bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phylogenetic studies of acridoid grasshoppers comparing 2n2‐ and 4‐base recognizing endonucleases
Authors: Colgan D. J. 
Published: December 2004

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

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

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

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

AbstractIn this paper we attempt to investigate relationships between the amount of genetic divergence in nuclear genes and the degree of morphological differentiation for different sets of characters in Dolichopoda cave crickets.Six populations representing five Dolichopoda species from Central and Southern Italy have been studied. The overall genetic divergence at nuclear genes was estimated both by single copy DNA‐DNA hybridization and allozyme frequencies at 26 loci. Euclidean distances for two multivariate sets of morphometric variables: one describing body and appendage morphology, the other male epiphallus shape. Results showed a close agreement between the branching patterns of ΔTm values from DNA hybridization and Nei's allozyme distance values. On the other hand, patterns of morphological divergence revealed independent trends, although the branching pattern based on epiphallus morphology matched to some extent the phylogenies inferred from molecular data. The relative value of molecular and morphological characters as reliable phylogenetic tracers was evaluated in relation to their dependence on evolutionary factors.Implications of these findings on the calibration of molecular clocks are also discussed. The absolute rate of molecular change based on scDNA was estimated to be at least 0.98% divergence/my/lineage. This result is in agreement with calibrations attempted on other insects. Estimates of time of divergence based on allozymes (Nei's D) were highly consistent with the estimate from geological data.
Constancy and change of basipodial variation patterns: a comparative study of crested and marbled newts —Triturus cristatus, Triturus marmoratus — and their natural hybrids
Authors: Rienesl J. , Wagner G. P. 
Published: December 2004

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

AbstractWe analyzed patterns of variation in polymorphic loci across a contact zone between two subspecies of tiger salamander, Ambystoma tigrinum nebulosum and A. t. mavortium, in west‐central New Mexico. We found no fixed differences between A. t. mavortium and A. t. nebulosum. Allele frequencies across the contact zone did not vary concordantly among loci, but frequencies at two loci varied with elevation. Gene flow extends through the contact zone from A. t. mavortium into A. t. nebulosum, but not conversely. A. t. mavortium and A. t. nebulosum have no obvious impediments to gene flow within this contact zone, but some populations differ in time of reproduction. The contact zone comprises a variety of habitats, approximating typical A. t. mavortium or A. t. nebulosum habitats. There is an irregular pattern of differences in allelic frequencies among populations that covaries with habitats and is consistent with a model of a mosaic contact zone.Our results contrast with those of a study along the Front Range in Colorado, where allelic composition at some loci changed abruptly across a narrow zone of contact. These contrasting results suggest that the dynamics shaping the contact zone between the same taxa may differ. Absence of a similar pattern of genetic differentiation between A. t. mavortium and A. t. nebulosum in New Mexico and in Colorado suggests a complex set of evolutionary interactions along the eastern front of the Rocky Mountain axis.
Gender variation and the evolution of dioecy in Wurmbea dioica (Liliaceae)
Authors: Barrett Spencer C. H. 
Published: December 2004

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

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

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

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

Abstract We manipulated developmental time and dry weight at eclosion in 15 genotypes of Drosophila melanogaster by growing the larvae in 9 environments defined by 3 yeast concentrations at 3 temperatures. We observed how the genetic and various environmental components of phenotypic variation scaled with the mean values of the traits.Temperature, yeast, within‐environmental factors and genotype influenced the genotypic and environmental standard deviations of the two traits in patterns that point to very different modes of physiological and developmental action of these factors. Since different factors affected the environmental and genetic components of the phenotypic variation either in parallel or inversely, we conclude that environmental heterogeneity may have small or large effects on evolutionary rates depending on which factors cause the heterogeneity. The analysis also suggests that the scaling of variances with the mean is not as trivial as is often assumed when coefficients of variation are computed to “standardize” variation.
The evolution of unusual chromosomal systems in coccoids: extraordinary sex ratios revisited
Authors: Haig David 
Published: December 2004

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

AbstractWe constructed a sex allocation model for parasitic wasps to explain the wide variation in their sex ratio, considering the effects of local mate competition, partial dispersal of progeny before mating, and heterogeneity in host quality among patches. We conducted an experiment to compare with the predictions of our model. We considered the following situations. First, the hosts are distributed in discrete patches: a number of female wasps visit and oviposit in each patch. Second, all the progeny do not mate within the natal patch; some of them disperse to take part in population‐wide random mating. We calculated ES sex ratios in cases where there are two kinds of patches: good ones and poor ones. We examined the dependency of ES sex ratios on several parameters, i.e., 1) the probability that a daughter mates in her natal patch, 2) the ratio of the female fitness of the good patch to that of the poor patch, 3) the proportion of poor patches, and 4) the number of foundresses in a patch. The result of our experiment showed the same tendency as the calculation in case where the LMC effect is high in each patch. We briefly discuss a possible selection pressure for dispersal of progeny, with special reference to the mating structure of parasitic wasps.
Inheritance of body size in the Barnacle Goose under different environmental conditions
Authors: Larsson Kjell 
Published: December 2004

AbstractHeritabilities, genetic variances and covariances for body size traits, i.e. tarsus length, head length and body mass, were estimated under different environmental conditions in a Barnacle Goose (Branta leucopsis) population. Under poor growth conditions, that is, when average body size of fully grown offspring in a given cohort was small, the offspring‐parent regressions and full‐sib analyses yielded heritability estimates not significantly different from zero. By contrast, when growth conditions were normal or good the heritability estimates were generally significantly positive. Comparisons of genetic covariance estimates indicated that they also differed across the analysed environmental conditions. This result, together with similar results obtained in studies of passerine birds, suggests that genotype‐environment interactions might be frequent within the range of environments normally encountered by birds in natural populations. If general, such results might question the validity of assuming approximate constancy of additive genetic variances and covariances over time and environments in evolutionary models.
Evolution of the alternation of haploid and diploid phases in life cycles. II. Maintenance of the haplo‐diplontic cycle
Authors: Richerd Sophie , Couvet Denis , Valéro Myriam 
Published: December 2004

AbstractThe relative duration of the haploid and the diploid phases during the reproductive cycle varies greatly between organisms. This paper addresses the question of the evolution of haploid, diploid, and haplo‐diplontic life cycles. When the life span of haploid and diploid individuals is constant whatever their cycle, we show that the haplo‐diplontic cycle has an advantage, which depends on the sex‐ratio in anisogamous species and on the probability of fertilization in isogamous species. This is because meiosis and fertilization occur half as often in the haplo‐diplontic cycle as in haploid or diploid cycles, for the same number of generations of individuals. This argument is demonstrated using a model which considers a genetic determination of the cycle, and fixed haploid and diploid fitnesses. The relevance of measures of fitness of haploid and diploid individuals in predicting the evolution of life cycles is discussed. Measures obtained in algae are compared with theoretical predictions.