bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct and correlated responses to selection for larval ethanol tolerance in Drosophila melanogaster
Authors: Fry J. D. 
Published: March 2003

Abstract
Ethanol is an important larval resource and toxin for natural Drosophila melanogaster populations, and ethanol tolerance is genetically variable within and among populations. If ethanol-tolerant genotypes have relatively low fitness in the absence of ethanol, as suggested by the results of an earlier study, genetic variation for ethanol tolerance could be maintained by variation in ethanol levels among breeding sites. I selected for ethanol tolerance in large laboratory populations by maintaining flies on ethanol-supplemented media. After 90 generations, the populations were compared with control populations in egg-to-adult survival and development rate on ethanol-supplemented and unsupplemented food. When compared on ethanol-supplemented food, the ethanol-selected populations had higher survival and faster development than the control populations, but on unsupplemented food, the populations did not differ in either trait. These results give no evidence for a ‘trade-off’ between the ability to survive and develop rapidly in the presence of ethanol and the ability to do so in its absence. The effect of physiological induction of ethanol tolerance by exposing eggs to ethanol was also investigated; exposing eggs to ethanol strongly increased subsequent larval survival on ethanol-supplemented food, but did not affect survival on regular food, and slowed development on both ethanol-supplemented and regular food, partly by delaying egg hatch.
Effects of assay conditions in life history experiments with Drosophila melanogaster
Authors: Ackermann M. , Bijlsma R. , James A. C. , Partridge L. , Zwaan B. J. , Stearns S. C. 
Published: March 2003

Abstract
Selection experiments with Drosophila have revealed constraints on the simultaneous evolution of life history traits. However, the responses to selection reported by different research groups have not been consistent. Two possible reasons for these inconsistencies are (i) that different groups used different environments for their experiments and (ii) that the selection environments were not identical to the assay environments in which the life history traits were measured. We tested for the effect of the assay environment in life history experiments by measuring a set of Drosophila selection lines in laboratories working on life history evolution with Drosophila in Basel, Groningen, Irvine and London. The lines measured came from selection experiments from each of these laboratories. In each assay environment, we measured fecundity, longevity, development time and body size. The results show that fecundity measurements were particularly sensitive to the assay environment. Differences between assay and selection environment in the same laboratory or differences between assay environments between laboratories could have contributed to the differences in the published results. The other traits measured were less sensitive to the assay environment. However, for all traits there were cases where the measurements in one laboratory suggested that selection had an effect on the trait, whereas in other laboratories no such conclusion would have been drawn. Moreover, we provide good evidence for local adaptation in early fecundity for lines from two laboratories.
Lateral plate asymmetry, diet and parasitism in threespine stickleback
Authors: Reimchen T. E. , Nosil P. 
Published: March 2003

Abstract
Individuals with random left–right departures from bilateral symmetry are predicted to exhibit fitness reduction including increased parasitism. In an insular lake population of stickleback (Gasterosteus aculeatus) from the Queen Charlotte Islands, Western Canada, phenotypes with high or low number of lateral bony plates exhibited increased plate asymmetry relative to modal phenotypes. Asymmetric lateral plate phenotypes had increased prevalence and to a lesser extent intensity of parasitism relative to symmetric individuals, suggesting that differences in genetic resistance to pathogens contributed to unequal parasitism. The effect occurred mainly in the larger adults and during the warmest season, which may be due to the high metabolic costs incurred during the summer breeding season. Dietary differences between symmetric and asymmetric phenotypes were also detected and could contribute to unequal infection rates by mediating exposure to infected prey items. Our study, which is one of the first long-term field assessments of asymmetry and parasitism, yields results that are consistent with studies linking asymmetry to reduced fitness and indicate that lateral plate asymmetry can be an indicator of poor individual quality, despite its apparent directionality.
Interaction of a host plant and its holoparasite: effects of previous selection by the parasite
Authors: Koskela T. , Salonen V. , Mutikainen P. 
Published: March 2003

Abstract
If parasites decrease the fitness of their hosts one could expect selection for host traits (e.g. resistance and tolerance) that decrease the negative effects of parasitic infection. To study selection caused by parasitism, we used a novel study system: we grew host plants (Urtica dioica) that originated from previously parasitized and unparasitized natural populations (four of each) with or without a holoparasitic plant (Cuscuta europaea). Infectivity of the parasite (i.e. qualitative resistance of the host) did not differ between the two host types. Parasites grown with hosts from parasitized populations had lower performance than parasites grown with hosts from unparasitized populations, indicating host resistance in terms of parasite’s performance (i.e. quantitative resistance). However, our results suggest that the tolerance of parasitic infection was lower in hosts from parasitized populations compared with hosts from unparasitized populations as indicated by the lower above-ground vegetative biomass of the infected host plants from previously parasitized populations.
Fluctuating asymmetry, fecundity and development time in Drosophila: is there an association under optimal and stress conditions?
Authors: Woods R. E. , Sgrò C. M. , Hercus M. J. , Hoffmann A. A. 
Published: March 2003

