bluuebunny/crossref_metadata_2025 huggingface dataset:
Volcanism and freshwater fish biogeography in the northeastern North Island of New Zealand
Authors: McDowall R.M.
Published: December 2004

Major volcanic eruptions in the central North Island of New Zealand and, in particular, an eruption dated at ad 186, spread ignimbrite and volcanic ashes (tephra) over a broad area, deposition of which caused major defaunation of affected habitats. However, riverine freshwater fish faunas were undoubtedly affected far beyond the zones of ignimbrite deposition and ash settlement as a result of ash‐laden floods moving down rivers. In areas where entire river systems were covered with ash, fish faunas that recolonized rivers now consist almost entirely of diadromous species that have been able to recolonize the river systems by dispersing through the sea. However, some rivers, that were probably severely affected in their headwaters, have lower elevation and more distant tributaries whose catchments escaped ash showers; these provided refuges for non‐diadromous species which could recolonize upstream once rivers became inhabitable. In such rivers the fish faunas are now a mix of diadromous and non‐diadromous species.
Extending Rapoport's rule to Pacific marine fishes
Authors: Stevens George
Published: December 2004

The mean bathymetric (depth) range of assemblages of marine fishes is negatively correlated with the depth at which the assemblage is found and negatively correlated with species richness. These findings support the creation of a new biogeographic rule patterned after the terrestrial Rapoport's Rules for Latitude and Elevation. Previous work on Rapoport's rule is extended to include this bathymetric rule and the basis for all known Rapoport's rules is generalized in hopes of broadening the search for other Rapoport's rules. Species richness is found to be correlated with Rapoport phenomena, consistent with previous studies. Moreover, local species richness is found to be strongly influenced by regional patterns of species richness (so‐called macro‐ecological factors), not just local influences such as productivity in the immediate area.
Early menopause in women with Down's syndrome
Authors: Schupf N. , Zigman W. , Kapell D. , Lee J. H. , Kline J. , Levin B.
Published: December 2004

We used the AAMR's Adaptive Behavior Scale to ascertain current menstrual status in a population‐based sample of 157 women with Down's syndrome (DS) and 187 women with other intellectual disability, all 40 years of age or older. The age‐adjusted likelihood of menopause was twice as high in women with DS syndrome as in women with other intellectual disability (OR=2.3; 95% Cl= 1.1–4,9). Treated thyroid conditions did not influence menstrual status and did not modify the relationship between DS and menstrual status. These findings support the hypothesis that women with DS experience menopause at an earlier age and that this may be associated with accelerated aging.
Hypofibrinolysis in the insulin resistance syndrome: implication in cardiovascular diseases
Authors: Mavri A. , Alessi M.‐C. , Juhan‐Vague I.
Published: December 2004

Insulin resistance syndrome (IRS) is associated with increased cardiovascular morbidity and mortality. IRS is becoming one of the major health problems as its prevalence grows rapidly. Accelerated atherothrombotic process in the IRS is attributed to metabolic abnormalities, inflammation and to impaired fibrinolysis due to increased plasma plasminogen activator inhibitor type 1 (PAI‐1) levels. Proinflammatory cytokines may have an important role in PAI‐1 overexpression, particularly in the adipose tissue. Studies in genetically modified mice indicate that PAI‐1 might be involved in the aetiopathogenesis of obesity. Modifying PAI‐1 expression by PAI‐1 inhibitors may open a new field of research and may reveal the true role of PAI‐1 in atherosclerotic and insulin resistance processes.
Progressing dermatofibromas following surgery
Authors: Zheng Peishu , Hanke C. William , Faust Holly B. , Hazelrigg Donald E. , Hood Antoinette F.
Published: December 2004

A 39‐year‐old woman, had a lesion on her right thigh that first developed when she was 6 weeks old. This lesion was said to have resembled “spider bites,” and was initially treated with cryotherapy. It continued to enlarge and was biopsied in May 1969, when she was 13 years old. The patient was told she had “neurofibroma.” In 1971, the lesion was rebiopsied and a question of a sarcoma was raised in the pathology report. She underwent extensive surgery to remove the lesion, requiring a skin graft at the operation sife. Multiple lesions subsequently developed around her graft. Biopsies of several lesions were interpreted as dermatofibroma, and she was referred to the Indiana University, Department of Dermatology. When seen in 1995, she had a well‐healed 30 cmx14 cm hypopigmenfed split‐thickness skin graft present on the lateral right thigh. The margin of the graft was outlined by multiple red‐brown firm papules and plaques. Some of the papules and plaques extended beyond the margin of the graft by several centimeters (Fig. 1). Histopathology of the satellite lesions showed epidermal hyperplasia and diffuse spindle cell proliferation in the upper and lower dermis (Fig. 2). The majority of the spindle cells stained positively for Factor Xllla (a marker for dermal dendrocytes). They did not stain with CD34 (a marker for dermatofibrosarcoma protuberans).
Cutaneous electron microscopic study of sclerodermia diffusa in childhood
Authors: Tabata Hideyuki , Ohtsuka Shun , Yamakage Akio , Yamazaki Soji
Published: December 2004

