bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coexistence of ecologically similar colonising species. II. Population differentiation in Drosophila aldrichi and D. Buzzatii for competitive effects and responses at different temperatures and allozyme variation in D. aldrichi
Authors: Krebs Robert A. , Barker J. S. F. 
Published: December 2004

Abstract Drosophila aldrichi
and
D. buzzatii
are cactophilic species that colonised Australia about 55–60 years ago. They are sympatric only in Australia. Thus they may be in the process of adapting to new environments and to each other, and diversifying among local, possibly isolated, populations. Larval competitive effects for three populations of each species (Roma, Planet Downs, and Binjour) were measured on semi‐natural cactus rots at three temperatures, with preadult viability, developmental time and adult body weight scored for each sex and species. Populations of both species varied in their responses to the other species as competitor, and one
D. buzzatii
population (Roma) reduced larval performance of
D. aldrichi
significantly more than did other
D. buzzatii
populations. Geographic divergence for the three traits was similar in both species, with a relative performance index derived from these traits highest for Roma, second for Binjour, and least for the Planet Downs population of each species. The Roma
D. aldrichi
population was the most different from the other populations for the performance index and in terms of genetic distances derived from allozyme frequencies. Additionally, comparisons of climatic variables among the population localities showed that the Roma environment was most different from the others. Differential natural selection in different areas of the cactus distribution may be a major cause of population divergence in both species.
Drosophila aldrichi
is superior for some fitness components at the highest temperature. Thus temperature variation throughout the cactus distribution may contribute to the different ranges of these two species, with competitive exclusion of
D. aldrichi in the southern, cooler region of the cactus distribution, but coexistence in the northern, warmer region.
Inheritance of size and shape in a natural population of collared flycatchers, Ficedula albicollis
Authors: Merilä Juha , Gustafsson Lars 
Published: December 2004

AbstractFour external skeletal and three feather dimensions were measured on adult collared flycatchers (Ficedula albicollis) and their adult offspring. By using mid‐offspring‐midparent regressions, all traits were found to be heritable with an arithmetic mean heritability of 0.46. Heritability estimates from full‐sib analyses were about 1.5 times higher (mean 0.67), indicating that variation in traits was affected by shared nest environment among full‐sibs. The overall body size as measured by principal component one (PC1) was found to be heritable (h2 = 0.40). However, this multivariate measure of heritability was not significant in offspring‐father comparison, while highly so in offspring‐mother comparison (h2 = 0.60). Low offspring‐father resemblance was evident also in univariate estimates of heritability. Possible causes of this (extra‐pair copulations, maternal effects, sex‐linked variance) are discussed.Genetic correlations among seven traits were estimated to be low (mean 0.22), and of similar magnitude or higher than phenotypic correlations (mean 0.18). All genetic correlations were positive. Genetic and phenotypic correlations as well as covariances were fairly similar to each other (r = 0.85 and r = 0.87, respectively). Environmental correlations did not follow the pattern of genetic correlations (r = 0.11), but were more similar to phenotypic correlations (r = 0.60). Given the low genetic correlations and moderate heritabilities, the overall conclusion is that the external morphology of collared flycatchers is largely under additive genetic control and that there is a strong potential for evolutionary change in morphology even under complex multivariate selection.
Relationships of reproductive traits and body size with attainment of sexual maturity and age in Blanding's turtles (Emydoidea blandingi)
Authors: Congdon Justin D. , Van Loben Sels Richard C. 
Published: December 2004

AbstractTo place associations among body size, age at maturity, age, and reproductive traits of a long‐lived organism in the context of current life history models based on the concept of norms of reaction, we examined data from a mark‐recapture study of Blanding's turtles (Emydoidea blandingi) in southeastern Michigan during 24 of the years between 1953 and 1988. Females matured between 14 and 20 years of age. Both the smallest and largest adult females in the population were reproducing for the first time in their lives. This result suggests that a combination of differences in juvenile growth rates and ages at maturity, and not indeterminate growth, are the primary cause of variation in body size among adults. Body size variation among individuals was not related to age at sexual maturity. Females that had slower growth rates as juveniles matured later at similar mean body size compared to those with more rapid growth that matured at an earlier age. As a result, a linear model of age at sexual maturity with growth rates of primiparous females between hatching and maturity was significant and negative (R2 = 0.76). Frequency of reproduction of the largest and smallest females was not significantly different. Clutch size did not vary significantly with age among either primiparous or multiparous females. Clutch sizes of primiparous females and multiparous females were not significantly different. However, older females (>55 years minimum age) reproduced more frequently than did younger females (minimum age <36 y).
Genotypic variation for reproductive characters, and the influence of pollen‐ovule ratio on selfing rate in rape seed (Brassica napus)
Authors: Damgaard Christian , Loeschcke Volker 
Published: December 2004

