bluuebunny/crossref_metadata_2025 huggingface dataset:
Mauricio Goihman‐Yahr, MD, PhD, Editor
Authors: Chiang Chih‐Tei , Chan Heng‐Leong , Kuo Tseng‐Tong , Wang Po‐Nan
Published: December 2004

The Correspondence Section serves as a forum for opinion exchange about subjects of general interest such as dermatologic 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 to Mauricio Goihman‐Yahr, MD, PhD, Editor, Jet International M‐154, PO Box 020010, Miami, FL 33102.
Do the British Guidelines for Asthma Management facilitate concordance?
Authors: Steven Karen , Marsden Wendy , Neville Ronald G , Hoskins Gaylor , Sullivan Frank M , Drummond Neil
Published: December 2004

Background  Asthma is an example of a common, chronic illness in which clinicians are encouraged to promote concordance and adhere to guidelines. Some existing research suggests that these aims may be incompatible.

Objectives  To describe patient goals for life and for asthma management in order to inform concordance with people with asthma.

Design  A cross‐sectional, qualitative survey.

Setting and participants  A purposive sample of 47 adults with asthma from Dundee, UK. The subjects were identified from general practice asthma registers and had a range of ages and asthma severity but no significant comorbidity.

Methods  Tape‐recorded semi‐structured interviews. The topic guide was based on the literature and had been piloted in a previous study.

Results  The participants focussed on improving their lives, only aiming to improve their asthma as a means of improving their lives. Three aspects of asthma were reported to help or hinder improving life: the use of asthma medication, trigger avoidance and exercise. People integrated these three aspects of asthma in order to maximize life.

Conclusions  The study supports the more individualized goals of the recently revised British Guidelines for Asthma Management but highlights the need to develop this further in future revisions. It also provides an explanation for patients’ acceptance of less than ‘perfect’ asthma control and it suggests that shared goals may be achieved in practice by considering the advantages and disadvantages of medication and allergen avoidance on everyday life rather than on asthma.
Are codon usage patterns in unicellular organisms determined by selection‐mutation balance?
Authors: Bulmer Michael
Published: December 2004

Strongly biased codon usage is common in unicellular organisms, particularly in highly expressed genes. The bias is most simply explained as a balance between selection and mutation, with selection favouring those codons which are more efficiently translated. In a review Ikemura (1985) has proposed four rules for predicting which codons will be preferred, based on the properties of the transfer RNAs responsible for translating messenger RNA into protein. In this paper codon usage in E. coli and yeast is re‐examined using the recent compilation of Maruyama et al. (1986). The codon adaptation index of Sharp and Li (1986a) is used as a measure of gene expression to investigate the importance of this factor. It is found that Ikemura's rules successfully predict preferred codons for yeast, but that two of them work less well for E. coli, and it is suggested that some of the apparent bias in weakly expressed genes of E. coli may be due to contextual effects on mutation rates.
Dispersal, kinship and inbreeding in an island population of the Great Tit
Authors: Van Tienderen P. H. , Van Noordwijk A. J.
Published: December 2004

We investigated the kinship structure of an island population of the Great Tit (Parus major). Kinship of birds could be inferred by comparing their family trees. Dispersal was also studied to explain the observed pattern of kinship.

On the island of Vlieland the tits breed in several wooded areas. Both males and females preferred to breed in their natal area; males did so more strongly than females. Hence gene flow between the areas is restricted. However, within the largest wooded area females showed random dispersal, while males showed a slight tendency to breed near their natal site.

The degree of kinship of neighbouring birds is a suitable control group for the relatedness of partners that takes into account the effects of dispersal. In the largest wooded area, birds were on average equally related to their partner and to their neighbours. Moreover, the mean coefficient of kinship between male and female neighbours was equal to the average kinship in this part of the population.

We conclude that mating is random with respect to kinship. There is no evidence for avoidance of inbreeding. It is unlikely that kin recognition plays an important role in the process of mate choice in this population of Great Tits. We suggest that ecological factors are the main causes for the observed patterns of dispersal and mating.

On the island more female than male immigrants enter the population each year. Incidental data indicate an exchange of birds between the population studied and surrounding populations. Ancestries of immigrants are not known, and indeed a first analysis of all birds, including immigrants, showed that males were more closely related than females. However, differential immigration could not fully explain the observed difference in kinship. The presence of local adaptation in males is suggested as a possible additional cause.
Genetic and maternal influences on life history plasticity in milkweed bugs (Oncopeltus): response to temperature
Authors: Groeters Francis R. , Dingle Hugh
Published: December 2004

