Does lethal control of top-predators release mesopredators? A re-evaluation of three Australian case studies

Top-predators can sometimes be important for structuring fauna assemblages in terrestrial ecosystems. Through a complex trophic cascade, the lethal control of top-predators has been predicted to elicit positive population responses from mesopredators that may in turn increase predation pressure on prey species of concern. In support of this hypothesis, many relevant research papers, opinion pieces and literature reviews identify three particular case studies as supporting evidence for top-predator control-induced release of mesopredators in Australia. However, many fundamental details essential for supporting this hypothesis are missing from these case studies, which were each designed to investigate alternative aims. Here, we re-evaluate the strength of evidence for top-predator control-induced mesopredator release from these three studies after comprehensive analyses of associated unpublished correlative and experimental data. Circumstantial evidence alluded to mesopredator releases of either the European Red Fox (Vulpes vulpes) or feral Cat (Felis catus) coinciding with Dingo (Canis lupus dingo) control in each case. Importantly, however, substantial limitations in predator population sampling techniques and/or experimental designs preclude strong assertions about the effect of lethal control on mesopredator populations from these studies. In all cases, multiple confounding factors and plausible alternative explanations for observed changes in predator populations exist. In accord with several critical reviews and a growing body of demonstrated experimental evidence on the subject, we conclude that there is an absence of reliable evidence for top-predator control-induced mesopredator release from these three case studies. Well-designed and executed studies are critical for investigating potential top-predator control-induced mesopredator release.

Evaluation and histological examination of a Campylobacter fetus subsp. venerealis small animal infection model

Bovine genital campylobacteriosis (BGC), caused by Campylobacter fetus subsp. venerealis, is associated with production losses in cattle worldwide. This study aimed to develop a reliable BGC guinea pig model to facilitate future studies of pathogenicity, abortion mechanisms and vaccine efficacy. Seven groups of five pregnant guinea pigs (1 control per group) were inoculated with one of three strains via intra-peritoneal (IP) or intra-vaginal routes. Samples were examined using culture, PCR and histology. Abortions ranged from 0 to 100 and re-isolation of causative bacteria from sampled sites varied with strain, dose of bacteria and time to abortion. Histology indicated metritis and placentitis, suggesting that the bacteria induce inflammation, placental detachment and subsequent abortion. Variation of virulence between strains was observed and determined by culture and abortion rates. IP administration of C. fetus subsp. venerealis to pregnant guinea pigs is a promising small animal model for the investigation of BGC abortion.

Evaluation of Inoculated Lablab Silage for Growing Dairy Heifers

A summer grown forage legume crop – Lablab (Lablab purpureus) harvested in autumn, was ensiled as plastic wrapped, large round bales. Of the 30 bales produced, 13 were inoculated with a bacterial inoculant containing Lactobacillus plantarum and Enterococcus faecium. Inoculant was premixed at 30 g/litre water, cultured overnight (18 hours) then sprayed onto cut forage during the baling and wrapping procedure at 1 litre per tonne of silage. A replicated feeding experiment was conducted in July - August 1998 (5 weeks), using 24 eight month old Holstein Friesian heifers group fed non-inoculated or inoculated silage to appetite plus 2 kg rolled sorghum grain/heifer.day. Chemical composition and nutritive value of well preserved bales of control and inoculated silages were similar (P>0.05) with 50% DM and 26 g N and 6.8 MJ ME per kg DM. Lactic acid and acetic acid concentrations were 11.4 v. 11.4 and 4.90 v. 3.75 g/kg DM for control and inoculated silages respectively (P>0.05). Heifers preferentially selected leaf from the silage offered and maintained liveweight gains of 0.70 and 0.61 kg/day respectively (P>0.05) during the silage feeding period. High DM and low WSC content of the parent forage may have reduced the opportunity for the bacterial inoculant to have effect. Animal production for a consuming world : proceedings of 9th Congress of the Asian-Australasian Association of Animal Production Societies [AAAP] and 23rd Biennial Conference of the Australian Society of Animal Production [ASAP] and 17th Annual Symposium of the University of Sydney, Dairy Research Foundation, [DRF]. 2-7 July 2000, Sydney, Australia.