AbstractThe variance component for genotypic effects and covariable plant vigor were estimated for pollen production, number of ovules, the weight of the flower without anther sacs and pistil, and the gender of the whole plant, in the rape seed variety Topas. There was a significant effect of the genotype for all measured characters. We did not find any trade‐off between the male and female functions. Small plants were relatively more male‐biased than large plants. The weight of the flower without anther sacs or pistil was positively correlated with pollen production. The selfing rates of the lines were positively correlated with the pollen‐ovule ratio, suggesting that the selfing rate of individual plants is positively correlated with pollen‐ovule ratio, thus supporting the “mass‐action” model. It is proposed that the observed increase in the population selfing rate during the flowering season for some species, including rape seed, can be caused by an overall decrease in male investment.
Reaction norms and the genetic basis of phenotypic plasticity in the wing pattern of the butterfly Bicyclus anynana
Authors: Windig J. J. 
Published: December 2004

AbstractThe genetic basis of the dry‐wet season polyphenism of wing pattern in response to temperature shown by Bicyclus anynana was studied, using a split‐family design over four temperatures. Reaction norms crossed, but were only linear in the three highest temperatures, and only when larval development time was used as the environmental axis. Significant full‐sib additive variances (VA) and heritabilities (h2) for plasticity were found using slopes of reaction norms in a bootstrap procedure. Heritabilities were lower in intermediate temperatures, mainly due to differences in the residual variances (VR). There was no clear trend in VA across temperatures, contrary to the expectation that VA would have been depleted by natural selection at the extreme temperatures and not depleted at the intermediate temperatures which occur less frequently in the field. Unpredictability in the onset of the following season at intermediate temperatures might lead to selection for diverse flresponses resulting in relatively high VRs. Theoretical models linking reaction norms to genetic parameters in separate environments were difficult to apply in this study, particularly because they are based on the assumption that VRs are constant. However the reaction norm approach combined with quantitative genetics provided a valuable insight into the evolution of the observed polyphenism.
Processes generating macroevolutionary patterns of morphological variation in birds: a simulation study
Authors: Björklund Mats 
Published: December 2004

AbstractMultivariate patterns of morphological variation in birds are analysed. In general, there are strong allometric patterns among characters such that most of the variation is confined to a major “size” axis. To analyse the possible evolutionary processes behind this pattern I employed a computer simulation of cladogenesis and anagenesis based on a genetic and a random walk model (drift). All runs started with one species and speciation occurred to generate 100 species. Three levels of correlations were allowed. The results from the simulations were compared with the pattern of variation in finches (Fringillidae).The simulations showed two things. First, the univariate drift model was inappropriate in terms of the level of variation; the observed level was lower than expected by drift. Univariate drift was also unable to create tight correlations among characters as observed in several taxa. Second, to create the pattern observed, either relatively strong genetic correlations (rg ≈ 0.5), or alternatively strong correlated selection, was needed. This suggests that morphological change in birds in general consists of changes in growth such that species become larger or smaller than their ancestors but retain their ancestral shape. The results stress the importance of stabilising selection in shaping the macroevolutionary patterns of morphological variation in birds.
Matching field and laboratory environments: effects of neglecting daily temperature variation on insect reaction norms
Authors: Brakefield Paul M. , Mazzotta Vincenzo 
Published: December 2004

AbstractThe tropical butterfly, Bicyclus anynana, exhibits seasonal polyphenism. The wet season form has large eyespots and a pale band while these characters are much less conspicuous or absent in the dry season form. This plasticity is induced in the laboratory by use of a standard series of constant temperatures in the larval stage yielding a continuous norm of reaction. Butterflies in this study were reared from hatchling larvae in seven regimes which differed with respect to thermoperiod or photoperiod. The effect of rearing treatment on the phenotypic plasticity of the adult wing pattern, on life history traits and on larval feeding rhythms was investigated. Photoperiod had little effect except that constant light produced a higher mortality and tended to produce a longer development time. Thermoperiod had a major effect on the life history traits in comparison to a constant temperature regime with the same daily mean: development time was shorter with higher growth rates. The faster development was associated with a substantial shift in the wing pattern towards the wet season form. Larvae feed mostly at night both under constant and thermoperiod (cool nights) conditions. The results are discussed with respect to the necessity of matching field and laboratory environments in studies of norms of reaction or of life history traits where the adaptive significance of the variation is important. Fluctuating conditions in nature, especially with respect to thermoperiod, must be taken into account.
Multiple morphs of sperm were required for the evolution of the Sex Ratio trait in Drosophila
Authors: Bircher U. , Jungen H. , Burch R. , Hauschteck‐Jungen E. 
Published: December 2004

