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One Population (one + population)
Selected AbstractsDescription and characterization of a chamber for viewing and quantifying cancer cell chemotaxisCYTOSKELETON, Issue 1 2005Lilian Soon Abstract Direct observations of cancer cell invasion underscore the importance of chemotaxis in invasion and metastasis. Yet, there is to date, no established method for real-time imaging of cancer chemotaxis towards factors clinically correlated with metastasis. A chamber has been designed and tested, called the Soon chamber, which allows the direct observation and quantification of cancer cell chemotaxis. The premise for the design of the Soon chamber is the incorporation of a dam, which creates a steep gradient while retaining stability associated with a pressure-driven system. The design is based on the characteristics of cancer cell motility such as relatively low speeds, and slower motility responses to stimuli compared to classical amoeboid cells like neutrophils and Dictyostelium. We tested MTLn3 breast carcinoma cells in the Soon chamber in the presence of an EGF gradient, obtaining hour-long time-lapses of chemotaxis. MTLn3 cells migrated further, more linearly, and at greater speeds within an EGF gradient compared to buffer controls. Computation of the degree of orientation towards the EGF/buffer source showed that MTLn3 cells were significantly more directional toward the EGF gradient compared to buffer controls. Analysis of the time-lapse data obtained during chemotaxis demonstrated that two populations of cancer cells were present. One population exhibited oscillations in directionality occurring at average intervals of 12 min while the second population exhibited sustained high levels of directionality toward the source of EGF. This result suggests that polarized cancer cells can avoid the need for oscillatory path corrections during chemotaxis. Cell Motil. Cytoskeleton 62:27,34, 2005. © 2005 Wiley-Liss, Inc. [source] Among- and within-population variability in tolerance to cadmium stress in natural populations of Daphnia magna: Implications for ecological risk assessmentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2002Carlos Barata Abstract Previous attempts to test the hypothesis that laboratory selection of isogenetic populations can produce test organisms with a significantly increased mean tolerance to toxic substances have failed. One possible explanation for such failure is that the tolerance of laboratory populations is largely constrained by their origins (were the source populations composed of tolerant genotypes?). To address this question, among- and within-population variability in stress tolerance was assessed by calculating the variance in individual fitness and longevity across a cadmium gradient (0,10 ,g/L). The study employed Daphnia magna clones from four geographically separate European populations. Results revealed significant differences in tolerance to lethal levels of toxic stress among populations. The distribution of tolerances within two of the studied populations showed high amounts of genetic variation in tolerance. Genetic relationships between tolerance traits and life history performance under nonstressful environments differed among the studied populations. One population showed significant but low costs associated with tolerance, whereas no costs were associated with tolerance in the other population. These results suggest that laboratory selection will favor individuals with high fitness or reproductive performance under optimal laboratory conditions resulting in laboratory populations with similar or lower tolerance to toxic stress than their original field populations. Given that populations can exhibit high levels of genetic variability in tolerance to toxic stress, minimizing genetic diversity in toxicity tests will increase the uncertainty attendant in extrapolating from the lab to the field. [source] Multiple predator-avoidance behaviours of the freshwater snail Physella heterostropha pomila: responses vary with riskFRESHWATER BIOLOGY, Issue 3 2000Thomas M. McCarthy Summary 1We examined the predator-avoidance behaviour, exhibited in response to chemical cues, of two populations of the snail Physella heterostropha pomila. Snails were subjected to four treatments simulating different degrees of predation risk: control water (low risk), or water from tanks containing nonforaging crayfish (intermediate risk), crushed conspecifics (high risk) or crayfish consuming conspecifics (high risk). Data were analysed using three-way ANOVA models (population × predator chemicals × injured conspecific chemicals). 2Physella increased its avoidance behaviour as risk increased. Crayfish cue elicited a significantly greater response than from controls. Cues from injured conspecifics elicited the strongest response. 3Physella exhibited several types of avoidance behaviour, including burial into the substratum, moving to the water surface, and crawling out of the water. The type of cue present influenced response type. Cues from crayfish reduced burial and increased movement to the water surface or out of the water. Cues from injured-conspecifics significantly increased crawling completely out of the water. 4The two populations differed in the type and degree of response exhibited. One population exhibited significantly greater ,reactivity' (i.e. any avoidance behaviour) in response to foraging crayfish, and more burial and crawl-out behaviours were exhibited in high-risk treatments. [source] CD4+ CD5+ regulatory T cells render naive CD4+ CD25, T cells anergic and suppressiveIMMUNOLOGY, Issue 4 2007Miao Qiao Summary CD4+ CD25+ Foxp3+ naturally occurring regulatory T cells (nTreg) are potent inhibitors of almost all immune responses. However, it is unclear how this minor population of cells is capable of exerting its powerful suppressor effects. To determine whether nTreg mediate part of their suppressor function by rendering naive T cells anergic or by converting them to the suppressor phenotype, we cocultured mouse nTreg with naive CD4+ CD25, T cells from T-cell receptor (TCR) transgenic mice on a RAG deficient (RAG,/,) background in the presence of anti-CD3 and interleukin-4 (IL-4) to promote cell viability. Two distinct responder cell populations could be recovered from the cocultures. One population remained undivided in the