Abstract
A number of studies have reported a significant negative association between fluctuating asymmetry (FA) of bilateral morphological traits and individual fitness traits, but almost all of these are unreplicated and based on small sample sizes using single trait estimates of FA. We therefore tested if there was a relationship between the FA of five bilateral traits and fecundity and development time in Drosophila in a multiple replicated experimental design. Stressed treatments were included to increase the variability of traits and to test whether associations among traits were affected by changes in the environment. Significant positive relationships were found between the size of wing characters and mean fecundity for the 5-day period and this relationship tended to be stronger in the stress treatments. No association was found between FA and mean fecundity for any of the traits measured. Similarly, a significant positive relationship was detected between wing trait size and development time but no association was detected between trait FA and development time. There were no differences between mean fecundity or development time of extreme asymmetry phenotypes compared with modal phenotypes. These results are discussed with reference to suggestions in the literature that FA can be used to estimate individual fitness.
Trade-offs to flight capability in Gryllus firmus: the influence of whole-organism respiration rate on fitness
Authors: Crnokrak P. , Roff D. A. 
Published: March 2003

Abstract
Wing dimorphism, where some macropterous long-winged (LW) individuals can fly whereas micropterous short-winged (SW) individuals cannot, is common in insects and believed to be maintained in part by trade-offs between flight capability and reproductive traits. In this paper we examine differences in whole-organism respiration rate between wing morphs of the sand cricket Gryllus firmus. We hypothesized that maintenance of the flight apparatus would result in elevated CO2 respired because of the high metabolic cost of these tissues, which, in turn, constrain resources available for egg production in females. As the trade-off involves calling behaviour in males, we predicted no equivalent constraint on organ development in this sex. We found female macropters (particularly older crickets) had significantly higher residual respiration rates than micropters. In males, we found only marginal differences between wing morphs. In both sexes there was a highly significant effect of flight muscles status on residual respiration rate, individuals with functional muscles having higher respiration rates. Both female and male macropters had significantly smaller gonads than micropters. Whole-organism residual respiration rate was negatively correlated with fecundity: macropterous females with high respiration rates had smaller gonads compared with macropterous females with lower respiration rates.
Impact of a population bottleneck on symmetry and genetic diversity in the northern elephant seal
Authors: Hoelzel A. R. , Fleischer R. C. , Campagna C. , Le Boeuf B. J. , Alvord G. 
Published: March 2003

Abstract
The northern elephant seal (NES) suffered a severe population bottleneck towards the end of the nineteenth century. Theoretical expectations for the impact of population bottlenecks include the loss of genetic diversity and a loss of fitness (e.g. through a disruption of developmental stability); however, there are few direct demonstrations in natural populations. Here, we report on the comparison of archive samples collected prior to and following the NES population bottleneck. Measures of genetic diversity show a loss of variation consistent with expectations and suggest a strong disruption in the pattern of allele frequencies following the bottleneck. Measures of bilateral characters show an increase in fluctuating asymmetry.
Are reward polymorphisms subject to frequency- and density-dependent selection? Evidence from a monoecious species pollinated by deceit
Authors: Castillo R. A. , Cordero C. , Domínguez C. A. 
Published: March 2003

Abstract
Most deceit-pollinated species involve floral dimorphisms characterized by the presence of rewarding male flowers and nonrewarding female flowers. It has been proposed that this polymorphism establishes the conditions for the action of frequency dependent selection (FDS). The tendency of foraging animals to aggregate in areas of high resource density suggests that pollination efficiency and fruit production may be positively influenced by flower density (density dependent selection, DDS). In this paper we offer a graphical model describing the effects of FDS and DDS on a monoecious species pollinated by deceit. We test the FDS and DDS assumptions and the predictions of the model using field observations and experimental populations of Begonia gracilis in which population sex ratio and flower density were controlled. We found a marked effect of both FDS and DDS on pollinator visitation, fruit-set, and on the probability of female flowers to setting fruits. We conclude that these two types of selection have had a strong influence on the evolution of deceit-pollinated species.
Interspecific variation in plumage colour among birds: species recognition or light environment?
Authors: McNaught Melinda K. , Owens Ian P. F. 
Published: March 2003