A 9‐year‐old Japanese boy presented in July 1994 with gradual skin sclerosis of the extremities and Raynaud's phenomenon of 10 months duration. He had been treated with oral prednisolone after the diagnosis of juvenile rheumatoid arthritis at the pediatric clinic. He had skin sclerosis with luster on his trunk and extremities (Fig. 1A). His skin score was III and IV, with the exception of his face (I, normal; II, edema; III, edematous sclerosis; IV, skin sclerosis; V, skin atropy). His hands showed finger contracture and he had reticular pigmentation on the back of both hands (Fig. 1B). He had no symptoms of digestive and respiratory organs.

Laboratory findings were as follows. Full blood count was almost normal, with the exception of hyper‐eosinophilia (eosinophil, 10%) and anemia (hemoglobin (Hb), 10.1 g/dL). The erythrocyte sedimentation rate (24 mm/h) was slightly elevated, but C‐reactive protein was normal. Serum gammaglobulin (32.2%) and immunoglobulin G (IgG) (2960 mg/dL) were at high levels. Creatine kinase was normal (60 IU/L). An immunologic profile showed anti‐nuclear antibody (ANA) × 10,240 and rheumatoid arthritis test × 160. All other immunologic auto‐antibodies were negative. A chest X‐ray and chest computed tomography (CT) scan revealed no pulmonary fibrosis. X‐Ray films of the extremities showed no abnormal findings of the joints. The inner pressure of the esophagus was within the normal range. Thermography of the hands showed no abnormal findings. Electromyography was normal. In siaolography, the apple tree sign was positive. A skin biopsy was prepared from his forearm. Fibrotic changes, including massiveness and homogenization of the collagen fibers in the dermis, were observed (Fig. 2A). Colloidal iron stain showed increased acid mucopolysaccharides in intercollagenous spaces. In the fascia under the fatty tissue, the same hypertrophic change in the collagen fibers and lymphocytic infiltration were seen (Fig. 2B). With an elastica stain, elastic fibers in the dermis and those in the fascia showed different distribution patterns. In the dermis, elastic fibers seemed to be reduced in size, granulated, and fragmented (Fig. 2C). In contrast, in the fascia, they were hypertrophic and band‐like (Fig. 2D). From the clinical findings, laboratory profile, and histologic characteristics, our patient was diagnosed as having sclerodermia diffusa (SDD) with sclerodermatous fasciitis (SF).

In order to examine the morphologic abnormality of the fragmented elastic fibers in the dermis, we observed them electron microscopically. Their structures were coarse and rough. Microfibrils were irregularly arranged and amorphous materials were not homogeneous (Fig. 3A). They showed vacuolization and irregular deposition of microfibrillar dense zones (Fig. 3B). Other noticeable findings were network‐like structures observed in the dermis (Fig. 3C).
Nevus lipomatosus superficialis on the face
Authors: Park Hong Jin , Park Chul Jong , Yi Jong Yuk , Kim Tae Yoon , Kim Chung Won
Published: December 2004

A 17‐year‐old woman presented with asymptomatic, multiple plaques around the right mandibular area of the face extending from the cheek to the neck. These lesions had gradually increased in size and number for 8 years, and then were stationary. When she came to us, there were a few skin‐colored or pale yellowish papules and plaques ranging from 0.2 to 1 cm in diameter (Fig. 1). The patient stated that initially the papules developed discretely, and then these papules were confluent and grouped slowly with new lesions. The most recent lesions were skin‐colored papules which were soft to the touch, the older lesions were yellowish plaques with firm consistency and a smooth shiny surface. The patient's general condition had been good at the initial visit and the laboratory findings including blood cell counts, urinalysis, and routine blood chemistry tests were all within normal limits. A roentgenogram of the mandibular area did not reveal any significant findings. The presumptive clinical diagnosis of connective tissue nevus was made.

Histologic examination of biopsy specimen taken from the neck showed lobules of fat cells embedded among the collagen bundles at the level of papillary dermis and collagen bundles were proliferated irregularly (Fig. 2). The individual fat cells were mature and of normal size. The lobules were not encapsulated and did not communicate with the subcutaneous fat tissue. The epidermal changes of the lesions consisted of mild hyperkeratosis with follicular plugging and slightly increased numbers of capillaries were observed around the dermal fat cells (Fig. 3). Therefore, it was diagnosed as nevus lipomatosus superficialis (NLS) which developed multiple lesions very rarely on the face. After surgical removal of the lesion, no evidence of recurrence has been observed 1 year postoperatively.
A consultation with Canadian rural women with breast cancer
Authors: Gray Ross E. , James Pamela , Manthorne Jackie , Gould Judy , Fitch Margaret I.
Published: December 2004

Objective  Relatively little research has been carried out on the health and supportive care needs of rural women living with breast cancer. In this study, results from a Canadian focus group study are used to highlight issues of importance to rural women.

