bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple nonmelanoma skin cancer in an exposed Australian population
Authors: Raasch Beverly A. , Buettner Petra G.
Published: March 2003

Background Patients with nonmelanoma skin cancer (NMSC) frequently develop multiple skin cancers. The study presents incidence rates and rates of excision of NMSC for a population living in a high‐risk environment for skin cancer.

Methods Between 1997 and 1999 a prospective population‐based study collected information on all histologically confirmed NMSCs in Townsville, Australia.

Results Of the 6708 patients recorded with NMSC, 38.5% had multiple lesions. Yearly age‐standardized incidence rates (per 100,000 inhabitants) of basal cell carcinoma (BCC) were 1444.8 for men, 942.7 for women, and of squamous cell carcinoma (SCC) were 805.0 for men, and 423.6 for women. Compared to incidence rates, age‐standardized rates of lesions of BCC were 2.1 times higher in men, 1.6 times higher in women, and of SCC were 1.8 times higher in men and 1.4 times higher in women.

Conclusions The occurrence of multiple NMSCs compromises results of short‐term studies on incidence. Further discussions on the most appropriate strategies to describe the real burden of NMSC are warranted.
Leprosy in type I reaction and diabetes mellitus in a patient with HIV infection
Authors: Belliappa Alamengada D. , Bhat Ramesh M. , Martis Jacintha
Published: March 2003

A 24‐year‐old man was referred to our department with history of a pale red raised lesion over the right side of the face with impaired sensation of 3 months’ duration. He also had generalized weakness and increased thirst for the past 1 month. He had been treated with multidrug therapy for leprosy for 3 months and oral prednisolone for 1 month by his general practitioner. He also presented with a history of multiple sexual exposures with commercial sex workers and an ulcer over the penis 2 years ago, which healed spontaneously.
Frequent use of tobacco and alcohol in Chinese psoriasis patients
Authors: Zhang Xuejun , Wang Hongyan , Te‐shao Hsu , Yang Sen , Wang Fuxi
Published: March 2003

Background This study aimed to explore smoking and drinking as risk factors in psoriasis.

Methods Data collected from 789 psoriasis patients and 789 healthy controls were analyzed to determine whether there was an association between smoking/drinking and psoriasis.

Results The proportion of male psoriasis patients using tobacco and alcohol was much higher than that of the control group (P < 10−6), whereas no statistical differences were found between female smokers and the control group. In general, heavy smokers were more likely to have severe psoriasis.

Conclusion Tobacco use in patients is correlated with psoriasis.
Value of histopathology in vitiligo
Authors: F. Montes Leopold , Abulafia Jorge , Wilborn Walter H. , Hyde Barbara M. , Montes Carolina M.
Published: March 2003

Background Histopathologic studies of vitiligo have been rather limited in number, thus the microscopic features of this common disorder are not very well known.

Subjects and Methods Skin specimens from 20 human vitiligo patients and skin specimens from five equine vitiligo patients were studied by light and transmission electron microscopy.

Results and Discussion Absence of melanocytes, increased number of Langerhans’ cells, epidermal vacuolization, thickening of the basement membrane, T‐cell inflammatory infiltrate, and neural alterations were noted in the vitiligo lesions. These results may explain the development of depigmentation, but do not yet fully explain why and how this occurs.
Comparative evaluation of different hair removal lasers in skin types IV, V, and VI
Authors: Galadari Ibrahim
Published: March 2003

Background Lasers permit treatment of unwanted excess hair with less discomfort than other methods of epilation. Many lasers with different parameters are now available from which the dermatologist can choose. Improved clinical results are made possible by the high specificity and selectivity of the laser systems to pigmented hair because of the use of an appropriate wavelength with the proper pulse and duration.

Objectives We aimed to compare the results of treatment of skin types IV, V, and VI using three different laser systems.

Methods One hundred female patients were compared using different laser systems: 35 patients underwent epilation using a Nd‐Yag laser, 33 patients using an Alexandrite laser, and 32 patients using a Diode laser.

Results Follow up 12 months after the multiple treatments (three to six sessions) showed an insignificant difference between these three groups (35–40%).

Conclusion Our findings indicate that all three laser systems tested can be used for dark skin; however, one should select a system that minimizes side‐effects, primarily hypo‐ and hyper‐pigmentation, especially when used for skin types IV, V, and VI.
Natural and sexual selection on a plumage signal of status and on morphology in house sparrows, Passer domesticus
Authors: Pape Møller Anders
Published: March 2003

Temporal patterns of natural and sexual selection on male badge size and body traits were studied in a population of house sparrows, Passer domesticus. Badge size was a heritable trait as revealed by a significant father‐son regression. Survival during autumn dispersal and winter was not related to badge size or body traits in yearling male house sparrows. Badges that signal dominance status were affected positively by directional selection for mating. Adult male house sparrows suffered an opposing selection pressure on badge size during autumn.

