between samples collected in the low to mid‐canopy with ones collected in the high canopy. Numbers of both insects and non‐insects collected differed significantly with height in the subtropical forest and the distribution of insects across Orders was also significantly different in this forest type. In the tropical forests numbers of insects differed significantly between the two strata but neither the numbers of non‐insects nor the ordinal profiles of either insects or non‐insects were shown to be significantly di

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1993.tb00442.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA competitive interaction between two species of sympatric native rodents was demonstrated experimentally in Myall Lakes National Park (NSW, Australia). The previously documented replacement ofPseudomys gracilicaudatusbyRattus lutreolusin areas of wet heath in this region implied that competition may be the mechanism facilitating this succession. We present experimental evidence to support this suggestion. Removal of the largerR. lutreoluscaused a significant increase in abundance ofP. gracilicaudatuson five experimental sites in comparison to five unmanipulated control sites. The sites used in this experiment were chosen from three ages of wet heath regenerating after fire. These three ages represent key stages in the replacement ofP. gracilicaudatusbyR. lutreolusand the occurrence of competition in each of these ages indicates that competition plays an important role in this succession. In the initial stages of the experiment whenR. lutreoluswere removed they were replaced by newR. lutreolusindividuals. This has been interpreted as evidence of strong intraspecific competition. After removal ofR. lutreolus, P. gracilicaudatusexpanded its habitat range into microhabitats that had formerly been occupied byR. lutreolusand reduced its range in microhabitats previously occupied byP. gracilicaudatus. This leads us to believe thatP. gracilicaudatuswas occupying inferior microhabitat before the removal of R. lutreolus, which had excluded it from more preferable microhabitat.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1993.tb00443.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractSympatrically growing species ofDroserawere examined, including rosette forms, climbers and upright, self‐supporting species, in southwestern Australia, to see whether the height above ground of the capturing leaves influenced the kinds of prey caught. The leaves examined for invertebrate prey remains were all collected at the same time and the results thus represent a snapshot of the prey situation. Although the number of fully opened, active leaves and leaf size among species varied 40‐fold and 22‐fold, respectively, total catch per unit leaf area was relatively constant, regardless of growth form. Growth form was strongly correlated with the kinds of prey caught. Prostrate species caught mainly walking, non‐aerial prey, while self‐supporting and climbing species caught predominantly ae

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1993.tb00444.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPollen carried on the probosces ofHelicoverpa punctigera(Wallengren) andH. armigera(Hübner) trapped in western Queensland and in cropping areas of eastern Australia in September 1989 and 1990 was identified by scanning electron microscopy. Ninety‐five per cent of moths carried pollen. A total of 19 morphological pollen species’, representing 14 plant families, was found. Up to six pollen species were found on individual moths, and 61% carried more than one. Pollen from plants unsuitable for larval survival was common. Pollen loads generally reflected the abundance of locally flowering plants, but there were exceptions which suggested migration. Pollen ofPtilotus(Amaranthaceae),Velleia(Goodeniaceae) andEremophila(Myoporaceae), and the Asteraceae (Tubuliflorae) were found on moths trapped in the east. These plants either did not occur in the areas where the moths were caught, or did not flower there at the time the moths were caught. However, they were abundant in possible source areas such as western Queensland. Among moths caught in eastern regions, 30% ofH. punctigeraand 18% ofH. armigeracarried pollen from such plants. The value and limitations of moth‐borne pollen as a marker for migration are dis

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1993.tb00445.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe maximum density of resident honeyeaters in heathland near Sydney was very similar from one area and year to another, despite large variation in production of nectar‐energy. The most likely explanation for this is that density is determined by the spacing behaviour of birds rather than by nectar production or other factors. Within years, nesting by these residents was positively correlated with temporal variation in production of nectar‐energy and 90% of nesting occurred when the estimated average amount of energy available in the heathland per pair exceeded that required to support parents and young. Most nesting and the highest nectar production consistently occurred between April and J

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1993.tb00446.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractNon‐toxic strains (by mouse toxin assay test) of unicellularMicrocystis aeruginosaand short filamentousAnabaena cylindricawere fed toDaphnia carinatain the laboratory at an algal volume concentration of 4.0 mm3L−1at 24 ± 1°C. The filtering rates (FR, mL animal−1hr−1) ofD. carinataonM. aeruginosaandA. cylindricaincreased with increasing body length (L, mm), and were expressed as a power curve: FR = 0.061L209. and FR = 0.232L2.09, respectively. The potential for control of natural blue‐green algal populations byD. carinatagrazing is discus

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1993.tb00447.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA numerical classification of presence‐absence data of vascular plant species on a transect across a dry monsoon foresl‐Eucalyptussavanna boundary at Cobourg Peninsula was used to define savanna, ecotone or monsoon forest communities. The boundary was protected from fire. After 4 years noAglaia rufaseedlings had established in 24 permanent quadrats (1 × 4 m) in the savanna while threeDiospyros maritimaseedlings established in these savanna quadrats. The number of establishedA. rufaseedlings in 26 ecotone quadrats fell by 50% to one individual, the number ofD. maritimaseedlings increased by 43% to a total of seven individuals. After 3 months significantly more transplantedD. maritimaseedlings had died in the savanna than the monsoon forest, but survival ofA. rufawas high, and not significantly different, in both communities. Seedlings from both species did not have significantly greater survival in the monsoon forest compared to the savanna, 42 months after transplanta

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1993.tb00448.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY