bluuebunny/crossref_metadata_2025_split huggingface dataset:
What physiological processes permit insects to eat Eucalyptus leaves?
Authors: Cooper Paul D. 
Published: March 2003

AbstractMany species of insects eat Eucalyptus foliage despite its relatively low nutritional value and the many plant secondary metabolites (PSMs) present, for example, terpenes, phenols and formylated phloroglucinols (FPGs). Formylated phloroglucinols are a new class of PSMs that act as antifeedants for possums and koalas. What physiological processes are present that permit insects to eat eucalypt foliage and how do PSMs influence insect feeding or digestion? Some trees seem to be repeatedly infested with eucalypt‐feeding insects, possibly as a result of previous chemosensory cues remaining from parental selection of a plant. Avoidance or storage of PSMs permit jarrah leafminers (Perthida glyphopa) and sawflies (Perga sp.) to consume eucalypt foliage without dealing with the majority of these compounds. Some PSMs can be metabolized by polysubstrate membrane oxidases as found in caterpillars or sawflies that feed on eucalypts. High midgut pH may be advantageous for nutrient extraction and PSM metabolism, and midgut pH ranges between 8.5 and 8.9 for caterpillars of Hyalarcta huebneri. Plant secondary metabolites may not be absorbed as a result of the combined presence of the peritrophic matrix and endogenous surfactants. Excretion of PSMs can be as metabolites or intact compounds. Both putative metabolites and sideroxylonal‐A, an FPG, are present in the faeces of larvae of the case moth, H. huebneri. The presence of sideroxylonal‐A in the food had an effect on the presence of 5‐hydroxytryptamine (5HT) in the central nervous system of caterpillars, as larvae fed leaves with a high concentration of sideroxylonal‐A had relatively more 5HT in the brain and central nervous system ganglia than larvae fed leaves containing a low concentration. Further work is necessary to clarify how PSMs are handled by eucalypt‐feeding insects and what effect FPGs have on feeding and digestion.
Influence of previous frost damage on tree growth and insect herbivory of Eucalyptus globulus globulus
Authors: Thomson Vivien P. , Nicotra Adrienne B. , Steinbauer Martin J. 
Published: March 2003

AbstractThe plant stress hypothesis suggests that some herbivores favour stressed plants, whereas the plant vigour hypothesis proposes that other herbivores prefer vigorous plants. The effects of a prior stress, that of frost damage, were examined on the subsequent growth of Eucalyptus globulus globulus and on the response of insect herbivores. Frost damage affected tree growth by reducing new leaf area and increasing specific leaf area (SLA). However, herbivore abundance was not affected by prior frost damage. Two feeding trials using Anoplognathus chloropyrus and Hyalarcta huebneri and a morphometric study of Ctenarytaina eucalypti were conducted to assess the performance of herbivores on trees that had suffered more or less frost damage. Consumption by A. chloropyrus and H. huebneri was unaffected by foliage origin (damaged versus healthy). Hyalarcta huebneri grew faster when fed leaves from previously damaged trees, and C. eucalypti from previously damaged trees were larger than those from healthy trees. Enhanced insect performance on frost damaged plants may have resulted from the high specific leaf area (most likely thinner) leaves. The herbivore abundance data did not support the hypothesis that previously frost damaged plants are preferred by insects. However, increased growth of H. huebneri and larger body size of C. eucalypti on damaged trees indicates that previously stressed trees may produce leaves of higher nutritional value.
Feeding ecology of a carnivorous bladderwort (Utricularia uliginosa, Lentibulariaceae)
Authors: Jobson Richard W. , Morris E. Charles 
Published: March 2003

AbstractThe terrestrial carnivorous bladderwort, Utricularia uliginosa Vahl. (Lentibulariaceae) was studied to determine the species assemblage present in traps of these plants in situ across four sites over 15 months. The immediate soil environment was also sampled to determine the fauna present, and to compare the fauna present in traps with the fauna in the environment. The soil fauna consisted of 10 taxon types, which occupied either pelagic, epibenthic or interstitial microhabitats. All were found in traps of U. uliginosa, with the main prey being interstitial taxa followed by epibenthic and occasionally pelagic taxa. Numbers of individuals of the two most abundant soil taxa (nematodes, Elaphoidella) varied independently across the four sites over the 15 months of the study, as did numbers of Elaphoidella in the traps of U. uliginosa. Numbers of nematodes in the traps of U. uliginosa showed significant differences among sites, but not differences among times. Comparison of the trap fauna with the soil fauna revealed differences in relative abundance between soil samples and trap samples for two of the three taxa examined. There was an under‐representation of nematodes in the traps relative to numbers in surrounding soil. There was an over‐representation of the copepod Elaphoidella in the traps of U. uliginosa relative to numbers in soil at some of the times of sampling. Acarina were equally abundant in soil and trap samples. The patterns observed for Elaphoidella and nematodes may be due to selectivity in trapping by U. uliginosa, and/or differences in digestibility of the prey. Elaphoidella individuals were found to be attracted to U. uliginosa in a behavioural experiment. This may contribute to the over‐representation of Elaphoidella in the traps of U. uliginosa in the field.
Effects of frequent fires and grazing on stable nitrogen isotope ratios of vegetation in northern Australia
Authors: Cook G. D. 
Published: March 2003

AbstractThe ratios of stable nitrogen isotopes expressed as δ15N values can indicate the openness of nitrogen cycles in ecosystems. Southwards through the Northern Territory, values of foliar δ15N in savanna trees increase as mean annual rainfall decreases from approximately 1800 mm to approximately 750 mm, with foliar δ15N thereafter decreasing toward arid central Australia. Recent literature argues that this pattern is caused by higher grazing intensity in semi‐arid savannas, but counter views have attributed the pattern more directly to variations in aridity. In this paper, grazed and ungrazed sites in a semi‐arid savanna are compared, and it is shown that grazing has a relatively small effect on the positive foliar δ15N values of grasses, but no effect on δ15N values of trees. This gives little support to the argument that variations in grazing pressure at the scale of hundreds of kilometres could result in detectable differences in the foliar δ15N values of trees. I then compare the semi‐arid savannas with mesic savannas, where fires are frequent, and with mesic rainforests, which are rarely burnt. Greater foliar δ15N values in rainforest and fire‐excluded mesic savannas than in frequently burnt savannas suggests that fire regimes affect foliar δ15N. The previously observed pattern in δ15N values along the rainfall gradient in the Northern Territory is consistent with trends in fire frequency and possible direct effects of fire, but further work is required to determine the relative impacts of aridity and fire. Within a particular rainfall regime, foliar δ15N values may indicate historical fire frequencies.
Measurement of leaf biomechanical properties in studies of herbivory: Opportunities, problems and procedures
Authors: Sanson G. , Read J. , Aranwela N. , Clissold F. , Peeters P. 
Published: March 2003

AbstractLeaf biomechanical properties have the potential to act as antiherbivore defences. However, compared with studies on chemical defences, there are few studies that have demonstrated that the physical or biomechanical structure of plants can prevent or influence herbivory. This difference in focus by ecologists may relate to the dominant paradigm of plant chemical defences in ecological research and the perceived difficulties that ecologists have with the engineering principles embedded in biomechanics. The advantage of using materials engineering concepts is that each property is precisely defined and quantifiable, although the latter may be difficult in leaves because of their composite and anisotropic nature. Most herbivory studies have used simple penetrometers to measure leaf properties, often termed ‘toughness’. As defined in materials engineering, the measured properties are ‘force to fracture’ and ‘strength’, not toughness. Measurement of strength, the resistance to crack initiation, is relevant to understanding herbivory. Measurement of ‘toughness’ as defined by materials engineering is also relevant. Toughness is the resistance to crack propagation and is a measure of the energy required to fracture the leaf. This requires more sophisticated equipment than simple penetrometers because it requires a simultaneous measure of the punch displacement. In addition, purists would argue that a punch cannot be used to measure true toughness because the crack is not controlled and plastic deformation is also involved. However, it may be the only method that allows detection of fine‐scale pattern in mechanical properties across a leaf surface at a scale that is relevant to herbivory. There is very little work on the scale at which these properties vary, particularly with regard to different sized herbivores. In addition, few studies have investigated a broad range of relevant biomechanical properties in relation to herbivory. Therefore, it is not possible yet to be definitive about the relative merits of the various types of tests. A single test might show a pattern in relation to herbivore damage at a gross level. However, to really understand the functional and ecological significance of leaf texture in relation to herbivory, a more reductionist approach is needed. Only then can we move on to the larger scales of pattern that many ecologists are seeking.
Ecological biogeography of species of Gelonus, Acantholybas and Amorbus in Australia
Authors: Steinbauer Martin J. , Yonow Tania , Reid Ian A. , Cant Russell 
Published: March 2003

