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The paper is aimed at the problem of restoring values of a function and its derivatives at intermediate points on the basis of given tabulated values. A special feature of the problem is that at a certain point, the tabulated values cease to be reliable and the process becomes stochastic. [ABSTRACT FROM AUTHOR]

The paper is aimed at the problem of restoring values of a function and its derivatives at intermediate points on the basis of given tabulated values. A special feature of the problem is that at a certain point, the tabulated values cease to be reliable and the process becomes stochastic. [ABSTRACT FROM AUTHOR]

Insight into the speed and predictability of local adaptation can be gained by studying organisms, such as invasive species, that have recently expanded their geographical ranges. Common garden studies were designed to address these issues with the California poppy, Eschscholzia californica, collected from a wide range of environments in both its native (California) and invasive (Chile) ranges. We found similar patterns of plant trait variation along similar abiotic gradients in plants collected from both areas. Multivariate analysis demonstrated that coastal plants from both areas tended to be shorter, smaller plants with smaller seeds and flowers that germinate and flower later than plants collected from inland locations. In addition, size and fecundity traits in both native and invasive poppies were correlated with average rainfall totals; the plants that grew the largest and were the most fecund during the first year of growth originated from the driest areas. This parallel variation suggests that these traits are adaptive and that these patterns have evolved in Chile during the 110–150 years since introduction. [ABSTRACT FROM AUTHOR]

A primary goal of molecular ecology is to understand the influence of abiotic factors on the spatial distribution of genetic variation. Features including altitudinal clines, topography and landscape characteristics affect the proportion of suitable habitat, influence dispersal patterns, and ultimately structure genetic differentiation among populations. We studied the effects of altitude and topography on genetic variation of long-toed salamanders ( Ambystoma macrodactylum), a geographically widespread amphibian species throughout northwestern North America. We focused on 10 low altitude sites (<1200m) and 11 high-altitude sites in northwestern Montana and determined multilocus genotypes for 549 individuals using seven microsatellite loci. We tested four hypotheses: (1) gene flow is limited between high- and low-altitude sites; and, (2) gene flow is limited among high-altitude sites due to harsh habitat and extreme topographical relief between sites; (3) low-altitude sites exhibit higher among-site gene flow due to frequent flooding events and low altitudinal relief; and (4) there is a negative correlation between altitude and genetic variation. Overall FST values were moderate (0.08611; P<0.001). Pairwise FST estimates between high and low populations and a population graphing method supported the hypothesis that low-altitude and high-altitude sites, taken together, are genetically differentiated from each other. Also as predicted, gene flow is more prominent among low-altitude sites than high-altitude sites; low-altitude sites had a significantly lower FST (0.03995; P<0.001) than high altitude sites ( FST = 0.10271; P<0.001). Use of Bayesian analysis of population structure (BAPS) resulted in delineation of 10 genetic groups, two among low-altitude populations and eight among high-altitude populations. In addition, within high altitude populations, basin-level genetic structuring was apparent. A nonequilibrium algorithm for detecting current migration rates supported these population distinctions. Finally, we also found a significant negative correlation between genetic diversity and altitude. These results are consistent with the hypothesis that topography and altitudinal gradients shape the spatial distribution of genetic variation in a species with a broad geographical range and diverse life history. Our study sheds light on which key factors limit dispersal and ultimately species’ distributions. [ABSTRACT FROM AUTHOR]

In this paper, we present results of the first comprehensive study of the introgression of both autosomal and sex-chromosome markers across the central European portion of the hybrid zone between two house mouse subspecies, Mus musculus musculus and M. m. domesticus. More than 1800 individuals sampled from 105 sites were analyzed with a set of allozyme loci (hopefully representing neutral or nearly neutral markers) and X-linked loci (which are assumed to be under selection). The zone center is best modeled as a single straight line independent of fine-scale local geographic or climatic conditions, being maintained by a balance between dispersal and selection against hybrids. The width (ω) of the multilocus autosomal cline was estimated as 9.6 km whereas the estimate for the compound X-chromosome cline was about 4.6 km only. As the former estimate is comparable to that of the Danish portion of the zone (assumed to be much younger than the central European one), zone width does not appear to be related to its age. The strength (B) of the central barrier was estimated as about 20 km; with dispersal (σ) of about 1 km/gen1/2, this means effective selection (s*) is approximately 0.06-0.09 for autosomal loci and about 0.25 for X-linked loci. The number of loci under selection was estimated as N = 56-99 for autosomes and about 380 for X-linked loci. Finally, we highlight some potential pitfalls in hybrid zone analyses and in comparisons of different transects. We suggest that conclusions about parts of the mouse genome involved in reproductive isolation and speciation should be drawn with caution and that analytical approaches always providing some estimates should not be used without due care regarding the support or confidence of such estimates, especially if conclusions are based on the difference between these estimates. Finally, we recommend that analysis in two-dimensional space, dense sampling, and rigorous treatment of data, including inspection of likelihood profiles, are essential for hybrid zone studies. [ABSTRACT FROM AUTHOR]

We obtained eight collections of DNA samples from ethnically matched systemic lupus erythematosus (SLE) patients and controls from five European countries totaling 783 patients and 1210 controls. A highly significant cline in the frequency of the PD1.3 A allele was found among controls but not among SLE patients. The frequency of the PD1.3 A allele increased from the Northeast to the Southwest of Europe. The cline was clearly apparent (P=1.2 × 10−6) when data from controls of other five SLE susceptibility studies were included in the analysis. This variation has severely biased SLE association studies owing to the lack of parallel changes in SLE patients. As a consequence, the PD1.3 A allele was more common in SLE patients than in controls in the Northeast and Center of Europe, similar to controls in Southeast Europe, and less frequent than in the controls in the Southwest of the Continent. This dissociation in allele frequencies between SLE patients and controls in different subpopulations indicated that programmed cell death 1 variation and disease susceptibility are not independent but the type of relationship is currently unclear. As allele frequency clines are common in other polymorphisms their impact in genetic epidemiology studies should be carefully considered.Genes and Immunity (2007) 8, 138–146. doi:10.1038/sj.gene.6364370; published online 18 January 2007 [ABSTRACT FROM AUTHOR]