Abstract
The traditional explanation for interspecific plumage colour variation in birds is that colour differences between species are adaptations to minimize the risk of hybridization. Under this explanation, colour differences between closely related species of birds represent reproductive character displacement. An alternative explanation is that interspecific variation in plumage colour is an adaptive response to variation in light environments across habitats. Under this explanation, differences in colour between closely related species are a product of selection on signal efficiency. We use a comparative approach to examine these two hypotheses, testing the effects of sympatry and habitat use, respectively, on divergence in male plumage colour. Contrary to the prediction of the Species Isolation Hypothesis, we find no evidence that sympatric pairs of species are consistently more divergent in coloration than are allopatric pairs of species. However, in agreement with the Light Environment Hypothesis, we find significant associations between plumage coloration and habitat use. All of these results remain qualitatively unchanged irrespective of the statistical methodology used to compare reflectance spectra, the body regions used in the analyses, or the exclusion of areas of plumage not used in sexual displays. Our results suggest that, in general, interspecific variation in plumage colour among birds is more strongly influenced by the signalling environment than by the risk of hybridization.
The evolution of infertility: does hatching rate in birds coevolve with female polyandry?
Authors: Morrow E. H. , Arnqvist G. , Pitcher T. E. 
Published: March 2003

Abstract
Natural levels of infertility in many taxa are often remarkably high, amounting to a considerable fitness cost which one expects to be minimized by natural selection. Several mechanisms have been proposed as potential causes of infertility, including inbreeding depression, genetic incompatibilities and selfish genetic elements. Infertility may also be an inherent result of conflict over fertilization between the sexes in polyandrous species, either because too many sperm enter the egg or because of over-efficient barriers to such polyspermic fertilizations. We generated phylogenetic independent contrasts to examine the variation in hatching success for a maximum of 58 species of birds in relation to two measures of female polyandry. Hatching success varied enormously across species (range: 61–100%), with a mean of 12% of eggs failing to hatch, but was not related to either the rate of extrapair paternity or to relative testes size. Thus, the causes of this significant fitness cost remains unclear and merits further examination by evolutionary biologists.
Detection of punctuated equilibrium from molecular phylogenies
Authors: Bokma F. 
Published: March 2003

Abstract
The theory of ‘punctuated equilibrium’ hypothesises that most morphological change in species takes place in rapid bursts triggered by speciation. Eldregde and Gould postulated the theory in 1972, as an alternative to the idea that morphological change slowly accumulates in the course of time, a then common belief they dubbed ‘phyletic gradualism’. Ever since its introduction the theory of punctuated equilibrium has been the subject of speculation rather than empirical validation. Here I present a method to detect punctuated evolution without reference to fossil data, based on the phenotypes of extant species and on their relatedness as revealed by molecular phylogeny. The method involves a general mathematical model describing morphological differentiation of two species over time. The two parameters in the model, the rates of punctual (cladogenetic) and gradual (anagenetic) change, are estimated from plots of morphological diversification against time since divergence of extant species.
Mitochondrial DNA variation and the phylogeography of the grey partridge (Perdix perdix) in Europe: from Pleistocene history to present day populations
Authors: Liukkonen-Anttila T. , Uimaniemi L. , Orell M. , Lumme J. 
Published: March 2003

Abstract
For a phylogeographical analysis of European grey partridge (Perdix perdix) we sequenced 390 nucleotides of the 5′ end of the mitochondrial control region (CR) of 227 birds from several localities. The birds were divided into two major clades (western and eastern) which differed in control region 1 (CR1) by 14 nucleotide substitutions (3.6%). For estimation of the time of divergence, the whole CR of 14 specimens was sequenced. The major clades differed by 2.2%, corresponding to an estimated coalescence time of c. 1.1 million years. On CR1, 45 haplotypes were found. Western clade haplotypes were found in France, England, Germany, Poland, Italy and Austria. Eastern clade haplotypes were found in Finland, Bulgaria, Greece, and Ireland. One Finnish population and all Bulgarian and Irish populations were mixed, but only in Bulgaria was the mixing assumed to be natural. Nucleotide and haplotype diversities varied between populations, and both clades showed geographical structuring. The distribution of pairwise nucleotide differences in the eastern clade fitted the expectations of an expanding population. About 80% of the genetic structure in the grey partridge could be explained by the clades. The western clade presumably originates on the Iberian Peninsula (with related subtypes in Italy), and the eastern clade either on the Balkan or Caucasian refugia. Large-scale hand-rearing and releasing of western partridges have introduced very few mtDNA marks into the native eastern populations in Finland.
Evolutionary ecology of Datura stramonium: equal plant fitness benefits of growth and resistance against herbivory
Authors: Valverde P. L. , Fornoni J. , Núñez-Farfán J. 
Published: March 2003