AbstractIn Sex Ratio males of D. subobscura Y sperm degenerate. Nevertheless, Sex Ratio males can produce as many offspring as non‐Sex Ratio males. In order to find an explanation for the high number of offspring of Sex Ratio males we analysed spermatogenesis and sperm storage in females. Because D. subobscura has two morphs of sperm, short and long sperm, we studied the relationship of sperm heteromorphism to the Sex Ratio trait in this species.Spermatids of both lengths developed simultaneously in the testes. The first mature sperm produced by a young male were nearly all short sperm. This result indicates that short cysts need less time to mature than long cysts. Thus in a given time more short cysts than long cysts can mature. In the testes of Sex Ratio males more short cysts and fewer long cysts were formed than in the tests of non‐Sex Ratio males. Thus in a unit time Sex Ratio males can produce as many or more sperm than non‐Sex Ratio males.Females mated to Sex Ratio males had more sperm in their storage organs than those which were mated to non‐Sex Ratio males. From the transferred sperm females stored selectively more long than short sperm after mating to a Sex Ratio male than after mating to a non‐Sex Ratio male.The effect of the high amount of sperm in Sex Ratio males is twofold: the loss of Y sperm is compensated, and probably in nature a second copulation is prevented by the complete filling of the female storage organs.From these results we conclude that the development and persistence of the Sex Ratio trait in natural populations depends on the presence of sperm heteromorphism.
Ecological genetics of a cyclical parthenogen in temporary habitats
Authors: Gómez África , Temprano Miguel , Serra Manuel 
Published: December 2004

AbstractPopulations of the rotifer Brachionus plicatilis inhabiting three temporary ponds in Torreblanca Marsh (Castellón, Spain) were regularly screened for allozyme variation, sexual reproduction levels and population densities during an annual cycle. Relevant ecological parameters in the ponds were also recorded. The electrophoretic survey of the three ponds (Poza Sur, Poza Norte and Canal Central) revealed a high level of overall genetic polymorphism in four marker loci, but only 13 multilocus genotypes were found. We classified clones into three clonal groups (SS, SM, L) characterized by unique arrays of alleles in the four marker loci, and significant differences in body shape and size. Clonal group succession took place in Poza Sur; SM clones occurring in spring, SS clones from spring to fall, and L clones from fall to spring. Despite the partial overlapping of sexual periods, the absence of heterozygotes indicates that gene flow is strongly restricted between clonal groups. In the transition periods, the population was far from Hardy—Weinberg equilibrium due to hetereozygote deficiencies in all four markers. In clonal group L, the only polymorphic locus, Pgi, was in Hardy—Weinberg equilibrium. In clonal group SM, both polymorphic loci were in Hardy—Weinberg equilibrium in Poza Norte, but not in Poza Sur. Factor analysis on the limnological parameters recorded during field sampling indicates that genetically different clonal groups are also ecologically specialized. These findings suggest that the taxonomical species B. plicatilis is in fact a species complex. The complete genetic discontinuity model of rotifer population succession is supported by these data. Our results are similar to those found in cladocerans inhabiting temporary habitats.
Good genes and old age: Do old mates provide superior genes?
Authors: Hansen T. F. , Price D. K. 
Published: December 2004

AbstractIt has been suggested that female preference for older mates in species without parental care has evolved in response to an alleged higher genetic quality of older individuals. This is based on the widespread assumption that viability selection produces older individuals that are genetically superior to younger individuals. In contrast, we propose that the oldest individuals rarely are genetically superior. Quantitative genetic models of life history evolution indicate that young to intermediately aged individuals are likely to possess the highest breeding values of fitness. This conclusion is based on four arguments: 1) Viability selection on older individuals may decrease or at least not substantially increase breeding values of fitness, because there may exist negative genetic correlations between late‐age and early‐age life history parameters, 2) Fertility selection is likely to raise the fitness of gametes produced by young individuals more than those produced by old individuals, because the covariance between fertility and fitness often decreases with age, 3) The history of selection on their parents makes younger individuals more fit than older individuals, 4) Germ‐line mutations, which are generally deleterious, significantly decrease the breeding value of fitness of an individual throughout its lifespan, especially in males. Therefore, females that mate with the oldest males in a population are doing so for reasons other than to obtain offspring of high genetic quality.
Genetic evidence for natural hybridization and apparent introgression between freshwater snail species (Viviparus ater and V. contectus)
Authors: Katoh M. , Ribi G. 
Published: December 2004