Comma butterflies (Nymphalidae: Polygonia c-album L.) from one Belgian site and three Spanish sites were crossed with butterflies from a Swedish population in order to investigate inheritance of female host plant choice, egg mass and larval growth rate. We found three different modes of inheritance for the three investigated traits. In line with earlier results from crosses between Swedish and English populations, the results regarding female oviposition preference (choice between Urtica dioica and Salix caprea) showed X-linked inheritance to be of importance for the variation between Sweden and the other sites. Egg mass and growth rate did not show any sex-linked inheritance. Egg mass differences between populations seem to be controlled mainly by additive autosomal genes, as hybrids showed intermediate values. The growth rates of both hybrid types following reciprocal crossings were similar to each other but consistently higher than for the two source populations, suggesting a nonadditive mode of inheritance which is not sex-linked. The different modes of inheritance for host plant preference vs. important life history traits are likely to result in hybrids with unfit combinations of traits. This type of potential reproductive barrier based on multiple ecologically important traits deserves more attention, as it should be a common situation for instance in the early stages of population divergence in host plant usage, facilitating ecological speciation. [ABSTRACT FROM AUTHOR]

Three major mitochondrial DNA (mtDNA) haplogroups were identified in 5 data sets for North Pacific and Bering Sea walleye pollock. The common haplogroup A showed mirror-image clines on both sides of the North Pacific with high frequencies in southern areas (PA > 0.84) and low frequencies in the Bering Sea (PA < 0.36). Two additional haplogroups showed complimentary, but weaker, clines in the opposite direction. These clines are unlikely to have arisen by chance during postglacial colonizations of coastal waters in the North Pacific and Bering Sea, and they do not appear to reflect isolation by distance. Contrary to these trends, pollock at the western end of the Aleutian Island Archipelago were genetically more similar to Asian than to North American pollock, a pattern likely reflecting postglacial colonization. Haplogroup FST values for a given haplotype diversity were significantly larger than expected under the island model of migration and random drift, a result implicating natural selection. Frequencies of haplogroup A were highly correlated with sea surface temperature (r > 0.91), whereas frequencies of groups B and C showed negative correlations with temperature. Selection may be operating directly on mtDNA variability or may be mediated through cytonuclear interactions. This biogeographic evidence adds to a growing body of literature indicating that selection may play a greater role in sculpting mtDNA variability than previously thought. [ABSTRACT FROM AUTHOR]

Chromosomal rearrangements have been considered as important barriers to gene flow and were often used in the delineation of species. The original taxonomic designation of Drosophila americana americana and Drosophila americana texana is based on the presence/absence of a centric fusion between the X- and fourth chromosomes. D. a. americana presents the derived fused state, whereas Drosophila a. texana presents the freely segregating ancestral state. The degree of genetic separation between the two chromosomal forms is still controversial, with different genetic markers yielding contrasting results even when the same populations were analyzed. Using 27 polymorphic microsatellites, we re-evaluated patterns of genetic differentiation between six D. americana populations sampled through a transition zone of both chromosomal forms in the central United States. Our results clearly reject a scenario of two differentiated species forming a hybrid zone in a region of parapatry and indicate that gene flow minimizes genome-wide differentiation associated with the two chromosomal arrangements.Heredity (2006) 97, 291–295. doi:10.1038/sj.hdy.6800860; published online 5 July 2006 [ABSTRACT FROM AUTHOR]

Bergmann's and Rensch's rules describe common large-scale patterns of body size variation, but their underlying causes remain elusive. Bergmann's rule states that organisms are larger at higher latitudes (or in colder climates). Rensch's rule states that male body size varies (or evolutionarily diverges) more than female body size among species, resulting in slopes greater than one when male size is regressed on female size. We use published studies of sex-specific latitudinal body size clines in vertebrates and invertebrates to investigate patterns equivalent to Rensch's rule among populations within species and to evaluate their possible relation to Bergmann's rule. Consistent with previous studies, we found a continuum of Bergmann (larger at higher latitudes: 58 species) and converse Bergmann body size clines (larger at lower latitudes: 40 species). Ignoring latitude, male size was more variable than female size in only 55 of 98 species, suggesting that intraspecific variation in sexual size dimorphism does not generally conform to Rensch's rule. in contrast, in a significant majority of species (66 of 98) male latitudinal body size clines were steeper than those of females. This pattern is consistent with a latitudinal version of Rensch's rule, and suggests that some factor that varies systematically with latitude is responsible for producing Rensch's rule among populations within species. Identifying the underlying mechanisms will require studies quantifying latitudinal variation in sexspecific natural and sexual selection on body size. [ABSTRACT FROM AUTHOR]

We are currently experiencing a resurgence of interest in ecogeographical rules, which describe general trends in morphology and related traits along geographical gradients. In order to develop a more comprehensive understanding of the generality and underlying causal mechanisms for these patterns, we recommend a new, more integrated research agenda. In particular, we recommend studies that simultaneously consider different clines in morphology, geographical ranges and diversity as intricately related phenomena; all being ecological, evolutionary and biogeographical responses of organisms to selection regimes that vary non-randomly over space and time, and among species with different ecological and evolutionary histories. [ABSTRACT FROM AUTHOR]

Geophilomorph centipedes have numerous leg-bearing segments, always an odd number. Previous research has shown the significant role of latitudinal clines and temperature on intraspecific variation, supporting the view that species of geophilomorphs from cold and temperate regions tend to have fewer segments than those from warmer regions. Here, data are presented on segment numbers of Pachymerium ferrugineum (C. L. Koch, 1835) from the south Aegean Archipelago. Within the framework of a study of the centipede fauna of the south Aegean Islands, three adjacent geographical areas with discrete geological histories were studied (Crete, Cyclades, and Dodecanese). There is no evidence to indicate that a latitudinal trend is present across these three main geographical regions. Apart from Crete, there is no demonstration of a cline along the longitudinal axis of the Aegean. However, the insular characteristics of the central and south-east Cyclades could possibly support higher modal segment numbers. In addition, examination of males and females of P. ferrugineum confirmed the existence of latitudinal clines in certain cases among the islands of Crete, Cyclades, and Dodecanese. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88, 533–539. [ABSTRACT FROM AUTHOR]