This study was designed to examine life history flexibility arising from phenotypic plasticity in response to temperature and from maternal effects in response to reproductive diapause in a temperate zone population of the milkweek bug (Oncopeltus fasciatus). We employed a split‐family, first‐cousin, full‐sib design with siblings reared at different temperatures in order to quantify phenotypic plasticity, maternal effects, and variation for each. The following traits were analyzed: development time, age at first reproduction, longevity, early‐life fecundity, and wing length. We found both life history plasticity and maternal effects on life history traits which tend to enhance the colonizing ability of offspring born to mothers that have undergone reproductive diapause. We were unable to demonstrate additive genetic variation for plasticity for any of the traits, while for development time and wing length we found variation due to non‐additive genetic or common‐environmental sources. We were also unable to demonstrate additive genetic variation for maternal effects, although variation may exist at low levels that are difficult to detect using cousin‐families. The apparent lack of variation in this population would constrain evolution of life history flexibility even though considerable flexibility exists in the phenotype.
Variation in gene flow levels among predominantly self‐pollinated plants
Authors: Govindaraju Diddahally R.
Published: December 2004

Levels of gene flow, Nm, were calculated for 34 predominantly self‐pollinated plants, using information on differentiation among populations, Gst. Gene flow levels varied from 0.01 to 6.55, and departed significantly from a uniform distribution. High, medium and low levels of gene flow were found among 15, 38, and 47 percent of the species, respectively. The average heterozygosity (H) and the Nm values showed a positively significant association. These results were compared to gene flow levels obtained with a limited number of predominantly outcrossed plants. Gene flow levels in several self‐pollinated species were comparable to those characteristic of some outcrossed species. Pollen flow, combined with long distance dispersal of propagules through various vectors may be responsible for the high levels of gene flow observed in self‐pollinated species. High gene flow may provide the genetic flexibility required for successful colonization, which is an essential feature of self‐pollinated plants.
The causes and consequences of constrained sex allocation in haplodiploid animals
Authors: Godfray H. C. J.
Published: December 2004

Males of haplodiploid species develop from unfertilized eggs. An unmated female, or a female in some other way prevented from fertilising eggs, is thus still able to produce male offspring. The presence of females constrained to produce only male progeny distorts the population sex ratio and leads to selection on unconstrained females to produce a daughter‐biased sex ratio. With panmictic mating, the response of unconstrained females maintains a population sex ratio of equality. In populations with strong local mate competition, the presence of constrained females has only a minor affect on the sex ratio of unconstrained females. If unconstrained females modulate their sex ratio in response to all‐male oviposition, there is still no penalty to the production of all‐male broods as constrained oviposition becomes more common, providing less than 50% females are so constrained. When there is local mate competition or if there is no sex ratio response by unconstrained females, there will be unequal costs and benefits to all‐male production, some of which are discussed. The paper also contains a review of the factors leading to constrained oviposition in parasitic wasps and a discussion of how the percentage constrained oviposition can be measured in natural populations.
Floral variation in Eichhornia paniculata (Spreng.) Solms (Pontederiaceae): I. Instability of stamen position in genotypes from northeast Brazil
Authors: Seburn Carolyn N. L. , Dickinson Timothy A. , Barrett Spencer C. H.
Published: December 2004

Floral instability in the mid‐styled morph of tristylous Eichhornia paniculata (Spreng.) Solms (Pontederiaceae) was investigated in 14 genotypes from three Brazilian populations of contrasting morph structure (trimorphic, dimorphic, and monomorphic) and levels of inbreeding. Floral instability was described using uni‐ and multivariate methods, in terms of the degree and pattern of variation and covariation in 14 floral measurements from plants grown under uniform glasshouse conditions. The greatest variability was exhibited by filaments of the two lateral short‐level stamens, within and between genotypes from the dimorphic and monomorphic populations. Elongation of one of the stamens to a position adjacent to the stigma results in automatic self‐pollination of flowers. Genotypes were found to differ more in the pattern of covariation between measurements than in multivariate variability. Differences between genotypes in the correlation structure of floral traits were most pronounced in the monomorphic population, and primarily involved measurements of unmodified, rather than modified, stamens. There was no consistent relationship between multivariate variability and whether genotypes produced modified flowers. This pattern suggests that short‐stamen modification arises from changes at specific loci rather than through generalised floral instability brought about by genome‐wide homozygosity.
A phylogenetic interpretation of sexual dimorphism in body size and ornament in relation to mating system in birds
Authors: Björklund Mats
Published: December 2004

Sexual dimorphism in body size and ornament is commonly assumed to be a result of sexual selection. Therefore, a pattern among species is expected where the type of mating system correlates with the degree of sexual dimorphism. This was analysed using comparative data on birds using an autocorrelation model. Mating system did correlate with sexual dimorphism in ornament (tail), but was only weakly correlated with sexual size (tarsus) dimorphism. Polygynous species were significantly larger than monogamous species. After correcting for size, there was no difference in size dimorphism between polygynous and monogamous species. The reverse was true for tail dimorphism; polygynous species exhibited a larger degree of tail dimorphism, but there was no difference in absolute size of the tail. This pattern suggests that an evolutionary change in mating system is associated with a change in overall size, and in degree of dimorphism in secondary sexual traits.
Heterochrony of tooth root initiation in rabbits
Authors: Sych L. S. , Reade P. C.
Published: December 2004