AbstractGeographic ranges and host plants of 10 species of Australian coreid, Gelonus
tasmanicus, Acantholybas brunneus, Amorbus alternatus, Am. atomarius,
Am. biguttatus, Am. bispinus, Am. obscuricornis, Am. rhombifer,
Am. robustus and Am. rubiginosus, were summarized using data from specimen
collection labels and sampling. One process (CLIMEX) and two correlative
range‐modelling programs (BIOCLIM and DOMAIN) were
used to infer the bioclimatic profiles of each species. By inference from the maximum
range predictions made by CLIMEX, the suggestion that G. tasmanicus,
Am. atomarius and Am. obscuricornis are temperate species was supported.
Similarly, the suggestions that Ac. brunneus was a subtropical species and
Am. biguttatus and Am. rhombifer are predominantly tropical species
were supported. That Am. alternatus, Am. robustus and Am. rubiginosus
are apparently ubiquitous species was supported. Comparison of the bioclimatic profiles
of the habitats of G. tasmanicus and Am. obscuricornis within Tasmania
using BIOCLIM supported information available in the published literature,
that is, that G. tasmanicus is better suited to sites at higher elevations
than Am. obscuricornis. In addition, the suggestion that the regions of high
Amorbus species endemism should overlap with regions of high eucalypt species
endemism was also supported. This finding is taken as evidence that the evolutionary
radiation of Amorbus has followed that of the eucalypts. Using these models we have obtained preliminary insights into the biology of each species and the environmental characteristics of their preferred climatic envelope. This is an achievement that might never have been attained through concentrated study given that these insects can vary from being rare to, at best, locally common in occurrence.
The late Quaternary vegetation history of the south‐central highlands of Victoria, Australia. II. Sites below 900 m
Authors: McKenzie G. Merna 
Published: March 2003

AbstractThe late Quaternary vegetation communities of the south‐central highlands of Victoria are constructed from analyses of pollen and charcoal, and macroscopic plant remains preserved inSphagnumbogs. The sites, located in eucalypt forest or woodland, form an altitudinal sequence with the componentEucalyptusspecies varying with altitude and with small pockets ofNothofagus cunninghamii(Hook.) Oerst. in close proximity to the higher sites. The record from the sites above 900 m covers the last 32 000 years, and the record from the lower sites extends from at least 12 000BP. Around 32 000BPthe region was predominantly covered by a mosaic of alpine feldmark and herbfield, with small patches ofEucalyptusandNothofaguswoodland close to sea level when summer temperatures were probably 5°C lower than present. Lowest values, probably 7°–8°C below present, occurred between 19 800 and 16 900BP, when alpine communities were most widespread and much of the Central Highlands was treeless. Around 12 000BPalpine taxa disappeared or were greatly reduced, first at the lower sites. There was an associated rise in the treeline with the movement upslope ofNothofagusand eucalypt forest as a result of a general increase in temperature and probably effective precipitation. By 6000BPwet eucalypt forest andNothofagusreached their maximum postglacial extent at all sites, possibly related to a further increase in temperature, at least 2°C lower than present, and higher effective precipitation. A continuing increase in temperature, or an increase in continentality, and a decrease in effective precipitation led to increased fire hazard and retraction of rainforest and wet sclerophyll or tall open forest toward present‐day values.Nothofagusdisappeared from the sites below 900 m. The activities of humans pose further threats to remaining forest communities. The record of vegetation and environmental change derived from the local and regional picture from eight sites reinforces and complements that from the individual sites. For example, combining the records overcomes to some extent taphonomic problems such as the effect of streams that flow close to all sites, and other limitations including problems of dating, poor preservation and variable sedimentation rates.
Comparison of two rolled sandy heath communities within a single fire patch in Ngarkat Conservation Park, South Australia
Authors: Pelton Grant A. , Conran John G. 
Published: March 2003