Drosophila melanogaster has colonized temperate habitats on multiple continents over a historical time period, and many traits vary predictably with latitude. Despite considerable attention paid to clinal variation in Drosophila, the mechanisms generating such patterns in nature remain largely unidentified. In D. melanogaster, the expression of reproductive diapause can be induced by exposure to low temperatures and shortened photoperiods. Both diapause expression itself and the underlying genetic variance for diapause expression have widespread impacts on organismal fitness, and diapause incidence exhibits a 60% cline in frequency in the eastern United States. The major aim of this study was to evaluate whether the relative fitness of diapause and nondiapause genotypes varies predictably with environment. In experimental population cages in the laboratory, the frequency of genotypes that express diapause increased over time when flies were exposed to environmental stress, whereas the frequency of nondiapause genotypes increased when flies were cultured under benign control conditions. Other fitness traits correlated with the genetic variance for diapause expression (longevity, mortality rates, stress resistance, lipid content. preadult viability, fecundity profiles, and development time) also diverged between experimental treatments. Similarly. sampling of isofemale lines from natural populations revealed that the frequency of diapause incidence cycled over time in seasonal habitats: diapause expression was at high frequency following the winter season and subsequently declined throughout the summer months. In contrast, diapause expression was low and temporally homogeneous in isofemale line collections from human-associated urban habitats. These data suggest that genetic variation underlying the diapause-nondiapause dichotomy may be actively maintained by selection pressures that vary spatially and temporally in natural populations. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented about single locus clines as a result of spatially restricted gene flow.

Flowering time differences between metal-tolerant and nontolerant populations of the grass Anthoxanthum odoratum growing across a mine boundary have persisted for over 40 years. These flowering time differences result in a high degree of prezygotic genetic isolation (isolation index=0.43) between the tolerant mine populations and nontolerant pasture populations. Previous work showing genetic determination of flowering time and a high turnover of individual plants argues strongly for the selective maintenance of this difference.Heredity (2006) 97, 33–37. doi:10.1038/sj.hdy.6800835; published online 26 April 2006 [ABSTRACT FROM AUTHOR]

Abstract: The semilinear parabolic system that describes the evolution of the gene frequencies in the diffusion approximation for migration and selection at a multiallelic locus without dominance is investigated. The population occupies a finite habitat of arbitrary dimensionality and shape (i.e., a bounded, open domain in ). The selection coefficients depend on position; the drift and diffusion coefficients may depend on position. The primary focus of this paper is the dependence of the evolution of the gene frequencies on λ, the strength of selection relative to that of migration. It is proved that if migration is sufficiently strong (i.e., λ is sufficiently small) and the migration operator is in divergence form, then the allele with the greatest spatially averaged selection coefficient is ultimately fixed. The stability of each vertex (i.e., an equilibrium with exactly one allele present) is completely specified. The stability of each edge equilibrium (i.e., one with exactly two alleles present) is fully described when either (i) migration is sufficiently weak (i.e., λ is sufficiently large) or (ii) the equilibrium has just appeared as λ increases. The existence of unexpected, complex phenomena is established: even if there are only three alleles and migration is homogeneous and isotropic (corresponding to the Laplacian), (i) as λ increases, arbitrarily many changes of stability of the edge equilibria and corresponding appearance of an internal equilibrium can occur and (ii) the conditions for protection or loss of an allele can both depend nonmonotonically on λ. Neither of these phenomena can occur in the diallelic case. [Copyright &y& Elsevier]

Within‐species variation in body size of males and females of an ant‐eating spider Zodarion rubidum was studied by analysing 15 populations across Europe. The relationship between the body size of both sexes was allometric with female‐biased sexual size dimorphism. Body size of males did not change with latitude or temperature, while that of females changed significantly with temperature. Larger females were found in regions with higher temperature which is presumably a result of an optimal climate: higher temperature and longer season provide higher prey availability which accelerates the growth rate of females, leading to a larger body size. As female size varied more than male size, a sexual size dimorphism cline was observed in Z. rubidum. Larger sexual size dimorphism was found in warmer regions. These results thus suggest that environmental conditions (temperature) influence intraspecific variation in sexual size dimorphism in Z. rubidum. [ABSTRACT FROM AUTHOR]

Various management strategies aim at maintaining pesticide resistance frequency under a threshold value by taking advantage of the benefit of the fitness penalty (the cost) expressed by the resistance allele outside the treated area or during the pesticide selection ‘off years.’ One method to estimate a fitness cost is to analyze the resistance allele frequency along transects across treated and untreated areas. On the basis of the shape of the dine, this method gives the relative contributions of both gene flow and the fitness difference between genotypes in the treated and untreated areas. Taking advantage of the properties of such migration-selection balance, an artificial dine was built up to optimize the conditions where the fitness cost of two herbicide-resistant mutants (acetolactate synthase and auxin-induced target genes) in the model species Arabidopsis thaliana could be more accurately measured. The analysis of the microevolutionary dynamics in these experimental populations indicated mean fitness costs of ∼15 and 92% for the csr1-1 and axr2-1 resistances, respectively. In addition, negative frequency dependence for the fitness cost was also detected for the axr2-1 resistance. The advantages and disadvantages of the dine approach are discussed in regard to other methods of cost estimation. This comparison highlights the powerful ability of an experimental dine to measure low fitness costs and detect sensibility to frequency-dependent variations. [ABSTRACT FROM AUTHOR]

Many unresolved issues in the ecology and evolution of marine populations center on how far planktonic larvae disperse away from their parents. Genetic tools provide a promising way to define the spatial spread of larvae, yet their accurate interpretation depends on the extent to which genetic loci are under selection. Genetic dines, geographic zones in which genetically differentiated populations interbreed, provide opportunities to explicitly and simultaneously quantify the relative roles of selection and dispersal. Here, we review the theory and analysis of genetic dines and apply these techniques to published studies of multilocus dines in the sea. The geographic width of a stable genetic dine is determined by a balance between the homogenizing effects of dispersal and the diversifying effects of selection. For marine researchers, the power of genetic dines is that, if selection and clinal width are quantified, then the average geographic distances that larvae move can be inferred. Measuring selection or dispersal through laboratory or field-based experimentation, is possible, though logistically difficult, for pelagically dispersed organisms. Instead, dispersal may be more robustly quantified from the degree of linkage disequilibrium between two or more loci, because linkage disequilibrium integrates selection across multiple life stages and generations. It is also relatively insensitive to whether exogenous or endogenous selection operates. Even without quantifying linkage disequilibrium, the theory of genetic dines indicates that the average dispersal distance of larvae is a fraction (i.e., generally <35%) of the clinal width. Because dine theory is based on several underlying assumptions, including near-equilibrium between selection and migration, the dispersal distances inferred from empirical data should be of the correct order but may not be precise. Even so, such estimates of larval dispersal are valuable, as they can be utilized to design appropriate scales for future investigations and provide some guidance to conservation efforts. [ABSTRACT FROM AUTHOR]

