bluuebunny/crossref_metadata_2025 huggingface dataset:
Habitat quality ranking depends on habitat‐independent environmental factors: a model and results from Callosobruchus maculatus
Authors: KAWECKI T. J.
Published: December 2004

1. Survival and reproduction in different habitats of a heterogeneous environment are affected by intrinsic habitat properties as well as by habitat‐independent extrinsic factors. It is argued that the ranking of habitats according to quality may depend on extrinsic environmental factors that act with the same intensity in all habitats. This can happen if, across habitats, high reproductive success in the absence of extrinsic mortality is coupled with late reproduction.

2. In a model of a semelparous organism with overlapping generations that uses two habitats, the effect of different patterns of extrinsic mortality on habitat quality are analysed, as measured by the reproductive value of an egg, which estimates its expected contribution to the future gene pool.

3. Measurements of fitness components in Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) on four host species demonstrate that, across hosts, long development can be associated with high reproductive success in the absence of extrinsic mortality. As a result, the quality ranking of three out of the four hosts would be different in a stable population regulated by intraspecific competition and egg parasitoids than in a growing population or a stable population regulated by age‐independent larval mortality.

4. It is suggested that habitat‐independent mortality may play a role in the evolution of ecological niches.
Resource dynamics and plant growth: a self‐assembling model for individuals, populations and communities
Authors: COLASANTI R. L. , HUNT R.
Published: December 2004

1. We describe a new model of plant growth that is general, deterministic, non‐stationary and mechanistic in nature. Its purpose is to investigate the extent to which the morphology and function of the whole plant can be determined by resource acquisition and utilization on the part of its components.

2. The model is a two‐dimensional section, showing the plant in its above‐ and below‐ground environments. The whole plant is represented by a branching structure made up from standard ‘modules’. The behaviour of the complete plant is determined exclusively by a rule set that acts only at the level of the individual module.

3. At the level of the whole plant, the model displays a classic S‐shaped growth curve, plasticity in root–shoot allocation, and foraging in heterogeneous environments.

4. At the level of the plant population, the model exhibits self‐thinning along a –2/1 self‐thinning line. This accords with the behaviour expected of a two‐dimensional system and also adds weight to the ‘geometric’ interpretation of the –3/2 self‐thinning line commonly seen in crowded populations of real plants.

5. An imposed ‘mutation’ in one of the modular rules allows us to produce a modified plant type that displays active foraging. In a set of simulations involving a model community containing both the modified and standard plant types, the modified type predominates in resource‐rich environments, and vice versa.

6. The simulations demonstrate the effectiveness of modular rule‐based methods from which whole‐plant behaviour can arise as an emergent property. The model suggests that active foraging carries a cost that cannot satisfactorily be borne at low levels of resource availability. It also implies that competition for resources, both above and below ground is in the form of a ‘contest’ (rather than a ‘scramble’). The success of the modular model highlights the primacy of resource acquisition and utilization in determining the ecological status of the plant.
Assessing and preparing students for distance preceptorship placements
Authors: Yonge Olive
Published: December 2004

Preparing students for distant preceptorship placements requires knowledge of individual students through formal and informal mechanisms. Since they receive support via telephone, fax or mail, the first onus is on students to manage their preceptorship situations effectively. In order to enhance their abilities in preceptorship situations, students can be assessed for their learning and personality styles. Findings from two style assessment tools, Kolb's Learning Style Inventory and Myers‐Briggs Type Indicator, can be used to gain insight into students' interactions with preceptors and to assist instructors in giving the right kind of support and direction after students are placed.
Identifying the health needs of elderly people using the Omaha Classification Scheme
Authors: Maggs Christopher , Abedi Heidar Ali
Published: December 2004

An examination of what constitutes assessment would help to clarify those aspects which are essential for establishing a suitable nursing plan for clients. There is no consensus on one assessment tool in nursing, and many methods are used. The important areas in a comprehensive assessment (physiological, mental, social and environmental factors) which need to be addressed are covered by the Omaha Classification Scheme (OCS). This paper discusses the application of a research tool (OCS) for assessing the health needs of a given population. The primary focus of this paper is upon the methodology used in the study. A random sample of 500 elderly people was drawn from all elderly people aged 65 years and over, who lived in the rural areas of Isfahan province, Iran. Data were collected to identify the health needs of the population under study using the OCS. The reliability of this research tool was tested for quantitative scores using Cronbach's alpha test. The results showed an acceptable score for reliability (r=0.78).
The implications of Project 2000 and the formation of links with higher education for the professional and academic needs of nurse teachers in the United Kingdom
Authors: Kirk Susan , Carlisle Caroline , Luker Karen A.
Published: December 2004