coculture and was non-responsive to restimulation with anti-CD3 or exogenous IL-2, and could not up-regulate IL-2 mRNA or CD25 expression upon TCR restimulation. Those responder cells that had divided in the coculture were anergic to restimulation with anti-CD3 but responded to restimulation with IL-2. The undivided population was capable of suppressing the response of fresh CD4+ CD25, T cells and CD8+ T cells, while the divided population was only marginally suppressive. Although cell contact between the induced regulatory T cell (iTreg) and the responders was required for suppression to be observed, anti-transforming growth factor-, partially abrogated their suppressive function. The iTreg did not express Foxp3. Therefore nTreg are not only able to suppress immune responses by inhibiting cytokine production by CD4+ CD25, responder cells, but also appear to modulate the responder cells to render them both anergic and suppressive. [source] Reproductive modes and genetic polymorphism in the tardigrade Richtersius coronifer (Eutardigrada, Macrobiotidae)INVERTEBRATE BIOLOGY, Issue 1 2003Lorena Rebecchi Abstract. Allozymes were assessed by starch gel electrophoresis in 3 populations of a eutardigrade, Richtersius coronifer, with different reproductive modes. One population from Italy (with 2 sub-populations) was amphimictic and 2 populations (1 from Italy and 1 from Sweden) were parthenogenetic. All populations, irrespective of their reproductive mode, were diploid with the same chromosome number (2n=12) and had bivalents in the oocytes. Of the 14 loci analyzed, only 3 were polymorphic. The amphimictic population had a higher degree of genetic variability (mean heterozygosity >0.25) than the parthenogenetic populations (mean heterozygosity of the 2 populations <0.01). In all female populations, allele frequencies at all 3 loci deviated from Hardy-Weinberg equilibria due to heterozygote deficiency. These results support a hypothesis of automictic parthenogenesis in R. coronifer. [source] Skin-type antifreeze protein expression in integumental cells of larval winter flounderJOURNAL OF FISH BIOLOGY, Issue 6 2002H. M. Murray Wholemount in situ hybridization using an antisense riboprobe complementary to a winter flounder Pleuronectes americanus skin-type antifreeze protein mRNA (WFp9) and immuno histochemistry using polyclonal antibodies to the corresponding protein detected cells expressing this gene in larval winter flounder integument. Immunohistochemistry revealed two distinct populations of cells. One population extended laterally along the length of the fish and was detectable using in situ hybridization. Staining in these cells declined following yolk-sac absorption suggesting that expression was only important here during early larval development. The polyclonal antibody for skin-type antifreeze protein also reacted with another population of cells scattered throughout the integument. These cells stained with alcian blue suggesting that they were integumental mucous cells. In situ hybridization using the above probe was not able to detect the corresponding transcript within the same cells. This suggests that another gene may be involved in the production of a similar protein in this case. These data suggest that two distinct populations of cells within the larval integument are involved in skin-type antifreeze protein expression and possibly involve the activity of at least two different genes. [source] Comparison of bobuck (Trichosurus cunninghami) demography in two habitat types in the Strathbogie Ranges, AustraliaJOURNAL OF ZOOLOGY, Issue 4 2007J. K. Martin Abstract The demographic characteristics of populations are determined by the life-history strategies of their constituent individuals. Habitat characteristics, such as the availability of key resources, shape life-history strategies; thus habitat variation may result in intraspecific variability in demography. We studied two neighbouring populations of bobucks or mountain brushtail possums Trichosurus cunninghami within a fragmented forest system. One population occurred in a forest patch that was selectively logged in the last 40 years; the other occupied narrow strips of linear roadside remnant vegetation that have not been logged for at least 100 years. Many demographic parameters of the two populations were similar, and were consistent with those described previously for a bobuck population living in continuous forest. For example, both sexes were long-lived (at least 12 years), but there were fewer males in the oldest age classes at both sites. Most females produced one young per year and reproduction was highly seasonal. Females in the oldest age classes produced young, but none of these survived to pouch emergence. There were also marked differences between our two study populations: the sex ratio of adults was equal at the forest site but female-biased (1.7:1) at the roadside site. Forest males weighed significantly less than males at the roadside site and females at both sites. The peak of births occurred more than a month later at the roadside than at the forest site. The sex ratio of roadside offspring did not differ significantly from parity; however, the sex ratio of young at the forest site was significantly male-biased (62% of young). This demographic variation may be explained by differences in habitat characteristics (particularly logging history); a detailed investigation of resource availability at the two sites is warranted. Our results highlight the importance of studying multiple populations when attempting to describe the population ecology of a species. [source] Increase in mate availability without loss of self-incompatibility in the invasive species Senecio inaequidens (Asteraceae)OIKOS, Issue 2 2007Lucile Lafuma The evolution of the strength of self-incompatibility in Senecio inaequidens, a native of South Africa was investigated in relation to its invasion in Europe. Levels of self-incompatibility were estimated with hand-pollinations in five populations in greenhouse conditions. One population came from the native range of the species and four populations were sampled in Europe from two independent transects of colonization with old and recent populations. Contrary to Baker's law predictions, our results suggest that the species has a sporophytic self-incompatible system maintained in all populations. We suggest that the ability