Background. Cancer control efforts have had limited effect in reducing the inequities for minorities and the medically underserved. One factor is the lack of theory-based conceptualization of the terms used to define race, ethnicity, and culture. Method. Guidelines are provided to develop more accurate use of the terms race, ethnicity, and culture to determine standards of comparability across studies of cancer incidence, survival, and quality of life in diverse populations rather than stereotypes. Results and Conclusions. Our ability to use theoretically based criteria to differentiate groups of people could increase our ability to more effectively eliminate these disparities. [ABSTRACT FROM AUTHOR]

Steep environmental gradients offer important opportunities to study the interaction between natural selection and gene flow. Allele frequency clines are expected to form at loci under selection, but unlinked neutral alleles may pass easily across these clines unless a generalized barrier evolves. Here we consider the distribution of forms of the intertidal gastropod Littorina saxatilis, analyzing shell shape and amplified fragment length polymorphism (AFLP) loci on two rocky shores in Britain. On the basis of previous work, the AFLP loci were divided into differentiated and undifferentiated groups. On both shores, we have shown a sharp cline in allele frequencies between the two morphs for differentiated AFLP loci. This is coincident with a habitat transition on the shore where the two habitats (cliff and boulder field) are immediately contiguous. The allele frequency clines coincide with a cline in shell morphology. In the middle of the cline, linkage disequilibrium for the differentiated loci rises in accordance with expectation. The clines are extremely narrow relative to dispersal, probably as a result of both strong selection and habitat choice. An increase in FST for undifferentiated AFLPs between morphs, relative to within-morph comparisons, is consistent with there being a general barrier to gene flow across the contact zone. These features are consistent either with an episode of allopatric divergence followed by secondary contact or with primary, nonallopatric divergence. Further data will be needed to distinguish between these alternatives. [ABSTRACT FROM AUTHOR]

Steep clines in ecologically important traits may be caused by divergent natural selection. However, processes that do not necessarily invoke ongoing selection, such as secondary contact or restricted gene flow, can also cause patterns of phenotypic differentiation over short spatial scales. Distinguishing among all possible scenarios is difficult, but an attainable goal is to establish whether scenarios that imply selection need to be invoked. We compared the extent of morphological and genetic differentiation between geographically structured red and yellow floral races of Mimulus aurantiacus (bush monkeyflower; Phrymaceae). Flower color was assessed in a common garden as well as in the field to determine whether variation was genetic and to quantify the extent of geographical differentiation. Population genetic differentiation at marker loci was measured for both chloroplast and nuclear genomes, and the degree of population structure within and among the floral races was evaluated. Flower color shows both a strong genetic basis and a sharp geographic transition, with pure red-flowered populations in western San Diego County and pure yellow-flowered populations to the east. In the zone of contact, both pure and intermediate phenotypes occur. Patterns of genetic differentiation at marker loci are far less pronounced, as little of the variation is partitioned according to the differences in flower color. Phenotypic differentiation (QST) between populations with different flower colors is much greater than neutral genetic differentiation (FST). When comparisons are made between populations of the same flower color, the opposite trend is evident. Limited neutral genetic structure between the floral races, combined with sharp differentiation in flower color, is consistent with the hypothesis that current or recent natural selection maintains the cline in flower color. [ABSTRACT FROM AUTHOR]

Previously, we observed that without using prior information about individual sampling locations, a clustering algorithm applied to multilocus genotypes from worldwide human populations produced genetic clusters largely coincident with major geographic regions. It has been argued, however, that the degree of clustering is diminished by use of samples with greater uniformity in geographic distribution, and that the clusters we identified were a consequence of uneven sampling along genetic clines. Expanding our earlier dataset from 377 to 993 markers, we systematically examine the influence of several study design variables - sample size, number of loci, number of clusters, assumptions about correlations in allele frequencies across populations, and the geographic dispersion of the sample - on the "clusteredness" of individuals. With all other variables held constant, geographic dispersion is seen to have comparatively little effect on the degree of clustering. Examination of the relationship between genetic and geographic distance supports a view in which the clusters arise not as an artifact of the sampling scheme, but from small discontinuous jumps in genetic distance for most population pairs on opposite sides of geographic barriers, in comparison with genetic distance for pairs on the same side. Thus, analysis of the 993-locus dataset corroborates our earlier results: if enough markers are used with a sufficiently large worldwide sample, individuals can be partitioned into genetic clusters that match major geographic subdivisions of the globe, with some individuals from intermediate geographic locations having mixed membership in the clusters that correspond to neighboring regions. [ABSTRACT FROM AUTHOR]

Sexual segregation outside the mating season is common in vertebrates, and has been attributed to sexual differences in predator escape performance in ungulates and fish, but not in birds. Here, we tested the hypothesis that sex- and latitude-specific predator escape performance underlies the differential nonbreeding distribution of western sandpipers ( Calidris mauri), a migratory shorebird. Females overwinter further south along the American Pacific coast, creating a latitudinal cline in sex ratio. Escape performance is reduced with increasing body mass, and birds generally carry less fat further south. Western sandpipers with poor escape performance were therefore predicted to prefer southern sites to reduce the risk of mortality posed by predators. Data from four nonbreeding latitudes showed that wing loading, used as an index of escape performance, was overall higher for females, and that it decreased with latitude in both sexes. Within latitudes, wing loading was lower at smaller, and presumably more dangerous, sites. Flight response to a predatory attack was longer in the south. Mortality risk offers a novel and candidate explanation for differential distribution patterns in western sandpipers and possibly other avian migrants. [ABSTRACT FROM AUTHOR]