A national study was conducted between 1991 and 1994 to explore and describe the changing role of the nurse teacher following the introduction of Project 2000 pre‐registration nursing courses. Multiple methods were used to collect data from a wide variety of respondents (nurse teachers, midwife teachers, clinical nurses, health service managers and higher education lecturers). This paper presents the findings relating to the impact of Project 2000 and the move into higher education on the continuing educational needs of nurse teachers. Views on college strategies for staff development, the changing nature of teachers'academic and professional development needs and the problems of the conflicting demands experienced are reported. The research highlights the need for clinical credibility to be clearly defined in relation to nurse teachers and for educational institutions to place more emphasis on teachers'clinical development if the rhetoric of policy is to become a reality.
Evaluating the impact of in‐patient bed reduction and community nurse increases in one English Mental Healthcare Trust
Authors: Ward Martin F. , Jones Martin
Published: December 2004

This Mental Health Task Force funded project was designed to evaluate the impact of organizational changes in Northampton, a traditional English Mental Healthcare Trust. Services in Northampton were typically provided by a large ‘watertower’ Victorian hospital on the outskirts of the town. The hospital had been, over a period of some years, reducing the use of in‐patient beds. In February 1995 a further 10 beds were withdrawn enabling the closure of a complete building and the re‐deployment of some staff into the community. By reducing in‐patient beds, and increasing the number of community staff it was hoped that there would be a significant effect upon both hospital admissions, length of stay with resultant cost savings, and an increase in community nurse–patient contacts. To establish baselines quantitative data were gathered about pre‐existing acute and community services, with comparisons made from qualitative and quantitative data gathered during the initial change period. Information was collected concerning in‐patient admissions within the acute services, community psychiatric nurse (CPN) caseloads including new admissions, care delivery costs and interviews with service managers. The project found that changes in the general patient profile could not be attributed solely to the reduction in available beds but there did appear to be a direct correlation between bed reduction, increase in percentage bed occupancy and more demanding CPN caseloads. Concern was expressed about the ability of community staff to meet the needs of an increasingly female (age 20–39 years) user group. Savings to the Trust were estimated at £300 000 per annum. The paper concludes with recommendations for future changes.
Community psychiatric nurse caseloads and the ‘worried well’: misspent time or vital work?
Authors: Bowers Len
Published: December 2004

Community psychiatric nurses (CPNs) in the United Kingdom are being repeatedly urged to focus their attention upon those with serious and enduring psychotic illnesses, and to withdraw from working with the ‘worried well’ in the primary health care setting. In view of this pressure, it is important to discover the nature of community psychiatric nurses' non‐psychotic caseloads. The aim of this study was to describe these cases, what precipitated their referral, what problems they suffered from, what effects these problems had upon their lives and what kinds of therapeutic interventions they were receiving. A random sample was drawn of non‐psychotic CPN patients. The community psychiatric nurses then received a structured interview about the history, care and treatment of these patients. These patients did not, in general, suffer from minor, self‐limiting conditions. They typically had had 5 years of contact with psychiatric services, and their psychiatric symptoms blighted their occupational, social and personal lives. Their condition caused significant carer burden, and there was frequently a risk of suicide. The CPNs case‐managed a complex combination of interventions for these patients, of which psychotherapeutic methods were only one part. The findings show that community psychiatric nurses have a valid role to play in the care of those with non‐psychotic mental disorders, and should continue to receive the opportunity, and appropriate training, to do so.
The relationship between research and the nursing process in clinical practice
Authors: Mason Geraldine M.C. , Attree Moira
Published: December 2004

The nursing process was originally adopted by the North American nursing profession from the general systems theory (GST) and quickly became a symbol of contemporary nursing as well as a professionalist nurse ideology. In contrast its initial introduction in the United Kingdom (UK) was not a complete success. This could be attributed to the mode of its implementation, which utilized a power‐coercive change strategy, that is, comprising of imposition from above without sufficient time for education regarding its scientific and philosophical foundations. Consequently the nursing process was initially regarded as a professional and educational mandate rather than an organizational component of nursing care delivery. It has been maintained that the theoretical basis from which the nursing process was derived, together with the theoretical developments in diagnostic and intervention studies, has established the nursing process as a key element of the nurse's role in research, education and practice. This paper will briefly review the early theoretical developments and fate of the nursing process as a tool for clinical practice and research. It will then examine recent attempts to revitalize and modernize the theory for practice through research into nursing diagnosis.
Questions and answers to psychological assessment schedules: hidden troubles in ‘quality of life’ interviews
Authors: Antaki C. , Rapley M.
Published: December 2004