Contrary to males, female house sparrows did not experience significant directional or stabilizing selection on any body trait. Directional sexual selection on male badge size due to female choice moves male sparrows away from their survival optimum. Opposing directional natural selection on badge size due to autumn mortality caused by predation maintains a stable badge size.
A general model of the relation between phenotypic selection and genetic response
Authors: Van Tienderen P. H. , De Jong G.
Published: March 2003

The phenotypic view of selection assumes that genetic responses can be predicted from selective forces and heritability — or in the classical quantitative genetic equation: R = h2S. However, data on selection in bird populations show that often no selection responses is found, despite consistent selective forces on phenotypes and significant heritable variation. Such discrepancies may arise due to the assumption that selection only acts on observed phenotypes. We derive a general selection equation that takes into account the possibility that some relevant (internal or external) traits are not measured. This equation shows that the classic equation applies if selection directly acts on the measured, phenotypic traits. This is not the case when, for instance, there are unknown internal genetic trade‐offs, or unknown common environmental factors affecting both trait and fitness. In such cases, any relationship between phenotypic selection and genetic response is possible. Fortunately, the classical model can be tested by comparing phenotypic and genetic covariances between traits and fitness; an indication that important internal or external traits are missing can thus be obtained. Such an analysis was indeed found in the literature; for selection on fledging weight in Great Tits it yielded valuable extra information.
The genetic control of heterochrony: Evidence from developmental mutants of Pisum sativum L.
Authors: Wiltshire R. J. E. , Murfet I. C. , Reid J. B.
Published: March 2003

Heterochrony, as a means of evolution in which the rate or timing of developmental events of the descendant is altered compared with that of the ancestor, is of significance because it suggests that rapid and dramatic morphological changes are possible with few genetic changes. The putative origin of plant taxa by this means of evolution is becoming increasingly frequent in the literature but there is little evidence of the extent of the genetic change necessary to alter the timing of developmental events to produce such changes. This study shows that the onset of flowering can be altered independently from the vegetative transition in leaf form in at least one genotype of Pisum in response to different environments. Further, it identifies 9 mutations that act in a heterochronic manner to produce dramatic morphological changes that can be described as progenesis, neoteny, hypermorphosis or acceleration. In addition, it is demonstrated that the same heterochronic process (e.g. progenesis) may be caused by genes controlling distinctly different physiological processes. It is suggested that Pisum is an ideal model species for studies of heterochrony and that few genetic changes are necessary to bring about dramatic heterochronic changes.
Evolution in populations of Swedish sand lizards: genetic differentiation and loss of variability revealed by multilocus DNA fingerprinting
Authors: Gullberg  , Olsson  , Tegelström
Published: March 2003

The Swedish sand lizard (Lacerta agilis) is a relict species from the period of warmth following the last glacial episode and has a fragmented distribution in central Sweden and a more continuous distribution in the southern part of the country. We used this model system of colonization–extinction for a study of genetic variability within and among Swedish populations from different parts of the distribution range using multilocus DNA fingerprinting. The results from the Swedish populations are then contrasted with those from a large Hungarian population in the centre of the species geographical distribution range, which is likely to closely resemble the ancestral founding population of Sweden. Swedish populations have a low level of genetic variability compared with the Hungarian reference population, which showed a genetic variability within the range described for outbred populations. Within the Swedish populations, the average bandsharing was 0.61, the mean heterozygosity 0.45 and the estimated number of alleles 2.7. The figures for the Hungarian population were a bandsharing of 0.19, a heterozygosity of 0.89 and an estimated number of alleles of 9.8. A population bottleneck, common to all Swedish sand lizards, is indicated by less than 20% of the alleles in the Hungarian population being retained in the Swedish populations, and higher bandsharing similarity between different Swedish populations (0.33) as opposed to the Hungarian population (0.19). The limited variability found in Swedish sand lizards is strongly subdivided between populations, with an average FST of 0.32, indicating a very limited gene flow between the isolated populations, as well as between populations in the region where the sand lizard has a more or less continuous distribution (FST = 0.41).
Latitudinal variation in wild populations of Drosophila melanogaster: heritabilities and reaction norms
Authors: Land J. Van ‘t , Putten P. Van , Zwaan  , Kamping  , Delden W. Van
Published: March 2003

Large amounts of genetic variation for wing length and wing area were demonstrated both within and between Drosophila melanogaster populations along a latitudinal gradient in South America. Wing length and wing area showed a strong positive correlation with latitude in both wild flies and laboratory-raised descendants. Large population differences were observed for heritability and coefficient of variation of these two traits, whereas relatively small population differences were found for development time, viability, pupal mortality, sex ratio and their norms of reaction to four developmental temperatures. No clear-cut latitudinal clines were established for these life-history characters. These results are discussed in the light of Bergmann's Rule and the relation between larval development and adult body size.
Genetics of a wing size difference between two Nasonia species
Authors: Weston  , Qureshi  , Werren
Published: March 2003