of S. inaequidens to colonize new sites with a self-incompatibility system is promoted by its ecological characteristics (perenniality, extended reproductive period, massive seed production, generalist pollinators). In addition, we found that mate availability was increased (1) in the introduced range compared to the native range, (2) in marginal versus central European populations. Possible explanations for this surprising result are discussed. [source] Discriminating tastes: self-selection of macronutrients in two populations of grasshoppersPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2008DENNIS J. FIELDING Abstract The capacity to self-select an optimal balance of macronutrients (protein and carbohydrate) is studied in two populations of Melanoplus sanguinipes F. (Orthoptera: Acrididae). One population derives from the subarctic (interior of Alaska) and the other from the temperate zone (Idaho, U.S.A.). Over the duration of the fourth and fifth stadia, Alaskan grasshoppers consistently self-select a diet centred on a 0.90 ratio of protein : carbohydrate, whereas protein and carbohydrate intake by the Idaho grasshoppers is contingent on the particular food choices presented to them. When restricted to imbalanced diets, the Alaskan grasshoppers develop more rapidly than the Idaho grasshoppers, regardless of diet composition. The Idaho grasshoppers also have a greater amount of lipid than the Alaskan grasshoppers across all diets. Performance measures (body mass, survival, developmental times) are more sensitive to dietary imbalances in the Alaskan grasshoppers than in the Idaho grasshoppers. When fed diets with low, but balanced, proportions of protein and carbohydrate, grasshoppers of both populations are able to increase consumption to compensate for the low concentration of nutrients. The results suggest that demographic responses of insects to changes in host plant quality, such as may result from climate change, may differ among populations within a species. [source] Fine-Scale Spatial Genetic Structure of the Distylous Primula veris in Fragmented HabitatsPLANT BIOLOGY, Issue 3 2007F. van Rossum Abstract: In Flanders (northern Belgium), the distylous self-incompatible perennial herb Primula veris is common, but mainly occurs in fragmented habitats. Distyly, which favours disassortative mating, is characterized in P. veris by two genetically determined floral morph types (pin or thrum). Using 18 polymorphic loci, we investigated fine-scale spatial genetic structure (SGS) and spatial distribution of the morphs within four populations from two regions that differ in degree of habitat fragmentation. We studied the contributions made by sexual reproduction and clonal propagation and compared the SGS patterns between pin and thrum morph types. Clonal growth was very restricted to a few individuals and to short distances. One population showed a non-random spatial distribution of the morphs. Pin and thrum individuals differed in SGS patterns at a small scale, suggesting intrapin biparental inbreeding, also related to high plant densities. This may be explained by partial self-compatibility of the pin morph combined with restricted seed dispersal and pollinator behaviour. There is an indication of more pronounced SGS when populations occur in highly fragmented habitats. From our findings, we may hypothesize disruption of the gene flow processes if these large populations evolve into patchworks of small remnants, but also a possible risk for long-term population survival if higher intrapin biparental inbreeding leads to inbreeding depression. Our study emphasizes the need for investigating the interactions between the heterostylous breeding system, population demographic and genetic structure for understanding population dynamics in fragmented habitats and for developing sustainable conservation strategies. [source] Complex phylogeographical patterns, introgression and cryptic species in a lineage of Malagasy dung beetles (Coleoptera: Scarabaeidae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009H. WIRTA Many taxa, including dung beetles, exhibit small-scale microendemism in Madagascar, which has contributed to the high level of species' diversity on the island. Species in the genus Nanos are numerically dominant in the dung beetle communities in rainforests in eastern Madagascar, but typically just one species occurs in any one locality. The two northern species, N. clypeatus and N. dubitatus, cannot be distinguished by either a mitochondrial or a nuclear genetic marker (cytochrome oxidase subunit I and internal transcription spacer 2). One population of the southern N. viettei is genetically highly divergent, although morphologically indistinguishable. Genetic data indicate that introgression occurred from N. dubitatus to N. viettei 1,2 Mya, and these species may continue to hybridize. Complex genetic patterns have mostly evolved within the last 2 Myr. During this time, the glacial cycles in the northern hemisphere were reflected in the oscillating climatic conditions in Africa, which repeatedly fragmented and re-united the rainforests in eastern Madagascar, possibly leading to the observed complex phylogeographical patterns in Nanos. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 942,955. [source] Randomized double-blind controlled trial of roxithromycin for prevention of abdominal aortic aneurysm expansion (Br J Surg 2001: 88: 1066,72)BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 1 2002Article first published online: 5 NOV 200 Tho original article to which this Corrigendum refers was published in British Journal of Surgery 2001: 88: 1066,72) The revised abstract is included below. Background:, Macrolide treatment has been reported to lower the risk of recurrent ischaemic heart disease. The influence of macrolides on the expansion rate of abdominal aortic aneurysms (AAAs) remains unknown. The aim was to investigate the effect of roxithromycin on the expansion rate of small AAAs. Methods:, A total of 92 subjects with a small AAA were recruited from two populations. One population consisted of 6339 men aged 65,73 years who were offered a hospital-based mass screening programme for AAA. From this population 66 subjects were recruited. The remaining 26 men were recruited from among 49 subjects diagnosed at interval screening for an initial aortic diameter between 25 and 29 mm. Subjects