• Previous studies suggest that the hybrid zone between two taxa in thePiriqueta carolinianacomplex in central Florida (south-eastern North America) has recently expanded with hybrids replacing parental genotypes across a broad region of the Florida peninsula.• Here I use patterns of genetic disequilibria and levels of differentiation among populations to infer historical patterns of introgression across this broad hybrid zone.• There were strong positive associations among taxon-specific alleles at the southern extent of hybridization, but disequilibria values were close to zero across the central and northern portions of the hybrid zone. Levels of among-population differentiation in the central portion of the hybrid zone were relatively low, and increased towards the northern extent of hybridization.• The high levels of disequilibria are coincident with the sharp clines at the southern end of the hybrid zone, suggesting that there is a tension zone in this region that is maintained by selection against hybrids and dispersal from parental regions. The levels of disequilibria within populations and patterns of differentiation among populations are consistent with historical introgression and northward expansion of this hybrid zone, which may have slowed or ceased in recent generations.New Phytologist(2005)doi: 10.1111/j.1469-8137.2005.01410.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

Abstract: To check the behaviour of physical experiments of simple rollover anticlines over listric normal faults, several fault-slip, bed-length and area parameters are measured for different beds in two stages of evolution of two physical experiments. Given a certain amount of extension, the heave and dip of the displacement vary for different beds, whereas the throw is approximately constant for small amounts of extension and the displacement remains constant for high amounts of extension. Neither bed lengths nor areas beneath beds remain constant with increasing extension. A number of techniques allow amounts of extension and detachment depth to be estimated given one or more marker horizons, the portion of the fault between hanging-wall and footwall cut off points, the depth to detachment and/or the shear angle. These techniques are applied to the physical experiments of listric normal faults analysed. Since many of these techniques rely on parameters measured on the physical experiments such as fault slip, bed length and area, the influence of these parameters on the different magnitudes of extension and detachment depths estimated using different techniques is discussed and the accuracy of the results is compared. [Copyright &y& Elsevier]

Drosophila subobscura is a European (EU) species that was introduced into South America (SA) approximately 25 years ago. Previous studies have found rapid clinal evolution in wing size and in chromosome inversion frequency in the SA colonists, and these clines parallel those found among the ancestral EU populations. Here we examine thermoplastic changes in wing length in flies reared at 15, 20, and 25°C from 10 populations on each continent. Wings are plastically largest in flies reared at 15°C (the coldest temperature) and genetically largest from populations that experience cooler temperatures on both continents. We hypothesize that flies living in cold temperatures benefit from reduced wing loading: ectotherms with cold muscles generate less power per wing beat, and hence larger wings and/or a smaller mass would facilitate fight. We develop a simple null model, based on isometric growth, to test our hypothesis. We find that both EU and SA flies exhibit adaptive plasticity in wing loading: flies reared at 15°C generally have lower wing loadings than do flies reared at 20°C or 25°C. Clinal patterns, however, are strikingly different. The ancestral EU populations show adaptive clinal variation at rearing a temperature of 15°C: flies from cool climates have lower wing loadings. In the colonizing populations from SA, however, we cannot reject the null model: wing loading increases with decreasing clinal temperatures. Our data suggest that selective factors other than flight have favored the rapid evolution of large overall size at low environmental temperatures. However, selection for increased flight ability in such environments may secondarily favor reduced body mass. [ABSTRACT FROM AUTHOR]

We report a study in Drosophila melanogaster of latitudinal dines for 23 SNPs embedded in 13 genes (Pgi, Gapdh1, UGPase, Pglym78, Pglym87, Eno, Men, Gdh, Sod, Pgk, Mdh1, TreS, Treh) representing various metabolic enzymes. Our samples are from 10 populations spanning latitude from southern Florida to northern Vermont. Three new dines with latitude were detected. These are the amino acid polymorphisms in the NAD-dependent glutamate dehydrogenase (Gdh) and trehalase (Treh) genes, and a silent site polymorphism in the UDP-glucose pyrophosphorylase gene (UGPase). The result, when combined with the overall incidence and pattern of reports for six other genes (Adh, Gpdh, Pgm, G6pd, 6Pgd, Hex-C), presents a picture of latitudinal dines in metabolic genes prevalent around the branch point of competing pathways. For six of the seven amino acid polymorphisms showing significant latitudinal dines in North America, the derived allele is the one increasing with latitude, suggesting temperate adaptation. This is consistent with a model of an Afrotropical ancestral species adapting to temperate climates through selection favoring new mutations. [ABSTRACT FROM AUTHOR]

The semilinear parabolic system that describes the evolution of the gene frequencies in the diffusion approximation for migration and selection at a multiallelic locus is investigated. The population occupies a finite habitat of arbitrary dimensionality and shape (i.e., a bounded, open domain in Rd). The selection coefficients depend on position and may depend on the gene frequencies; the drift and diffusion coefficients may depend on position. Sufficient conditions are given for the global loss of an allele and for its protection from loss. A sufficient condition for the existence of at least one internal equilibrium is also offered, and the profile of any internal equilibrium in the zero-migration limit is obtained. [Copyright &y& Elsevier]

A long-standing issue in marine biology is identifying spatial scales at which populations of sessile adults are connected by planktonic offspring. We examined the genetic continuity of the acorn barnacle Balanus glandula, an abundant member of rocky intertidal communities of the northeastern Pacific Ocean, and compared these genetic patterns to the nearshore oceanography described by trajectories of surface drifters. Consistent with its broad dispersal potential, barnacle populations are genetically similar at both mitochondrial (cytochrome oxidase I) and nuclear (elongation factor 1-alpha) loci across broad swaths of the species’ range. In central California, however, there is a striking genetic cline across 475 km of coastline between northern and southern populations. These patterns indicate that gene flow within central California is far more restricted spatially than among other populations. Possible reasons for the steep cline include the slow secondary introgression of historically separated populations, a balance between diversifying selection and dispersal, or some mix of both. Geographic trajectories of oceanic drifters closely parallel geographical patterns of gene flow. Drifters placed to the north (Oregon; ∼44°N) and south (Santa Barbara, California; ∼34° N) of the cline disperse hundreds of kilometres within 40 days, yet over the long-term their trajectories never overlapped. The lack of communication between waters originating in Oregon and southern California probably helps to maintain strong genetic differentiation between these regions. More broadly, the geographical variation in gene flow implies that focusing on species-level averages of gene flow can mask biologically important variance within species which reflects local environmental conditions and historical events. [ABSTRACT FROM AUTHOR]