AbstractCross‐ribbed rolling is a technique routinely used to construct firebreaks along the margins and access tracks of Ngarkat Conservation Park, South Australia. These breaks, approximately 20 m wide, contain regenerating heath communities with an overstorey of mallee. The effects of cross‐ribbed rolling on community composition and succession were examined in a single fire patch on the western boundary of Ngarkat Conservation Park across 12 sites located in vegetation burnt approximately 35 years ago. Two areas at each site were investigated, one on rolled communities and the other running parallel on the adjacent unrolled vegetation. There was also a difference in the rolled communities sampled; six were on a 3‐year‐old break, whereas the remainder were on a 5‐year‐old break. Results indicate no changes to species richness or diversity when comparing rolled and unrolled areas, but there was some alteration to species composition in rolled communities. These results suggest that under current rolling regimes, the main effect is a reduction in biomass and some accompanying alteration to species composition, but not a reduction in overall species diversity or an increase in weeds.
Sexual divergence in diets and morphology in Fijian sea snakes Laticauda colubrina (Laticaudinae)
Authors: Shetty S. , Shine R. 
Published: March 2003

AbstractIn the Fiji Islands, female yellow‐lipped sea kraits (Laticauda colubrina) grow much larger than males, and have longer and wider heads than do conspecific males of the same body length. This morphological divergence is accompanied by (and may be adaptive to) a marked sex divergence in dietary habits. Adult female sea kraits feed primarily on large conger eels, and take only a single prey item per foraging bout. In contrast, adult males feed upon smaller moray eels, and frequently take multiple prey items. Prey size increases with snake body size in both males and females, but the sexes follow different trajectories in this respect. Female sea kraits consume larger eels relative to predator head size and body length than do males. Thus, the larger relative head size of female sea kraits is interpreted as an adaptation to consuming larger prey items. Our results are similar to those of previous studies on American water snakes (natricines) and Australian file snakes (acrochordids), indicating that similar patterns of sex divergence in dietary habits and feeding structures have evolved convergently in at least three separate lineages of aquatic snakes.
Breeding system and population genetics of the vulnerable plantDillwynia tenuifolia(Fabaceae)
Authors: Rymer P. D. , Morris E. C. , Richardson B. J. 
Published: March 2003

Abstract Dillwynia tenuifoliaSieber ex DC. is a vulnerable species endemic to the Sydney region in Australia. This investigation focused on the breeding system and genetic structuring of the species in locations encompassing its entire geographical range. A field pollination experiment showed thatD. tenuifoliaproduced fruit from both self‐ and cross‐pollination events, and thus has a facultative breeding system. Fruiting success from self‐ pollination was approximately half that observed from cross‐pollination. The genetic structure ofD. tenuifoliapopulations was investigated by using allozyme electrophoresis. A survey of 16 loci revealed a high level of genetic variation with approximately two‐thirds of the loci being polymorphic and a mean of 1.84 alleles per loci. The genotype frequencies deviated from the Hardy–Weinberg equilibrium, with the observed level of heterozygosity significantly less than expected. The inbreeding coefficient was 0.31. There was very little divergence between populations (FST= 0.04) but the fixation indices were high within populations. Spatial autocorrelation, using Moran’sI, showed that neighbouring plants were closely related (I> 0.4). The genetic neighbourhood and effective population size in the species were estimated at one location as 1.1 ha and 104plants, respectively.
Effects of extra food on population fluctuation patterns of the muroid rodent Calomys venustus
Authors: Castellarini F. , Polop J. 
Published: March 2003