were randomized to receive either oral roxithromycin 300 mg once daily for 28 days or matching placebo, and followed for a mean of 1·5 years. Results:, During the first yearthe mean annual expansion rate of AAAs was reduced by 44 per cent in the intervention group (1·56 mm per year), compared with 2·80 mm per year following placebo (P = 0·02). During the second year the difference was only 5 per cent. Multiple linear regression analysis showed that roxithromycin treatment and initial AAA size were significantly related to AAA expansion when adjusted for smoking, diastolic blood pressure and immunoglobulin A level of 20 or more. Logistic regression analysis confirmed a significant difference in expansion rates above 2 mm annually between the intervention and placebo groups: odds ratio = 0·09 (95 per cent confidence interval 0·01,0·83). Conclusion:, In comparison to placebo, roxithromycin 300 mg daily for 4 weeks reduced the expansion rate of AAAs. © 2002 British Journal of Surgery Society Ltd [source] Temperature and hen harrier productivity: from local mechanisms to geographical patternsECOGRAPHY, Issue 5 2002S. M. Redpath Climate is an important factor limiting demography and distribution patterns in many organisms. For species with a broad geographical distribution, the mechanism by which climate influences demography is likely to vary dramatically from one end of the range to the other. In this paper we first assess, in a Scottish population of hen harriers Circus cyaneus, how temperature and rainfall influence adult behaviour and chick mortality patterns at the nest. We then test for associations between harrier productivity and weather across Scotland, towards the northern edge of the range, and Spain, towards the southern edge of the range. We show that during the nestling period, female brooding time increased in cold weather. Male provisioning rate was negatively related to temperature and rainfall. Chick mortality increased in cold temperatures and was most likely to occur at nests where male prey delivery rates were low relative to temperature. Annual values of harrier fledged brood size across Scotland were positively related to summer temperature suggesting that the patterns seen in one population held at a national scale. In Spain, however, the opposite patterns were observed with fledged brood size being negatively related to temperature. This shows that whilst the impact of weather on productivity may be equally strong at two ends of a geographical range, the mechanisms vary dramatically. Large-scale predictive models need to take such patterns into account. [source] Parasitism by the mite Trombidium breei on four U.K. butterfly speciesECOLOGICAL ENTOMOLOGY, Issue 6 2002L. Conradt Abstract 1. The incidence of parasitism by larvae of the mite species Trombidium breei was reported in one population of the lycaenid butterfly Polyommatus icarus, four populations of the satyrine butterfly Maniola jurtina, one population of the satyrine butterfly Aphantopus hyperanthus, and two populations of the satyrine butterfly Pyronia tithonus, as well as on one specimen of the dipteran Alophorus hemiptera. A considerable proportion of butterflies (11-50%) was infested in all study populations. 2. The pattern of infestation was examined in detail in M. jurtina. Males had a significantly higher incidence of infestation than females, and middle-aged butterflies had a higher incidence of infestation than old or young butterflies. The incidence of infestation peaked in the middle of the flight season, and this seasonal effect was independent of the effect of butterfly age. 3. Using a model based on capture-recapture data, it was estimated that a hypothetical ideal male M. jurtina that lives exactly the mean expected lifespan of 9-10 days has an approximately 75% chance of becoming infested with mites at least once during its lifetime, a mean time to first infestation of 3-4 days, and an average infestation persistence time of 2-3 days. 4. Capture-recapture data failed to show any effect of mite infestation on the lifespan or within-habitat movement rate of M. jurtina. 5. In experiments in which individual butterflies were taken out of their normal habitat and released, M. jurtina and P. tithonus that were infested with mite larvae did not differ from uninfested individuals in the efficiency with which they returned to suitable habitat. Thus, parasitism by T. breei larvae had no detectable effects on flight performance or orientation ability. 6. The results suggest that trombidiid mite larvae have limited potential in the biological control of insect pests. [source] Food abundance affects both morphology and behaviour of juvenile perchECOLOGY OF FRESHWATER FISH, Issue 2 2008J. Borcherding Abstract,,, Behaviour and morphology were both shown to differ between 1+ perch from two lakes that in earlier studies showed differences in size-specific predation risk. As the level of nourishment is known to affect behaviour and morphology, we fed perch of the two lakes in tanks for 40 days with two food levels, to study whether observed differences remain stable with changes in food availability. The perch fed in excess grew significantly, while the perch at the low food conditions lost weight, clearly indicating undernourishment. In aquarium experiments, the starved perch from both lakes were much bolder in the trade-off between foraging and predator avoidance than their well-fed conspecifics. In addition, the shape of perch differed significantly between feeding treatments. At low food levels perch got a more slender body, while at high food levels they developed a deeper body and a relatively smaller head. Independent of feeding level, the comparison between the two lakes revealed a clearly deeper body and a larger head area for one population, a shape difference that remained stable after the feeding period. The results give evidence that the level of nourishment is an important factor that quickly alters risk-taking behaviour. In body morphology, however, more stable shape characteristics must be distinguished from more flexible ones. Consequently, the level of nourishment is a potential factor that may quickly hide other proximate cues and must be considered attentively in studies, in which shape changes and behaviour are related to environmental factors like diet, predation pressure or habitat diversity. [source] FREQUENCY