Setting and participants  A total of 276 rural women with breast cancer divided into 17 focus groups participated in the study conducted across Canada. A standardized protocol for discussion was employed. Issues of access to information, support and services were discussed, with women describing their experiences in trying to find appropriate programmes and services.

Main results  The major theme identified through analysis of qualitative data was ‘becoming aware of and/or gaining access to health care information, support and services.’ Other major themes included: (1) dealing with isolation; (2) having to travel; (3) feeling the financial burden and (4) coping with changing work.

Conclusions  Rural women with breast cancer have supportive care challenges related to their circumstances. A series of recommendations were generated through the consultation process which are contributing to the development of a national strategy focusing on the development and extension of programmes for rural women with breast cancer. Although the research on the project was not to specified standards, and suffered from less attention than community capacity building and advocacy, it proved to be of worth and revealed potential benefits from collaborations between researchers and community organizations.
Patient‐friendly hospital environments: exploring the patients’ perspective
Authors: Douglas Calbert H. , Douglas Mary R.
Published: December 2004

Objective  To investigate the perceptions and attitudes of patients to the built environments of NHS Trust hospitals, in order to inform design excellence so as to make future hospitals places and spaces responsive to patient needs.

Design  An exploratory study of patients perceptions based on qualitative semi‐structured personal interviews.

Setting and participants  Fifty one‐to‐one interviews held with hospital in‐patients across the four directorates of surgery, medicine, care of the elderly and maternity at Salford Royal Hospitals NHS Trust, Salford, UK.

Results  The research found that there was much similarity in the priorities, issues and concerns raised by patients in each of the four directorates. Patients perceived the built environment of the hospital as a supportive environment. Their accounts in each area pointed to the significance of the factors that immediately impacted on them and their families. Patients identified having a need for personal space, a homely welcoming atmosphere, a supportive environment, good physical design, access to external areas and provision of facilities for recreation and leisure. Responses suggest that patient attitudes and perceptions to the built environment of hospital facilities relates to whether the hospital provides a welcoming homely space for themselves and their visitors that promotes health and wellbeing.

Conclusions  The findings have important implications for capital development teams, clinical staff, managers and NHS Estates personnel. Although the study has immediate relevance for Salford Royal Hospitals Trust, findings and recommendations reported provide NHS Estates and other relevant stakeholders with evidence‐based knowledge and understanding of patients’ perceptions and expectations of and preferences for particular facilities and estates provision in NHS hospitals.
The influence of variation and of developmental constraints on the rate of multivariate phenotypic evolution
Authors: Wagner G. P.
Published: December 2004

A model of multivariate phenotypic evolution is analysed under the assumption that all characters have the same variance or at least constant ratios of variance. The rate of evolution is examined as a function of the amount of phenotypic variance in a variety of adaptive landscapes (fitness functions). It is demonstrated that the effect of variation depends on the type of adaptive landscape. In “well behaved” adaptive landscapes the rate of evolution can theoretically increase without limits, depending on the amount of heritable phenotypic variation. However, in other adaptive landscapes there are upper limits to the rate of evolution which cannot be exceeded if phenotypic variation is developmentally unconstrained, i. e. if it is the same for all characters. Further it is shown that the maximal rate of evolution becomes small if the number of characters becomes large. Fitness functions of this type are called malignant. It is argued that malignant fitness functions are more adequate models for the evolution of typical organismic systems, because they are models of functionally interdependent characters. It is concluded that there are upper limits to the rate of phenotypic evolution if the variation of functionally interdependent characters is developmentally unconstrained. The possible role of developmental constraints in adaptive phenotypic evolution is discussed.
Recombination and the immortality of the germ line
Authors: Bell Graham
Published: December 2004

Asexual populations irreversibly accumulate mildly deleterious mutations through the occasional stochastic loss of their least‐loaded line, a process known as “Muller's Ratchet”. This paper explores the dynamics of this process, and the role of recombination in halting the Ratchet. Simulation studies show that an optimal class comprising no individuals is lost in about 10no generations, implying that adaptedness may deteriorate rather rapidly in geological time. Asexual organisms will persist only if they are very numerous, or if they have very small genomes, or if there is extensive negative interaction among nonallelic mutations. Otherwise, long‐term persistence requires that unloaded genomes be continually generated by recombination. An approximate expression for the rate of recombination needed to halt the Ratchet is developed, and shows that substantial recombination is necessary in populations of fewer than about 1010 individuals. A further complication is introduced by mutations in sequences which specify proofreading enzymes. Since these will reduce the fidelity of their own replication, a process of positive feedback leading to an ever‐accelerating loss of function is conceivable.
Reproductive correlates of mating system variation in Eichhornia paniculata (Spreng.) Solms (Pontederiaceae)
Authors: Morgan Martin T. , Barrett Spencer C. H.
Published: December 2004

