bluuebunny/crossref_metadata_2025_split huggingface dataset:
Processes at the origin of similarities in dispersal behaviour among siblings
Authors: Massot  , Clobert  
Published: March 2003

Abstract
Processes which generate natal dispersal are largely unknown. This is particularly the case for the sources of differences among families. Three types of processes can generate the variability among families: genetic, prenatal and postnatal. We first tested the family resemblance of dispersal behaviour in the common lizard (Lacerta vivipara). We then experimentally investigated the role of pre- and postnatal factors in the variability of dispersal among families. From 1989 to 1992, we studied dispersal of juveniles from pregnant females captured in the field and maintained in laboratory until parturition. We manipulated the conditions of gestation to test for prenatal effects on juvenile dispersal. We tested postnatal effects by releasing siblings of the same family in contrasted environments. We also examined covariances of natal dispersal with maternal and offspring traits. The results showed that: (1) dispersal behaviour was similar among siblings, (2) determinants of offspring dispersal differed between sexes and years, (3) offspring dispersal was related to litter sex-ratio and offspring corpulence at birth, (4) postnatal conditions influenced male dispersal, (5) short-term prenatal conditions (i.e. maternal conditions during gestation) influenced juvenile dispersal, varying per year, (6) long-term prenatal conditions (i.e. maternal conditions during gestation in the previous year) could also influence juvenile dispersal (marginally significant).
Thus, several types of processes determine natal dispersal in the common lizard. Resemblance among siblings can partly be explained by both pre- and postnatal effects. The environment seems to be the major factor influencing juvenile dispersal in this species, i.e. dispersal essentially appears condition-dependent. The genetic basis of dispersal in vertebrates remains to be demonstrated by studies controlling for both prenatal and postnatal conditions.
Reproductive performance of clonal and sexual bark beetles (Coleoptera: Scolytidae) in the field
Authors: Løyning  
Published: March 2003

Abstract
In Ips acuminatus (Gyll.) parthenogenetic females occur together with sexual females and with sexual males upon which they depend for sperm. In a reciprocal-transplant experiment, I studied fecundity differences among parthenogenetic and sexual females from two populations that differ dramatically in the proportion of clonal females. In a second experiment, I studied competition between larvae from different mothers and between females from the two source populations. Fecundity measured by the number of eggs per egg tunnel was influenced by the ambient environment at the sites of the experiment as well as the origin of the female, and was generally higher for clonal than for sexual females at both sites. In experimental groups where larvae competed with larvae from their own population (pure treatments), the number of surviving pupae was significantly lower than in groups where females from the two source populations were mixed. The high fecundity of clonal females makes coexistence of the two types of females difficult to explain. It makes the reproductive advantage associated with clonality in I. acuminatus even higher than the two-fold difference due to asexuality per sé. The significant differences in the number of pupae in mixed vs. pure groups suggest ecological divergence between sexual and clonal females. This would make the mortality of larvae not only density dependent, but also frequency dependent, which could explain the coexistence of sexual and clonal females.
Factors influencing the composition of mixed populations of a hemiclonal hybrid and its sexual host
Authors: Hellriegel B. , Reyer H.-U. 
Published: March 2003

Abstract
Hemiclonal/hybridogenetic hybrids combine demographic superiority of asexuals and genetic diversity of sexuals, but their need for backcrossing with a parental species tightly couples them with this sexual host. How can systems like this persist in ecological and evolutionary time? Two discrete-time mathematical models describing the complex life cycle and mating system of hybridogenetic waterfrogs (Rana esculenta) identified four factors and their interactions as important. Although female mating preferences, in combination with differences in fecundity, determine species coexistence, differences in larval competitiveness seem to be more important for the hybrid‘s actual frequency. However, coexistence is possible even when host and hybrid are equally fecund and competitive. Dispersal and competition interact in their influence on species composition, but ecological and reproductive dispersal has opposing effects. In ecological terms our results explain the remarkable stability of observed species ratios over time within natural hybridogenetic populations, and indicate why the species composition can vary so widely between localities. In evolutionary terms they explain the old age of these and other hybridogenetic systems. They also suggest interesting consequences for other tightly coupled systems.
Sperm competition and small size advantage for males of the golden orb-web spider Nephila edulis
Authors: Schneider J. M. , Herberstein M. E. , De Crespigny F. C. , Ramamurthy S. , Elgar M. A. 
Published: March 2003