Abstract
This study evaluated how natural selection act upon two proposed alternatives of defence (growth and resistance) against natural enemies in a common garden experiment using genetic material (full-sibs) from three populations of the annual plant Datura stramonium. Genetic and phenotypic correlations were used to search for a negative association between both alternatives of defence. Finally, the presence/absence of natural enemies was manipulated to evaluate the selective value of growth as a response against herbivory. Results indicated the presence of genetic variation for growth and resistance (1 – relative damage), whereas only population differentiation for resistance was detected. No correlation between growth and resistance was detected either at the phenotypic or the genetic level. Selection analysis revealed the presence of equal fitness benefits of growth and resistance among populations. The presence/absence of natural herbivores revealed that herbivory did not alter the pattern of selection on growth. The results indicate that both strategies of defence can evolve simultaneously within populations of D. stramonium.
Genetic variation of polygenic characters and the evolution of genetic degeneracy
Authors: Frank S. A. 
Published: March 2003

Abstract
The classical model of mutation–selection balance for quantitative characters sums the effects of individual sites to determine overall character value. I develop an alternative version of this classical model in which character value depends on the averaging of the effects of the individual sites. In this new averaging model, the equilibrium patterns of variance in allelic effects and character values change with the number of sites that affect a character in a different way from the classical model of summing effects. Besides changing the patterns of variance, the averaging model favours the addition of loci to the control of character values, perhaps explaining in part the recent observation of widespread genetic degeneracy.
Worker interests and male production in Polistes gallicus, a Mediterranean social wasp
Authors: Strassmann J. E. , Nguyen J. S. , Arévalo E. , Cervo R. , Zacchi F. , Turillazzi S. , Queller D. C. 
Published: March 2003

Abstract
The resolution of social conflict in colonies may accord with the interests of the most numerous party. In social insect colonies with single once-mated queens, workers are more closely related to the workers' sons than they are to the queens' sons. Therefore, they should prefer workers to produce males, against the queen's interests. Workers are capable of producing males as they arise from unfertilized eggs. We found Polistes gallicus to have colonies of single, once-mated queens, as determined by microsatellite genotyping of the workers, so worker interests predict worker male production. In colonies lacking queens, workers produced the males, but not in colonies with original queens. Thus worker interests were expressed only when the queen was gone. The high fraction of missing queens and early end to the colony cycle relative to climate so early in the season is surprising and may indicate a forceful elimination of the queen.
Species concepts and species reality: salvaging a Linnaean rank
Authors: Lee M. S. Y. 
Published: March 2003

Abstract
The validity of the species category (rank) as a distinct level of biological organization has been questioned. Phenetic, cohesion and monophyletic species concepts do not delimit species-level taxa that are qualitatively distinct from lower or higher taxa: all organisms throughout the tree of life exhibit varying degrees of similarity, cohesion, and monophyly. In contrast, interbreeding concepts delimit species-level taxa characterized by a phenomenon (regular gene flow) not found in higher taxa, making the species category a distinct level of biological organization. Only interbreeding concepts delimit species-level taxa that are all comparable according to a biologically meaningful criterion and qualitatively distinct from entities assigned to other taxonomic categories. Consistent application of interbreeding concepts can result in counterintuitive taxonomies – e.g. many wide polytypic species in plants and narrow cryptic species in animals. However, far from being problematic, such differences are biologically illuminating – reflecting differing barriers to gene flow in different clades. Empirical problems with interbreeding concepts exist, but many of these also apply to other species concepts, whereas others are not as severe as some have argued. A monistic view of species using interbreeding concepts will encounter strong historical inertia, but can save the species category from redundancy with other categories, and thus justify continued recognition of the species category.
Microarray technology: the future of blood testing?
Authors: Petrik J. 
Published: March 2003

The increasing pace of development in molecular biological techniques during the last 10–15 years has had a direct effect on mass testing and diagnostic applications, including blood screening. Nucleic acid amplification techniques (NAT), usually based on the polymerase chain reaction (PCR), have been successfully applied to blood grouping and implemented recently in screening of blood donations for hepatitis C virus (HCV). The majority of microarray technologies involve an amplification step, yet the main benefits of this technology come from simultaneous analysis of thousands of analytes. Microarrays were developed to utilize the huge amount of information provided by genome projects, but they have clear potential in mass screening and diagnostics. The application of microarray technology may revolutionize blood testing, providing for the first time the prospect of an integrated platform for comprehensive donor and donation testing, replacing multiple individual assays. Design features of a blood‐testing chip and various technologies with potential application in this field are discussed in this review.