Evaluation of aerial photography for predicting trends in structural attributes of Australian woodland including comparison with ground-based monitoring data

The accurate assessment of trends in the woody structure of savannas has important implications for greenhouse accounting and land-use industries such as pastoralism. Two recent assessments of live woody biomass change from north-east Australian eucalypt woodland between the 1980s and 1990s present divergent results. The first estimate is derived from a network of permanent monitoring plots and the second from woody cover assessments from aerial photography. The differences between the studies are reviewed and include sample density, spatial scale and design. Further analyses targeting potential biases in the indirect aerial photography technique are conducted including a comparison of basal area estimates derived from 28 permanent monitoring sites with basal area estimates derived by the aerial photography technique. It is concluded that the effect of photo-scale; or the failure to include appropriate back-transformation of biomass estimates in the aerial photography study are not likely to have contributed significantly to the discrepancy. However, temporal changes in the structure of woodlands, for example, woodlands maturing from many smaller trees to fewer larger trees or seasonal changes, which affect the relationship between cover and basal area could impact on the detection of trends using the aerial photography technique. It is also possible that issues concerning photo-quality may bias assessments through time, and that the limited sample of the permanent monitoring network may inadequately represent change at regional scales

Summative evaluation of climate application activities with pastoralists in western Queensland

Survey methods were engaged to measure the change in use and knowledge of climate information by pastoralists in western Queensland. The initial mail survey was undertaken in 2000-01 (n=43) and provided a useful benchmark of pastoralists climate knowledge. Two years of climate applications activities were completed and clients were re-surveyed in 2003 (n=49) to measure the change in knowledge and assess the effectiveness of the climate applications activities. Two methods were used to assess changes in client knowledge, viz., self-assessment and test questions. We found that the use of seasonal climate forecasts in decision making increased from 36% in 2001 (n=42) to 51% in 2003 (n=49) (P=0.07). The self-assessment technique was unsatisfactory as a measure of changing knowledge over short periods (1-3 years), but the test question technique was successful and indicated an improvement in climate knowledge among respondents. The increased levels of use of seasonal climate forecasts in management and improved knowledge was partly attributed to the climate applications activities of the project. Further, those who used seasonal forecasting (n=25) didn't understand key components of forecasts (e.g. probability, median) better than those who didn't use seasonal forecasts (n=24) (P>0.05). This identifies the potential for misunderstanding and misinterpretation of forecasts among users and highlights the need for providers of forecasts to understand the difficulties and prepare simply written descriptions of forecasts and disseminate these with the maps showing probabilities. The most preferred means of accessing climate information were internet, email, 'The Season Ahead' newsletter and newspaper. The least preferred were direct contact with extension officers and attending field days and group meetings. Eighty-six percent of respondents used the internet and 67% used ADSL broadband internet (April 2003). Despite these findings, extension officers play a key role in preparing and publishing the information on the web, in emails and newsletters. We also believe that direct contact with extension officers trained in climate applications is desirable in workshop-like events to improve knowledge of the difficult concepts underpinning climate forecasts, which may then stimulate further adoption.