Quality of life (QOL) has become a topic of much debate in the learning difficulties literature. Increasing use is made of questionnaire‐driven interview schedules in an effort to find out v/hat clients believe in their own words. However, in this paper, the authors argue that the use made of such questionnaires may actually distort interviewees ‘own words’ by severely underestimating the degree to which the questions and answers are changed by the subtle dynamics of the interview. In the first ever close examination of what actually happens in a QOL assessment interview, the qualitative insights of conversation analysis are used to show that the typical administration of a well‐known instrument will involve: (1) distortions of the questions brought about by the need to paraphrase complex items, and the inevitable use of pre‐questions and response listing; and perhaps more disturbingly, (2) distortions of answers brought about by interviewers’pursuit of legitimate answers and non‐take‐up of interviewees’ matters. The authors believe that these difficulties make it hard for researchers to draw conclusions from simple aggregation of recorded responses to this questionnaire, and, perhaps, to any questionnaire using a fixed‐response schedule. On the other hand, the kind of close evidence used here may allow inferences to be drawn about clients’ feelings of well being, but even so, these will need to be cast in terms which acknowledge the interactive and constructive nature of feeling‐avowals.
Schizophrenia in people with intellectual disability: the role of pregnancy and birth complications
Authors: O'Dwyer J. M.
Published: December 2004

The literature suggests that mental illness is more common in people with intellectual disability than in the general population. Having reviewed the literature, Turner (1989)[Psychological Medicine19, 301–14] suggested that about 3% of people with intellectual disability also have schizophrenia. As pregnancy and birth complications (PBCs) occur more commonly in people with intellectual disability than in the general population and are also implicated in the aetiology of schizophrenia, it is possible that these conditions share a common aetiology. This study reports on the occurrence of PBCs in those people with intellectual disability who develop schizophrenia. Fifty people with intellectual disability and schizophrenia were matched for age, sex, degree of intellectual disability and presence of epilepsy with a control group who did not suffer from schizophrenia or a schizophreniform psychosis. The obstetric history was obtained and events rated on a scale specifically designed for this study. This PBCs scale consists of six sub‐scales covering areas of general maternal health, pregnancy, delivery, medication in labour, total medication score and neonatal score, as well as an overall total score. The study found that people with intellectual disability who develop schizophrenia have significantly higher rates of PBCs than controls. All of the sub‐scales on the PBCs scale were significantly higher in people with schizophrenia, with the exception of the medication scales. Only five out of the 50 people with schizophrenia had not had a major obstetric complication, compared to 13 subjects from the control group. A number of abnormalities were specifically higher in people who later developed schizophrenia. These included: abnormally long or short labour; maternal episiotomy; maternal preeclamptic toxaemia; induction of labour; dysmaturity; maternal smoking in pregnancy; and a delay in neonatal crying. The results suggest that PBCs are important in the aetiology of schizophrenia in people with intellectual disability.
Sexual abuse perpetrated by men with intellectual disabilities: a comparative study
Authors: Brown H. , Stein J.
Published: December 2004

This paper compares cases of sexual abuse of adults with intellectual disabilities, reported across the South East of England, which were perpetrated by men with intellectual disabilities, with those committed by other male perpetrators. The comparison provides some support for the findings of other studies, which have suggested that men with intellectual disabilities offend against more male victims than non‐disabled sex offenders and that their offences are somewhat less serious, but otherwise indicates common patterns of abusive behaviour across this divide but differential service responses and support for victims. So called ‘peer abuse’ is a widespread problem which service agencies have failed to address: repeated offences are frequent and lack of appropriate intervention is the norm.
Monday and non‐Monday concentrations of lifestyle‐related blood components in the Oslo Diet and Exercise Study
Authors: Urdal P. , Anderssen S. A. , Holme I. , Hjermann I. , Mundal H. H , Haaland A. , Torjesen P.
Published: December 2004

Urdal P, Anderssen SA, Holme I, Hjermann I, Mundal HH, Haaland A, Torjesen P (Ullevål University Hospital; Norwegian University of Sport and Physical Education; and Aker University Hospital, Oslo, Norway). Monday and non‐Monday concentrations of lifestyle‐related blood components in the Oslo Diet and Exercise Study. J Intern Med 1998; 244: 507–13.

Objective We hypothesized that participants of intervention studies have an unfavourable lifestyle at the weekend compared with the rest of the week, thus affecting the concentrations of components in samples drawn on Mondays.

Design The hypothesis was examined using data from the Oslo Diet and Exercise Study, a 2 × 2 randomized intervention trial on diet and exercise involving 209 participants. Each person chose which day of the week to attend for blood sampling, both before and after the 1 year of intervention.

Main outcome measures Comparison of mean concentrations of the components measured, in samples drawn on Mondays vs. non‐Mondays, both at the start and at the end of intervention.