One of the considerable evolutionary modifications to the dentition of rabbits and other lagomorphs has been the transition from teeth of finite growth, characterized by the presence of brachydontic roots in ancestral species, to teeth in which their generative parts operate as cell renewal systems to maintain a continuous growth of teeth in contemporary species. In contemporary lagomorphs evidence for the existence of vestigial roots in the “rootless”, continuously growing permanent cheek teeth has not been described. It was the purpose of this study to examine developing molariform teeth for evidence of such structures. The basis for the examination was serial histological sections of maxillae and mandibles of contemporary rabbits (Oryctolagus cuniculus L.) harvested from foetuses and postnatals aged from the 15th day postconception to birth and from birth to the 90th postnatal day respectively. The fossil teeth of the Miocene lagomorphs from the genus Amphilagus and Titanomys were used for direct comparisons together with evidence from the literature. It was found that of the 3 root openings which appeared during the early development of permanent molariform teeth, the two lateral ones were homologous with the 2 lateral brachydontic roots present in adult molariform teeth of ancestral lagomorphs. The time required for initiation of the root openings, counted from the day of appearance of the cap stage, was found to be 6 days for deciduous teeth and 3 to 4 days for permanent ones. Four stages in the ontogenesis and evolution of the odontogenic cell renewal system of lagomorphs have been described.
Interspecific transfer of P elements by crosses between Drosophila simulans and Drosophila mauritiana
Authors: Montchamp‐Moreau Catherine , Périquet G. , Anxolabéhère D.
Published: December 2004

Interspecific crosses were carried out between P element‐transformed strains of D. simulans and a strain of D. mauritiana, a species devoid of this transposable element family. Four lines were established from hybrid females backcrossed with D. mauritiana males for four generations, and then maintained by intra‐line mass mating. In situ hybridization of polytene chromosomes and southern blots showed that full‐length and deleted P elements were present in all of the lines after 15 generations. We conclude that at least some of the P elements observed in two lines result from their transposition into D. mauritiana genome. Gonadal sterility, induced at 29°C in D. melanogaster by P elements also occurred with these two latter lines.
The evolutionary history of Drosophila buzzatii. XVI. Fitness component analysis in an original natural population from Argentina
Authors: Hasson Esteban , Vilardi Juan C. , Naveira Horacio , Fanara Juan J. , Rodriguez Constantina , Reig Osvaldo A. , Fontdevila Antonio
Published: December 2004

The adaptive significance of the chromosomal polymorphism of Drosophila buzzati has been studied by means of fitness component analysis in an original population from Argentina. The results show evidence of selection acting through pupal viability, longevity (adult viability) and fecundity on the second chromosome polymorphism, and through pupal viability and virility on the fourth chromosome polymorphism.

Changes in chromosomal inversion frequencies throughout the life‐cycle suggested an endocyclic pattern of directional selection, which at first seems to be the only detectable mechanism responsible for the maintenance of the polymorphism. However, slow, long‐term frequency changes cannot be ruled out. The way in which endocyclic selection acts on this population is different from that in a colonized population previously studied; that is, different fitness components are involved in the maintenance of chromosomal polymorphism. The possible factors that may explain these differences are discussed.
Allozyme analysis and phyletic relationships of two new stick‐insects from north‐west Sicily: Bacillus grandii benazzii and B. rossius‐grandii benazzii (Insecta Phasmatodea)
Authors: Mantovani Barbara , Scali Valerio , Tinti Fausto
Published: December 2004

Two new Sicilian stick‐insects have been discovered within the genus Bacillus. Evidence concerning the subspecific differentiation of Bacillus grandii benazzii and the hybrid constitution of B. rossius‐grandii benazzii by means of allozyme analysis is given, and is consistent with morphological and karyological data on the differentiation of these two north‐west Sicilian morphs from south‐eastern B. g. grandii and B. whitei. B. g. benazzii is more polymorphic than B. g. grandii and B. rossius‐g. benazzii embodies its genetic variability, thus differing sharply from the south‐eastern parallel hybrid B. whitei ( = B. rossius × B. g. grandii). Reproductive mechanisms also appear to be different in the two interspecific hybrids, involving parthenogenesis in the latter and hybridogenesis in the former. Finally, the phyletic relationships among all Sicilian Bacillus taxa are summarized in a revised scheme, which also takes into account new evidence that B. atticus has contributed to hybrid constitution of the triploid B. lynceorum.
Microgeographic variation in Anolis oculatus, on the island of Dominica, West Indies
Authors: Malhotra Anita , Thorpe Roger S.
Published: December 2004