Evaluation of a remote drafting system for regulating sheep access to supplement

Remote drafting technology now available for sheep makes possible targeted supplementation of individuals within a grazing flock. This system was evaluated by using 68 Merino wethers grazing dry-season, native Mitchell grass pasture (predominantly Astrebla spp.) as a group and receiving access to lupin grain through a remote drafter 0, 1, 2, 4 or 7 days/week for 8 weeks. The sole paddock watering point was separately fenced and access was via a one-way flow gate. Sheep exited the watering point through a remote drafter operated by solar power and were drafted by radio frequency identification (RFID) tag, according to treatment, either back into the paddock or into a common supplement yard where lupins were provided ad libitum in a self-feeder. Sheep were drafted into the supplement yard on only their first time through the drafter during the prescribed 24-h period and exited the supplement yard via one-way flow gates in their own time. The remote drafter operated with a high accuracy, with only 2.1% incorrect drafts recorded during the experimental period out of a total of 7027 sheep passes through the remote drafter. The actual number of accesses to supplement for each treatment group, in order, were generally less than that intended, i.e. 0.02, 0.69, 1.98, 3.35 and 6.04 days/week. Deviations from the intended number of accesses to supplement were mainly due to sheep not coming through to water on their allocated day of treatment access, although some instances were due to incorrect drafts. There was a non-linear response in growth rate to increased frequency of access to lupins with the growth rate response plateauing at similar to 3 actual accesses per week, corresponding to a growth rate of 72.5 g/head. day. This experiment has demonstrated the application of the remote drafting supplementation system for the first time under grazing conditions and with the drafter operated completely from solar power. The experiment demonstrates a growth response to increasing frequency of access to supplement and provides a starting point with which to begin to develop feeding strategies to achieve sheep weight-change targets.

Evaluation of Ustilago sporoboli-indici as a classical biological control agent for invasive Sporobolus grasses in Australia

Sporobolus pyramidalis, S. africanus, S. natalensis, S. fertilis and S. jacquemontii, known collectively as the weedy Sporobolus grasses, are exotic weeds causing serious economic losses in grazing areas along Australia's entire eastern coast. In one of the first attempts to provide biological control for a grass, the potential of a smut, Ustilago sporoboli-indici, as a biological control agent for all five weedy Sporobolus spp. found in Australia was evaluated in glasshouse studies. Application of basidiospores to 21-day-old Sporobolus seedlings and subsequent incubation in a moist chamber (26 °C, 90% RH, 48 h) resulted in infection of S. pyramidalis, S. africanus, S. natalensis and S. fertilis but not S. jacquemontii. Host-range trials with 13 native Australian Sporobolus spp. resulted in infection of four native species. Evaluation of damage caused by the smut on two Australian native and two weedy Sporobolus spp. showed that the total numbers of flowers infected for the four grasses were in the following order: S. creber > S. fertilis > S. elongatus > S. natalensis with percentage flower infections of 21%, 14%, 12% and 3%, respectively. Significant differences (P = 0.001) were found when the numbers of infected flowers caused by each treatment were compared. The infection of the four native Sporobolus spp. by the smut indicated that it was not sufficiently host specific for release in Australia and the organism was rejected as a potential biological control agent. The implications of these results are discussed.

Pre-release evaluation of the efficacy of the leaf-sucking bug Carvalhotingis visenda (Heteroptera: Tingidae) as a biological control agent for cat's claw creeper Macfadyena unguis-cati (Bignoniaceae)

In classical weed biological control, assessing weed response to simulated herbivory is one option to assist in the prioritization of available agents and prediction of their potential efficacy. Previously reported simulated herbivory studies suggested that a specialist herbivore in the leaf-feeding guild is desirable as an effective biological control agent for cat's claw creeper Macfadyena unguis-cati (Bignoniaceae), an environmental weed that is currently a target for biological control. In this study, we tested (i) whether the results from glasshouse-based simulated herbivory can be used to prioritise potential biological control agents by evaluating the impact of a leaf-sucking tingid bug Carvalhotingis visenda (Drake & Hambleton) (Hemiptera: Tingidae) in quarantine; and (ii) the likely effectiveness of low- and high-densities of the leaf-sucking tingid after its release in the field. The results suggest that a single generation of C. visenda has the potential to reduce leaf chlorophyll content significantly, resulting in reduced plant height and leaf biomass. However, the impact of one generation of tingid herbivory on below-ground plant components, including the roots and tuber size and biomass, were not significant. These findings are consistent with results obtained from a simulated herbivory trial, highlighting the potential role of simulated herbivory studies in agent prioritisation.