Latitudinal clinal variation in wing size and shape has evolved in North American populations of Drosophila subobscura within about 20 years since colonization. While the size cline is consistent to that found in original European populations (and globally in other Drosophila species), different parts of the wing have evolved on the two continents. This clearly suggests that `chance and necessity' are simultaneously playing their roles in the process of adaptation. We report here rapid and consistent thermal evolution of wing shape (but not size) that apparently is at odds with that suggestion. Three replicated populations of D. subobscura derived from an outbred stock at Puerto Montt (Chile) were kept at each of three temperatures (13, 18 and 22°C) for 1 year and have diverged for 27 generations at most. We used the methods of geometric morphometrics to study wing shape variation in both females and males from the thermal stocks, and rates of genetic divergence for wing shape were found to be as fast or even faster than those previously estimated for wing size on a continental scale. These shape changes did not follow a neat linear trend with temperature, and are associated with localized shifts of particular landmarks with some differences between sexes. Wing shape variables were found to differ in response to male genetic constitution for polymorphic chromosomal inversions, which strongly suggests that changes in gene arrangement frequencies as a response to temperature underlie the correlated changes in wing shape because of gene-inversion linkage disequilibria. In fact, we also suggest that the shape cline in North America likely predated the size cline and is consistent with the quite different evolutionary rates between inversion and size clines. These findings cast strong doubts on the supposed ‘unpredictability’ of the geographical cline for wing traits in D. subobscura North American colonizing populations. [ABSTRACT FROM AUTHOR]

Four natural Greek populations of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), was studied for genetic variability at 25 enzyme loci. The comparison of polymorphism within and between populations shows two loci with high between-population heterozygosity (HT) and very high fixation index (Fsx) values, suggesting the presence of balancing selection. The gradual decline of common allele frequency of the polymorphic loci tested indicated that latitudinal clines are present in Greece. Indirect estimates of gene flowbased both on Wright's method (Nm) and on the Slatkin's method (Nm*), which depends on the frequencies of rare alleles found in only one population, revealed a substantial amount of gene flow (Nm = 3.493 and Nm* = 3.197). These estimates of gene flow may well explain why the "introduced" Greek populations of C. capitata, in spite of their low genetic variability, display the same polymorphic loci. Gene flow in combination with natural selection and genetic drift may have played an important role to genetic differentiation in this species in Greece. [ABSTRACT FROM AUTHOR]

Drosophila subobscura is geographically widespread in the Old World. Around the late 1970s, it was accidentally introduced into both South and North America, where it spread rapidly over broad latitudinal ranges. This invading species offers opportunities to study the speed and predictability of trait evolution on a geographic scale. One trait of special interest is body size, which shows a strong and positive latitudinal cline in many Drosophila species, including Old World D. subobscura. Surveys made about a decade after the invasion found no evidence of a size cline in either North or South America. However, a survey made in North America about two decades after the invasion showed that a conspicuous size cline had evolved and (for females) was coincident with that for Old World flies. We have now conducted parallel studies on 10 populations (13° of latitude) of flies, collected in Chile in spring 1999. After rearing flies in the laboratory for several generations, we measured wing sizes and compared geographic patterns (versus latitude or temperature) for flies on all three continents. South American females have now evolved a significant latitudinal size cline that is similar in slope to that of Old World and of North American flies. Rates of evolution (haldanes) for females are among the highest ever measured for quantitative traits. In contrast, the size cline is positive but not significant for South or North American males. At any given latitude, South American flies of both sexes are relatively large; this in part reflects the relatively cool climate of coastal Chile. Interestingly, the sections of the wing that generate the size cline for females differ among all three continents. Thus, although the evolution of overall wing size is predictable on a geographic scale (at least for females), the evolution of size of particular wing components is decidedly not. [ABSTRACT FROM AUTHOR]

Bananaquits (Coereba flaveola) on the island of Grenada in the West Indies have a plumage color polymorphism in which individuals are either yellow and black or all black. In the southwest of the island there is a cline in plumage morphs in which the frequency of black individuals increases with distance from the island's southwestern tip. We describe the present position (September 2002) and form of this cline in comparison to when it was last mapped, 21 years ago. There has been no net movement of the cline during this period. We suggest that previous movement in the cline could have been related to long-term variation in rainfall. [ABSTRACT FROM AUTHOR]

Morphological and genetic analyses of Eonycteris spelaea from 15 islands along the Banda Arc, from Sumatra to Timor and including Kalimantan and Sulawesi, revealed considerable divergence between islands and geographical patterning. On the basis of both morphology and genetics, the populations on the large islands of Greater Sunda (Sumatra, Java, Kalimantan and Sulawesi) are generally distinct from one another and from those on the islands in Nusa Tenggara (Lombok to Timor), which form a more cohesive cluster. These differences may be the result of the Nusa Tenggara populations having been colonized more recently than those on the Greater Sunda, and probably from a single source. All biological measures of the relationships between island populations are positively associated with the extent of the sea-crossing between them, indicating the sea is an important barrier to movement. Multivariate analyses show the presence of a marked trend for body size to increase from west to east. However, individuals from Kalimantan are not consistent with this trend, being smaller than predicted, and on the two outer Banda Arc islands of Sumba and Timor animals are a little larger than predicted from the longitudinal trend. These differences could be due to the relative isolation of these populations or differing environmental conditions. There is also a negative relationship between body size and island area, but this is confounded by the longitudinal trend. No significant longitudinal trends in the genetic data were detected and the trend in body size may be an adaptive response to an environmental cline that is known to occur in this region. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79, 511–522. [ABSTRACT FROM AUTHOR]

Examines the clinal patterns of variation in mean egg-to-adult development time among Drosophila serrata in Australia. Function of latitudinal clines; Factors affecting genetic variance; Association of trait mean and latitude with the genetic variance.

