bluuebunny/crossref_metadata_2025_split huggingface dataset:
Population genetic structure of the gynodioecious Thymus vulgaris L. (Labiatae) in southern France
Authors: Tarayre M. , Thompson J. D. 
Published: December 2004

AbstractIn a self‐compatible gynodioecious species, the abundance of female plants (which are obligate outcrossers) relative to hermaphrodites (which may self and outcross) may be a critical factor influencing genetic diversity and population structure. In the gynodioecious Thymus vulgaris L., female frequency varies from 5 to 95%, providing a suitable model to examine this issue. In this study, we use allozyme markers to (1) evaluate the relationship between female frequency, genetic diversity and population structure, (2) determine whether females and hermaphrodites vary in heterozygote deficiency and (3) examine whether other factors such as plant density are related to heterozygote deficiency. Twenty three natural populations, with female frequencies ranging from 11 to 92%, were sampled in and around the St‐Martin‐de‐Londres basin in southern France. Based on four polymorphic allozyme loci, we found no significant correlation between female frequency and heterozygote deficiency. A significant (P < 0.05) FIS value over loci and over populations of 0.11 was detected. The FIS value per population showed a significant heterozygote deficiency in 11 of the 23 populations. However, no significant difference between female and hermaphrodite FIS values was found. A significant heterozygote deficiency only occurred in populations of intermediate density. There was little differentiation among populations (FST = 0.038) nor among subpopulations within each population. The significant FIS values are thus mostly due to inbreeding effects. The lack of a correlation between FIS values and female frequency may be due to outcrossing in hermaphrodites and/or restoration of male fertility which may occur to a greater extent at low female frequency. The similarity of female and hermaphrodite FIS values indicates that females may occasion high levels of biparental inbreeding.
Phylogenetic relationships in Monanthes (Crassulaceae) based on morphological, chloroplast and nuclear DNA variation
Authors: Mes T. H. M. , Wijers G.‐J. , Hart H. 't 
Published: December 2004

AbstractPhylogenetic relationships of all 10 recognized taxa of the genus Monanthes which is endemic to the Canary Islands and Salvage Islands, were investigated using the four data sets: morphology, sequences of the chloroplast DNA trnL (UAA) — trnF (GAA) intergenic spacer, ITS2 sequences of the nuclear ribosomal region and Random Amplified Polymorphic DNAs (RAPDs). In contrast to the molecular data, the morphological data were internally inconsistent which probably resulted from parallel or convergent evolution of morphological characters. The molecular data sets indicated that the genus is not monophyletic due to inclusion of the annual M. icterica which is the putative sister taxon of Aichryson, that M. polyphylla is the sister taxon of the perennial species of the genus, that M. muralis from Hierro is of allotetraploid origin and that M. lowei, M. minima, M. brachycaulos, M. laxiflora, M. anagensis and M. muralis from La Palma are closely related. Combined ITS2 sequences, trnL — trnF sequences and morphological data indicated that the relationships among three types of perennial growth forms, i.e. tiny rosettes, small, branched shrubs and diffuse branches shrublets, are highly dependent on the outgroup used. After deletion of the most distant outgroup and a taxon of alleged hybrid origin (M. muralis) relationships among the growth forms of Monanthes still could not be consistently resolved.
The ratio of replacement to silent divergence and tests of neutrality
Authors: Nielsen R. 
Published: December 2004

AbstractComparisons of replacement to silent divergence have been used in a variety of studies aimed at detecting selection. Here, such comparisons are shown to be very sensitive to the pattern of rate variation in replacement sites. Saturation may play an important role even at surprisingly low levels of divergence if the substitution rate varies across replacement sites. For example, saturation in replacement sites may be of importance in the evolution of the HIV‐1 envelope gene. However, the pattern of saturation in replacement and silent sites may, in itself, provide valuable insight into the causes of DNA evolution. 210 DNA sequences from 15 different loci/systematic groups are analyzed, and evidence for positive selection is demonstrated in at least one of these data sets, through an analysis of the distribution of substitution rates along the sequence.
The basic body plan of arthropods: insights from evolutionary morphology and developmental biology
Authors: Zrzavý J. , Štys P. 
Published: December 2004