Results At the start, nine components, from haemostasis, carbohydrate and lipid metabolism, showed a difference of more than 10% between Monday and non‐Monday values, all Monday values differing from the non‐Monday values in a cardiovascularly unfavourable direction. Participants starting and ending on a Monday showed the unfavourable profile both times, and those who were examined both times on a non‐Monday showed a consistently favourable profile, whereas those who changed the day of examination at the start and end changed profile accordingly.

Conclusion The lifestyle‐related components examined here showed differences between Monday and non‐Monday values, which were not due to a selection bias. We suggest they may be related to a different lifestyle at the weekend compared with ordinary working days. If such effects are not recognized and properly taken into account, they may markedly affect the outcome of intervention studies.
Continuous ST‐segment monitoring of patients with left bundle branch block and suspicion of acute myocardial infarction
Authors: Gunnarsson G. , Eriksson P. , Dellborg M.
Published: December 2004

Objectives.  Patients with left bundle branch block comprise 5–9% of all patients with acute myocardial infarction. Limited data exist on the usefulness of continuous electrocardiographic monitoring of these patients. We have investigated prospectively the usefulness of real‐time continuous vectorcardiography for monitoring patients with left bundle branch block and suspicion of acute myocardial infarction.

Design.  A prospective multi‐centre study.

Setting.  Fourteen Swedish coronary care units.

Subjects.  Patients with left bundle branch block and suspicion of acute myocardial infarction with <6‐h symptom duration were included.

Main outcome measures.  All patients were monitored with continuous vectorcardiography for 12–24 h.

Results.  One hundred thirty‐three patients were included, 47% had acute myocardial infarction. Patients with acute myocardial infarction showed a marked relative decrease in ST‐vector than those without (P = 0.0002). These changes were most marked in the first 90 min. When comparing patients with acute myocardial infarction receiving thrombolytic therapy or not, those treated with thrombolytics showed more marked decline in ST‐vector magnitude (P < 0.0001) and in shorter time (P = 0.0017). All patients showed STC‐vector magnitude changes that were more marked in patients with acute myocardial infarction (P = 0.0002). An STC‐vector magnitude cut‐off value of 65 μV after 90 min of monitoring gave 54% sensitivity and 72% specificity for diagnosis of acute myocardial infarction.

Conclusion.  Real‐time continuous vectorcardiographic monitoring of patients with left bundle branch and suspicion of acute myocardial infarction shows significant differences between those with and without acute myocardial infarction and could be of use for early diagnosis and subsequent monitoring.
Mauricio Goihman‐Yahr, MD, PhD, Editor
Authors: Wilairatana Polart , Looareesuwan Sornchai , Riganti Mario , Teja‐lsavadharm Paktiya , Keeratithakul Duangsuda , Eickmeyer Sirikit , Walsh Douglas S.
Published: December 2004

The Correspondence Section serves as a forum for opinion exchange about subjects of general interest such as dermatoiogic training, relations between dermatologists and pharmaceutical houses, governmental control of dermatology and medical practice in general, peculiarities of dermatology related to geographic, climatic, or racial factors, the flow of information and publications, as well as other concerns the readership might have. Contributions are welcome and should conform to the usual format for correspondence. Manuscripts will undergo standard editorial procedures. Submit all correspondence to Mauricio Goihman‐Yahr, MD, phD, Editor, Jet International M‐154, PO Box 020010, Miami, FL 33102.
The genetics of phenotypic plasticity. II. Response to selection
Authors: Scheiner Samuel M. , Lyman Richard F.
Published: December 2004

We selected on phenotypic plasticity of thorax size in response to temperature in Drosophila melanogaster using a family selection scheme. The results were compared to those of lines selected directly on thorax size. We found that the plasticity of a character does respond to selection and this response is partially independent of the response to selection on the mean of the character. One puzzling result was that a selection limit of zero plasticity was reached in the lines selected for decreased plasticity yet additive genetic variation for plasticity still existed in the lines. We tested the predictions of three models of the genetic basis of phenotypic plasticity: overdominance, pleiotropy, and epistasis. The results mostly support the epistasis model, that the plasticity of a character is determined by separate loci from those determining the mean of the character.
Phylogenetic analysis and the evolution of queen number in eusocial Hymenoptera
Authors: Ross Kenneth G. , Carpenter James M.
Published: December 2004

Analyses of the evolution of colony queen number in eusocial insects have generally been conducted without specific reference to phylogenetic relationships, leading to incomplete evolutionary explanations for this key attribute of social organization. Consideration of queen number in a phylogenetic context in the highly eusocial Hymenoptera reveals that its evolution has been very conservative in the bees but that it is a highly labile character in most ants. The wasps appear intermediate in this respect, with some large and widespread clades characterized by little or no phylogenetic variability in queen number. This hierarchy of phylogenetic lability suggests that while ant populations may often be responsive to selection on colony queen number linked with local ecology, bees and wasps appear less responsive in this regard, with a significant element of phylogenetic conservatism involved in the expression of this social trait in the latter two groups.
Parental effects in Lychnis flos‐cuculi. II: Selection on time of emergence and seedling performance in the field
Authors: Biere A.
Published: December 2004

Selection on the timing of seedling emergence was investigated in an experimental population of Lychnis flos‐cuculi, a perennial hay‐meadow species. Seeds obtained from a full diallel cross of 8 genotypes from a field population were sown along an environment gradient that included the parental site.