Comparative studies of related plant species indicate that evolutionary shifts in mating systems are accompanied by changes in reproductive attributes such as flower size, floral morphology, and pollen/ovule ratio. Recent theoretical work suggests that patterns of investment in reproduction should also change with the mating system. In a glasshouse study, we investigated the extent to which mating system differences among populations of Eichhornia paniculata (Pontederiaceae) were correlated with changes in allocation to male and female function, floral display, and the regulation of investment in reproduction through fruit and ovule abortion.

Significant differences in the amount of biomass allocated to reproductive structures were evident among six populations of E. paniculata. As predicted by sex allocation theory, the proportion of dry weight allocated to male function decreased with the outcrossing rate of populations. Six of the eight attributes used to characterize floral display also differed significantly among populations. However, with the exception of two attributes describing the number of flowers produced by inflorescences, these were not correlated with outcrossing rate. Levels of fruit and ovule abortion were determined in two populations with contrasting mating systems under different nutrient and pollination treatments. Virtually all fruits initiated by plants from a self‐fertilizing population were matured, while the amount of fruit abortion in an outcrossing population increased with flower production. Ovule abortion was low in both populations. Our results demonstrate that the evolution of self‐fertilization in E. paniculata is associated with changes in investment to reproduction that normally distinguish selfing and outcrossing species.
Density limits and survival of local populations in 64 carabid species with different powers of dispersal
Authors: Den Boer P. J.
Published: December 2004

Patterns of density fluctuations and survival times were estimated for the 64 most abundant carabid species, sampled continuously over 23 years with pitfalls in 89 sites in Drenthe (The Netherlands). I show that for most carabid populations density fluctuated between years, either randomly or between wider bounds than expected with random fluctuations. This was true for all groups, not just those occupying temporary habitats. I discuss the selective processes connected with dispersal (flight) abilities inside and outside populations of species occupying different kinds of habitat, and conclude that under natural conditions the powers of dispersal usually favour an optimal chance of survival of the species; this fits Wright's shifting balance model. Under cultivation, stable habitats have been drastically reduced and fragmented, so that local populations have become highly isolated and the risk of extinction is no longer spread over local groups. This has accelerated selection against dispersal features in isolated populations, so that species with low powers of dispersal apparently can no longer compensate for population extinctions by (re)foundings. Without adequate measures such species are doomed in these areas. Our work leads us to the conclusion that the current ideas on regulation of numbers and on group selection do not adequately describe the situation.
Evolutionary changes of heterogametic sex in the phylogenetic history of amphibians
Authors: Hillis David M. , Green David M.
Published: December 2004

A survey of sex‐determining systems in amphibians revealed widespread variation in the heterogametic sex and the extent of sex chromosome differentiation. Systems of sex determination have now been resolved in 63 species of salamanders and frogs. Species with ZW female heterogamety, OW female heterogamety, and XY male heterogamety have all been reported. A phylogenetic analysis suggests that the ancestral state for amphibians was female heterogamety. XY/XX sex determination has evolved independently at least seven times, whereas there is only one case in which the data suggest that male heterogamety has subsequently reversed to female heterogamety. Differentiation of heteromorphic sex chromosomes in Amphibia has occured repeatedly. A model of an ancestral two‐locus sex‐determination mechanism, based on the findings of the phylogenic analysis and the condition found in the primitive frog Leiopelma hochstetteri, allows a recessive mutation to result in the eventual acquisition of male heterogamety. Reversal to female heterogamety requires de novo evolution of a functional control locus under the model. The model is consistent with all information on sex determination in amphibians, and explains the observed bias in evolution from ZW/ZZ to XY/XX systems.
Multi‐residue gaps, a class of molecular characters with exceptional reliability for phylogenetic analyses
Authors: Lloyd David G. , Calder Victoria L.
Published: December 2004

Qualitative methods of obtaining phylogenies seek distinct classes of characters that collectively are common, yet individually are insufficiently improbable that they provide reliable indications of monophyly. Multi‐residue gaps (insertions or deletions) in DNA and protein sequences are easily recognised and are available in diverse organisms and loci. They are likely to experience few homoplasies, because these require two separate events to be matched in both starting position and length. Two tests of the ability of multi‐residue gaps to recognise clades are conducted. (1) Among the 10.76 kb of noncoding DNA sequences from the ψη‐globin region of 5 primates, there are 7 analysable multi‐nucleotide gaps. These provide a corroborated and noncontradictory, fully resolved gene tree of hominoids. (2) Among the 35 amino acid sequences of globin chains available in 1978, there are 9 nonoverlapping multi‐amino acid gaps. These indicate 8 noncontradictory divisions that agree with recognised taxa and gene categories. In the 412 realigned globin sequences available in 1989, 8 of the gaps are still analysable. These show a maximum of two homoplasies among the 8 × 412 = 3296 species‐characters. Multi‐residue gaps have a high potential to indicate clades. They could be used to reduce the computing labour required in a quantitative study or pooled from different data sets to examine particularly important or difficult phylogenetic questions.
Sex differences in recombination
Authors: Burt Austin , Bell Graham , Harvey Paul H.
Published: December 2004