Improving the agent selection, release and evaluation process: the role of bioclimatic modelling

The value of CLIMEX models to inform biocontrol programs was assessed, including predicting the potential distribution of biocontrol agents and their subsequent population dynamics, using bioclimatic models for the weed Parkinsonia aculeata, two Lantana camara biocontrol agents, and five Mimosa pigra biocontrol agents. The results showed the contribution of data types to CLIMEX models and the capacity of these models to inform and improve the selection, release and post release evaluation of biocontrol agents. Foremost among these was the quality of spatial and temporal information as well as the extent to which overseas range data samples the species’ climatic envelope. Post hoc evaluation and refinement of these models requires improved long-term monitoring of introduced agents and their dynamics at well selected study sites. The authors described the findings of these case studies, highlighted their implications, and considered how to incorporate models effectively into biocontrol programs.

Understanding and management of resistance to Group M, L and I Herbicides

This project will develop better understanding of resistance to glyphosate, paraquat and Group I herbicides to better inform weed management. The project will develop a range of tools for farm advisors to improve their confidence in decision making with respect to reducing the risk of glyphosate, Group I and paraquat resistance. These will include risk assessments, case studies and scenario exploring tools. The project will discuss with commercial providers the potential for new herbicide registrations. The project will establish farm advisor learning groups to work on the application of the research in local areas where resistance is already a major problem and to improve adoption of research outcomes from this and other projects.

Evaluation of wood characteristics of tropical post-mid rotation plantation Eucalyptus cloeziana and E. pellita: Part (a) Natural durability of timber.

This project evaluated the timber quality, processing and performance characteristics of 19-year-old Eucalyptus cloeziana (Gympie messmate) and 15-year-old Eucalyptus pellita (red mahogany). Studies were undertaken to evaluate wood and mechanical properties, accelerated seasoning and veneer and plywood production. Above-ground and in-ground durability field tests were established at three locations in Queensland. Ground proixmity tests and L-joint tests were installed to gather data applicable to above-ground, weather-exposed end-use applications, and stake tests were installed to gather data applicable to in-ground, weather-exposed end-use applications.

Evaluation of wood characteristics of tropical post-mid rotation plantation Eucalyptus cloeziana and E. pellita: Part (c) Wood quality and structural properties.

This study provides information about wood quality, structural properties, processing characterists and product suitability of wood harvested from fast-grown hardwood plantations. Wood quality attributes tested included density, extractive content, unit shrinkage, heartwood proportion and sapwood width. Structural properties tested included small clear and full section strength and stiffness, hardness, joint group, visual grade assessment and natural vibration-based grade assessment. The variation between the inner, intermediate and outer heartwood zones and the variation between provenances was also tested. Overall, the wood qualtiy attributes measured for 19 year-old E. cloeziana and 15 year-old E. pellita plantation material fall between those expected from the wood of mature, native forest trees and those found in younger plantation material of the same species.

A phylogenetic and taxonomic re-evaluation of the Bipolaris - Cochliobolus - Curvularia Complex

Three genera, Cochliobolus, Bipolaris and Curvularia form a complex that contains many plant pathogens, mostly on grasses (Poaceae) with a worldwide distribution. The taxonomy of this complex is confusing as frequent nomenclatural changes and refinements have occurred. There is no clear morphological boundary between the asexual genera Bipolaris and Curvularia, and some species show intermediate morphology. We investigated this complex based on a set of ex-type cultures and collections from northern Thailand. Combined gene analysis of rDNA ITS (internal transcribed spacer), GPDH (glyceraldehyde 3-phosphate dehydrogenase), LSU (large subunit) and EF1-α (translation elongation factor 1-α) shows that this generic complex divides into two groups. Bipolaris and Cochliobolus species clustered in Group 1 along with their type species, whereas Curvularia species (including species named as Bipolaris, Cochliobolus and Curvularia) clustered in Group 2, with its generic type. The nomenclatural conflict in this complex is resolved giving priority to the more commonly used established generic names Bipolaris and Curvularia. Modern descriptions of the genera Bipolaris and Curvularia are provided and species resolved in this study are transferred to one of these genera based on their phylogeny. © 2012 Mushroom Research Foundation.