Very little is known about the genetics of morphological differences between species. This study investigates the genetic basis of a significant morphological difference between males of two closely related species of the parasitoid wasp Nasonia. One of the defining characters of species in the genus Nasonia is male forewing size. The forewings of Nasoniagiraulti males are 2.4 times larger than the forewings of Nasoniavitripennis males. Genetic analysis of hybrids between these species indicates that this difference is due to the effect of a few genes. Also discussed is the possible role of ‘pseudo linkage’ in analysis of F2 hybrids. Pseudo linkage occurs when genes affecting a trait are linked to interacting hybrid lethal loci, and can lead to an overestimation of the number of regions involved in a phenotype. The large wing trait of N. giraulti was introgressed into a N. vitripennis background. Analysis of this introgression line indicates that 44% of the difference in wing size between the species is due to the presence of a single gene, or a few tightly linked genes, located on linkage group IV. Furthermore, the introgressed region appears to affect the width of the wing more strongly than the length. Indirect results suggest that this region affects wing cell size, rather than cell number. Results are consistent with the view that morphological and adaptive differences between species can have a simple genetic basis.
Evolution of colour patterns in East African cichlid fish
Authors: Seehausen  , Mayhew  , Alphen J. J. M. Van
Published: March 2003

African cichlid fishes have undergone outbursts of explosive speciation in several lakes, accompanied by rapid radiations in coloration and ecology. Little is known about the evolutionary forces that triggered these events but a hypothesis, published by Wallace Dominey in 1984, has figured prominently. It states that the evolution of colour patterns is driven by sexual selection and that these colour patterns are important in interspecific mate choice, a combination which holds the potential for rapid speciation. Here we present phylogenetic analyses that describe major events in colour evolution and test predictions yielded by Dominey's hypothesis. We assembled information on stripe patterns and the presence or absence of nuptial coloration from more than 700 cichlid species representing more than 90 taxa for which molecular phylogenetic hypotheses were available. We show that sexual selection is most likely the selection force that made male nuptial coloration arise and evolve quickly. In contrast, stripe patterns, though phylogenetically not conserved either, are constrained ecologically. The evolution of vertical bar patterns is associated with structurally complex habitats, such as rocky substrates or vegetation. The evolution of a horizontal stripe is associated with a piscivorous feeding mode. Horizontal stripes are also associated with shoaling behaviour. Strength of sexual selection, measured in terms of the mating system (weak in monogamous, strong in promiscuous species), has no detectable effects on stripe pattern evolution. In promiscuous species the frequency of difference between sister species in nuptial hue is higher than in pair bonding and harem forming species, but the frequency of difference in stripe pattern is lower. We argue that differences between the two components of coloration in their exposure to natural selection explain their very different evolutionary behaviour. Finally, we suggest that habitat-mediated selection upon chromomotor flexibility, a special form of phenotypic plasticity found in the river-dwelling outgroups of the lake-dwelling cichlids, explains the rapid and recurrent ecology-associated radiation of stripe patterns in lake environments, a new hypothesis that yields experimentally testable predictions.
On the potential for evolutionary change in meristematic cell lineages through intraorganismal selection
Authors: Pineda-Krch  , Fagerström
Published: March 2003

In the absence of sexual recombination somatic mutations represent the only source of genetic variation in clonally propagating plants. We analyse the probability of such somatic mutations in the shoot apical meristem being fixed in descendant generations of meristems. A model of meristem cell dynamics is presented for the unstratified shoot apical meristem. The fate of one mutant initial is studied for a two- and three-celled shoot apical meristem. The main parameters of the model are the number of apical initials, the time between selection cycles, number of selection cycles and cell viability of the mutant genotype. As the number of mitotic divisions per selection cycle and number of selection cycles increases the chimeric state dissipates and the probability of mutation fixation approaches an asymptote. The value of this fixation asymptote depends primarily on cell viability, while the time to reach it is mainly influenced by the total number of mitotic divisions as well as the number of initials.

In contrast to the presumed operation of Muller’s Ratchet in plants the chimeric state may represent an opportunity for deleterious mutations to be eliminated through intraorganismal selection or random drift. We conclude that intraorganismal selection not only can be a substantial force for the elimination of deleterious mutations, but also can have the potential to confer an evolutionary change through a meristematic cell lineage alone.
Does polyovulation counterbalance a high abortion rate in humans?
Authors: Lummaa  , Haukioja  , Lemmetyinen
Published: March 2003