The current study provides a quantitative description of the pattern of geographic variation in three morphological character systems of Anolis oculatus, on the ecologically diverse island of Dominica. Causal relationships were investigated by comparing observed patterns of variation to hypothesised patterns (derived from six ecological variables), using Mantel tests, partial correlations and canonical correlations. The similarity between generalised morphological and ecological matrices was highly significant. Partial correlations indicated which of the ecological factors had the most significant influence on individual characters, while canonical correlations showed that characters formed constellations which were influenced by constellations of ecological factors. This analysis also illustrates the incongruence of patterns of variation which result from ecogenetic adaptation. The conventional subspecific categories cannot adequately reflect this variation and consequently, in such cases, the use of subspecies is inappropriate.
Nestling growth in the Great Tit I. Heritability estimates under different environmental conditions
Authors: Gebhardt‐Henrich Sabine G. , Van Noordwijk Arie J.
Published: December 2004

Evolutionary change requires natural selection in the presence of heritable variation for the trait(s) under selection. Since heritabilities and selection pressures are known to vary with environmental conditions, it is crucial to know how much genetic variation is expressed under which conditions. This study addresses the question of how the expression of genetic variation for fledgling body size of Great Tits varies with the environment. Different environmental conditions were created experimentally by manipulating brood sizes. The treatment affected body size, measured as either fledging weight or tarsus length, and interacted with natural temporal variation in food availability. Both measurements show stabilizing selection.

A cross‐fostering design was carried out to separate genetic and environmental causes of variation. Heritabilities as measured from offspring‐midparent regressions and from full‐sib analyses were substantial for both traits, except that no heritability was found for weight under poor conditions. Instead, fledging weights were significantly correlated with the weights of their unrelated guardians' ( = fosterparents') weight under poor conditions.

We propose that under poor conditions, when selection on fledging weights is expected to be directional and strong, only little genetic variance is expressed. Any evolutionary response to this selection on fledging weight might therefore be slow, if the increase in selection pressure is not greater than the decrease in heritability.
Genetic prenatal maternal effects on organ size in mice and their potential contribution to evolution
Authors: Cowley David E.
Published: December 2004

Two embryo transfer experiments were carried out in order to estimate the magnitude of prenatal maternal effects, independent of postnatal maternal factors, on the growth of internal organs and fat pads in mice. Reciprocal embryo transfers between the inbred mouse strains C3HeB/FeJ and SWR/J yielded three significant findings. First, all traits were not equally influenced by prenatal maternal factors. Genetic prenatal maternal factors, stemming from the genotype of the uterine mother, had a significant effect on testis weight, subcutaneous fat pad weight and epididymal fat pad weight in 21 day old progeny, but they had no effect on cranial capacity, an index of brain size, kidney weight, or liver weight. Prenatal litter size, defined as the sum of live and dead pups at birth, had a significant negative relationship with 21 day testis weight and kidney weight, and a significant positive association with subcutaneous and epididymal fat pad weights. Cranial capacity and liver weight at 21 days postnatally were not influenced by prenatal litter size. Second, the experiments demonstrated that there was ontogenetic variability in the strength of prenatal maternal effects. At 70 days of age, only subcutaneous fat pad weight was significantly influenced by genetic prenatal effects, and prenatal litter size had a significant negative relationship only with subcutaneous fat pad weight and body weight. Third, genetic prenatal effects had a significant influence on the among‐trait covariances at 21 days postnatally, but not at 70 days. Because multivariate evolution involves covariances among characters, the latter results suggest that prenatal effects due to the mother's genotype can affect phenotypic evolution of mammals, especially for selection imposed early in life.
Colony‐level sex ratio selection in the eusocial Hymenoptera
Authors: Boomsma J. J. , Grafen A.
Published: December 2004

We present an inclusive fitness model on worker‐controlled sex investments in eusocial Hymenoptera which expands the existing theory for random mating populations as formulated by Trivers and Hare (1976) and Benford (1978). We assume that relatedness asymmetry is variable among colonies — owing to multiple mating, worker reproduction and polygyny — and that workers are able to assess the relatedness asymmetry in their own colony. A simple marginal value argument shows that “assessing” workers maximize their inclusive fitness by specializing on the production of the sex to which they are relatively more related than the average worker in the population is related to that sex. The model confirms our earlier verbal argument on this matter (Boomsma and Grafen, 1990) and gives further quantitative predictions of the optimal sex ratio of relatedness‐asymmetry classes for both infinite and finite, random mating populations.

It is shown that in large populations all but one of the relatedness‐asymmetry classes should specialize on the production of one sex only. The remaining, balancing class is selected to compensate any bias induced by the other class(es) such that the population sex ratio reflects the relatedness asymmetry of that balancing class. In the absence of worker‐reproduction, the sex ratio compensation by the balancing‐class is generally close to 100%, unless the population is very small.

