Modelling Disease Introduction as Biological Control of Invasive Predators to Preserve Endangered Prey

Invasive species are a significant cause of bio-diversity loss particularly in island ecosystems. It has been suggested to release pathogenic parasites as an efficient control measure of these mostly immune-naïve populations. In order to explore the potential impacts of such bio-control approach, we construct and investigate mathematical models describing disease dynamics in a host population that acts as a predator embedded in a simple food chain. The consequences of Feline Immunodeficiency Virus (FIV) introduction into a closed ecosystem are addressed using a bi-trophic system, comprising an indigenous prey (birds) and an introduced predator (cats). Our results show that FIV is unlikely to fully eradicate cats on sub-Antarctic islands, but it can be efficient in depressing their population size, allowing for the recovery of the endangered prey. Depending on the ecological setting and disease transmission mode (we consider proportionate mixing as well as mass action), successful pathogen invasion can induce population oscillations that are not possible in the disease-free predator–prey system. These fluctuations can be seen as a mixed blessing from a management point of view. On the one hand, they may increase the extinction risk of the birds. On the other hand, they provide an opportunity to eradicate cats more easily in combination with other methods such as trapping or culling.     

Trichoderma–Plant–Pathogen Interactions: Advances in Genetics of Biological Control

Trichoderma spp. are widely used in agriculture as biofungicides. Induction of plant defense and mycoparasitism (killing of one fungus by another) are considered to be the most important mechanisms of Trichoderma-mediated biological control. Understanding these mechanisms at the molecular level would help in developing strains with superior biocontrol properties. In this article, we review our current understanding of the genetics of interactions of Trichoderma with plants and plant pathogens.     

Learning from Past Attempts: Does Classical Biological Control of Noogoora Burr (Asteraceae: Xanthium occidentale) Have a Promising Future?

Noogoora burr (Asteraceae: Xanthium occidentale) is an annual from the Neotropics that is a serious weed of rangeland and agricultural regions in many parts of the world. It was one of the first weeds to be systematically targeted for biological control and there were two major phases in the Australian program; 1929-1940, and 1953-1975. Past attempts at biological control are reviewed to identify opportunities for renewed efforts, and for its historical value. Only one insect species was released in the first phase, but host-specificity restrictions were loosened during the second phase resulting in the release of two other insect species. None have been effective. A fourth agent, released primarily for parthenium weed, has had limited impact. However, the rust, Puccinia xanthii, was accidentally introduced in 1975. It has resulted in complete control of Noogoora burr in much of eastern Australia, but has had little or no impact in far northern Australia. Past failures, judged through hindsight, can be attributed to a failure to identify the full native range, lack of consideration for pathogens prior to 1975, and poor understanding of plant compensatory mechanisms and other challenges that an agent must overcome to be effective. A renewed effort specifically targeting Noogoora burr in far northern Australia holds considerable promise. It should include surveys for new agents within the native range of the Xanthium complex, and a systematic search for isolates of the P. xanthii rust that are climatically adapted to tropical conditions in Australia.     

Predator-Mediated Coexistence of Exotic and Native Crustaceans in a Freshwater Lake?

The predatory effects of a Dipteran insect, Chaoborus, on the competition between exotic cladoceran Daphnia lumholtzi and two natives, D. catawba and D. pulex, were studied for a period of three years in a freshwater reservoir, Lake James, North Carolina (USA). D. lumholtzi was first encountered in September 1997 and it was present only between August and October when population densities of native species were low and that of Chaoborus sp. was high. The patterns observed in the population dynamics of the exotic D. lumholtzi and two natives, Chaoborus suggest that a predator mediated coexistence phenomenon might be taking place in Lake James. The strong positive correlation between Chaoborus and D. lumholtzi and the negative correlation between Chaoborus, D. catawba and D. pulex is supportive of this hypothesis.     

Will Limited Land, Water, and Energy Control Human Population Numbers in the Future?

Nearly 60% of the world’s human population is malnourished and the numbers are growing. Shortages of basic foods related to decreases in per capita cropland, water, and fossil energy resources contribute to spreading malnutrition and other diseases. The suggestion is that in the future only a smaller number of people will have access to adequate nourishment. In about 100 years, when it is reported that the planet will run out of fossil energy, we suggest that a world population of about two billion might be sustainable if it relies on renewable energy technologies and also reduces per capita use of the earth’s natural resources.     

Biodiversity Loss following the Introduction of Exotic Competitors: Does Intraguild Predation Explain the Decline of Native Lady Beetles?