Within ectotherms, increases in body size with latitude are thought to be the consequence of the effect of a decline in development temperature, which results in a larger final body size. In contrast, latitudinal declines in body size are usually ascribed to limited resources. It has been suggested that if generation time is similar to or constitutes a significant proportion of the growing season length, then season length is likely to have a considerable influence on body size because of constraints on resource availability, so resulting in a decline in body size with temperature (latitude). However, if generation time declines relative to season length, resources effectively become available for longer. Temperature influences on growth and differentiation are likely to be most significant, resulting in an increase in body size with latitude. Here, we test the hypothesis by comparing intraspecific altitudinal body size clines in a monophyletic group of weevils from two regions that differ substantially in seasonality. On the relatively a seasonal Marion Island, body size increases with altitude, whereas on the more seasonal Heard Island the opposite is found. In addition, overlapping generations on Marion Island indicate year-round resource availability, whereas more discrete generations on Heard Island indicate winter cessation of growth and development. Our data provide support for the hypothesis that the seasonality of resource availability has a major influence on body size clines. Furthermore, we argue that analysis of interspecific body size clines should be preceded by nested analyses of variance to determine the influence of clinal replacement of higher taxa on these patterns. [ABSTRACT FROM AUTHOR]

A number of large, mainly NE-trending, and a few NNE-trending, Cenozoic to Recent anticlines have been identified from commercial seismic reflection data within the NE Faroe–Shetland Basin. Regional seismic markers have enabled the timing of formation of these structures to be ascertained and they appear to have developed mainly during early to mid-Miocene times, but there is also some evidence of activity through to early Pliocene to Recent, and even of pre-Miocene activity. The ages of the Cenozoic folds within the NE Faroe–Shetland Basin partly overlap with those observed on the Norwegian margin and around the Faroe Islands and the Hatton-Rockall areas, although in general, these regions have an important older component of development. Mechanisms for the formation of the folds are controversial, though results from this study indicate that the NE orientations of many of the folds in the NE Faroe–Shetland Basin are compatible with compression approximately orthogonal to the continental margin. The change from NE- to NNE-trending anticlines in the vicinity of the Magnus and Erlend lineaments/transfer zones may suggest that the development of these folds was related to sinistral strike-slip movement along these major structures. Speculatively, Quaternary strike-slip movement along these zones may also have triggered significant slope failure and the formation of mud volcanoes and mud intrusions as evidenced by the close spatial association of the Miller Slide Headwall and the ‘Pilot Whale Diapirs’. [Copyright &y& Elsevier]

In an effort to characterize further the patterns of selection and adaptive evolution at the methuselah locus in Drosophila species, we extended an analysis of geographical variation to include single nucleotide polymorphisms (SNPs) in adjacent genes on either side of the mth locus, and examined the molecular variation in a neighbouring methuselah paralogue (mth2 ). An analysis of 13 SNPs spanning a region of nearly 19 kilobases surrounding the mth locus demonstrated that a clinal pattern associated with the most common mth haplotype does not extend to adjacent gene loci, providing compelling evidence that the clinal pattern results from selection on as yet unidentified sites associated with the functional mth locus. mth2 exhibited a significant pattern of adaptive divergence among D. melanogaster , D. simulans and D. yakuba similar to that seen at mth . However, K[sub a] : K[sub s] ratios indicate a difference in levels of functional constraint at the two methuselah , loci with mth2 exhibiting a five- to six-fold reduction in levels of amino acid divergence relative to mth . [ABSTRACT FROM AUTHOR]

Develops a null model that quantifies the impact of regulatory behaviors on body temperature and on performance of ectotherms. Overview of the phenomenon called the Bogert effect; Contradiction to the classical view that behavior is invariably the driving force in evolution; Diverse effects of behavior on the directions and rates at which other traits evolve.

Abstract Many organisms show latitudinal variation for quantitative traits that is assumed to be due to climatic adaptation. These clines provide an opportunity to study the genetics of the adaptive process both at the phenotypic and the underlying molecular levels. Yet researchers rarely try to link variation in quantitative traits to their underlying molecular genetic basis. We describe a novel approach for exploring the genetic basis for clinal variation in size and stress traits in Drosophila melanogaster . We look for associations between genetic markers and traits that exhibit clinal patterns on the east coast of Australia using a single, geographically central population. There are strong associations between markers found within In(3R)Payne and variation in size, suggesting that this inversion explains much of the clinal variation in this trait. We also find that development time is associated with the Adh allozyme locus, cold resistance is negatively associated with the In(3L)Payne inversion and a genetic marker for Hsp70, a heat-shock protein, is associated with heat resistance. Finally we discuss the importance of inversions in clinal variation for quantitative traits and for identifying quantitative trait loci. [ABSTRACT FROM AUTHOR]

Presents an example of a moving hybrid zone in warningly colored Heliconius butterflies, a system which is considered to be a possible cause of shifting balance evolution. Importance of shifting clines and hybrid zones to evolutionary change; Width, position and velocity of the hybrid zone; Color pattern evolution and the shifting balance.

1 Seven populations of Beta vulgaris ssp. maritima (wild beet) situated along a latitudinal cline were studied for their vernalization requirement and its consequences for fitness. 2 Various cold regimes were applied in glasshouses and experimental gardens with plants of different ages. Three additional experimental sites (on the French Mediterranean, Atlantic and North Sea coasts) situated near three of the sampled populations, and thus including a reciprocal transplant design, were used to evaluate the influence of latitude under natural conditions. Survival and plant size were measured over 3 years. 3 The vernalization requirement was greater in plants from more northern origins. The level of cold required to allow flowering overcompensated for the colder springs, so that northern plants in northern sites flowered less than southern plants in southern sites. 4 Young seedlings were more difficult to vernalize than plants that had already developed vegetative rosettes. 5 Differences in vernalization requirement seem to be an adaptive response to spring temperatures and season length in a particular latitude. A whole winter vernalization almost always led to flowering in the subsequent year whatever the latitude or geographical origin. 6 Plants from the Atlantic and Channel coasts showed the highest lifetime reproductive success at all sites. Southern populations were better adapted to disturbed habitats as shown by their higher first-year reproductive success. The North Sea population had a lower reproductive success than the Atlantic populations, even in its native environment. [ABSTRACT FROM AUTHOR]

