Looking backwards, looking forward: hopes for bioethics' next twenty-five years

I reflect on the past, present, and future of the field of bioethics. In so doing, I offer a very situated overview of where bioethics has been, where it now is, where it seems to be going, where I think we could do better, and where I dearly hope the field will be heading. I also propose three ways of re-orienting our theoretic tools to guide us in a new direction: (1) adopt an ethics of responsibility; (2) explore the responsibilities of various kinds of actors and relationships among them; (3) expand the types of participants engaged in bioethics.     

Organic ion transport during seven decades. The amino acids

The amino acids are ions of various charge combinations, and one can argue that historically they were the first ions for which the ongoing problem of membrane transport was presented; also that among transported ions these may undergo a highly detailed molecular recognition. Furthermore, the distribution of charge on the amino acid molecule determines by what route or routes it is conducted across the biological membrane, with what directional and structural specificity, and therefore what regulation is imposed, and where. Cases where a presumably charged chemical group behaves as if it were somehow absent from the amino acid have been observed to fall into several categories: Straightforward cases where the pH has been low enough or high enough to remove the charge by protonation or deprotonation, even in free solution. Cases where that protonation or deprotonation is facilitated at the binding site, and perhaps by the total transport process. The cystine molecule can apparently thus be rendered either a tripolar anion or a tripolar cation for transport. Cases where an otherwise co-transported Na+ is omitted to redress charge, or where a Na+ serves as a surrogate for a missing charged group on the amino acid molecule. A case where the protonation occurs reversibly at the receptor site rather than on the amino acid molecule.     

Dispersal among habitats varying in fitness: reciprocating migration through ideal habitat selection

Current evolutionary models of dispersal set the ends of a continuum where the number of individuals emigrating from a habitat either equals the number of individuals immigrating (balanced dispersal) or where emigrants flow from a source habitat to a corresponding sink. Theories of habitat selection suggest a more sophisticated conditional strategy where individuals disperse from habitats where they have the greatest impact on fitness to habitats where their per capita impact is lower. Asymmetries between periods of population growth and decline result in a reciprocating dispersal strategy where the direction of migration is reversed as populations wax and wane. Thus, for example, if net migration of individuals flows from high- to low-density habitats during periods of population growth, net migration will flow in the opposite direction during population decline. Stochastic simulations and analytical models of reciprocating dispersal demonstrate that fitness, carrying capacity, stochastic dynamics, and interference from dominants interact to determine whether dispersal is balanced between habitats, or whether one habitat or the other acts as a net donor of dispersing individuals. While the pattern of dispersal may vary, each is consistent with an underlying strategy of density-dependent habitat selection.     

Mimicry on the edge: why do mimics vary in resemblance to their model in different parts of their geographical range?

Batesian mimics-benign species that predators avoid because they resemble a dangerous species-often vary geographically in resemblance to their model. Such geographical variation in mimic-model resemblance may reflect geographical variation in model abundance. Natural selection should favour even poor mimics where their model is common, but only good mimics where their model is rare. We tested these predictions in a snake-mimicry complex where the geographical range of the mimic extends beyond that of its model. Mimics on the edge of their model's range (where the model was rare) resembled the model more closely than did mimics in the centre of their model's range (where the model was common). When free-ranging natural predators on the edge of the model's range were given a choice of attacking replicas of good or poor mimics, they avoided only good mimics. By contrast, those in the centre of the model's range attacked good and poor mimics equally frequently. Generally, although poor mimics may persist in areas where their model is common, only the best mimics should occur in areas where their model is rare. Thus, counter-intuitively, the best mimics may occur on the edge of their model's range.     

Factors influencing the distribution of the mole rat, Cryptomys zechi (Rodentia, Bathyergidae) in Ghana

Factors influencing the distribution of the Ghana mole rat Cryptomys zechi were investigated in a small part of the middle Volta basin of Ghana where it is endemic. Soil type appeared to be the most important factor controlling mole rat distribution in the area; the mole rats preferred areas where the soil was silt loam. In areas where mole rats were found, local distribution was influenced by food availability and land preparation methods for farming. The highest concentrations of mole rat colonies were found in farmlands where traditional hoe ploughing is used for land preparation and where plants with underground storage organs were more diverse; the lowest concentration was in farms where mechanized ploughing is used for land preparation.     