We tested the fertilization insurance hypothesis of human twinning, which suggests that twin births should be seen as an unadaptive consequence of polyovulation compensating for high spontaneous abortion rates in humans. Females with high incidence of polyovulation were predicted to benefit by becoming pregnant more rapidly and by having a higher likelihood of successful pregnancy than other females. As a disadvantage, polyovulating mothers should be more prone to presumably maladaptive twin deliveries. We studied birth intervals of twin and singleton mothers living in pre-industrial Finland by using demographic records of local churches. The analysis revealed that, contrary to the prediction of the fertilization insurance hypothesis, polyovulating females did not display shorter intervals between deliveries. Therefore, if the tendency towards polyovulation and therefore occasional twin births in humans is adaptive and maintained by natural selection, other benefits should be evident.
Spatial patterns of polygenic variation in Impatiens capensis, a species with an environmentally controlled mixed mating system
Authors: Paoletti  , Holsinger
Published: March 2003

Impatiens capensis displays a mixed mating system in which individual out-crossing rate is expected to increase with light and resource availability. We investigated the amount and spatial distribution of polygenic variation for 15 morphological traits within and among six natural populations of I. capensis growing in three distinct light habitats (shaded, mixed, full sun). We grew individuals from each population in uniform greenhouse conditions and detected significant genetic variation among families within populations for all the quantitative traits examined. However, only the features related to the vegetative characteristics of seedlings and sexually mature plants show also differentiation at the population level. Surprisingly, even though light availability is likely to be the most important factor affecting the mating system of I. capensis, we find that: (1) trait means of individuals from similar light environments are not more similar than those from different light environments; (2) partitioning of polygenic variance within and among families differs both among populations from the same light habitat and among characters within each population. If natural selection is maintaining such variation, it must operate primarily through heterogeneous selection pressure within, rather than between, populations.
Clonal diversity and polyphyletic origins of hybrid and spontaneous parthenogenetic Campeloma (Gastropoda: Viviparidae) from the south-eastern United States
Authors: Johnson  , Leefe
Published: March 2003

Some theories for the maintenance of sexual reproduction indicate that parthenogens may persist if there is high clonal diversity and high dispersal rates. Using allozymic variation, we report on the origin, clonal diversity and population structure of hybrid and spontaneous parthenogens from south-eastern United States populations of the freshwater snail Campeloma. Independent origins of triploid hybrid parthenogens in the Florida panhandle occurred by hybridization between an Atlantic coastal species (C. limum or C. floridense) and the Florida sexual species (C. geniculum). Allozyme genotypic diversity is similar between these hybrid parthenogens and sexuals. Diploid spontaneous parthenogens originated multiple times from nonlocal C.limum sexual populations in Atlantic coastal rivers, and levels of genotypic diversity are significantly higher in sexual C. limum. How parthenogens originate, the degree of clonal diversity, and their subsequent dispersal influence whether basic assumptions of evolution-of-sex models are met.
Unbiased estimation of individual asymmetry
Authors: Van Dongen
Published: March 2003

The importance of measurement error (ME) for the estimation of population level fluctuating asymmetry (FA) has long been recognized. At the individual level, however, this aspect has been studied in less detail. Recently, it has been shown that the random slopes of a mixed regression model can estimate individual asymmetry levels that are unbiased with respect to ME. Yet, recent studies have shown that such estimates may fail to reflect heterogeneity in these effects. In this note I show that this is not the case for the estimation of individual asymmetry. The random slopes adequately reflect between-individual heterogeneity in the underlying developmental instability. Increased levels of ME resulted in, on average, lower estimates of individual asymmetry relative to the traditional unsigned asymmetry. This well-known shrinkage effect in Bayesian analysis adequately corrected for ME and heterogeneity in ME resulting in unbiased estimates of individual asymmetry that were more closely correlated with the true underlying asymmetry.
Dispersal distances predict subspecies richness in birds
Authors: Belliure  , Sorci  , Møller  , Clobert
Published: March 2003

Dispersal ability has been hypothesized to reduce intraspecific differentiation by homogenizing populations. On the other hand, long-distance dispersers may have better opportunities to colonize novel habitats, which could result in population divergence. Using direct estimates of natal and breeding dispersal distances, we investigated the relationship between dispersal distances and: (i) population differentiation, assessed as subspecies richness; (ii) ecological plasticity, assessed as the number of habitats used for breeding; and (iii) wing size, assessed as wing length. The number of subspecies was negatively correlated with dispersal distances. This was the case also after correcting for potential confounding factors such as migration and similarity due to common ancestry. Dispersal was not a good predictor of ecological plasticity, suggesting that long-distance dispersers do not have more opportunities to colonize novel habitats. Residual wing length was related to natal dispersal, but only for sedentary species. Overall, these results suggest that dispersal can have a homogenizing effect on populations and that low dispersal ability might promote speciation.
The trade-off to macroptery in the cricket Gryllus firmus: a path analysis in males
Authors: Crnokrak  , Roff
Published: March 2003