AbstractPhylogenetic, morphological, and developmental data concerning the Arthropoda are reviewed and discussed with the aim of reconstructing the ancestral body plan of the mandibulate arthropods (Myriapoda, Hexapoda, Crustacea). Comparative morphology as well as embryology of malacostracans and hexapods (cell‐lineages, patterns of mitotic domains, patterns of en‐stripe formation, expression zones of pair‐rule, homeotic, and gap‐like genes) suggest that (a) the basic boundary subdividing the mandibulate body into the primary embryonic regions, anterior protocephalon and posterior protocorm, runs anteriorly to parasegment PS1 (=within the mandibular segment); (b) protocephalon (pregnathal region) probably is not a unitary body region; (c) maxillary segments are closely related to the postgnathal trunk segments; (d) the “typical” mandibulate head (pregnathal‐mandibular‐maxillary) is not developed in all Mandibulata and has evolved several times in parallel; and (e) postcephalic tagmosis is much less conserved, and probably more recent, than tagmosis of more anterior areas. The arachnomorphan anterior tagma, the prosoma, is compared with the hypothesized ancestral mandibulate head.
The effect of life cycle stage and genotype on desiccation tolerance in the colonizing parthenogenetic cockroach Pycnoscelus surinamensis and its sexual ancestor P. indicus
Authors: Gade B. , Parker E. D. 
Published: December 2004

AbstractWe compared the desiccation tolerance of nymphs of diploid and triploid clones of the colonizing parthenogenetic cockroach, Pycnoscelus surinamensis, and strains of its sexual ancestor, P. indicus, as a test of the general‐purpose genotype hypothesis and the polyploidy hypothesis for geographic parthenogenesis in this species complex. Desiccation tolerance is strongly associated with nymphal size. Clones of P. surinamensis are highly variable in nymphal desiccation tolerance, adjusted for body weight by analysis of covariance. This heterogeneity is mirrored by significant differences among recently isolated sublines of a lab population of P. indicus. As a group, the clones are not more tolerant than the sexual strains. Likewise, the four triploid clones were not more resistant to desiccation than the four diploid clones tested. A second experiment revealed a negative association between adult and last instar desiccation tolerance, due to developmental factors not associated with size. These patterns of variation in the sexual and parthenogenetic forms are consistent with the conclusion that extensive genetic variation in desiccation tolerance in the sexual ancestor has been preserved in the clonal lineages, but that desiccation tolerance has not been selected on strongly during the dispersal of clones of P. surinamensis.
Coevolution of traits determining migratory tendency: correlated response of a critical enzyme, juvenile hormone esterase, to selection on wing morphology
Authors: Fairbairn D. J. , Yadlowski D. E. 
Published: December 2004

AbstractMigratory tendency in insects is a complex trait, composed of a suite of correlated behavioural, physiological, morphological and life history traits. We investigate the genetic and physiological basis of the coevolution of this suite of traits using laboratory lines of the wing dimorphic cricket, Gryllus firmus, selected for increasing and decreasing incidence of macroptery. Selection on wing morphology has produced strong direct responses in proportion macropterous as well as correlated (indirect) responses in wing muscle histolysis, flight propensity and fecundity. We investigate the hypothesis that these responses have been mediated by changes in the metabolism of juvenile hormone (JH) during the final nymphal stadium (the critical period for wing morph determination). Previous studies of Gryllus sp. have established that JH titre in this period is determined primarily by the activity of the degradative enzyme, juvenile hormone esterase (JHE). Assays of JHE activity in the final nymphal stadium of the replicated control and selected lines demonstrate highly significant differences in both mean activity and the probability of macroptery for a given level of activity (i.e., the threshold activity required to induce wing formation). These correlated responses in JH metabolism support the general hypothesis that the correlations among traits determining migratory tendency result at least in part from the common influence of JH during the final nymphal stadium. We discuss these results in the context of the quantitative genetic model for the evolution of polygenic, dichotomous traits (the threshold model), and present four general predictions concerning the coevolution of traits associated with ecological (i.e., trophic, life history, behavioural) dimorphisms.
Testing multivariate patterns of within‐island differentiation in Podarcis dugesii from Madeira
Authors: Báez M. , Brown R. P. 
Published: December 2004

Abstract Podarcis dugesii is a polymorphic species found on the ecologically‐heterogeneous Atlantic island of Madeira. Patterns of geographic variation in size‐free body dimensions (body shape), scalation, and size were portrayed on maps with isophene contours. There was no dominant pattern of among‐site variation as seen in several other island lizards, although some linear combinations of morphological variables showed evidence of clines towards the east coast. Multivariate statistical techniques were developed to evaluate whether morphological variation contained an ecology‐related spatial pattern, after removal of the effects of statistical non‐independence of studied populations. Specifically, a partial correlation matrix comparison method provided evidence to support a proposed elevation model of among‐site divergence in scalation and body size, with both an alternative rainfall model and spatial non‐independence held constant. Similar divergence in scalation has been observed in other lizard species on other island archipelagos as well on some continental areas. The rainfall model was rejected for both body shape and scalation. The degree of within‐population polymorphism in body shape and scalation showed no clear geographic trends in general, although the elevation and rainfall models could not be rejected for female scalation.
Genetics of sex allocation in Mimulus (Scrophulariaceae)
Authors: Fenster C. B. , Carr D. E. 
Published: December 2004