AND SPATIAL PATTERNING OF CLONAL REPRODUCTION IN LOUISIANA IRIS HYBRID POPULATIONSEVOLUTION, Issue 1 2000John M. Burke Abstract., The plant genera in which natural hybridization is most prevalent tend to be outcrossing perennials with some mechanism for clonal (i.e., asexual) reproduction. Although clonal reproduction in fertile, sexually reproducing hybrid populations could have important evolutionary consequences, little attention has been paid to quantifying this parameter in such populations. In the present study, we examined the frequency and spatial patterning of clonal reproduction in two Louisiana iris hybrid populations. Allozyme analysis of both populations revealed relatively high levels of genotypic diversity. However, a considerable amount of clonality was apparent. Nearly half of all genets (47%) in one population and more than half (61%) in the other had multiple ramets. Furthermore, both populations exhibited relatively high levels of genetic structuring, a pattern that resulted from the aggregation of clonal ramets. The occurrence of clonal reproduction in hybrid populations could not only facilitate introgression through an increase in the number of flowering ramets per genet and/or the survivorship of early generation hybrids, but might also influence the mating system of such populations. Any potential increase in the selfing rate due to cross-pollination among ramets of the same genet may, in turn, increase the likelihood of homoploid hybrid speciation. [source] Bystander signaling between glioma cells and fibroblasts targeted with counted particlesINTERNATIONAL JOURNAL OF CANCER, Issue 1 2005Chunlin Shao Abstract Radiation-induced bystander effects may play an important role in cancer risks associated with environmental, occupational and medical exposures and they may also present a therapeutic opportunity to modulate the efficacy of radiotherapy. However, the mechanisms underpinning these responses between tumor and normal cells are poorly understood. Using a microbeam, we investigated interactions between T98G malignant glioma cells and AG01522 normal fibroblasts by targeting cells through their nuclei in one population, then detecting cellular responses in the other co-cultured non-irradiated population. It was found that when a fraction of cells was individually irradiated with exactly 1 or 5 helium particles (3He2+), the yield of micronuclei (MN) in the non-irradiated population was significantly increased. This increase was not related to the fraction of cells targeted or the number of particles delivered to those cells. Even when one cell was targeted with a single 3He2+, the induction of MN in the bystander non-irradiated population could be increased by 79% for AG01522 and 28% for T98G. Furthermore, studies showed that nitric oxide (NO) and reactive oxygen species (ROS) were involved in these bystander responses. Following nuclear irradiation in only 1% of cells, the NO level in the T98G population was increased by 31% and the ROS level in the AG0 population was increased by 18%. Treatment of cultures with 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (c-PTIO), an NO scavenger, abolished the bystander MN induction in non-irradiated AG01522 cells but only partially in non-irradiated T98G cells, and this could be eliminated by treatment with either DMSO or antioxidants. Our findings indicate that differential mechanisms involving NO and ROS signaling factors play a role in bystander responses generated from targeted T98G glioma and AG0 fibroblasts, respectively. These bystander interactions suggest that a mechanistic control of the bystander effect could be of benefit to radiotherapy. © 2005 Wiley-Liss, Inc. [source] Genetic structure and gene flow in wild beet populations: the potential influence of habitat on transgene spread and risk assessmentJOURNAL OF APPLIED ECOLOGY, Issue 6 2006A. N. CURETON Summary 1The consequences of the movement of transgenes from genetically modified (GM) crops into wild populations of plants continues to be of concern to ecologists and conservationists because of the possible threat posed to those populations in terms of their continued survival and because of the further knock-on effects that might occur to habitats in which they occur. 2We examined five UK sea beet Beta vulgaris ssp. maritima populations from each of two major habitat types, cliff top and drift line. We assessed population genetic parameters, genetic diversity, gene flow, population differentiation and isolation by distance, to enable determination of the likelihood and consequences of spread to wild populations of genes from cultivated sugar beet group Beta vulgaris ssp. vulgaris, which could in the future be transgenic. 3Drift line populations were more diverse than cliff top populations and also showed greater levels of gene flow. 4Isolation by distance was identified in both habitats, but the relationship between genetic and geographical distance was detectable over longer distances for drift line populations. However, clear indications of vicariance (the subdivision of a population into distinct taxa by the appearance of a geological barrier) between cliff and drift line populations were also evident, because of the restriction of gene flow between the two habitats occurring more in one direction than the other. 5Synthesis and applications. The likelihood of transgene spread from crop to wild populations is habitat dependent and conservation management decisions could therefore vary from one population to another, for example water courses were found to facilitate seed dispersal. This should be taken into account when estimating isolation distances for GM beet, and when predicting transgene frequencies (exposure estimates) for environmental risk assessments of GM beet. [source] Sorption and permeation behavior for CO2 in NH3 -plasma-treated and untreated polystyrene membranesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Y.