Significant directional selection for early emergence was found and the intensity of selection varied among sites. Emergence time varied significantly among progeny families of different maternal and paternal genotypes. These differences could be attributed to parental effects whereas narrow‐sense heritabilities were close to zero. Survivorship until autumn differed among progeny of paternal families. Survivorship of maternal progeny varied among sites. Whereas differences in survival and plant size among individuals from different emergence cohorts persisted over the winter, the significance of these differences among progeny from different parental genotypes disappeared.

It is suggested that a response to selection on emergence time might be low since (1) the narrow sense heritability was low, (2) parental genotypes differed in their effect on offspring emergence time when used as female parent or as pollen donor and (3) there was a family x site interaction for survival. Families with relatively early emerging seedlings also had a significantly higher seed weight, emergence percentage, and plant weight although the strength of these among‐family correlations varied among sites. It is therefore not likely that simultaneous selection on emergence time and either of these traits would retard a response to selection on emergence time.
The heritability of sexually dimorphic traits in the yellow dung fly Scathophaga stercoraria (L.)
Authors: Simmons Leigh W. , Ward Paul I.
Published: December 2004

A precise method was used for estimating the proportion of heritable variation in two life history parameters of the yellow dung fly, whereby environmental components of variance were minimized. Significant heritable variation for body size was revealed for father to son and mother to daughter relationships. Variation in development time was not significantly heritable. There is a marked sexual dimorphism in body size in this species which is discussed in the light of the observed sex‐genotype interaction in heritabilities and low genetic correlation for size between the sexes. It is suggested that opposing pressures of sexual and natural selection and/or genetic pleotropy may be responsible for the maintenance of heritable variation, and the evolution of sexual dimorphism in these two traits.
Experimental study of temperature effects on the sex ratio of broods in Terrestrial Crustacea Armadillidium vulgare Latr. Possible implications in natural populations
Authors: Rigaud T. , Juchault P. , Mocquard J. P.
Published: December 2004

The woodlouse Armadillidium vulgare is characterized by female heterogamety (ZW) and male homogamety (ZZ). However, in several populations, sex determination is influenced by cytoplasmic sex factors (endosymbiotic bacteria = F). At 20 °C these maternally transmitted bacteria reverse genetic males into functional neo‐females (ZZ + F) producing highly female broods.

When these neo‐females were reared at 30° C, the sex ratio of their broods became male‐biased. The major process involved in this heat‐induced sex ratio inversion was the disappearance of bacteria in embryos in the course of their development, which allowed the young to express a phenotype that conforms with their genotype (i.e. male ZZ). No heat‐sensitive stage of development was observed, but at least 35 days at 30° C seem to be necessary to induce F‐degradation. The presence of F at 30° C (before its degradation) also induced mortality during vitellogenesis.

Daily thermoperiods including a thermophase at 30° C had effects on F similar to that of a constant temperature of 30° C. A. vulgare can live in climates having such thermoperiods (at least during one period of the year), temperature appears to be capable of limiting the presence of F‐bacteria in natural populations, and then modifying the evolution of sex‐determining mechanisms in such populations.
Limits to runaway sexual selection: The wallflower paradox
Authors: De Jong Mart C. M. , Sabelis Maurice W.
Published: December 2004

In his mathematical treatment of Fisher's ideas on sexual selection (so‐called runaway selection) Lande (1981) predicted that males may evolve increasingly elaborate sexual characters despite opposing viability selection as a consequence of the associated costs.

Lande thereby assumed that female mate preferences are not subject to selection since (1) females are all inseminated and (2) the quantity and quality of their offspring are independent of the female's mate preferences. Kirkpatrick (1985) removed the latter assumption and investigated the consequences for the mean phenotype with respect to both female and male traits. He also explored the dynamics of the (co)‐variance matrix by numerical methods.

In this paper we consider a simpler model with just two multi‐allelic loci. This enables us to derive explicit expressions for (co)‐variances under steady state conditions. Rather than assume natural selection through differential fertility (as in Kirkpatrick, 1985), we take sexual selection on females into account by modelling the preference‐dependent risk that females remain unmated.