Abstract
Sexual selection, through female choice and/or male–male competition, has influenced the nature and direction of sexual size dimorphism in numerous species. However, few studies have examined the influence of sperm competition on size dimorphism. The orb-web spider Nephila edulis has a polygamous mating system and extreme size dimorphism. Additionally, the frequency distribution of male body size is extremely skewed with most males being small and few large. The duration of copulation, male size and sexual cannibalism have been identified as the significant factors determining patterns of sperm precedence in spiders. In double mating trials, females were assigned to three treatments: either they mated once with both males or the first or the second male was allowed to mate twice. Paternity was strongly associated with the duration of copulation, independent of mating order. Males that were allowed to mate twice not only doubled the duration of copulation but also their paternity. Small males had a clear mating advantage, they copulated longer than large males and fertilized more eggs. Males of different sizes used different tactics to mate. Large males were more likely to mate through a hole they cut into the web, whereas small males approached the female directly. Furthermore, small males usually mated at their first attempt but large males required several attempts before mating took place. There was no obvious female reaction towards males of different sizes.
Population differences in early life-history traits in grayling
Authors: Haugen T. O. , Vøllestad L. A. 
Published: March 2003

Abstract
In this paper we test population differences in early life-history traits in three grayling Thymallus thymallus populations. The grayling shared ancestors some 80–90 years ago. We performed common-garden experiments at three temperatures (mimicking population-specific summer temperatures), and measured survival and growth rates during early development. We found significant additive genetic variance in size (length and yolk-sac volume) measured at hatching, swim-up and termination of the experiment, and significantly different reaction norms for growth rate and survival during the period of first feeding. In general, each population did best at the temperature experienced in nature. These differences in early life-history traits suggest that natural selection has resulted in local adaptation in a time period of 13–18 generations.
Direct and indirect responses to selection on pollen size in Brassica rapa L.
Authors: Sarkissian T. S. , Harder L. D. 
Published: March 2003

Abstract
Pollen size varies little within angiosperm species, but differs extensively between species, suggesting the action of strong selection. Nevertheless, the potential for genetic responses of pollen size to selection, as determined by additive genetic variance and genetic correlations with other floral traits, has received little attention. To assess this potential, we subjected Brassica rapa to artificial selection for large and small pollen during three generations. This selection caused significant divergence in pollen diameter, with additive genetic effects accounting for over 30% of the observed phenotypic variation in pollen size. Such heritable genetic variation suggests that natural selection could effect evolutionary change in this trait. Selection on pollen size also elicited correlated responses in pollen number (–), flower size (+), style length (+), and ovule number (+), suggesting that pollen size cannot evolve independently. The correlated responses of pollen number, flower size and ovule number probably reflect the genetically determined and physically constrained pattern of resource allocation in B. rapa. In contrast, the positive correlation between pollen size and style length may represent a widespread gametic-phase disequilibrium in angiosperms that arises from nonrandom fertilization success of large pollen in pistils with long styles.
Role of ageing and temperature in shaping reaction norms and fecundity functions in insects
Authors: Kindlmann P. , Dixon A. F. G. , Dostálková I. 
Published: March 2003

Abstract
The existing energy partitioning models assume that fecundity is constant throughout adult life. In insects, however, fecundity is a triangular function of time: after maturation, it initially sharply increases and after reaching its maximum it slowly declines as the mother ages. These models also fail to explain that empirical data generally indicate an increase in juvenile growth rate caused by improvement in food quality results in larger adults, whereas that caused by an increase in ambient temperature results in smaller adults. This ‘life history puzzle’ has worried many biologists for a long time.
An energy-partitioning model for insects is presented with soma and gonads as its components, which – contrary to other models – assumes ageing of soma. This model explains the triangular shape of the fecundity function, and also offers an explanation of the ‘life history puzzle’. The differential response in adult size to changes in food quality and temperature in nature may result from the differential responses of our model’s parameters to changes in these environmental parameters. Better food quality results in bigger adults, because food quality affects the assimilation rate, but not the rate of conversion of gonadal biomass into offspring, or the rate of senescence. In contrast, an increase in temperature speeds up all the processes. That is, temperature affects the assimilation rate, the conversion rate of gonadal biomass into offspring, and the rate of senescence equally. Therefore, an increase in temperature results in larger or smaller adults, depending on the shape of the senescence function.
Costs of intersexual conflict in the isopod Idotea baltica
Authors: Jormalainen V. , Merilaita S. , Riihimäki J. 
Published: March 2003

Abstract
In sexual reproduction one sex can increase its reproductive success at the cost of the other, a situation known as intersexual conflict. In the marine isopod Idotea baltica, males guard females before copulation. The guarding phase is preceded by struggles as females resist males’ attempts to initiate guarding. We determined whether the struggle and/or mate-guarding result in fitness costs in the form of decreasing fecundity and lower levels of the energy storage compounds, glycogen and lipids. Females that underwent the period of struggles with males had decreased glycogen levels compared with females maintained alone. No such cost was found for males. Females guarded by a male also had smaller eggs than females that were not guarded. Thus the intersexual conflict, imposed by the fitness maximization strategy of the males, gave rise to both a fecundity cost and an energetic cost for females. The fecundity cost confirms the existence of intersexual conflict in I. baltica. This cost is shared by males, suggesting that the intersexual conflict restrains the reproductive output of both sexes.
Female remating in butterflies: interaction between female genotype and nonfertile sperm
Authors: Wedell N. 
Published: March 2003