-S. Yang Abstract In our preceding work, the simultaneous deviation from the conventional dual-mode sorption and mobility model was observed in a case of CO2 in polystyrene (PS) membrane (glass transition temperature of pure polymer = 95°C) at 60 and 70°C. The plasticization effect of sorbed CO2 on both the sorption and diffusion processes tends to be brought about in glassy polymer membranes near the glass transition temperature. The behavior was simulated based on the concept that only one population of sorbed gas molecules of plasticizing ability to the polymer should exist. In the present work, the sorption and permeation behavior for CO2 in NH3 -plasma-treated and untreated PS membranes at 40°C was investigated, where NH3 -plasma treatment was executed at plasma discharge powers of 40, 80, 120, and 160 W for an exposure time of 2 min. The sorption isotherm could be described by the sorption theory of Mi et al. (Macromolecules 1991, 24, 2361), where the glass transition temperature is depressed by a concentration of sorbed CO2 of plasticizing ability. NH3 -plasma treatment on PS membrane had little influence on the sorption behavior of CO2 at plasma discharge powers up to 160 W. The mean permeability coefficients were somewhat increased only at a discharge power of 160 W. At CO2 pressures below 0.9 MPa, the pressure dependencies of mean permeability coefficients for CO2 in both NH3 -plasma-treated and untreated PS membranes at 40°C could also be simulated on the basis of the concept that only one population of sorbed gas molecules of plasticizing ability should exist. At CO2 pressures above 0.9 MPa, however, a plasticization action of sorbed CO2 had much more influence on the diffusion process rather than on the sorption one, and such a combined concept underestimated the mean permeability coefficient. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1798,1805, 2007 [source] Isozyme variation and recent biogeographical history of the long-lived conifer Fitzroya cupressoidesJOURNAL OF BIOGEOGRAPHY, Issue 2 2000A. C. Premoli Abstract Aim Palaeoenvironmental records of Pleistocene glaciation and associated vegetation changes in Patagonia have led to the hypothesis that during the last glacial maximum (LGM) tree species survived locally in favourable habitats. If present populations originated from spread from only one refugium, such as an ice-free area of coastal Chile (Single Refugium hypothesis), we would expect that eastern populations would be genetically depauperate and highly similar to western populations. In contrast, if the ice cap was not complete and tree species persisted in forest patches on both slopes of the Andes (Multiple Refugia hypothesis), we would expect a greater degree of genetic divergence between populations either on opposite sides of the Cordillera (Cordillera Effect scenario) or towards its present-day southern distributional limit where the ice sheet reached its maximum coverage (Extent-of-the-Ice scenario). Location We tested this refugia hypothesis using patterns of isozyme variation in populations sampled over the entire modern range of the endemic conifer Fitzroya cupressoides (Mol.) Johnst. (Cupressaceae) in temperate South America. Methods Fresh foliage was collected from twenty-four populations and analysed by horizontal electrophoresis on starch gels. Results Twenty-one putative loci were reliably scored and 52% were polymorphic in at least one population. Populations from the eastern slope of the Andes were genetically more variable than those from the western slope; the former had a greater mean number of alleles per locus, a larger total number of alleles and rare alleles, and higher polymorphism. Genetic identities within western populations were greater than within eastern populations. Discriminant analyses using allelic frequencies of different grouping schedules of populations were non significant when testing for the Single Refugium hypothesis whereas significant results were obtained for the Multiple Refugia hypothesis. Main conclusions Our results indicate that present Fitzroya populations are the result of spreading from at least two, but possibly more, glacial refugia located in Coastal Chile and on the southern flanks of the Andes in Argentina. [source] Reproductive life history of Thornicroft's giraffe in ZambiaAFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Fred B. Bercovitch Abstract Knowledge of the reproductive life history of giraffe in the wild is sparse. Giraffe have two fairly unusual reproductive patterns among large mammals: they can become pregnant while lactating, and calf mortality is extremely high. Longitudinal records are largely absent, so tracking reproductive parameters tends to combine information from captive and field studies. In this study, we examine longitudinal data obtained over a 33-year period in one population of Thornicroft's giraffe in order to chart their reproductive careers. We found that age at first parturition was 6.4 years, or slightly later than in captivity. Giraffe bred throughout the year, with cows producing offspring on average every 677.7 days. About half of the calves died before one year of age, but death of a calf did not reduce interbirth interval. We conclude that the lifetime reproductive success of giraffe is more dependent on longevity and calf survivorship than on reproductive rate. Résumé La connaissance de la biologie reproductive de la girafe dans la nature est lacunaire. La girafe présente deux schémas de reproduction plutôt inhabituels chez les grands mammifères : elles peuvent être fécondées tout en allaitant, et la mortalité du jeune est extrêmement élevée. On manque cruellement de rapports longitudinaux, c'est pourquoi la recherche des paramètres de la reproduction a tendance à combiner les informations provenant d'études réalisées en captivité et sur le terrain. Dans ce rapport, nous examinons les données longitudinales recueillies sur une période de 33 ans dans une population de girafes de Thornicroft afin de dresser le tableau de leur carrière reproductive. Nous avons découvert que l'âge de la première parturition était de 6,4 ans, ou légèrement plus tard en captivité. Les girafes se reproduisent toute l'année, et les femelles mettent bas en moyenne tous les 677,7 jours. Près de la moitié des jeunes meurent avant l'âge d'un an, mais la mort du jeune ne réduit pas l'intervalle entre deux naissances. Nous concluons que la réussite de la vie reproductive d'une girafe dépend davantage de sa longévité et de la survie des jeunes que du taux de reproduction. [source] Co-variation between the intensity of behavioural manipulation and parasite development time in an acanthocephalan,amphipod systemJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 10 2010N. FRANCESCHI Abstract Pomphorhynchus laevis, a fish acanthocephalan