We argue that this wallflower effect is a realistic feature of any mating system, since it merely depends on the existence of (1) variation in mating preferences and (2) a finite mating season. Our approach provided an insight into the dynamic behaviour of the means of the phenotypes. This is because the dynamics of the means depend on the steady state (co)‐variance matrix. Thus, an insight into the former requires explicit expressions for the latter.

Whereas Lande and Kirkpatrick predicted runaway processes, despite opposing viability selection, our model predicts a globally stable steady state, i.e. no runaway, even without opposing viability selection (under the assumption of an asymptotically stable steady state of the (co)‐variances. Admittedly, we have no analytic proof of this stability but only support for it, based on simulations.) The absence of the runaway processes in our model is caused by the wallflower effect, since it imposes constraints on the steady state of the (co)‐variance matrix.

When mutational input applies to female traits but not to male traits, explicit expressions for the (co)‐variances under steady state conditions can be derived, and these show that: (1) both the genetic covariance and the variance of male traits are equal to zero, but (2) the variance of the female trait exceeds to zero. Should there be mutational input influencing the male trait, then these results would suggest that the male‐to‐female ratio of variances is much smaller than unity. This prediction is of tremendous importance for speciation through founding events.
Sex allocation in an hermaphroditic plant: the case of gynodioecy in Thymus vulgaris L.
Authors: Atlan A. , Gouyon P. H. , Fournial T. , Pomente D. , Couvet D.
Published: December 2004

Resource allocation to male and female functions was investigated in Thymus vulgaris L. (thyme), a gynodioecious species, in which females produce twice as many seeds as hermaphrodites. Negative correlations were found between male and female fertility of hermaphrodites, providing evidence of a trade‐off. There was a high variability in sexual investment, some of the hermaphrodites functioning almost as males, and others almost as females. Estimation of the relative cost of male and female gametes showed that the female advantage in seed production was mainly due to reallocation of the resources not allocated to male function into female function. The determination of sex allocation was shown to have a genetic component, and there were some evidence that an interaction between nuclear and cytoplasmic genomes was involved.
The genetic basis and evolution of acoustic mate recognition signals in a Ribautodelphax planthopper (Homoptera, Delphacidae) 1. The female call
Authors: De Winter A. J.
Published: December 2004

Both sexes of the planthopper Ribautodelphax imitans produce species specific acoustic signals. Earlier experiments have shown that isolation between Ribautodelphax species in captivity is at least partly due to male preference for calls of conspecific females. The genetic basis of the female call is studied by bi‐directional artificial selection for large and small interpulse intervals (IPI). This resulted in non‐overlapping distributions of IPI after only five generations. The mean of eight realized heritability estimates over five generations was above 80%; estimates over ten generations were generally well above 50%. The character is shown to be of a polygenic nature, determined by at least 6 segregating genetic factors. The other features of the female call, strophe duration, and modulation of pulse repetition frequency within the strophe, showed significantly correlated responses. Sexual isolation tests after 10 generations of selection revealed significant symmetrical assortative mating, but coselected males did not exhibit a significant preference for playback calls of females from their own selection line. In view of the high heritability for the call character, and the considerable ecological isolation among Ribautodelphax species, it seems unlikely that the female call differentiated as an adaptation to prevent hybridization (reinforcement). More likely, call and call preference were shaped by sexual selection during allopatry, and may have (had) incidentally an effect in species isolation.
Chloroplast DNA variation within and among five Plantago species
Authors: Wolff Kirsten , Schaal Barbara
Published: December 2004

Chloroplast DNA variation was studied within and among five Plantago species. We determined polymorphism by surveying 86% of the chloroplast genome using 9 or 11 restriction enzymes for intra or interspecific variation, respectively. All five species were polymorphic for both site and length mutations. The outcrossing P. lanceolata has six chloroplast haplotypes of which some were found in the Netherlands as well as in the United States. The highly selfing P. major had five haplotypes and Dutch and United States populations were differentiated from each other in cpDNA. Plantago species are highly differentiated from each other. Of 252 restriction‐sites, 52% were variable among species. Most of this variation was localized in part of the large single copy region. We derived a molecular phylogeny of the five species from restriction‐site variability using PAUP 3.0. P. coronopus and P. maritima form a group as do P. major and P. media. P. lanceolata is more distantly related to the other four species. In a consensus tree both P. major haplotypes and both P. media haplotypes were connected to one node.
Phenotypic plasticity for life history traits in Drosophila melanogaster. I. Effect on phenotypic and environmental correlations
Authors: Gebhardt M. D. , Stearns S. C.
Published: December 2004