One of the stronger empirical generalizations to emerge from the study of genetic systems is that achiasmate meiosis, which has evolved 25–30 times, is always restricted to the heterogametic sex in dioecious species, usually the male. Here we collate data on quantitative sex differences in chiasma frequency from 54 species (4 hermaphroditic flatworms, 18 dioecious insects and vertebrates and 32 hermaphroditic plants) to test whether similar trends hold. Though significant sex differences have been observed within many species, only the Liliaceae show a significant sexual dimorphism in chiasma frequency across species, with more crossing over in embryo mother cells than in pollen mother cells; chiasma frequencies are unrelated to sex and gamety in all other higher taxa studied. Further, the magnitude of sexual dimorphism, independent of sign, does not differ among the three main ecological groups (dioecious animals, plants, and hermaphroditic animals), contrary to what would be expected if it reflected sex‐specific selection on recombination. These results indicate that the strong trends for achiasmate meiosis do not apply to quantitative sex differences in recombination, and contradict theories of sex‐specific costs and benefits. An alternative hypothesis suggests that sex differences may be more‐or‐less neutral, selection determining only the mean rate of recombination. While male and female chiasma frequencies are more similar than would be expected under complete neutrality, a less absolute form of the hypothesis is more difficult to falsify. In female mice the sex bivalent has more chiasmata for its length than the autosomes, perhaps compensating for the absence of recombination in males. Finally, we observe that chiasma frequencies in males and females are positively correlated across species, validating the use of only one sex in comparative studies of recombination.
Floral variation in Eichhornia paniculata (Spreng.) Solms (Pontederiaceae) II. Effects of development and environment on the formation of selfing flowers
Authors: Barrett Spencer C. H. , Harder Lawrence D.
Published: December 2004

Genotypes of the mid‐styled morph of tristylous Eichhornia paniculata (Spreng.) Solms (Pontederiaceae) exhibit developmental instability in the position of short‐level stamens under both field and glasshouse conditions. Elongation of one of the stamens to a position adjacent to the stigma results in automatic self‐pollination of flowers. This modification initiates subsequent changes to floral morphology leading to the evolution of predominant self‐fertilization in E. paniculata. The influence of genetic, developmental and environmental factors on the expression of stamen instability was investigated in experiments with genotypes from two populations from northeast Brazil and interpopulation hybrids. Genotypes from the three sources differed significantly in the degree and pattern of stamen instability expressed under uniform growing conditions. Significant position effects in the production of modified flowers were detected among genotypes using logistic regression techniques. Modified flowers were most frequently produced on later inflorescence branches in the flowering sequence and at proximal flower positions within an inflorescence branch. However, these patterns were complex, varying among genotypes and experimental conditions. Stamen modification increased in clones grown under water stress or at high temperature, demonstrating a significant environmental component to floral instability.
Morphological and growth rate differences among outcrossing and self‐pollinating races of Arenaria uniflora (Caryophyllaceae)
Authors: Hill J. P. , Lord E. M. , Shaw R. G.
Published: December 2004

Populations of Arenaria uniflora exhibit intraspecific variation in floral size and degree of protandry in association with the evolution of self‐pollination. Heterochrony, or a simple change in the absolute timing or rate of developmental events, is proposed as the evolutionary mechanism underlying the origin of the small, self‐pollinating flowers from their large, outcrossing progenitors. Inflorescence growth in two autogamous populations and their related outcrossing progenitors was studied to provide the temporal data necessary for testing the hypothesis of heterochrony. All four races showed significant variation in the growth and mature length of inflorescence organs. Inflorescences of selfing races were smaller, and had slower relative growth rates and a two‐fold increase in the plastochron relative to outcrossing populations. The large‐flowered races were both significantly protandrous. A more detailed growth analysis of flower development in two races indicated that the selfing flowers develop at a slower rate and for a longer duration relative to outcrossing flowers. The implications of these temporal changes in floral ontogeny for the heterochronic origin of self‐pollinating floral forms are considered.
Tests of sib diversification theories of outcrossing in Impatiens capensis: Effects of inbreeding and neighbour relatedness on production and infestation
Authors: Burt Austin , Bell Graham
Published: December 2004