AbstractTheoretical models of the evolution of resource allocation patterns to male and female function make the assumption that there are inherent trade‐offs between the two. Here we use a quantitative genetic approach to quantify trade‐offs between male and female function and to determine whether plant populations could readily respond to natural selection by quantifying the amount of genetic variation for pollen and ovule production. Both intra‐ and interspecific crossing designs were applied to two populations of the predominantly outcrossing Mimulus guttatus and two populations of the highly selfing congener, M. micranthus.The only significant correlations observed among pollen number, pollen size and ovule number were positive. Positive genetic correlations among the traits were sometimes reduced after removing the effect of flower size but still no significant negative correlations were detected. These results suggest that positive correlations between pollen and ovule production may be due to the joint positive correlation of these characters with the resource pool available for pollen and ovule production, as reflected by flower size. Heritabilities were moderate to high for ovule production but low for pollen number and pollen size and suggest that responses to selection would differ between the two traits. Crosses between the species revealed that there are additional genetic factors contributing to differences between the two species for corolla width, vs. pollen:ovule ratio. This is consistent with the hypothesis that genetic variation for resource acquisition may in part be responsible for the overall lack of a negative correlation between pollen and ovule production and provides a genetic explanation for little evidence of trade‐offs between sexual functions in Mimulus.
Comparative evidence for a positive correlation between haematozoan prevalence and mortality in waterfowl
Authors: Sorci G. , Møller A. P. 
Published: December 2004

AbstractHamilton and Zuk (1982) suggested a new hypothesis to explain the evolution of secondary sexual characters, namely that male ornaments may represent honest signals of male capacity to resist parasites. Since then several authors have addressed the question of the role played by parasites in the evolution of host secondary sexual characters. Comparative analyses of Hamilton and Zuk's hypothesis have, however, failed to show the predicted positive association between parasitism levels and sexually‐selected traits. One possible explanation for this discrepancy involves a low pathogenicity of the parasites used to test the hypothesis. Here we show that haemosporidians are positively correlated with mortality rates in a sample of waterfowl, and that the correlation between the two variables is of similar magnitude in both males and females. Contrary to the expectations based on the Hamilton and Zuk's hypothesis, we did not find any correlation between plumage brightness and haemosporidian prevalence. These results indicate that haemosporidians may have a pathogenic effect on their avian hosts and that plumage brightness is likely to have evolved in response to ecological factors other than parasitism infections.
Life history evolution in Asobara tabida: plasticity in allocation of fat reserves to survival and reproduction
Authors: Ellers J. , Van Alphen J. J. M. 
Published: December 2004

AbstractLife history variation can be genetically based, or it may be due to environmental effects on the phenotype. In this paper we examine life history variation in relation to differences in habitat in the parasitoid Asobara tabida. Differences in the spatial distribution of host patches, the length of the season, host suitability, and competition between parasitoids all contribute to the selection for differences in life history between strains from northern and southern Europe.Strains were compared with respect to the allocation between reproduction and survival in experimental environments that varied with regard to the availability of food or to the number of hosts offered per day. Upon emergence parasitoids originating from southern Europe have higher egg loads and smaller fat reserves than parasitoids originating from northern Europe. Parasitoids from both southern and northern Europe show plasticity in allocation: food shortage causes a decrease in egg production, and rich breeding opportunities an increase in egg production. This plasticity is greater in the northern strain. Fat reserves play a central role in the physiology of this allocation. Fat can be used for both reproduction and survival. There is no oosorption, so once fat is allocated to reproduction it can no longer be used for survival. Differences in plasticity in allocation can therefore be considered as differences in the timing of egg production.
The relationship between eyespot shape and wing shape in the butterfly Bicyclus anynana: A genetic and morphometrical approach
Authors: Monteiro A. , Brakefield P. M. , French V. 
Published: December 2004