Among the Orthoptera, wing dimorphism, where one morph is long-winged and flight capable while the other is short-winged and flight incapable, is common and believed to be maintained in populations due to trade-offs to flight capability. In males, macropterous individuals call less than micropterous individuals and as a consequence obtain fewer matings. This trade-off is hypothesized to be mediated by the energetic costs of calling. In this paper we report results for a path analysis examining lipid weight and DLM (dorso longitudinal muscle) condition of male Gryllus firmus. We found that as DLM condition changes from a nonfunctional to a functional state, call duration decreases, and as lipid weight increases, call duration increases. The most important linked path was wing morph → DLM condition → call duration. This model is consistent with the prediction that the trade-off between wing morph and call duration is mediated via DLM and lipid stores.
Microsatellite mutations in litters of the Australian lizard Egernia stokesii
Authors: Gardner  , Bull  , Cooper  , Duffield
Published: March 2003

Seven tetranucleotide (AAAG) loci were analysed in a population (including 19 litters) of the Australian lizard Egernia stokesii. In an examination of 76 offspring we observed 13 mutations involving five loci. Two of our loci were highly mutable, with observed mutation rates of 2.7% and 4.2%, representing some of the highest mutations rates reported so far. A high proportion of mutations (46.2%) could not be assigned to changes involving only a single repeat, suggesting that mutations in at least two of the loci follow a multistep model. There was no significant bias of mutations leading to an increase or decrease in allele size; however, all multistep mutations involved a loss of repeats. These results add to increasing evidence casting doubt on microsatellite mutations being primarily single step mutations.
Selection on apomictic lineages of Taraxacum at establishment in a mixed sexual–apomictic population
Authors: De Kovel  , De Jong
Published: March 2003

A species’ mode of reproduction, sexual or asexual, will affect its ecology and evolution. In many species, asexuality is related to polyploidy. In Taraxacum, apomicts are triploid, and sexuals are diploid. To disentangle the effects of ploidy level and reproductive mode on life-history traits, we compared established apomictic Taraxacum genotypes with newly synthesized apomictic genotypes, obtained from diploid–triploid crosses. Diploid–triploid crossing is probably the way that most apomictic lineages originate. New genotypes had on average a much lower seed set than established genotypes. Established genotypes differed on average from new genotypes, in particular under shaded conditions: the established genotypes had longer leaves and flowered later. The differences between new and established triploids resembled the differences that have been found between sexual diploids and established apomictic triploids. We conclude that ploidy differences alone are not directly responsible for observed differences between sexual diploid and apomictic triploid dandelions.
A theoretical basis for measures of kin selection in subdivided populations: finite populations and localized dispersal
Authors: Rousset  , Billiard
Published: March 2003

The analysis of kin selection in subdivided populations has been hampered by the lack of well-defined measures of genealogical relatedness in the presence of localized dispersal. Furthermore, the usual arguments underlying the definition of game-theoretical measures of inclusive fitness are not exact under localized dispersal. We define such measures to give the first-order effects of selection on the probability of fixation of an allele. The derived measures of kin selection and relatedness are valid in finite populations and under localized dispersal. For the infinite island model, the resulting measure of kin selection is equivalent to a previously used measure. In other cases its definition is based on definitions of relatedness which are different from the usual ones. To illustrate the approach, we reanalyse a model with localized dispersal. We consider sex ratio evolution under sex-specific dispersal behaviour, and the results confirm the earlier conclusion that the sex ratio is biased towards the sex with the dispersal rate closer to the optimal dispersal rate in the absence of sex-specific dispersal behaviour.
Reconciling gene trees with organism history: the mtDNA phylogeography of three Nesotes species (Coleoptera: Tenebrionidae) on the western Canary Islands
Authors: Rees D. J. , Emerson B. C. , Oromí P. , Hewitt G. M.
Published: March 2003

The processes of island colonization and speciation are investigated through mtDNA studies on Canary Island beetles. The genus Nesotes (Coleoptera: Tenebrionidae) is represented by 19 endemic species on the Canary Islands, the majority of which are single island endemics. Nesotes conformis is the most widespread, occurring on Gran Canaria, Tenerife, La Palma and El Hierro. Nesotes conformis forms a paraphyletic assemblage, with a split between Gran Canaria and the other three islands. Nesotes conformis of the western Canary Islands cluster with Nesotes altivagans and Nesotes elliptipennis from Tenerife. Fifty-two individuals from this western islands species complex have been sequenced for 675 base pairs of the mtDNA cytochrome oxidase II gene, representing Tenerife, La Palma and El Hierro. A neighbour joining analysis of maximum likelihood distances resulted in three distinct mtDNA lineages for N. conformis, two of which also include mitotypes of N. altivagans and N. elliptipennis. Through application of parametric bootstrap tests, we are able to reject hypotheses of monophyly for both N. conformis and N. altivagans. Nesotes altivagans and N. elliptipennis are poorly separated morphologically and mtDNA sequence data adds support to this being one species with a highly variable morphology. We propose that N. altivagans/N. elliptipennis is recently derived from two ancestral mtDNA lineages within N. conformis from the Teno region of Tenerife. We further propose colonization of the younger islands of La Palma and El Hierro by N. conformis from a mitochondrial lineage within the Teno massif (colonization; diversification; mitochondrial DNA; Canary Islands; Coleoptera).
Analysis of asymmetries in the African fruit bats Eidolon helvum and Rousettus egyptiacus (Mammalia: Megachiroptera) from the islands of the Gulf of Guinea. II. Integration and levels of multivariate fluctuating asymmetry across a geographical range
Authors: Juste J. , López-González C. , Strauss R. E.
Published: March 2003