Abstract Population dynamics in the South American muroid rodent Calomys venustus are described from a 14‐year continuous data series, using the auto‐regressive integrated moving average (arima) model. Population responses to experimental food addition were analysed in two experimental areas, over two periods, using intervention analysis. There was no consistent evidence that food quantity leads to peaks in population density. Significant increases were related to densities of transients and juvenile individuals.
Response of a rare herb (Trioncinia retroflexa) from semi‐arid tropical grassland to occasional fire and grazing
Authors: Fensham R. J. , Fairfax R. J. , Holman J. E. 
Published: March 2003

Abstract  Trioncinia retroflexa (Asteraceae) is a rare perennial herb endemic to Dichanthium‐dominated grasslands on basaltic soils in central Queensland. Trioncinia lives for approximately 5 years and some seed remains viable in the soil for at least 18 months. Population densities increased sixfold over 4 years, coinciding with recovery during a period of above‐average rainfall after a 4‐year drought preceding this study. The species’ lifespan, which can exceed 5 years, coupled with its extended seed‐bank viability ensures that populations can endure drought despite low levels of seedling recruitment. The restricted occurrence of the species to spasmodically grazed stock routes provides evidence that Trioncinia is sensitive to the continuous grazing that typically occurs in paddocks. The hypothesis that the species requires occasional disturbance for survival was experimentally tested. Recruitment was depressed with burning and inflorescence production enhanced with both burning and simulated intense spasmodic grazing after the first application of treatments. However, these effects were not evident after a second application of the treatments and there were no significant effects of treatment on population densities at the completion of the 4‐year experiment. Although not requisite, sporadic dry‐season grazing and burning of these areas would appear to be compatible with the survival of Trioncinia. This project highlights the value of stock routes for rare plant conservation.
Responses of vertebrates to pastoralism, military land use and landscape position in an Australian tropical savanna
Authors: Woinarski J. C. Z. , Ash A. J. 
Published: March 2003

Abstract Despite the hegemony of pastoralism over most of Australia’s tropical savannas, its impacts upon biodiversity are poorly known. There is even less knowledge about the impacts of military training, a recent, but rapidly expanding, alternative land use. We compare impacts of these land uses upon mammals, birds, reptiles and frogs at a site in north‐eastern Australia, with sampling from 24 quadrats stratified by four landscape positions (upper slope to riparian) and three current land‐use types (pastoralism, military training and undisturbed). Prior to exclusion in 1967, the whole study area had been subjected to grazing over the course of approximately 100 years, so differences observed strictly reflect responses to changed land use (largely cessation from grazing) over the period of 32 years subsequent to the imposition of the present regime. The four classes of vertebrates showed contrasting responses. Frog distribution was unrelated to land use, but strongly associated with landscape position. Reptiles showed a very strong response to land‐use type but not to landscape position. The total abundance and richness of reptiles was greater in ungrazed (i.e. military and undisturbed) than in grazed quadrats. The total abundance and species richness of birds varied strongly with landscape position but was unrelated to land use. However, many individual bird species showed significant responses to land‐use type, and bird species composition was significantly related to both land‐use type and landscape position. The richness of the mammal fauna was weakly related to landscape position and not related to land‐use type. A few individual mammal species showed significant responses to either or both factors, but mammal species composition was significantly (albeit weakly) related only to land‐use type. With due regard to some interpretative constraints in the study design, and the history of the site prior to this study, these results suggest that pastoralism leads to a substantial rearrangement of the vertebrate fauna, and particularly so for reptiles and those mammals and birds associated with the ground and understorey layers. Given the extent of pastoralism across the tropical savannas, these results suggest that this industry has contributed to major and widespread change in the savanna fauna. In contrast to pastoralism, military land use (at least at the relatively low intensity examined here) produced little change in vertebrate assemblages.