AbstractWe examined six allozyme markers and shell morphology to study gene flow between the naturally sympatric freshwater snail species Viviparus ater and V. contectus in Lake Garda, Italy, using offspring from experimental crosses and snails collected from natural populations. Hybrid offspring obtained from experimental crosses and hybrids collected from natural populations were heterozygous at four or five out of five diagnostic loci. Shell morphology was a poor predictor of the hybrid status of individual snails. Backcrossed offspring from experimentally bred hybrids and either of the parental species morphologically resembled the parental species. There was no evidence of segregation distortion at the six loci. Linkage analysis revealed one pair of linked loci (GPI and PNP). These cross experiments indicated a Mendelian type hybrid system in which gene introgression may occur. F1 hybrids were found at four out of six sampling sites of Lake Garda, Italy. Local frequencies of F1 hybrids ranged from 0% to 1.6% (estimated average = 0.74%) of the total population including both species. Alleles typical of V. ater were found at low frequencies in V. contectus at all six sampling sites. Alleles typical of V. contectus were found at low frequencies in V. ater at three out of six sampling sites. This is consistent with the hypothesis of introgression in both directions.
A hybrid zone between two subspecies of Chorthippus parallelus. X‐chromosome variation through a contact zone
Authors: Serrano L. , García de la Vega C. , Bella J. L. , López‐Fernández C. , Hewitt G. M. , Gosálvez J. 
Published: December 2004

SummaryTwo grasshopper subspecies, Chorthippus parallelus parallelus (Cpp) and Chorthippus parallelus erythropus (Cpe), meet along the Pyrenees where they hybridize and produce a hybrid zone. A contact zone located in the Col de Portalet has been analyzed for the distribution of chromosome markers on the sex (X) chromosome in pure and hybrid populations. C‐banding allowed us to distinguish both pure subspecific forms and recombinant forms, and to demonstrate their different frequencies through the contact zone. Interestingly, the distal C‐band (P) on the X chromosome that characterizes Cpp individuals occurs at very high frequency through the zone and then drops sharply, close to where pure Cpe populations are found. A novel interstitial C‐band (H) has been found, probably derived from that characterizing Cpe individuals (E). This marker band is only present in hybrid populations. These data are discussed in the light of the dynamics of the hybrid zone.
Causes of covariation of phenotypic traits among populations
Authors: Armbruster W. S. , Schwaegerle K. E. 
Published: December 2004

AbstractMorphological and life‐history traits often vary among populations of a species. Traits generally do not vary independently, but show patterns of covariation that can arise from genetic and environmental influences on phenotype. Covariance of traits may arise at an among‐population level when genetically influenced traits diverge among populations in a correlated manner. Genetic correlations caused by pleiotropy and/or gene linkage can cause traits to evolve together, but among‐population covariance can also arise among traits that are not genetically correlated. For example, “selective covariance” can arise when natural selection directly causes correlated change in a suite of traits. Similarly, mutation, migration, and drift may also sometimes cause correlated genetic changes among populations. Because covariation of traits among populations can arise by several different processes, the evolution of suites of traits must be interpreted with great caution. We discuss the sources of among‐population covariance and illustrate one approach to identifying the sources' using data on floral traits of Dalechampia scandens (Euphorbiaceae).
Polymorphism of the Drosophila melanogaster — sigma virus system
Authors: Fleuriet A. 
Published: December 2004

AbstractIn natural populations of D. melanogaster, a minority of flies are usually infected by the sigma Rhabdovirus, which is not contagious but vertically transmitted. A few parameters have been identified that affect the evolution of the Drosophila — sigma system. Various sets of values of these parameters in males mutually adapted to one another have been established in different populations. This study analyses female characteristics that were previously reputed not to vary much between populations. The newly collected data show that these characteristics (mainly transovarial transmission here) may also be polymorphic in the wild, and may contribute to the diversity of equilibria established between the virus and its host. The observations presented here, obtained from various populations, confirm the complexity of this system of two coevolving organisms: as already noted there seem to be as many different sets of values of parameters as there are populations.