parasite, manipulates the behaviour of its gammarid intermediate host to increase its trophic transmission to the definitive host. However, the intensity of behavioural manipulation is variable between individual gammarids and between parasite populations. To elucidate causes of this variability, we compared the level of phototaxis alteration induced by different parasite sibships from one population, using experimental infections of Gammarus pulex by P. laevis. We used a naive gammarid population, and we carried out our experiments in two steps, during spring and winter. Moreover, we also investigated co-variation between phototaxis (at different stages of infection, ,young' and ,old cystacanth stage') and two other fitness-related traits, infectivity and development time. Three main parameters could explain the parasite intra-population variation in behavioural manipulation. The genetic variation, suggested by the differences between parasite families, was lower than the variation owing to an (unidentified) environmental factor. Moreover, a correlation was found between development rate and the intensity of behavioural change, the fastest growing parasites being unable to induce rapid phototaxis reversal. This suggests that parasites cannot optimize at the same time these two important parameters of their fitness, and this could explain a part of the variation observed in the wild. [source] Morph-specific selection on floral traits in a polymorphic plantJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2010D. VANHOENACKER Abstract Correlations between phenotypic traits are common in many organisms, but the relative importance of nonadaptive mechanisms and selection for the evolution and maintenance of such correlations are poorly understood. In polymorphic species, morphs may evolve quantitative differences in additional characters as a result of morph-specific selection. The perennial rosette herb Primula farinosa is polymorphic for scape length. The short-scaped morph is less damaged by grazers and seed predators but is more strongly pollen limited than the long-scaped morph. We examined whether morph-specific differences in biotic interactions are associated with differences in selection on two other traits affecting floral display (number of flowers and petal size) and on one trait likely to affect pollination efficiency (corolla tube width) in three P. farinosa populations. Differences in selection between morphs were detected in one population. In this population, selection for more flowers and larger petals was stronger in the short-scaped than in the long-scaped morph, and although there was selection for narrower corolla tubes in the short-scaped morph, no statistically significant selection on corolla tube width could be detected in the long-scaped morph. In the study populations, the short-scaped morph produced more and larger flowers and wider corolla tubes. Current morph-specific selection was thus only partly consistent with trait differences between morphs. The results provide evidence of morph-specific selection on traits associated with floral display and pollination efficiency, respectively. [source] Genetic architecture for normal and novel host-plant use in two local populations of the herbivorous ladybird beetle, Epilachna pustulosaJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2003H. Ueno Abstract Trade-offs in host-plant use are thought to promote the evolution of host specificity. However, usually either positive or no genetic correlations have been found. Whereas factors enhancing variation in overall viability have been claimed to mask negative genetic correlations, alternative hypotheses emphasize the sequential changes in genetic correlation in the course of host-range evolution. In this study, the genetic architectures of performances on different hosts were compared in two populations of the herbivorous ladybird beetle, Epilachna pustulosa, using three host plants, one being normal for both, one novel for only one population, and the other novel for both populations. The genetic correlations between larval periods on normal hosts were significantly positive whereas those between normal and novel hosts were not different from zero. There was no evidence for reduced genetic variation on the normal host-plants. These results suggest that the host-range is not restricted by the antagonistic genetic associations among exploitation abilities on different plant species, but rather that selection of different host-plants may improve the coordination between genes responsible for the use of different plants. [source] Sex-specific selection and sexual size dimorphism in the waterstrider Aquarius remigisJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2000Ferguson We estimated selection on adult body size for two generations in two populations of Aquarius remigis, as part of a long-term study of the adaptive significance of sexual size dimorphism (SSD). Net adult fitness was estimated from the following components: prereproductive survival, daily reproductive success (mating frequency or fecundity), and reproductive lifespan. Standardized selection gradients were estimated for total length and for thorax, abdomen, genital and mesofemur lengths. Although selection was generally weak and showed significant temporal and spatial heterogeneity, patterns were consistent with SSD. Prereproductive survival was strongly influenced by date of eclosion, but size (thorax and genital lengths in females; total and abdomen lengths in males) played a significant secondary role. Sexual selection favoured smaller males with longer external genitalia in one population. Net adult fitness was not significantly related to body size in females, but was negatively related to size (thorax and total length) in males. [source] Antibody response of two populations of common carp, Cyprinus carpio L., exposed to koi herpesvirusJOURNAL OF FISH DISEASES, Issue 4 2009S St-Hilaire Abstract Common carp, Cyprinus carpio L., exposed to koi herpesvirus (KHV) may become persistently infected and populations containing such virus-infected individuals may transmit the virus to other fish when co-habited. Detection of virus-infected fish in a population is thus critical to surveillance and control programmes for KHV. A study was therefore designed to detect anti-KHV serum antibodies, with an enzyme-linked immunosorbent