All 36 possible crosses among 6 homozygous lines of Drosophila melanogaster were tested for their phenotypic response in developmental time and dry weight at eclosion to variation in temperature and yeast concentration. This method was chosen because it allows one to produce the same heterozygous offspring repeatedly for testing under more conditions than could be handled at once. We estimated the effects of yeast concentration and temperature and their interaction on both the phenotypic and the environmental components of variation and covariation of the two traits. Development was slower at low temperatures and yeast concentrations, and dry weight and viability were lower at higher temperatures and lower yeast levels. Interactions of the two factors with the crosses and with each other indicated that there were genetic differences in plasticity and that the sensitivity of a trait to one factor depended on the level of the other. The covariation of the two traits was generally weak within an environment. Across environments, its sign depended on the factor that changed between the environments: positive for temperature, negative for yeast concentration. These findings can be explained in terms of an established growth model for Drosophila larvae. We conclude that for plastic traits with moderate or low heritability, the relationship between the phenotypic and genetic covariance matrices may be a complex function of the environmental factors that affect the traits. Some implications for the prediction of the evolution in fluctuating environments are outlined.
Morphological differentiation in Carduelis finches: Adaptive vs. constraint models
Authors: Björklund Mats , Merilä Juha
Published: December 2004

In this study we show that morphological diversification in the avian genus Carduelis (Carduelinae) has to a large extent been conservative. Using multivariate methods, we found only minor deviations from the common (ancestral) body‐plan. In particular, variation in bill morphology was found to be more conservative than variation in other parts of the body.

We argue that constraint models of population differentiation can successfully account for the variation in bill morphology in this genus, but are less successful in accounting for variation in other traits. This can be interpreted as a result of long‐term overall stabilizing selection for a certain bill morphology which is related to the way the birds open seeds. A trait combination that is adaptive on the evolutionary time scale may thus act as a constraint on changes in bill morphology on the microevolutionary scale. We conclude that the most parsimonious explanation for low divergence in bill morphology in this genus is that all species have retained the ancestral bill morphology. This may mean that each species chooses its environment rather than being moulded by it. This argument seems to apply to bill morphology, but other traits studied in this genus appear to have evolved in a less constrained fashion. A new index of morphometric integration is introduced to describe covariance structures.
Sexual size dimorphism in the great tit (Parus major) in relation to history and current selection
Authors: Björklund Mats , Lindén Mats
Published: December 2004

We investigated the possible causes of the evolution of sexual size and shape dimorphism in the great tit (Parus major) by using two different approaches. First, we used the equilibrium approach, i.e. analysing current selection to see whether it was possible to find directional selection in the direction of the dimorphism, or stabilising selection maintaining dimorphism at its current level. Second, we used the historical approach, i.e. putting the degree of dimorphism in a phylogenetic perspective to analyse what kind of changes (if any) have occurred. This was carried out in the following way: (i) we described the level of sexual dimorphism in a population of Swedish great tits by means of path model. (ii) We used the path model design to analyse survival and reproductive selection in this population. (iii) We compared the level of dimorphism in relation to size in the great tit with that of the closest congener, the blue tit P. caeruleus. (iv) We compared the amount of interspecific morphological variation with that which would be expected under a drift model.

We found no evidence of either stabilising or directional survival or reproductive selection. Size and shape variation in the great tit seemed unrelated to fitness in adults. Dimorphism was somewhat greater in the great tit compared to the blue tit, but only with an amount predictable by its larger size. In terms of phenotypic standard deviations, the great tit was not more dimorphic than the blue tit, although it was larger. The amount of interspecific variance with regard to size was lower or equal to that expected by the drift model, showing that long‐term directional selection for an increase in size and dimorphism is improbable. These results agree with recent theoretical findings that size and dimorphism should be related and that strong conservatism with regard to dimorphism is to be expected. They also agree with the view that in equilibrium populations, fitness components (if there are many of them) should appear neutral with regard to total fitness.
Direct and correlated responses to selection for desiccation resistance: a comparison of Drosophila melanogaster and D. simulans
Authors: Hoffmann Ary A. , Parsons P. A.
Published: December 2004

Replicate lines of Drosophila melanogaster and D. simulans originating from the same location in Australia were selected at two selection intensities (50%, 85% mortality) for increased resistance to desiccation, and scored for correlated responses to see if similar physiological changes were associated with the selection responses. Realized heritabilities were much higher in D. melanogaster. Selected lines of both species were more resistant than control lines to starvation and a toxic ethanol concentration. Both species also showed similar correlated responses for traits underlying the selection response: selected lines lost water at a slower rate and had reduced activity levels in a dry environment, but they did not differ in wet or dry body weight or in water content. For D. melanogaster, realized heritabilities for lines selected at 85% mortality were higher than for lines selected at 50% mortality, but there was no effect of selection intensity for D. simulans. Comparative studies of this nature may be useful in predicting the extent to which species can adapt to stress in the wild.
Genetic coordination of demography and phenology in the pitcher‐plant mosquito, Wyeomyia smithii
Authors: Hard Jeffrey J. , Bradshaw William E. , Holzapfel Christina M.
Published: December 2004