Exotic species are widely accepted as a leading cause of biodiversity decline. Lady beetles (Coccinellidae) provide an important model to study how competitor introductions impact native communities since several native coccinellids have experienced declines that coincide with the establishment and spread of exotic coccinellids. This study tested the central hypothesis that intraguild predation by exotic species has caused these declines. Using sentinel egg experiments, we quantified the extent of predation on previously-common (Hippodamia convergens) and common (Coleomegilla maculata) native coccinellid eggs versus exotic coccinellid (Harmonia axyridis) eggs in three habitats: semi-natural grassland, alfalfa, and soybean. Following the experiments quantifying egg predation, we used video surveillance to determine the composition of the predator community attacking the eggs. The extent of predation varied across habitats, and egg species. Native coccinellids often sustained greater egg predation than H. axyridis. We found no evidence that exotic coccinellids consumed coccinellid eggs in the field. Harvestmen and slugs were responsible for the greatest proportion of attacks. This research challenges the widely-accepted hypothesis that intraguild predation by exotic competitors explains the loss of native coccinellids. Although exotic coccinellids may not be a direct competitor, reduced egg predation could indirectly confer a competitive advantage to these species. A lower proportion of H. axyridis eggs removed by predators may have aided its expansion and population increase and could indirectly affect native species via exploitative or apparent competition. These results do not support the intraguild predation hypothesis for native coccinellid decline, but do bring to light the existence of complex interactions between coccinellids and the guild of generalist predators in coccinellid foraging habitats.     

Biological Motion: A Perceptual Life Detector?

Detecting the direction of motion of other animals is critical for a variety of adaptive behaviours, including filial attachment and hunting prey. Two new studies support the view that some vertebrates, including humans, have primitive brain systems for the visual detection of other legged vertebrates.     

Actin and Microtubules in Cell Motility: Which One is in Control?

The cytoskeleton is composed of three distinct elements: actin microfilaments, microtubules and intermediate filaments. The actin cytoskeleton is thought to provide protrusive and contractile forces, and microtubules to form a polarized network allowing organelle and protein movement throughout the cell. Intermediate filaments are generally considered the most rigid component, responsible for the maintenance of the overall cell shape. Cytoskeletal elements must be coordinately regulated for the cell to fulfill complex cellular functions, as diverse as cell migration, cell adhesion and cell division. Coordination between cytoskeletal elements is achieved by signaling pathways, involving common regulators such as the Rho guanosine-5'-triphosphatases (GTPases). Furthermore, evidence is now accumulating that cytoskeletal elements participate in regulating each other. As a consequence, although their functions seem well defined, they are in fact overlapping, with actin playing a role in membrane trafficking and microtubules being involved in the control of protrusive and contractile forces. This cytoskeletal crosstalk is both direct and mediated by signaling molecules. Cell motility is a well-studied example where the interplay between actin and microtubules appears bidirectional. This leads us to wonder which, if any, cytoskeletal element leads the way.     

Matrix Matters:?Differences of Grand Skink Metapopulation Parameters in Native Tussock Grasslands and Exotic Pasture Grasslands

Modelling metapopulation dynamics is a potentially very powerful tool for conservation biologists. In recent years, scientists have broadened the range of variables incorporated into metapopulation modelling from using almost exclusively habitat patch size and isolation, to the inclusion of attributes of the matrix and habitat patch quality. We investigated the influence of habitat patch and matrix characteristics on the metapopulation parameters of a highly endangered lizard species, the New Zealand endemic grand skink (Oligosoma grande) taking into account incomplete detectability. The predictive ability of the developed zxmetapopulation model was assessed through cross-validation of the data and with an independent data-set. Grand skinks occur on scattered rock-outcrops surrounded by indigenous tussock (bunch) and pasture grasslands therefore implying a metapopulation structure. We found that the type of matrix surrounding the habitat patch was equally as important as the size of habitat patch for estimating occupancy, colonisation and extinction probabilities. Additionally, the type of matrix was more important than the physical distance between habitat patches for colonisation probabilities. Detection probability differed between habitat patches in the two matrix types and between habitat patches with different attributes such as habitat patch composition and abundance of vegetation on the outcrop. The developed metapopulation models can now be used for management decisions on area protection, monitoring, and the selection of translocation sites for the grand skink. Our study showed that it is important to incorporate not only habitat patch size and distance between habitat patches, but also those matrix type and habitat patch attributes which are vital in the ecology of the target species.     

Changes in the Prevalence,Treatment and Control of Hypertension in Germany? A Clinical-Epidemiological Study of 50.000 Primary Care Patients

Introduction

Medical societies have developed guidelines for the detection, treatment and control of hypertension (HTN). Our analysis assessed the extent to which such guidelines were implemented in Germany in 2003 and 2001.

Methods

Using standardized clinical diagnostic and treatment appraisal forms, blood pressure levels and patient questionnaires for 55,518 participants from the cross-sectional Targets and Essential Data for Commitment of Treatment (DETECT) study (2003) were analyzed. Physician’s diagnosis of hypertension (HTN_doc) was defined as coding hypertension in the clinical appraisal questionnaire. Alternative definitions used were physician’s diagnosis or the patient’s self-reported diagnosis of hypertension (HTN_doc,pat), physician’s or patient’s self-reported diagnosis or a BP measurement with a systolic BP≥140 mmHg and/or a diastolic BP≥90 (HTN_doc,pat,bp) and diagnosis according to the National Health and Nutrition Examination Survey (HTN_NHANES). The results were compared with the similar German HYDRA study to examine whether changes had occurred in diagnosis, treatment and adequate blood pressure control (BP below 140/90 mmHg) since 2001. Factors associated with pharmacotherapy and control were determined.