Some general aspects of the distribution and epidemiology of bovine trypanosomosis in southern Africa

Bovine trypanosomosis occurs in vast areas of southern Africa. Its epidemiology and impact on cattle production is determined largely by the level of interaction between tsetse and cattle. Four situations can be distinguished. First, areas where cattle are absent. Second, zones where cattle have been introduced in game areas but where game is still abundant and constitutes the major source of food for tsetse. Third, areas where, often because of human interference, the density of game animals is low and cattle constitute the main source of food and finally, areas where cattle occur at the edge of tsetse-infested zones. In southern Africa, the impact of the disease on cattle production varies according to the epidemiological circumstances. The disease has an epidemic character with significant impacts on production in areas where cattle have been introduced recently or along the interface between tsetse-infested game areas and tsetse-free cultivated areas. Bovine trypanosomosis has an endemic character, with little impact on production, in areas where tsetse mainly feed on cattle and where the invasion of tsetse is low. Options for the control of bovine trypanosomosis will vary according to the epidemiological circumstance. In particular, the control of tsetse with insecticide-treated cattle will only be effective when a large proportion of feeds are taken from cattle over a large area and when the invasion of tsetse can be reduced sufficiently.     

In vitro culture of erythrocytic stages, including gametocytes of Plasmodium berghei (NK 65 strain) using candle jar method and a newly designed continuous medium flow apparatus

Three methods have been described for cultivation of erythrocytic stages, specially gametocytes of P. berghei NK65 strain, (1) by using vial candle jar where the cultures were subcultured by addition of fresh erythrocytes, (2) a newly designed simple and compact continuous medium flow apparatus, where medium was continuously perfused but fresh erythrocytes were not added and (3) where the subcultures were also done using simple and compact continuous medium flow apparatus for comparison. The maximum percentage of parasitized erythrocytes obtained by these methods was 24.3, 27.1 and 26.4% respectively. Parasites in vials could survive for more than 10 days with 3 to 4 subcultures with maximum 1.96% gametocytaemia. However, the gametocytaemia in continuous medium flow apparatus, where subcultures were not made reached 2.2% compared to that of 2.7% in this apparatus where subcultures were done. The asexual as well as sexual stages of this parasite survived for about 16-18 days in compact continuous medium flow apparatus, where at least 7 subcultures were done.     

Linear age-dependent population growth with harvesting

This paper studies the effect of harvesting a fraction of a population where the population growth is modelled by a linear age-dependent model, the Von Foerster equation. Two harvesting strategies are considered: the first is where a fraction of the population greater than agec is removed, and the second is where a fraction of the population of age greater thanc but less thanc+n is removed. In the case where the death rate and fertility rate are time independent, the effect of harvesting on the stable age distribution is examined. Research done at the University of New Mexico and partially supported there by NIH Grant No. RR-08139.     

Why we should conserve ‘limiting factors’, at least sometimes!

Körner's recent paper provided an excellent initial discussion of the term ‘limitation’ in ecology. I accept most of his arguments but would argue that there are some circumstances in applied ecology where the concept of limitation can be useful; these are (1) where there is a deficiency of a factor that prevents growth, and (2) where there is a need to manage an ecosystem so that a limitation is enforced.     