Demographic and phenological traits compose the basic elements of an insect's life‐history strategy in a seasonal environment. An insect's long‐term fitness depends on its ability to exploit favorable conditions, to avoid unfavorable conditions, and to convert from one life style to the other. For the pitcher‐plant mosquito, Wyeomyia smithii, we show that genetic variation exists in both development time (a demographic trait) and critical photoperiod (a phenological trait) in six populations spanning much of the species' geographical range. During the northward range expansion of W. smithii in North America, these traits have evolved independently under strong directional and stabilizing selection. The correlated response in critical photoperiod to divergent selection on development time reveals significantly positive genetic correlations in five populations and a negative correlation in one population. The positive correlations form a genetically coordinated phenotype: faster developing individuals use a shorter photoperiodic switch point and are able to exploit the late favorable season; slower developing individuals use a longer photoperiodic switch point and are able to avoid extending development into the unfavorable season. This genetic coordination of demography and phenology has not, however, prevented their independent evolution. We propose that evolutionary flexibility in W. smithii may arise in part from the reorganization of their genetic architecture following repeated founder events during their northward invasion of North America.
Molecular information on bowerbird phylogeny and the evolution of exaggerated male characteristics
Authors: Kusmierski R. , Borgia G. , Crozier R. H. , Chan B. H. Y.
Published: December 2004

Mitochondrial DNA cytochrome b sequences of 849 base pairs are reported from eight species of Australian bowerbirds. These sequences are used with three from the literature (Edwards et al., 1991) to investigate bowerbird phylogeny using maximum parsimony and maximum likelihood methods. With respect to the three outgroup species, bowerbirds are shown to be monophyletic with high confidence using the bootstrap. The monogamous Ailuroedus crassirostris (which does not clear display courts) is indicated as the sister group to other bowerbirds. The maypole‐builders (Amblyornis macgregoriae and Prionodura newtoniana) are significantly supported as a clade indicating a common origin for maypole type bowers, despite large differences in the design of these species' bowers. The avenue‐builders (Sericulus chrysocephalus, Ptilonorhynchus violaceus, Chlamydera maculata and C. nuchalis) are also monophyletic. The pattern of divergence in avenue builders accords with the predictions of Gilliard's (1956, 1963) “transferral effect”. The transference hypothesis is not supported by evidence suggesting that the dull plumage of Scenopoeetes is an ancestral condition in bowerbirds. The use of sticks to build bowers could have had a single evolutionary origin and been secondarily lost in Scenopoeetes, or evolved independently in the avenue and maypole builders.
Evolution of insecticide resistance in Culex pipiens populations: The Corsican paradox
Authors: Raymond Michel , Marquine Maïté
Published: December 2004

Culex pipiens
mosquitoes from Corsica have been subject to insecticide treatments since 1971, using temephos (an organophosphate). After 17 years, resistance has not developed beyond a 14‐fold level. This relatively low resistance is due to the presence of several identified resistance genes, including the insensitive target (
AceR ) and overproduced esterases (A1, A4 and B4). The fact that only a low resistance has developed after 17 years of treatment and that this low resistance level is the result of a relatively large number of resistance genes constitute a paradox. To understand this situation and explain why a higher temephos resistance level has not evolved in Corsica as in other parts of the world, it is proposed that the occurrence (through mutation or migration) of efficient resistance genes was a limiting step, and that the only resistance genes available at that time through migration from the surrounding Mediterranean countries had a low cross‐resistance to temephos. The local situation of Corsica is discussed in the light of recent data on the world distribution of the known organophosphate resistance genes in this species, and the relative role of mutation and migration in the evolution of insecticide resistance in natural populations.
Analytical results concerning linkage disequilibrium in models with genetic transformation and conjugation
Authors: Hudson Richard R.
Published: December 2004

Expressions are obtained for the expected levels of linkage disequilibrium under three different equilibrium neutral models that make different assumptions about how recombination takes place. A transformation model is considered in which exchange events involve only one locus at a time. Two conjugation models are considered one with a linear genome and one with a circular genome. In the conjugation models large blocks of genes can be transferred with each conjugation. Consistent with published simulation results, it is found that if the transformation rate per locus is more than twenty times the mutation rate per locus, then the levels of linkage disequilibrium are quite low. If the number of loci being sampled is greater than 10, conjugation with a circular genome can be considerably more effective than transformation in reducing linkage disequilibrium. When recombination rates are high, expected linkage disequilibrium is shown to be proportional to the inverse of the transformation rate (or conjugation rate.)