Using a set of cranial morphometric characters, trends of variation in multivariate fluctuating asymmetry were evaluated and compared in populations of African fruit bats Rousettus egyptiacus and Eidolon helvum from the Gulf of Guinea islands, and the adjacent mainland. Levels of asymmetry were compared across populations and species, and significant differences were found in both comparisons. Differences coincided with species-specific patterns of morphological and genetic differentiation. Concordance of correlation matrices of asymmetry was also compared. Results were significant; concordance is hypothesized to be a by-product of developmental processes that produce the ‘fox-like’ morphology shared by these species. Consistency of asymmetry patterns suggests that the developmental pathway producing it is highly canalized. A prediction of the above hypothesis is that a radical change in the ‘fox-like’ structural pattern would result in breakage of the asymmetry parameter associated with it.
Heterozygous fitness effects of clonally transmitted genomes in waterfrogs
Authors: Vorburger C.
Published: March 2003

The European waterfrog Rana esculenta (RL-genotype) is a natural hybrid between R. ridibunda (RR) and R. lessonae (LL) and reproduces by hybridogenesis, i.e. it eliminates the L-genome from the germline and produces gametes only containing the clonally transmitted R-genome. Because of the lack of recombination, R-genomes are prone to accumulate spontaneous deleterious mutations. The homozygous effects of such mutations become evident in matings between hybrids: their offspring possess two clonal R-genomes and are generally inviable. However, the evolutionary fate of R. esculenta mainly depends on the heterozygous effects of mutations on the R-genome. These effects may be hidden in the hybrid R. esculenta because it has been shown to benefit from spontaneous heterosis. To uncouple clonal inheritance from hybridity, I crossed R. esculenta with R. ridibunda to produce nonhybrid offspring with one clonal and one sexual R-genome, and compared their survival and larval performance with normal, sexually produced R. ridibunda tadpoles. Because environmental stress can enhance the negative effects of mutation accumulation, I measured the performance at high and low food levels. There was no indication that tadpoles with a clonal genome performed worse at either food level, suggesting that at least in the larval stage, R. esculenta benefits from heterosis without incurring any costs because of heterozygous effects of deleterious mutations on the clonally transmitted R-genome.
Collective action in an RNA virus
Authors: Brown S. P.
Published: March 2003

A recent empirical study by Turner and Chao on the evolution of competitive interactions among phage virus strains revealed that a strain grown at high rates of co-infection evolved towards lowered fitness relative to an ancestral strain. The authors went on to show that the fitness pay-off matrix between the evolved and ancestral strain conforms to the prisoners’ dilemma. In this paper, I use Turner and Chao’s data to parameterize a simple model of parasite collective action. The prisoners’ dilemma is based on pairwise interactions of a discrete cooperate/defect nature. In contrast, the collective action model explicitly deals with individual–group interactions where the extent of cooperation is a continuous variable. I argue here that the ‘collective action’ modelling approach is more appropriate than the prisoners’ dilemma for the biology of virus evolution, and hence better able to form a predictive framework for further work on related strains of virus, linking mixing ecology, cooperative phenotype and fitness. Furthermore, the collective action model is used to motivate discussion on the evolutionary ecology of viruses, with a focus on the ‘levels of selection’ debate and the evolution of virulence.
Evidence for an even sex allocation in haplodiploid cyclical parthenogens
Authors: Aparici E. , Carmona M. J. , Serra M.
Published: March 2003

Recent theoretical work has shown that haplodiploid cyclical parthenogens, such as rotifers, are expected to have an equal frequency of male-producing and resting-egg producing females during their sexual phase. We tested this prediction by following sexual reproduction dynamics in two laboratory populations and one field population of the rotifer Brachionus plicatilis through two growing seasons. We recorded population density, proportion of sexual females, and sex allocation (the proportion of male-producing sexual females as a fraction of total sexual females). We found this sex allocation ratio to vary from 0.3 to 1.0 in single sampling events. However, when we computed sex allocation by using the integrated densities of both male-producing sexual females and resting-egg producing sexual females over time, the two laboratory populations and one of the two field growing seasons showed sex allocation ratios that did not significantly differ from the expected value of 0.5.
Inversion and allozyme polymorphism show contrasting patterns of microgeographical population structure in a natural population of Drosophila buzzatii from Argentina
Authors: Fernández Iriarte P. J. , Rodríguez C. , Hasson E.
Published: March 2003