In the Discussion we address explicitly the likelihood of our relatedness‐assessment hypothesis and other assumptions made in the model. The relationship of our model with previous theory on sex allocation in eusocial Hymenoptera is worked out in the Appendix.
Parental effects in Lychnis flos‐cuculi. I: Seed size, germination and seedling performance in a controlled environment
Authors: Biere A.
Published: December 2004

Selection responses in natural plant populations depend on how the phenotypic variation of traits is composed. The contributions of nuclear genetic, maternal, paternal, environmental and inbreeding effects to variation in time to germination, germination percentage, and seed‐ and seedling size were studied in a population of Lychnis flos‐cuculi.

It was found that: (1) Maternal effects predominated in the determination of progeny seed size and germination characteristics; (2) Maternal environment during seed development was less important than maternal genotype; (3) Small but significant variation within maternal families could be observed among individuals sired by different fathers; (4) Additive genetic variance was significant for seedling size 4 weeks after germination. In conclusion, selection shortly after emergence will mainly favour particular maternal genotypes, while selection later in the life cycle may act upon zygotic genotypes. Inbreeding depression was significant, especially for vegetative growth.

Consistent differences were found among maternal genotypes in the degree of variation in the time to germination, suggesting that selection could operate to favour polymorphic or uniform germination behaviour.
Phylogenetic studies of acridoid grasshoppers comparing 2n2‐ and 4‐base recognizing endonucleases
Authors: Colgan D. J.
Published: December 2004

The frequency of loss of restriction sites may be a limiting factor in the application of RFLPA to phylogenetic investigations of higher taxonomic categories. One purpose of this work is to ascertain whether the applicability of RFLPA can be extended by the use of a class of restriction endonucleases which will here be termed 2n2 cutters, as any base may occupy the middle position of the recognition sequence. Such endonucleases should be less susceptible than, say, 4‐base cutters to the redundancy of the genetic code when this position coincides with the third base of a codon. Here the two types of endonucleases are compared by internal statistics summarizing the phylogenetic content of the data and by the concordance of their resulting dendrograms to six known relationships of thirteen acridid and eumustacid grasshoppers. Data were gathered for a mtDNA probe (expected to show redundancy effects) and an rDNA probe (not expected to show such effects). Phenetic and cladistic analyses were performed. There was no evidence that the 2n2‐cutting endonucleases produced more accurate dendrograms. In fact, in contrast with expectations and with, as yet, no apparent explanation, trees produced by 4‐base cutting endonucleases had greater concordance to present best estimates of grasshopper relationships. The second main purpose of the paper was to extend molecular studies of the phylogeny of the Acrididae. The two main results here were the finding of a close relationship between the Oxyinae and the Catantopinae and the apparent absence of a major endemic Australian radiation in the Acridinae.
The types of homology and their significance for evolutionary biology and phylogenetics
Authors: Haszprunar Gerhard
Published: December 2004

This paper comments on recently revived discussion about the most adequate definition of homology. Homologues are considered as similarities of complex structures or patterns which are based on a continuity of biological information or instruction. Dependent on the level of comparison four types of homology are defined: (1) Iterative ( = serial = homonomy), (2) ontogenetic, (3) di‐ or polymorphic, and (4) supraspecific homology. The significance of all four types for evolutionary biology and phylogenetic analysis is outlined.
Habitat selection by Drosophila melanogaster larvae
Authors: Rodriguez Lucy , Sokolowski Marla B. , Shore Joel S.
Published: December 2004

Drosophila melanogaster larvae are used to examine habitat choice behavior and its effect on a component of preadult fitness (pupal survivorship). We established strains of flies by collecting pupae from two microhabitats from an orchard. Strain differences in pupation site choice (on versus off fruit) persisted in a field‐like laboratory assay without artificial selection. To produce heterogeneous environments, air temperature and soil water content were varied in these assays. A habitat suitability difference measure was used to determine for each environment, which microhabitat (on or off fruit) resulted in greater pupal survivorship. We found 1) that habitat choice behavior had both plastic and heritable components, 2) that strain‐by‐environment interactions influenced habitat choice behavior and pupal survivorship and, 3) a significant positive correlation between habitat suitability and larval habitat choice behavior.
The genetics of phenotypic plasticity. IV. Chromosomal localization
Authors: Weber Stephanie L. , Scheiner Samuel M.
Published: December 2004

The contributions of each chromosome to the traits thorax size and plasticity of thorax size as affected by temperature in Drosophila melanogaster were measured. A composite stock was created from lines previously subjected to selection on thorax size or plasticity of thorax size. A chromosome extraction was performed against a uniform background lacking genetic variation, provided by a stock of marked balancer flies. With regard to amount of plasticity, chromosome I and the balancer stock showed no plasticity, the composite stock showed the greatest plasticity, and chromosomes II and III were intermediate. Chromosome I showed significant genetic variation for thorax size at both 19° C and 25° C, but not for plasticity, while chromosome II showed significant genetic variation for plasticity, but not for thorax size. Chromosome III showed significant genetic variation for both thorax size and plasticity. We tested the predictions of three models of the genetic basis of phenotypic plasticity: overdominance, pleiotropy, and epistasis. The results support the epistasis model, in agreement with earlier work. The amount of developmental noise was correlated with phenotypic plasticity at 25° C, in agreement with earlier work. A negative correlation was found at 19° C for chromosome II, contrary to earlier work.
Evolutionary divergence in Dolichopoda cave crickets: A comparison of single copy DNA hybridization data with allozymes and morphometric distances
Authors: Allegrucci Giuliana , Caccone Adalgisa , Cesaroni Donatella , Sbordoni Valerio
Published: December 2004