Results

The overall prevalence rate for hypertension was 35.5% according to HTN_doc and 56.0% according to NHANES criteria. Among those defined by NHANES criteria, treatment and control rates were 56.0% and 20.3% in 2003, and these rates had improved from 55.3% and 18.0% in 2001. Significant predictors of receiving antihypertensive medication were: increasing age, female sex, obesity, previous myocardial infarction and the prevalence of comorbid conditions such as coronary heart disease (CHD), hyperlipidemia and diabetes mellitus (DM). Significant positive predictors of adequate blood pressure control were CHD and antihypertensive medication. Inadequate control was associated with increasing age, male sex and obesity.

Conclusions

Rates of treated and controlled hypertension according to NHANES criteria in DETECT remained low between 2001 and 2003, although there was some minor improvement.     

A Common Parched Future? Research and Management of Australian Arid-zone Floodplain Wetlands

Wetlands in arid and semi-arid areas face intensifying pressure for their water resources yet harbour unique biota and ecological processes that rely on the “boom and bust” regime of alternating flood and drought. Recent research in Australia has revealed that models of ecosystem processes derived from northern temperate zone wetlands are often inapplicable to arid zone wetlands, confounding efforts to manage or protect these threatened habitats. We review four case studies from inland Australia that demonstrate different degrees of successful management, aiming to draw out lessons learned that will improve our sustainable use of these delicate systems. Inappropriate extrapolation across scales that ignores the inherent spatial and temporal variability of arid-zone wetlands, “reactive” rather than “collaborative” research and management, and a reluctance to adopt functional indicators to complement state variables are several common themes. We are optimistic that managers and researchers are collaborating to tackle these issues but warn that a parched future faces some wetlands where jurisdictional boundaries hamper their effective management or entrenched beliefs and community distrust of managers threaten ecologically sustainable resource use. In arid areas where water is so precious, environmental allocations are costly and their long-term effects are difficult to identify against a backdrop of high inherent variability. Preservation of this variability is the key to successful management of these “boom and bust” systems but diametrically opposes the desire for regulated, reliable water supplies for human use. Social and institutional acceptance and change now appear to be greater barriers than limited ecological understanding to effective management of many “parched wetlands” in Australia.     

Can Internalism and Externalism be Reconciled in a Biological Epistemology of Language?

This paper is an attempt at exploring the possibility of reconciling the two interpretations of biolinguistics which have been recently projected by Koster (Biolinguistics 3(1):61–92, 2009). The two interpretations—trivial and nontrivial—can be roughly construed as non-internalist and internalist conceptions of biolinguistics respectively. The internalist approach boils down to a conception of language where language as a mental grammar in the form of I-language grows and functions like a biological organ. On the other hand, under such a construal consistent with Koster’s (Biolinguistics 3(1):61-92, 2009), the non-internalist version does not necessarily have to be externalist in nature; rather it is a matter of mutual reinforcement of biology and culture under the rubric of a co-evolutionary dynamics. Here it will be argued that the apparent dichotomy between these two conceptions of biolinguistics can perhaps be resolved if we have a richer synthesis that accounts for both internalism and non-internalism.     

Control of tsetse flies and trypanosomiasis: Myth or reality?

The African trypanosomiasis are among Africa's most devastating diseases. The human disease, sleeping sickness, and the animal disease, nagana, are caused by trypanosomes, protozoan parasites transmitted by tsetse flies, Glossina spp. Attempts have been made to control tsetse and trypanosomiasis for over 70 years, supported by ever-increasing amounts of foreign aid. Although progress has been made in the control of sleeping sickness, this disease still persists in many countries. Nogono excludes cattle from many of the potentially most productive areas of Africa and is a major constraint on economic development. In this paper, Robert Dransfield, Brian Williams and Robert Brightwell review the control of tsetse and trypanosomiasis in the light of recent progress in our understanding of tsetse population dynamics, with special reference to the experience gained in tsetse control on a Maasai ranch at Ngurumon in the Rift Valley of Kenya, and make suggestions for the management and funding of future control programmes in relation to rural development.     

Control of MarRAB Operon in Escherichia coli via Autoactivation and?Autorepression

Choice of network topology for gene regulation has been a question of interest for a long time. How do simple and more complex topologies arise? In this work, we analyze the topology of the marRAB operon in Escherichia coli, which is associated with control of expression of genes associated with conferring resistance to low-level antibiotics to the bacterium. Among the 2102 promoters in E. coli, the marRAB promoter is the only one that encodes for an autoactivator and an autorepressor. What advantages does this topology confer to the bacterium? In this work, we demonstrate that, compared to control by a single regulator, the marRAB regulatory arrangement has the least control cost associated with modulating gene expression in response to environmental stimuli. In addition, the presence of dual regulators allows the regulon to exhibit a diverse range of dynamics, a feature that is not observed in genes controlled by a single regulator.