Second chromosome inversions and genotypic frequencies at seven allozyme loci were determined in a natural population of the cactophilic species Drosophila buzzatii that uses as breeding sites the necrotic cladodes of the prickly pear Opuntia quimilo and the rotting stems of cardón, Trichocereus terschekii. Different processes govern the evolutionary fate of inversion and allozyme polymorphisms. A pattern of heterotic balance for inversions seems to be acting uniformly in each breeding site and could depend on different regimes of density-dependent selection within cactus hosts. Patterns of variation of allozymes revealed significant heterogeneity in allele frequencies for Esterase-1 (Est-1) among O. quimilo rots and Aldehyde oxidase (Aldox) and Xanthine dehydrogenase (Xdh) among T. terschekii substrates and showed gene-cactus effects only for Esterase-2 (Est-2). Consistent and significant excesses of homozygotes were detected at both the within-rot and in the total population levels that could be accounted for by diversifying selection among individual breeding sites.
No reduction of female sexual receptivity following mating in a stalk-eyed fly, Cyrtodiopsis dalmanni (Diptera: Diopsidae)
Authors: Grant C. A. , Fowler K. , Chapman T.
Published: March 2003

The level of female sexual receptivity is an important component of male and female reproductive success. In many insects, mating itself causes a sharp decline in female receptivity. This can be a direct result of the physical act of mating, or because of actions of sperm or seminal fluid proteins. The degree to which males can decrease female receptivity will directly affect their reproductive success, by altering the chance that their sperm will be used in fertilizations in the interval before the female mates again. In this study, we investigated the effect of mating on female receptivity in the sexually dimorphic stalk-eyed fly, Cyrtodiopsis dalmanni. Our results showed no evidence for mating-induced reductions in female receptivity. In addition, we found that matings with males that differed in eyespan did not cause differences in the level of female receptivity. There was also no evidence that females remated sooner when presented with large eyespan males. These results are surprising, given the indirect benefits that females gain from matings with large eyespan males. Finally we demonstrate that males do not appear to discriminate between females on the basis of female mating status.
Can indirect selection and genetic context contribute to trait diversification? A transition-probability study of blossom-colour evolution in two genera
Authors: Armbruster W. S.
Published: March 2003

Darwin recognized that biological diversity has accumulated as a result of both adaptive and nonadaptive processes. Very few studies, however, have addressed explicitly the contribution of nonadaptive processes to evolutionary diversification, and no general procedures have been established for distinguishing between adaptive and nonadaptive processes as sources of trait diversity. I use the diversification of flower colour as a model system for attempting to identify adaptive and nonadaptive causes of trait diversification. It is widely accepted that variation in flower colour reflects direct, adaptive response to divergent selective pressures generated by different pollinators. However, diversification of flower colour may also result from the effects of nonadaptive, pleiotropic relationships with vegetative traits. Floral pigments that have pleiotropic relationships to vegetative pigments may evolve and diversify in at least two nonadaptive ways. (1) Indirect response to selection on the pleiotropically related nonfloral traits may occur (indirect selection). (2) Divergent evolution in response to parallel selective pressures (e.g. selection by pollinators for visually obvious flowers) may occur because populations are at different genetic starting points, and each population follows its own genetic `line of least resistance.' A survey of literature suggests that pleiotropic relationships between flower colour and vegetative traits are common. Phylogenetically informed analyses of comparative data from Dalechampia (Euphorbiaceae) and Acer (Aceraceae), based on trait-transition probabilities and maximum likelihood, indicated that floral and vegetative pigments are probably pleiotropically related in these genera, and this relationship better explains the diversification of floral colour than does direct selection by pollinators. In Dalechampia pink/purple floral bract colour may have originated by indirect response to selection on stem and leaf pigments. In Acer selection by pollinators for visually obvious flowers may to have led to the evolution of red or purple flowers in lineages synthesizing and deploying red anthocyanins in leaves, and pale-green or yellow flowers in species not deploying red anthocyanins in vegetative structures. This study illustrates the broader potential of indirect selection and parallel selection on different genetic starting points to contribute to biological diversity, and the value of testing directly for the operation of these nonadaptive diversifying processes.
Sperm competition selects for increased testes mass in Australian frogs
Authors: Byrne P. G. , Roberts J. D. , Simmons L. W.
Published: March 2003