Selection for intermediate mortality and reproduction rates in a spatially structured population

How local interactions influence both population and evolutionary dynamics is currently a key topic in theoretical ecology. We use a 'well-mixed' analytical model and spatially explicit individual-based models to investigate a system where a population is subject to rare disturbance events. The disturbance can only propagate through regions of the population where the density of individuals is sufficiently high and individuals affected by the disturbance die shortly after. We find that populations where individuals are sessile often exhibit very different dynamic behaviour when compared to populations where individuals are mobile and spatially well mixed. When mutations are allowed which affect either offspring birth rates or mortality rates, the well-mixed populations always evolve to a state where a single disturbance event leads to extinction. Populations often persist substantially longer if individuals are sessile and they disperse their offspring locally. We also find that for sessile populations selection may favour short-lived individuals with limited offspring production. Population dynamics are found to be strongly influenced by the host characters that are evolving and the rate at which host variation is introduced into the system.     

COINCIDENT BIOGEOGRAPHIC PATTERNS: INDO-WEST PACIFIC OCEAN

The majority of tropical marine families demonstrate their greatest concentration of species within the relatively small East Indies Triangle. In every direction, the species diversity decreases with distance from the East Indies. Other patterns suggest that the East Indies is where the average generic age is youngest, where some historical routes of dispersal originate, where the most apomorphic species occur, where genetic diversity is the greatest, and where extinctions are likely to originate. These coincident patterns provide support for the hypothesis that the East Indies has been operating as a center of evolutionary radiation. The driving force for this dynamic system is apparently the predominance of successful speciation involving relatively large populations with higher genetic diversity. This mechanism fits the centrifugal speciation model that was proposed more than 50 years ago.     

Fire,Flood, Fish and the Uncertainty Paradox

When the planet was created, the areas of the greatest biodiversity also happened to be the areas where mankind wants to reap the best reward of resources. It is not actually that complicated when you think about it, because where there is biodiversity happens to be where the resources are and it is where we happen to want to get them from. As it happened, the uranium was put in the middle of Kakadu and gold is in places where it is hard to get out. I think the creator of the universe decided to make things very interesting for environment ministers down the track. That is the reality… It is only a natural thing. (Senator Ian Campbell, Federal Minister for the Environment; Hansard 2006: 68–69)     

Setting Single-Period Optimal Capacity Levels and Prices for Substitutable Products

In this paper, we consider how a company that has the flexibility to produce two substitutable products would determine optimal capacity levels and prices for these products in a single-period problem. We first consider the case where the firm is a price taker but can determine optimal capacity levels for both products. We then consider the case where the firm can set the price for one product and the optimal capacity level for the other. Finally, we consider the case where capacity is fixed for both products, but the firm can set prices. For each case, we examine the sensitivity of optimal prices and capacities to the problem parameters. Finally, we consider the case where each product is managed by a product manager trying to maximize individual product profits rather than overall firm profits and analyze how optimal price and capacity decisions are affected.     

When is Open‐endedness Desirable in Restoration Projects?

A low‐intervention approach to restoration that also allows restoration outcomes to be framed as trajectories of ecosystem change can be described as “open‐ended” restoration. It is an approach which recognizes that long‐term ecosystem behavior involves continual change at small and large spatial and temporal scales. There are a number of situations in which it is appropriate to adopt an open‐ended approach to restoration including: in remote and large areas, where ecological limiting factors will be changed by future climates, where antecedent conditions cannot be replicated, where there are novel starting points for restoration, where restoration relies strongly on processes outside the restoration area, in inherently dynamic systems, where costs are high and where the public demands “wildness.” Where this approach is adopted managers need to explain the project and deal with public expectations and public risk. Monitoring biotic and abiotic components of the project are very important as an open‐ended approach does not equate to “abandon and ignore it.”     

Plant–animal interactions between carnivorous plants,sheet‐web spiders,and ground‐running spiders as guild predators in a wet meadow community