In this paper we attempt to investigate relationships between the amount of genetic divergence in nuclear genes and the degree of morphological differentiation for different sets of characters in Dolichopoda cave crickets.

Six populations representing five Dolichopoda species from Central and Southern Italy have been studied. The overall genetic divergence at nuclear genes was estimated both by single copy DNA‐DNA hybridization and allozyme frequencies at 26 loci. Euclidean distances for two multivariate sets of morphometric variables: one describing body and appendage morphology, the other male epiphallus shape. Results showed a close agreement between the branching patterns of ΔTm values from DNA hybridization and Nei's allozyme distance values. On the other hand, patterns of morphological divergence revealed independent trends, although the branching pattern based on epiphallus morphology matched to some extent the phylogenies inferred from molecular data. The relative value of molecular and morphological characters as reliable phylogenetic tracers was evaluated in relation to their dependence on evolutionary factors.

Implications of these findings on the calibration of molecular clocks are also discussed. The absolute rate of molecular change based on scDNA was estimated to be at least 0.98% divergence/my/lineage. This result is in agreement with calibrations attempted on other insects. Estimates of time of divergence based on allozymes (Nei's D) were highly consistent with the estimate from geological data.
DNA‐DNA hybridizations support ungulate ancestry of Cetacea
Authors: Milinkovitch Michel C.
Published: December 2004

Recent morphological data on Pakicetus spp. and Basilosaurus spp. fossils suggest that cetaceans (whales, dolphins and porpoises) originate from carnivorous Mesonychid land mammals (Condylarthra) and made a gradual transition from land to sea in early Eocene (Gingerich et al. 1983; 1990). On the other hand, there is convincing evidence that Artiodactyla and Perissodactyla have evolved from Condylarthra (Van Valen 1978, Carrol 1988). Therefore, the Pakicetus and Basilosaurus data suggest a close genetic relationship between cetaceans and ungulates. An approach based on molecular genetics was used in this study to test the morphological hypothesis. Liver samples of two Delphinoidea species were obtained from animals caught in a Peruvian gillnet fishery. 32P‐ or 35S‐labeled single copy nuclear genomes (scn‐DNA) of the two cetacean species were hybridized each with unlabeled total DNA of various cetaceans, ungulates and other mammals including primates, rodents, lagomorphs and carnivores. The Tmedian (Tm) and Tmode of all melting curves, used as a measure of the DNA‐DNA hybrids stability, clearly show a greater sequence similarity — and thus a lower genetic distance — between cetaceans and ungulates than between cetaceans and other mammals.
Constancy and change of basipodial variation patterns: a comparative study of crested and marbled newts —Triturus cristatus, Triturus marmoratus — and their natural hybrids
Authors: Rienesl J. , Wagner G. P.
Published: December 2004

To test the concept of stable and lineage‐specific developmental constraints the stability of biased limb skeletal variation patterns was examined by the comparative approach: 384 limbs of crested and marbled newts as well as their natural hybrids were cleared and stained for cartilage and bone. The variation in autopodium was recorded and compared between samples. The frequencies of variations were the same for crested and marbled newt samples. In the hybrids digital variation was significantly elevated, but the basipodium was as conservative as in the parental crested and marbled newts. The tarsus had to be excluded from further statistical analysis, since variation in tarsus was too rare to allow rigorous tests. The carpal variation was highly biased; out of twelve geometrically possible fusions of two neighbouring elements only three were found in the 219 forelimbs. The frequency of the fusions was the same in the parental as well as in the hybrid populations. In one sample of the marbled newt from a marginal population, the frequency of one fusion type was elevated, leading to an even more pronounced bias in phenotypic variation. Hence, neither in the hybrids nor in the marginal population could a breakdown of the constraint be observed. Also the pattern of variation was the same in all Triturus‐samples examined here. The comparison of our results with within‐population variation from other genera showed qualitative differences. The most common variant from our samples was found as a natural variant and even as the typical pattern in some species, but has not been observed in species of other genera. On, the other hand, fusions commonly observed in other genera were not observed in our sample. Even if all populations exhibit a highly bound variation pattern which may restrict the possible directions of morphological evolution, the direction of variation changes from genus to genus. It is suggested that shifts in constrained variation patterns have to be considered as key‐events in the evolution of a clade. The cause of these shifts are unknown.
Analysis of a hybrid zone between subspecies of the tiger salamander (Ambystoma tigrinum) in central New Mexico, USA
Authors: Jones Thomas R. , Collins James P.
Published: December 2004