Game theory predicts that investment in spermatogenesis will increase with the risk and intensity of sperm competition. Widespread support for this prediction has come from comparative studies of internal fertilizing species reporting positive associations between testes mass and the probability that females mate with more than one male. Data for external fertilizers have generated conflicting results. We investigated how risk of sperm competition affects testes size in two families of Australian frogs: the Myobatrachidae and the Hylidae. We also examined effects of clutch size, egg size and oviposition location as alternative factors that might influence sperm production. Species were ranked according to probability of group spawning, and hence risk of sperm competition. Controlling for body size and phylogenetic relationships, we demonstrated that within the Myobatrachidae, the risk of sperm competition explained a significant amount of variation in testes mass. Oviposition location had a weak influence, with species ovipositing into foam having smaller testes. No significant effects of clutch size or egg size were detected. In hylids, the relationship between testes mass and risk of sperm competition was positive but not significant, again with no predictable effects related to egg size or number. These data provide an important test of sperm competition theory for externally fertilizing taxa.
Oviposition tests of ant preference in a myrmecophilous butterfly
Authors: Fraser A. M. , Tregenza T. , Wedell N. , Elgar M. A. , Pierce N. E.
Published: March 2003

Butterflies in the family Lycaenidae that have obligate associations with ants frequently exhibit ant-dependent egg laying behaviour. In a series of field and laboratory choice tests, we assessed oviposition preference of the Australian lycaenid Jalmenus evagoras in response to different species and populations of ants. Females discriminated between attendant and nonattendant ant species, between attendant ant species, and to some extent, between populations of a single ant species. When preferences were found, ovipositing butterflies preferred their locally predominant attendant ant species and geographically proximate attendant ant populations. A reciprocal choice test using adults from a generation of butterflies reared in the absence of ants indicated a genetic component to oviposition preference. Individual females were flexible with respect to oviposition site choice, often ovipositing on more than one treatment during a trial. Preferences arose from a hierarchical ranking of ant treatments. These results are discussed in terms of local adaptation and its possible significance in the diversification of ant-associated lycaenids.
Mating system variation along a successional gradient in the allogamous and colonizing plant Crepis sancta (Asteraceae)
Authors: Cheptou P.-O. , Lepart J. , Escarre J.
Published: March 2003

We analysed mating system in an annual and colonizing plant, Crepis sancta, that occupies different successional stages in the French Mediterranean region. Based on a previous experiment, we hypothesized that low inbreeding depression measured in young successional stages should select for selfing whereas higher inbreeding depression in old stages should select for outcrossing. Nine populations of C. sancta (Asteraceae) from contrasting successional stages were used to analyse (1) Seed set after autonomous and enforced selfing in controlled conditions and (2) outcrossing rates in natural conditions using allozymes (progeny array analysis). We found that C. sancta possesses a pseudo-self-incompatibility system and that mating system varies among populations. Allozymes revealed that the population multilocus outcrossing rates vary from 0.77 to 0.99. The lowest outcrossing rates occur in the youngest successional stages and complete outcrossing is found in old stages. The data partially agree with the predictions we made and the results are more generally discussed in the light of factors changing during succession. We did not find any evidence of reproductive assurance in the nine populations, contrary to what is often assumed as a major factor governing mating system evolution in colonizing species. We propose that mating system variation can be interpreted as the result of the balance between the cost of outcrossing and inbreeding depression in a metapopulation context.
Genetic structure of lions (Panthera leo L.) in the Selous Game Reserve: implications for the evolution of sociality
Authors: Spong G. , Stone J. , Creel S. , Björklund M.
Published: March 2003

We use 14 microsatellites to examine the genetic structure of a lion (Panthera leo L.) population in southern Tanzania. Heterozygosity levels were high (0.75 ± 0.08). Relatedness estimates showed that prides often had close relatives in neighbouring prides, whereas few relatives were found in prides not sharing a border. The drop-off in relatedness with distance was highly significant. Female pridemates exhibited a higher mean relatedness (0.26 ± 0.07) to one another than did pride males (0.11 ± 0.07). Mean relatedness among females was significantly higher in small prides than in large ones. Prides exhibited significant inbreeding avoidance (FIL: −0.11). Mating did not detectably differ from random across prides (FIT: −0.02 ns). In addition to being recognizable behavioural and demographic units, prides were statistically distinct genetic units (FLT: 0.07). Some neighbouring prides grouped together both geographically and genetically, forming ‘superprides’ in the population (FZT = 0.05). Thus, although individual prides were genetically distinct, there was an important genetic structure above the level of social groups.
Gradual and quantum genome size shifts in the hystricognath rodents
Authors: Gallardo M. H. , Bickham J. W. , Kausel G. , Köhler N. , Honeycutt R. L.
Published: March 2003

We assessed genome size variation by flow cytometry within and among 31 species of nine families of African and South American hystricognath rodents. Interspecific variation was extensive and genome size was relatively high among the South American radiation whereas only moderate variation and smaller estimates of genome size were observed in the African counterparts. The largest genome size, indicating tetraploidy was recorded in the South American octodontid, Tympanoctomys barrerae (16.8 pg DNA). This quantum shift in DNA content represents a novel mechanism of genome evolution in mammals. As expected in polyploid organisms, varying nucleotypic effects were observed in the dimensions of the sperm cells and lymphocytes of T. barrerae. The role of control mechanisms that influence cell dimensions in polyploid organisms is discussed.