1. Plant–animal interactions are diverse and widespread shaping ecology, evolution, and biodiversity of most ecological communities. Carnivorous plants are unusual in that they can be simultaneously engaged with animals in multiple mutualistic and antagonistic interactions including reversed plant–animal interactions where they are the predator. Competition with animals is a potential antagonistic plant–animal interaction unique to carnivorous plants when they and animal predators consume the same prey.
2. The goal of this field study was to test the hypothesis that under natural conditions, sundews and spiders are predators consuming the same prey thus creating an environment where interkingdom competition can occur.
3. Over 12 months, we collected data on 15 dates in the only protected Highland Rim Wet Meadow Ecosystem in Kentucky where sundews, sheet‐web spiders, and ground‐running spiders co‐exist. One each sampling day, we attempted to locate fifteen sites with: (a) both sheet‐web spiders and sundews; (b) sundews only; and (c) where neither occurred. Sticky traps were set at each of these sites to determine prey (springtails) activity–density. Ground‐running spiders were collected on sampling days. DNA extraction was performed on all spiders to determine which individuals had eaten springtails and comparing this to the density of sundews where the spiders were captured.
4. Sundews and spiders consumed springtails. Springtail activity–densities were lower, the higher the density of sundews. Both sheet‐web and ground‐running spiders were found less often where sundew densities were high. Sheet‐web size was smaller where sundew densities were high.
5. The results of this study suggest that asymmetrical exploitative competition occurs between sundews and spiders. Sundews appear to have a greater negative impact on spiders, where spiders probably have little impact on sundews. In this example of interkingdom competition where the asymmetry should be most extreme, amensalism where one competitor experiences no cost of interaction may be occurring.

     

Losing anti‐predatory behaviour: A cost of translocation

Translocation of endangered species to habitats where exotic predators have been removed is now a common conservation practice around the world. Many of these translocated populations have thrived, and they are often used as sources for the harvesting of individuals for translocations to sites where exotic predators still exist, albeit at reduced densities. This study investigates how isolation from exotic predators affects the ability of individuals to recognize such predators using the North Island robin (Petroica longipes) as a model. The study was carried out in three robin populations in the North Island, New Zealand: a translocated population on Tiritiri Matangi Island, where exotic mammalian predators are absent; a population reintroduced from Tiritiri Matangi Island to Wenderholm Regional Park, a mainland site where these mammals are controlled to low densities; and a mainland population at Benneydale where exotic predatory mammals are common. The response intensity of robins to a model stoat was high at Benneydale and low at Tiritiri Matangi and Wenderholm. This result indicates that isolation from mammalian predators on Tiritiri Matangi has suppressed the ability of North Island robins to recognize these predators. It is possible that the low predatory mammal densities at Wenderholm have reduced robin contact with stoats, therefore reduced the opportunity for robins to learn to recognize stoats. Thus, translocation of individuals from populations without predators to places where key predators still exist could be unsuccessful if translocated individuals fail to perform appropriate anti‐predator behaviours.     

How to prioritize rat management for the benefit of petrels: a case study of the UK, Channel Islands and Isle of Man

Rats have been introduced to islands throughout the world. They have caused breeding failures, population declines and complete extirpation of vulnerable bird species. Such impacts can be difficult to diagnose in situations where extirpation occurred prior to the vulnerable species being recorded. Mitigating the impacts of rats on seabirds depends on quarantine measures for islands where rats are currently absent, and eradication or control campaigns on those where they are present. These measures can be challenging in terms of both costs and practicalities, and so can seldom be applied to all islands within a given region. Hence a prioritization exercise is often required to identify those islands where management would be most cost-effective. In this review we present a case study of rat management in the UK, Channel Islands and Isle of Man. We review rat management for the study area to date and present a simple scoring approach to prioritize islands for eradication campaigns, including those where the procellariiform priority species are currently absent. We recommend further research into rat management for the study area and on the applicability of this approach elsewhere in the world.     

Exact tests of goodness of fit of log-linear models for rates

We propose Metropolis-Hastings sampling methods for estimating the exact conditional p-value for tests of goodness of fit of log-linear models for mortality rates and standardized mortality ratios. We focus on two-way tables, where the required conditional distribution is a multivariate noncentral hypergeometric distribution with known noncentrality parameter. Two examples are presented: a 2 x 3 table, where the exact results, obtained by enumeration, are available for comparison, and a 9 x 7 table, where Monte Carlo methods provide the only feasible approach for exact inference.