We analyzed patterns of variation in polymorphic loci across a contact zone between two subspecies of tiger salamander, Ambystoma tigrinum nebulosum and A. t. mavortium, in west‐central New Mexico. We found no fixed differences between A. t. mavortium and A. t. nebulosum. Allele frequencies across the contact zone did not vary concordantly among loci, but frequencies at two loci varied with elevation. Gene flow extends through the contact zone from A. t. mavortium into A. t. nebulosum, but not conversely. A. t. mavortium and A. t. nebulosum have no obvious impediments to gene flow within this contact zone, but some populations differ in time of reproduction. The contact zone comprises a variety of habitats, approximating typical A. t. mavortium or A. t. nebulosum habitats. There is an irregular pattern of differences in allelic frequencies among populations that covaries with habitats and is consistent with a model of a mosaic contact zone.

Our results contrast with those of a study along the Front Range in Colorado, where allelic composition at some loci changed abruptly across a narrow zone of contact. These contrasting results suggest that the dynamics shaping the contact zone between the same taxa may differ. Absence of a similar pattern of genetic differentiation between A. t. mavortium and A. t. nebulosum in New Mexico and in Colorado suggests a complex set of evolutionary interactions along the eastern front of the Rocky Mountain axis.
Gender variation and the evolution of dioecy in Wurmbea dioica (Liliaceae)
Authors: Barrett Spencer C. H.
Published: December 2004

A major obstacle for empirical tests of hypotheses concerning the evolution of dioecy in flowering plants is the limited number of species that possess both cosexual and dioecious populations. Wurmbea dioica (Liliaceae) is a diminutive, fly‐pollinated geophyte native to temperate Australia. Marked geographical variation of floral traits is evident, particularly with respect to sex expression. A survey of phenotypic gender in 45 populations from Western Australia (WA), South Australia (SA), Victoria (Vic) and the Australian Capital Territory (ACT) revealed two contrasting patterns. Populations in SA, Vic, and ACT were uniformly dimorphic for gender, containing female and male plants, whereas populations in WA were either monomorphic or dimorphic. In most dimorphic populations varying numbers of male plants produced hermaphrodite flowers (male inconstancy). There was a significant negative relationship between female frequency and the proportion of inconstant male plants. Depending on region and population, male plants produced more flowers of larger size than females. In WA monomorphic populations often occurred on rich, moist soils at high density, whereas dimorphic populations were more commonly found at lower density on shallow soils in drier areas. In an area of sympatry, plants with contrasting sexual systems flowered at different times and were ecologically differentiated. The patterns of gender variation in W. dioica indicate that dioecy has evolved via the gynodioecious pathway. The spread of females in monomorphic populations may be favoured where ecological conditions result in increased selfing and inbreeding depression in hermaphrodites.
Sex‐ratios of the wasp Nasonia vitripennis from self‐versus conspecifically‐parasitized hosts: local mate competition versus host quality models
Authors: King Bethia
Published: December 2004

Sex ratio patterns in the parasitoid wasp Nasonia vitripennis are frequently cited in support of a major group of evolutionary sex ratio models referred to as local mate competition (LMC) models. It has been shown repeatedly that, as predicted by LMC models, females generally oviposit a greater proportion of sons in previously parasitized hosts than in unparasitized hosts. However, this sex ratio pattern is also a prediction of another group of sex ratio models, the host quality models. Here I test a prediction of LMC models that is not also a prediction of host quality models: a female should produce a greater proportion of sons when she parasitizes a host previously parasitized by a conspecific female than when she parasitizes a host previously parasitized by herself. Females made this predicted distinction between self‐ and conspecifically‐parasitized hosts under some conditions. There was no evidence that a female recognizes a self‐parasitized host when her exposure to the host is interrupted by exposure to an unparasitized host, or that a female can distinguish between hosts parasitized by sisters versus nonsisters.
Genetic variation in Ecballium elaterium (Cucurbitaceae): Breeding system and geographic distribution
Authors: Costich Denise E. , Meagher Thomas R.
Published: December 2004

