bluuebunny/crossref_metadata_2025_split huggingface dataset:
A general model of the relation between phenotypic selection and genetic response
Authors: Van Tienderen P. H. , De Jong G. 
Published: March 2003

AbstractThe 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

AbstractHeterochrony, 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.