Several models of the evolution of genetic systems posit very strong frequency‐dependent selection acting on small spatial scales; in such circumstances a genetically diverse sibship outperforms a genetically uniform sibship, and genes for mixis may spread in a population. Such selection regimes may derive from resource limitation and/or parasite transmission. We describe a greenhouse experiment designed to test these ideas, using the annual herb Impatiens capensis. Plants were potted in pairs; the genetic variance within pots was manipulated by using progeny from either inbred or outcrossed parents and by using either full sibs or unrelated individuals. Treatment combinations designed to increase genetic diversity resulted in greater phenotypic variance in both morphology and production, though not in the density of spider mites or whiteflies. Despite evidence of resource limitation, there was no effect of genetic diversity on productivity, nor was there an effect on infestation. These results fail to support either the sib competition or the sib contagion theory of outcrossing.
Parasites differentially increase the degree of fluctuating asymmetry in secondary sexual characters
Authors: Møller Anders Pape
Published: December 2004

The degree of fluctuating asymmetry has been demonstrated to reflect the ability of individuals to cope with different kinds of environmental stress (Parsons 1990). Parasites and diseases are one kind of environmental stress which most individuals encounter during their lifetime. Parasites have also been suggested to play an important role in sexual selection and the development of ornaments, since the full expression of ornaments may reflect the ability of hosts to cope with the debilitating effects of parasites. Here I report for the first time that a parasite, the haematophagous tropical fowl mite Ornithonyssus bursa (Macronyssidae, Gamasida), directly affects the degree of fluctuating asymmetry in a secondary sexual character of its host, the elongated tail of the swallow Hirundo rustica (Aves: Hirundinidae). I experimentally manipulated the mite load of swallow nests during one season by either increasing or reducing the number of mites, or keeping nests as controls. The degree of fluctuating asymmetry was measured in the subsequent year after the swallows had grown new tail ornaments under the altered parasite regime. The degree of fluctuating asymmetry was larger at increasing levels of parasites for male tail length, but not for the length of the shortest tail feather or wing length or for tail and wing length in females. These results suggest that the degree of fluctuating asymmetry in tail ornaments, but not in other feather traits, reliably reveals the level of parasite infestation. This has important implications for the ability of conspecifics to use the size and the expression of ornaments in assessment of phenotypic quality and thus in sexual selection.
Phenotypic plasticity and selection in Drosophila life‐history evolution. I. Nutrition and the cost of reproduction
Authors: Chippindale Adam K. , Leroi Armand M. , Kim Sung B. , Rose Michael R.
Published: December 2004

Earlier experiments have shown that the evolution of postponed senescent populations can be achieved by selection on either demographic or stress resistance characters. Both types of selection have produced results in which survival characters (stress resistance and longevity) have apparently traded‐off against early‐life fecundity.

Here we present the results of a series of experiments in which an environmental variable — the level of live yeast inoculate applied to the substrate — produces a qualitatively similar phenotypic response: longevity and starvation resistance are enhanced by lower yeast levels, at the expense of fecundity. For the starvation resistance versus fecundity experiments we show a negative and linear relationship between the norms of reaction for each character across a gradient of yeast levels. This phenotypic trade‐off is stable across the 20 populations and 4 selection treatments reported on here, and its general agreement with earlier selection results suggests that the evolutionary response and the phenotypically plastic response may share a common physiological basis. However, an important discrepancy in the lifetime fecundity data between the selection response and the dietary manipulations preclude strict analogy. The results broadly conform to a simple “Y‐model” of allocation, in which a limited resource is divided between survival and reproduction; here the characters are starvation resistance and longevity versus fecundity.
Experimental heterochrony in hydractiniid hydroids: Why mechanisms matter
Authors: Blackstone Neil W. , Buss Leo W.
Published: December 2004

As with most clonal organisms, hydractiniid hydroids display a range of morphological variation from sheet‐like to runner‐like forms. Life history differences correlate with these morphological traits, exhibiting patterns commonly found in studies of heterochrony. Experimental studies of two hydractiniid species show that both morphological and life history heterochronies correlate with patterns of gastrovascular circulation. Similar experimental perturbations of energy metabolism, however, have opposite heterochronic effects on the two species. Treatment with 2,4‐dinitrophenol, an uncoupler of oxidative phosphorylation, produced diminished peripheral circulation and sheet‐like peramorphic morphologies in the runner‐like species, Podocoryne carnea. In contrast, similar manipulations of the sheet‐like species, Hydractinia symbiolongicarpus, produced variable peripheral circulation and more runner‐like, juvenilized morphologies. These results diverge at the level of morphological and life history pattern, but are consistent when viewed in terms of the physiology of the gastrovascular system. Interpretations of patterns of heterochrony must focus on the physiological and developmental mechanisms which mediate the expression of heterochronic traits.
Population structure and genetic diversity of metamorphic and paedomorphic populations of the tiger salamander, Ambystoma tigrinum
Authors: Routman Eric
Published: December 2004