AbstractThe African butterfly, Bicyclus anynana, normally possesses circular eyespots on its wings. Artificial selection lines, which express ellipsoidal eyespots on the dorsal surface of the forewing, were used to investigate correlated changes in wing shape. Morphometric analysis of linear wing measurements and wing scale counts provided evidence that eyespot shape was correlated with localised shape changes in the corresponding wing‐cell, with overall shape changes in the wing, and with the density/arrangement of scales around the eyespot area.
Evolutionary aspects of migratory behavior in European warblers
Authors: Berthold Peter 
Published: December 2004

AbstractDuring the past 20 years, European Sylvia warblers have been used for a model study of the control mechanisms of bird migration and of evolutionary aspects of migratory behavior. Endogenous annual rhythms (‘circannual’ rhythms) and photo‐period have proved to be the essential internal and external controlling factors. It is unknown whether this basic system, that also controls migration in other bird species, is currently evolutionarily stable or is instead adapting birds to the present slightly changing environmental conditions. Using the Blackcap, the control of partial migration in a bird species was analyzed. Two‐way selective breeding experiments demonstrated a large selection response and high heritability values. These experiments have also indicated that a partially migratory population can become either almost completely migratory, or sedentary, in two to five generations. Hence, genetic influences are very important and presumably dominant over environmental factors in the expression of migratory or sedentary behavior. The large selection response implies a strikingly high evolutionary potential with respect to strong selection pressures. Further, in the Blackcap, migratory orientation behavior (in addition to migratory activity) was immediately transmitted into a F1‐generation when a cross‐breeding experiment was performed using birds from a migratory and a resident population. The hybrids displayed their migratory activity along an axis that is used by their migratory parents. Finally, a rapidly developing novel migratory habit (new migratory direction to new wintering areas) in the Blackcap is discussed with respect to a positive feedback‐mechanism, possibly including a series of advantages leading to above‐average fitness.
Life history plasticity in the satyrine butterfly Lasiommata petropolitana: investigating an adaptive reaction norm
Authors: Gotthard K. 
Published: December 2004

AbstractThis study addresses the general hypothesis that insects living in seasonal environments should shorten development times at progressively later dates in the growth season, and that insects living outside equatorial areas should use daylength as a cue to determine the date. Diapause strategies and reaction norms relating the duration of larval development to daylength was investigated in a French population of the butterfly, Lasiommata petropolitana. The results are compared with those of an earlier study of the species in Sweden. Because of the diapausing strategy and phenology of the population, it was expected that an adaptive reaction norm relating larval time to daylength should have a positive slope, i.e. relatively shorter daylengths induce faster growth and development. This prediction was supported, and the reaction norm was qualitatively similar to the one found in Swedish populations. In the French population it was, however, shifted to a range of shorter photoperiods which corresponds to the regime of shorter daylengths in southern Europe. Shorter larval development times and high growth rates were associated with a reduction in pupal size, suggesting a trade off between time and size at pupation. There was no evidence of a trade off between growth rate and starvation endurance. The results suggests that the daylength‐dependent decision of what growth trajectory an individual larva will follow, is not made continuously but rather at one or a few occasions during larval development.It is clear that larvae of L. petropolitana make developmental decisions in relation to the daylength they experience during larval growth. The result is a reaction norm that agrees closely to what is predicted by some life history models, suggesting that it is an adaptation for optimising life history traits in a seasonal environment.
Genetic population structure of two cryptic Gammarus fossarum types across a contact zone
Authors: Müller J. 
Published: December 2004

AbstractPrevious studies have revealed inconsistent results about the taxonomic status of European Gammarus fossarum forms. The variability in morphology and hybridization ability has not shown clear geographic patterns, whereas on a genetical basis two Central European G. fossarum forms have been proposed.In the present study the genetic structure of G. fossarum populations was investigated across a natural contact zone. For the first time direct comparisons of allotopic versus syntopic populations were feasible. 24 Populations of G. fossarum plus 4 populations of G. pulex (as outgroup) were sampled along 2 transects across the contact zone. The genotypes of about 60 individuals per population were revealed by allozyme electrophoresis at 6 polymorphic loci.Parallel step ‘clines’ in allele frequencies indicate secondary contact of the two G. fossarum forms. The level of genetic variation between the forms was comparable to an interspecific level (G. pulex versus G. fossarum). The pronounced genetic bipartition in syntopic G. fossarum populations and the lack of potential F1‐hybrids further corroborated the taxonomic status of the G. fossarum types. The geographic patterns of the genetic differentiation between and within the G. fossarum types, the allelic diversities and the genotypic disequilibria revealed recent introgression at the analysed loci to be insignificant. In addition it is shown that the population structure of the western G. fossarum type is out of equilibrium, which suggest a recent colonization of this type probably by displacement of the other type.