Aim Classical cline theory interprets clines as speciation processes in two stages: (1) smooth clines, typical of species with no marked subspecies, and (2) stepped clines, characteristic of species with marked subspecies, separated by hybrid zones, where the clines are steeper than within the areas of the subspecies. (These steeping clines eventually become vertical clines—a situation, where the taxa turn into separate species, termed `parapatric speciation'.) This theory, dating from the late 1930s, still has a number of active supporters. But, because results from population genetics suggest that barriers are necessary for speciation to take place, most authors nowadays reject both parapatric speciation and classical cline theory, the former appearing to be the logical consequence of the latter. The theory presented here does not involve parapatric speciation, but provides a revised cline theory including a third stage, the broken cline, which corresponds to the stage at which speciation finally takes place. I suggest that a cline theory without the prerequisite of parapatric speciation can be very useful, for it provides both an evolutionary interpretation of a given geographical distribution and also a method of quantitative analysis. Location An example is taken within a species complex of the chiffchaff, Phylloscopus collybita-ibericus (Aves, Sylviidae), using populations ranging from south Iberia to north Sweden for one variable and to south Belgium for three other variables. Methods I used regression analyses to interpret clinal variations, and Student's t -tests to evaluate the broken or continuous nature of the clines. Results In this example, the cline is broken between the adjacent populations of P. ibericus and P. c. collybita , and is continuous and gradual elsewhere. Main conclusions (1) Phylloscopus ibericus and P. c. collybita are good examples of taxa undergoing current speciation; (2) the southern and northern populations of P.... [ABSTRACT FROM AUTHOR]

Parallel latitudinal clines across species and continents provide dramatic evidence of the efficacy of natural selection, however little is known about the dynamics involved in cline formation. For example, several drosophilids and other ectotherms increase in body and wing size at higher latitudes. Here we compare evolution in an ancestral European and a recently introduced (North America) cline in wing size and shape in Drosophila subobscura. We show that clinal variation in wing size, spanning more than 15 degrees of latitude, has evolved in less than two decades. In females from Europe and North America, the clines are statistically indistinguishable however the cline for North American males is significantly shallower than that for European males. We document that while overall patterns of wing size are similar on two continents, the European cline is obtained largely through changing the proximal portion of the wing, whereas the North American cline is largely in the distal portion. We use data from sites collected in 1986/1988 (Pegueroles et al. 1995) and our 1997 collections to compare synchronic (divergence between contemporary populations that share a common ancestor) and allochronic (changes over time within a population) estimates of the rates of evolution. We find that, for these populations, allochronically estimated evolutionary rates within a single population are over 0.02 haldanes (2800 darwins), a value similar in magnitude to the synchronic estimates from the extremes of the cline. This paper represents an expanded analysis of data partially presented in Huey et al. (2000). [ABSTRACT FROM AUTHOR]

A dispersal–selection cline model is analysed to evaluate the role of the ratio of pollen to seed flow (r) in spatial genetic variation, with a focus on clines in additive and dominant variances of major genes affecting a quantitative trait, assuming one locus with two alleles, no genetic drift and no mutation. It is shown that under weak selection, steady-state departures from the value at Hardy–Weinberg equilibrium (HWE) for genotype frequency (D) and additive variance (ΔVa) generally display a small value on one side of the selection boundary point, a high value around the point, and a moderate value on the other side of the boundary point. A large value of r can enhance formation of this pattern. However, this is not the case for clines in the average effect of a gene substitution (Δα) or in dominance variance (ΔVd), where large values of r can eradicate the clines. Direct use of their values at HWE to approximate the real case is acceptable. There is an expected turning point that divides clines of either additive variance or dominance variance into two subclines, each with a shorter width than that of allele frequency. Integration of these properties can help to indicate the existence of major genes affecting a quantitative trait. [ABSTRACT FROM AUTHOR]

Summary 1. The fecundity of the forest tent caterpillar varies considerably across its geographic range. Field data indicate that populations in the southern United States (Gulf States) produce nearly twice as many eggs as females from Canada or the Lake States, with little or no difference in the size of adult females. 2. In controlled rearing experiments, female forest tent caterpillar from the southern United States (Louisiana) had much larger clutch sizes than same sized females from northern populations in Michigan or Manitoba, Canada. Increased fecundity in Louisiana females was achieved through a significant reduction in egg size and a concomitant increase in the allocation of resources to egg production. 3. Comparison of 10 forest tent caterpillar populations spanning a 27° latitudinal gradient, validated the results of detailed comparisons among the three populations above by confirming the strong negative correlation between latitude and clutch size. 4. Neonate forest tent caterpillars from Manitoba were significantly larger than larvae from either Michigan or Louisiana. Michigan larvae were intermediate in size. It is postulated that large neonates are advantageous in thermally limiting environments. More than three times as many degree-days are available to Louisiana neonates during the first 2 weeks after hatching. A consistently favourable climate during the vulnerable post-hatching period may have allowed the evolution of larger clutches at the expense of neonate size in southern populations. [ABSTRACT FROM AUTHOR]

Compares populations of nonbreeding dunlin or Calidris alpina pacifica from two latitudes along the Pacific flyway to determine whether, and to what degree, they exhibited sex ratios consistent with latitudinal cline. Principal hypotheses to explain the difference in winter range between males and females; Culmen distribution of dunlin; Hypothesized patterns of latitudinal clines in sex ratio in dunlin wintering along the Pacific coast.

Using data from four localities in peripheral areas of the British Isles, this article explores a conception of culture that emphasizes continuous variation, or clines, rather than boundaries. These localities are sites for the performance of cultural practices, many of which may be shared across socially constructed boundaries such as those of nation, ethnic group, and class. Consensus analysis provides a tool for exploring areas of greater or lesser sharing of cultural models indicated by responses to 21 brief narratives of everyday cultural practices. Informants were asked to judge on a 5-point scale whether the practices were characteristic of their location. With a high consensus in each site about typical practices, it was possible to compare the culturally correct profiles of responses between each of the sites, revealing incremental changes, or clines, from site to site. Edges, or the conjunction of clines, might be mapped using consensus analysis. [ABSTRACT FROM AUTHOR]

Analyzes the effects of molecular and morphological variations on the body size cline in Australian Drosophila melanogaster populations. Molecular variation in populations using polymorphic microsatellite loci; Linear regression model of relation between population mean body size and latitude.