Abstract
Female mating rate is fundamental to evolutionary biology as it determines the pattern of sexual selection and sexual conflict. Despite its importance, the genetic basis for female remating rate is largely unknown and has only been demonstrated in one species. In paternally investing species there is often a conflict between the sexes over female mating rate, as females remate to obtain male nutrient donations and males try to prevent female remating to ensure high fertilization success. Butterflies produce two types of sperm: fertilizing, eupyrene sperm, and large numbers of nonfertile, apyrene sperm. The function of apyrene sperm in the polyandrous, paternally investing green-veined white butterfly, Pieris napi, is to fill the female’s sperm storage organ thereby reducing her receptivity. However, there is large variation in number of apyrene sperm stored. Here, I examine the genetic basis to this variation, and if variation in number of apyrene sperm stored is related to females’ remating rate. The number of apyrene sperm stored at the time of remating has a genetic component and is correlated with female remating tendency, whereas no such relationship is found for fertilizing sperm. The duration of the nonreceptivity period in P. napi also has a genetic component and is inversely related to the degree of polyandry. Sexual conflict over female remating rate appears to be present in this species, with males using their apyrene sperm to exploit a female system designed to monitor sperm in storage. Ejaculates with a high proportion of nonfertile sperm may have evolved to induce females to store more of these sperm, thereby reducing remating. As a counter-adaptation, females have evolved a better detection system to regain control over their remating rate. Sexually antagonistic co-evolution of apyrene sperm number and female sperm storage may be responsible for ejaculates with predominantly nonfertile sperm in this butterfly.
Comparison of genetic differentiation at marker loci and quantitative traits
Authors: Merilä J. , Crnokrak P. 
Published: March 2003

Abstract
The comparison of the degree of differentiation in neutral marker loci and genes coding quantitative traits with standardized and equivalent measures of genetic differentiation (FST and QST, respectively) can provide insights into two important but seldom explored questions in evolutionary genetics: (i) what is the relative importance of random genetic drift and directional natural selection as causes of population differentiation in quantitative traits, and (ii) does the degree of divergence in neutral marker loci predict the degree of divergence in genes coding quantitative traits? Examination of data from 18 independent studies of plants and animals using both standard statistical and meta-analytical methods revealed a number of interesting points. First, the degree of differentiation in quantitative traits (QST) typically exceeds that observed in neutral marker genes (FST), suggesting a prominent role for natural selection in accounting for patterns of quantitative trait differentiation among contemporary populations. Second, the FST – QST difference is more pronounced for allozyme markers and morphological traits, than for other kinds of molecular markers and life-history traits. Third, very few studies reveal situations were QST &lt; FST, suggesting that selection pressures, and hence optimal phenotypes, in different populations of the same species are unlikely to be often similar. Fourth, there is a strong correlation between QST and FST indices across the different studies for allozyme (r=0.81), microsatellite (r=0.87) and combined (r=0.75) marker data, suggesting that the degree of genetic differentiation in neutral marker loci is closely predictive of the degree of differentiation in loci coding quantitative traits. However, these interpretations are subject to a number of assumptions about the data and methods used to derive the estimates of population differentiation in the two sets of traits.
The use of marker-based relationship information to estimate the heritability of body weight in a natural population: a cautionary tale
Authors: Thomas S. C. , Coltman D. W. , Pemberton J. M. 
Published: March 2003

Abstract
A number of procedures have been developed that allow the genetic parameters of natural populations to be estimated using relationship information inferred from marker data rather than known pedigrees. Three published approaches are available; the regression, pair-wise likelihood and Markov Chain Monte Carlo (MCMC) sib-ship reconstruction methods. These were applied to body weight and molecular data collected from the Soay sheep population of St. Kilda, which has a previously determined pedigree. The regression and pair-wise likelihood approaches do not specify an exact pedigree and yielded unreliable heritability estimates, that were sensitive to alteration of the fixed effects. The MCMC method, which specifies a pedigree prior to heritability estimation, yielded results closer to those determined using the known pedigree. In populations of low average relationship, such as the Soay sheep population, determination of a reliable pedigree is more useful than indirect approaches that do not specify a pedigree.
Sexually antagonistic selection on primate size
Authors: Lindenfors P. 
Published: March 2003