Genetic relationships, population subdivision and genetic diversity were estimated from mtDNA and allozyme data for two subspecies of tiger salamander, one of which is obligately metamorphic and the other polymorphic for paedomorphosis (larval reproduction). Far greater genetic differentiation exists between subspecies than within subspecies, suggesting that the subspecies have evolved in allopatry. Values of Fst calculated from both mtDNA and allozymes were greater than 0.400 for each subspecies. Significant population subdivision was detected even on a microgeographic scale. This extensive population subdivision indicates that populations can respond to extremely localized selection pressures. In the case of paedomorphosis, populations in permanent water should evolve paedomorphosis as long as the appropriate genes exist. For both mtDNA and allozymes, comparisons of population structure within the polymorphic subspecies and between polymorphic and metamorphic subspecies reveal no discernible effects of paedomorphosis. However, a comparison of paedomorphic and metamorphic populations of the polymorphic subspecies showed significantly higher mtDNA diversity in paedomorphic populations. The discrepancy between the allozyme and mtDNA results may be due to the lower effective population size of mtDNA compared to autosomal genes.
The evolution of hypervariable sex and supernumerary (B) chromosomes in the relict New Zealand frog, Leiopelma hochstetteri
Authors: Green David M. , Zeyl Clifford W. , Sharbel Timothy F.
Published: December 2004

Chromosomes exhibiting elevated levels of differentiation are termed hypervariable but no proposed mechanisms are sufficient to account for such enhanced evolutionary divergence. Both hypervariable sex and supernumerary (B) chromosomes were investigated in the endemic New Zealand frog, Leiopelma hochstetteri, which is chromosomally polymorphic both within and between populations and has sufficiently elevated variation that different populations can be identified solely by their C‐banded karyotypes. This frog is further distinguished by the univalent, female‐specific W‐chromosome (0W/00 sex determination) uniquely possessed by North Island populations. This sex chromosome exhibited variation in morphology, size, and heterochromatin distribution, sufficient to resolve 11 different types, including isochromosomes. Five of the 12 populations examined also had supernumerary chromosomes that varied in number (up to 15 per individual) and morphology. Specific variations seen among the hypervariable chromosomes could have resulted from heterochromatinisation, chromosome fusions, loss‐of‐function mutations, deletions, and/or duplications. Frogs of the same species from Great Barrier Island, however, had neither supernumeraries nor the female‐specific chromosome. The 0W/00 sex chromosome system must have been derived after the isolation of Great Barrier Island from North Island populations by raised sea levels between 14 000 and 8000 years ago. Furthermore, biochemical divergence between populations is minor and therefore the chromosomal variation seen is comparatively recent in origin. The one characteristic common to all known hypervariable chromosomes is curtailment or lack of recombination. Their accelerated evolution therefore is possible via the mechanism of Muller's ratchet, either alone or in concert with other factors.
Patterns of fluctuating asymmetry in sexual ornaments predict female choice
Authors: Møller Anders Pape
Published: December 2004

Extravagant secondary sexual characters are assumed to have arisen and be maintained by sexual selection. While traits like horns, antlers and spurs can be ascribed to intrasexual competition, other traits such as extravagant feather ornaments, displays and pheromones have to be ascribed to mate choice. A number of studies have tested whether females exert selection on the size of male ornaments, but only some of these have recorded female preferences for the most extravagantly ornamented males. Here I demonstrate that female choice can be directly predicted from the relationship between the degree of fluctuating asymmetry and the size of a secondary sexual character. Fluctuating asymmetry is an epigenetic measure of the ability of individuals to cope with stress, and it occurs when an individual is unable to undergo identical development of an otherwise bilaterally symmetric trait on both sides of its body. There is a negative relationship between the degree of fluctuating asymmetry and the absolute size of an ornament in those bird species with a female preference for the largest male sex trait, while there is a flat or U‐shaped relationship among species without a female preference. These results suggest that females prefer exaggerated secondary sexual characters if they reliably demonstrate the ability of males to cope with genetic and environmental stress. Some species may demonstrate a flat or U‐shaped relationship between the degree of fluctuating asymmetry and the absolute size of an ornament because (i) the genetic variance in viability signalled by the secondary sex trait has been depleted; (ii) the secondary sex trait is not particularly costly and therefore does not demonstrate condition dependence; or because (iii) the sex traits can be considered arbitrary traits rather than characters reflecting good genes.
Counterselection on sex chromosomes in the Mus musculus European hybrid zone
Authors: Dod Barbara , Jermiin Lars S. , Boursot Pierre , Chapman Verne H. , Nielsen J. Tönnes , Bonhomme François
Published: December 2004