Dioecy, the separation of sexes, has arisen independently many times in the course of angiosperm evolution. Avoidance of inbreeding is clearly involved in the evolution of dioecy, and as a consequence we predict that dioecious populations should maintain higher levels of genetic variation than closely related nondioecious populations. We tested that prediction by comparing allozymic variation in two closely related taxa, the monoecious and dioecious subspecies of the Mediterranean cucurbit, Ecballium elaterium. Thirteen polymorphic loci were screened for seeds sampled from 10 monoecious and 13 dioecious populations spanning the geographic ranges of the subspecies in Spain. The dioecious subspecies showed strikingly greater allelic diversity and heterozygosity than the monoecious subspecies. A hierarchical F‐statistic analysis clearly demonstrated considerable genetic variation within populations for the dioecious populations, whereas for the monoecious populations almost all genetic variation resulted from differences among populations. The general pattern of homozygosity within monoecious populations suggests that they are highly inbred. In order to assess historical influences on current patterns of genetic variation, we conducted a genetic‐distance analysis. The observed relationship between genetic distance and geographic distance between populations supports the hypothesis that the subspecies' current allopatric distributions on the Iberian Peninsula are the result of separate waves of colonization from the north (monoecious) and south (dioecious).
The population biology of Gehyra (Gekkonidae). III. Patterns of microgeographic variation
Authors: Moritz Craig
Published: December 2004

The distribution of allozymic and chromosomal polymorphisms was examined among central Australian populations of the chromosomally variable genus Gehyra to assess whether they typically have the small deme size and low gene flow levels required by some models of chromosomal speciation. Particular attention was given to comparisons between rock‐specialists (Gehyra nana) and habitat‐generalists (Gehyra variegata) to investigate whether the former have more restricted gene flow. Both allozyme and chromosome data sets showed greater among population differentiation in the rock‐specialists than the habitat‐generalists, consistent with predictions from a previous ecological study (Moritz, 1987), although this pattern could also be due to historical effects. This was evident from the relationships between genetic and geographic distance, the conditional frequency of alleles, and F‐statistics. However, both taxa appear to have substantial levels of gene flow. This indicates that Gehyra populations typically do not meet the stringent conditions for the fixation of strongly underdominant chromosome rearrangements through strong genetic drift. A consistent deficiency of heterozygotes does, however, suggest the possibility of inbreeding which would increase the likelihood of the establishment of underdominant rearrangements.
Phenotypic plasticity for life history traits in Drosophila melanogaster. II. Epigenetic mechanisms and the scaling of variances
Authors: Gebhardt M. D. , Stearns S. C.
Published: December 2004

Abstract We manipulated developmental time and dry weight at eclosion in 15 genotypes of Drosophila melanogaster by growing the larvae in 9 environments defined by 3 yeast concentrations at 3 temperatures. We observed how the genetic and various environmental components of phenotypic variation scaled with the mean values of the traits.

Temperature, yeast, within‐environmental factors and genotype influenced the genotypic and environmental standard deviations of the two traits in patterns that point to very different modes of physiological and developmental action of these factors. Since different factors affected the environmental and genetic components of the phenotypic variation either in parallel or inversely, we conclude that environmental heterogeneity may have small or large effects on evolutionary rates depending on which factors cause the heterogeneity. The analysis also suggests that the scaling of variances with the mean is not as trivial as is often assumed when coefficients of variation are computed to “standardize” variation.
The evolution of unusual chromosomal systems in coccoids: extraordinary sex ratios revisited
Authors: Haig David
Published: December 2004

Coccoids (scale insects) exhibit a wide variety of chromosomal systems. In many species, paternal chromosomes are eliminated from the male germline such that all of a male's sperm transmit an identical set of maternal chromosomes. In such species, an offspring's sex is determined by whether or not paternal chromosomes are inactivated in the egg's cytoplasm after fertilization. This paper presents a model of the evolution of paternal genome loss in coccoids from an ancestral system of XX‐XO sex determination. The model is based on Hamilton's (1967) theory that different genetic elements within the genome have different unbeatable sex ratios. In this model (1) meiotic drive by the X chromosome in XO males causes female‐biased sex ratios; (2) the maternal set of autosomes in males evolves effective sex linkage to exploit X‐drive; and (3) genes expressed in mothers are selected to convert some of their XX daughters into sons. A similar model may explain the evolution of haplodiploidy.
Sex allocation of parasitic wasps: local mate competition, dispersal before mating and host quality variation
Authors: Ikawa T. , Shimada M. , Matsuda H. , Okabe H.
Published: December 2004

We constructed a sex allocation model for parasitic wasps to explain the wide variation in their sex ratio, considering the effects of local mate competition, partial dispersal of progeny before mating, and heterogeneity in host quality among patches. We conducted an experiment to compare with the predictions of our model. We considered the following situations. First, the hosts are distributed in discrete patches: a number of female wasps visit and oviposit in each patch. Second, all the progeny do not mate within the natal patch; some of them disperse to take part in population‐wide random mating. We calculated ES sex ratios in cases where there are two kinds of patches: good ones and poor ones. We examined the dependency of ES sex ratios on several parameters, i.e., 1) the probability that a daughter mates in her natal patch, 2) the ratio of the female fitness of the good patch to that of the poor patch, 3) the proportion of poor patches, and 4) the number of foundresses in a patch. The result of our experiment showed the same tendency as the calculation in case where the LMC effect is high in each patch. We briefly discuss a possible selection pressure for dispersal of progeny, with special reference to the mating structure of parasitic wasps.