Abstract
Male intrasexual selection in haplorhine primates has previously been shown to increase male size and to a lesser degree also female size. I address the following questions: (1) why does female size increase when the selection is on males, and (2) why does female size not increase to the same extent as that of males. The potential for correlational selection on females through increased resource competition was analysed with independent contrasts analyses. No such effect was found, nor did matched pairs comparisons reveal females to increase in size because of selection to bear larger male offspring. Instead further matched pairs analyses revealed higher female postpartum investment, as indicated by a longer lactation period, in more sexually selected species, also after correcting for body weight. Concerning the second question, independent contrast analyses showed that large size has had negative effects on female reproductive rate across the primate order. Matched-pairs analyses on haplorhines revealed that females of species in more polygynous clades have lower reproductive rates than females of species in less polygynous clades. This is also true after the effects of body weight are removed. These results, both when correcting for body weight and when not, suggest that sexual selection has shifted female size from one favouring female lifetime fecundity to one favouring male success in competition. This depicts antagonistic selection pressures on female size and a trade-off for females between the ecologically optimal size of their foremothers and the larger size that made their forefathers successful.
Female choice of sexually antagonistic male adaptations: a critical review of some current research
Authors: Cordero C. , Eberhard W. G. 
Published: March 2003

Abstract
We contrast some recent uses of the concept of male-female conflict, with the type of conflict that is inherent in traditional Darwinian female choice. Females in apparent conflict situations with males may suffer reduced lifetime reproduction, but nevertheless benefit because they obtain sons with superior manipulative abilities. Female defences against male manipulations may not be ‘imperfect’ because of inability to keep pace with male evolution, but in order to screen males and favour those that are especially good manipulators. We examine the consequences of these ideas, and of the difficulties of obtaining biologically realistic measures of female costs, for some recent theoretical and empirical presentations of male–female conflict ideas, and find that male–female conflict in the new sense is less certain than has been commonly supposed. Disentangling previous sexual selection ideas and the new conflict of interest models will probably often be difficult, because the two types of payoffs are not mutually exclusive.
Inbreeding depression and genetic load of sexually selected traits: how the guppy lost its spots
Authors: Van Oosterhout C. , Trigg R. E. , Carvalho G. R. , Magurran A. E. , Hauser L. , Shaw P. W. 
Published: March 2003

Abstract
To date, few studies have investigated the effects of inbreeding on sexually selected traits, although inbreeding depression on such traits can play an important role in the evolution and ecology of wild populations. Sexually selected traits such as ornamentation and courtship behaviour may not be primary fitness characters, but selection and dominance coefficients of their mutations will resemble those of traits under natural selection. Strong directional selection, for instance, through female mate-choice, purges all but the most recessive deleterious mutations, and the remaining dominance variation will result in inbreeding depression once populations undergo bottlenecks. We analysed the effects of inbreeding on sexually selected traits (colour pattern and courtship behaviour) in the male guppy, Poecilia reticulata, from Trinidad, and found a significant decline in the frequency of mating behaviour and colour spots. Such effects occurred although the genetic basis of these traits, many of which are Y-linked and hemizygous, would be expected to leave relatively little scope for inbreeding depression. Findings suggest that these sexually selected traits could reflect the genetic condition or health of males, and thus may be informative mate-cue characters for female choice as suggested by the ‘good genes’ model.
An international collaborative study to establish a World Health Organization international standard for hepatitis B virus DNA nucleic acid amplification techniques
Authors: Saldanha J. , Gerlich W. , Lelie N. , Dawson P. , Heermann K. , Heath A. ,   The WHO Collaborative Study Group
Published: March 2003

Background and objectivesTwenty‐two laboratories from nine countries participated in an international collaborative study to establish a World Health Organization (WHO) international standard for hepatitis B virus (HBV) DNA nucleic acid amplification techniques (NAT).Materials and methodsThree samples, AA, BB (both of which were lyophilized) and CC (which was a liquid preparation), were analysed using several different NAT assays. The mean HBV DNA content of each sample was determined from the study.ResultsDespite the range of assays (commercial and in‐house) used by participants, there was good agreement among the overall mean ‘equivalents’/ml obtained by the different assays, except for one laboratory (laboratory 4). The variation in estimates of log10‘equivalents’/ml was 1·75–1·25 for the three samples if results from laboratory 4 were excluded. The mean log10‘equivalents’/ml for all laboratories were 6·42 for sample AA, 6·30 for sample BB and 5·03 for sample CC (exclusion of results from laboratory 4 made little difference). The difference in titres between the two lyophilized samples (AA and BB) was not statistically significant but the titre of the frozen sample (CC) was significantly lower. Material AA (code 97/746) was accepted as the first WHO international standard for HBV DNA NAT assays and assigned a potency of 106international units (IU)/ml.ConclusionsThe titres (genome equivalents/ml) of three HBV preparations were determined by several laboratories using different NAT assays. This study enabled the establishment of an international standard, 97/746, for HBV DNA NAT assays.