The extent to which alleles can disperse across a hybrid zone depends on the selection they are subjected to in the hybrid genetic background or, for those that are selectively neutral, on their ability to escape from the unfavourable environment by recombination. Three markers spanning a 45 cM segment in the center of the X chromosome were used to investigate the degree to which selection against X chromosome linked genes helps to maintain the barrier to gene flow in the hybrid zone between Mus musculus domesticus and M. m. musculus in Denmark. The introgression of all the sex chromosome specific markers was more limited than that of the autosomal enzymes (Idh1, Amy, Gpd1, Pgm1, Es1, Es2, Mpi, Np1, Es10, Sod1) and the mitochondrial DNA. The cline for DXPas2, which is in the center of the X chromosome, is extremely steep and shows that certain genes located in this region are strongly selected against in the hybrid background. The clines of the other two X‐linked markers, Hprt and DXPas1, and of the Y chromosome are not as abrupt and all three have similar asymmetric introgression patterns. Although the musculus variants appear to behave in much the same way as those of the autosomal genes, the domesticus variants do not introgress. The results show that X‐linked and to a lesser extent Y‐linked genes are more strongly selected against in the hybrid genome than the mitochondrial genome or the different autosomal loci. This suggests that co‐adapted gene systems involving the sex chromosomes may play an important role in the hybrid breakdown between the two subspecies.
DNA repair and the evolution of transformation IV. DNA damage increases transformation
Authors: Michod Richard E. , Wojciechowski Martin F.
Published: December 2004

Natural genetic transformation in the bacterium Bacillus subtilis provides a model system to explore the evolutionary function of sexual recombination. In the present work, we study the response of transformation to UV irradiation using donor DNAs that differ in sequence homology to the recipient's chromosome and in the mechanism of transformation. The four donor DNAs used include homologous‐chromosomal‐DNA, two plasmids containing a fragment of B. subtilis trp+ operon DNA and a plasmid with no sequence homology to the recipient cell's DNA. Transformation frequencies for these DNA molecules increase with increasing levels of DNA damage (UV radiation) to recipient cells, only if their transformation requires homologous recombination (i.e. is recA+‐dependent). Transformation with non‐homologous DNA is independent of the recipient's recombination system and transformation frequencies for it do not respond to increases in UV radiation. The transformation frequency for a selectable marker increases in response to DNA damage more dramatically when the locus is present on small, plasmid‐borne, homologous fragments than if it is carried on high molecular weight chromosomal fragments. We also study the kinetics of transformation for the different donor DNAs. Different kinetics are observed for homologous transformation depending on whether the homologous locus is carried on a plasmid or on chromosomal fragments. Chromosomal DNA‐ and non‐homologous‐plasmid‐DNA‐mediated transformation is complete (maximal) within several minutes, while transformation with a plasmid containing homologous DNA is still occurring after an hour. The results indicate that DNA damage directly increases rates of homologous recombination and transformation in B. subtilis. The relevance of these results and recent results of other labs to the evolution of transformation are discussed.
Multiple mating, sperm competition and meiotic drive
Authors: Haig David , Bergstrom Carl T.
Published: December 2004

Most discussions of ‘sperm competition’ have ignored the potential for competition among the different sperm genotypes present in the ejaculate of a single male. Rivalry within ejaculates may limit cooperation among the members of an ejaculate when they compete with sperm produced by other males. A gene that gains an advantage in competition within an ejaculate (a segregation distorter) may increase in frequency even if it is associated with significant costs to organismal fitness. Therefore, selection will favor genes expressed in males that suppress competition within ejaculates. This may explain why sperm function is largely controlled by the diploid genotype of the male progenitor, rather than by the genotypes of individual haploid sperm. Females who mate with multiple males reduce the relative advantage of a segregation distorter whenever the distorter impairs the competitive effectiveness of the ejaculates in which it occurs. If the distorter is associated with costs to organismal fitness, selection will favor female mating behavior that reduces the distorter's equilibrium frequency. Competition within ejaculates may thus be one reason why females choose to mate with multiple males.
Pollinators entering female dioecious figs: why commit suicide?
Authors: Patel Aviva , Anstett Marie‐Charlotte , Hossaert‐McKey Martine , Kjellberg Finn
Published: December 2004

In the dioecious fig/pollinator mutualism, the female wasps that pollinate figs on female trees die without reproducing, whereas wasps that pollinate figs on male trees produce offspring. Selection should strongly favour wasps that avoid female figs and enter only male figs. Consequently, fig trees would not be pollinated and fig seed production would ultimately cease, leading to extinction of both wasp and fig. We experimentally presented pollinators in the wild (southern India) with a choice between male and female figs of a dioecious fig species, Ficus hispida L. Our results show that wasps do not systematically discriminate between sexes of F. hispida. We propose four hypotheses to explain why wasp choice has not evolved, and how a mutualism is thus maintained in which all wasps that pollinate female figs have zero fitness.