assay, in common carp following experimental exposures to KHV under varying environmental conditions. The study determined that a proportion of fish within a population experimentally exposed to KHV (at least 10,25%) develop high antibody titres (1/1600 or greater) to the virus, and this immunological response was detectable for several months (observed at the termination of the experiments at 65, 46 and 27 weeks post-exposure). Furthermore, this response was detected in one population of fish that did not succumb to a high level of mortality when maintained at water temperatures that were non-permissive for KHV. Elevating the water temperatures to permissive conditions for KHV resulted in recurrence of disease despite the presence of anti-virus antibodies, suggesting that serum antibodies alone are not protective under the conditions of our trials. [source] Cerebrotendinous xanthomatosis: molecular characterization of two Scandinavian sistersJOURNAL OF INTERNAL MEDICINE, Issue 3 2002E. Rystedt Abstract.,Rystedt E, Olin M, Seyama Y, Buchmann M, Berstad A, Eggertsen G, Björkhem I (Karolinska Institutet, Stockholm, Sweden; OchanomizuUniversity, Tokyo, Japan; Medisinsk avdeling, Haukeland sykehus, Bergen). Cerebrotendinous xanthomatosis: molecular characterization of two Scandinavian sisters (Case report). Journal of Internal Medicine 2002; 252: 259,264. Cerebrotendinous xanthomatosis (CTX) is a hereditary disorder, which is inherited as an autosomally recessive disease, causing production of cholesterol and cholestanol xanthomas and mental retardation. The disease is caused by mutations in the gene for sterol 27-hydroxylase (CYP27A1). The only CTX patients diagnosed in Scandinavia are two Norwegian sisters from a consanguineous marriage. Here we have characterized the mutation and its functional consequences for the enzyme. Analysis of genomic DNA from cultured fibroblasts identified a base exchange C > T in position 1441, causing arginine at amino acid position 441 to be replaced by tryptophan. The same mutation was introduced by mutagenesis in the complimentary DNA (cDNA) for CYP27, ligated into the expression vector pcDNA4/HisMax and transfected into HEK293 cells. The mutated enzyme had less than 5% of the enzyme activity compared with the native enzyme. No abnormal catalytic products could be identified in the cell culture medium. Probably the mutation affects the haem binding within the holoenzyme. The mutation has also previously been reported in a Japanese family. This is the second example of a CTX-causing mutation that has been recognized in more than one population. [source] SEASONAL GROWTH AND PHENOTYPIC VARIATION IN PORPHYRA LINEARIS (RHODOPHYTA) POPULATIONS ON THE WEST COAST OF IRELAND,JOURNAL OF PHYCOLOGY, Issue 1 2007Elena Varela-Álvarez The phenology and seasonal growth of Porphyra linearis Grev. were investigated in two morphologically dissimilar populations from the west coast of Ireland. Thallus size and reproductive status of individuals were monitored monthly between June 1997 and June 1998. Both populations exhibited a similar phenology: gametophyte stages appeared on the shore in October, with spermatangial and zygotosporangial sori appearing the following February; the gametophyte stage began to degenerate in April and had disappeared completely by June. However, significant differences in growth and reproduction in the field and in cultures of plants from the two populations were observed. Thallus length and width of individuals from one population were significantly longer throughout the sample period, and reproduction and sporulation occurred 1 month earlier. Also, in situ relative growth rates (RGRs) of plants differed significantly and were correlated with different climatic factors (sunshine, day length, irradiance, rainfall, seawater temperature, and intertidal temperatures), suggesting that plants were affected by two different microhabitats. At one site, blades were more exposed to wave action, sunshine, and extreme minimum temperatures, while at the other site, blades were more protected in winter, spring, and early summer. In culture, RGRs of blades from the second site were higher than RGRs of blades from the first site under short days, corroborating the field results and suggesting a degree of phenotypic differentiation between the two populations. However, there were no sequence divergences of the RUBISCO spacer between strains of the two P. linearis populations. [source] Detecting changes in the mean of functional observationsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 5 2009István Berkes Summary., Principal component analysis has become a fundamental tool of functional data analysis. It represents the functional data as Xi(t)=,(t)+,1,l<,,i, l+ vl(t), where , is the common mean, vl are the eigenfunctions of the covariance operator and the ,i, l are the scores. Inferential procedures assume that the mean function ,(t) is the same for all values of i. If, in fact, the observations do not come from one population, but rather their mean changes at some point(s), the results of principal component analysis are confounded by the change(s). It is therefore important to develop a methodology to test the assumption of a common functional mean. We develop such a test using quantities which can be readily computed in the R package fda. The null distribution of the test statistic is asymptotically pivotal with a well-known asymptotic distribution. The asymptotic test has excellent finite sample performance. Its application is illustrated on temperature data from England. [source] When North and South don't mix: genetic connectivity of a recently endangered oceanic cycad, Cycas micronesica, in Guam using EST-microsatellitesMOLECULAR ECOLOGY, Issue 12 2010ANGÉLICA CIBRIÁN-JARAMILLO Abstract Subject to environmental changes and recurrent isolation in the last ca. 250 Ma, cycads are often described as relicts of a previously common lineage, with populations characterized by low genetic variation and restricted gene flow. We found that on the island of Guam, the endemic Cycas micronesica has most of the genetic variation of 14 EST-microsatellites distributed within each of 18 genetic populations, from 24 original sampling sites. There were high levels of genetic variation in terms of total number of alleles and private alleles, and moderate levels of inbreeding. Restricted but ongoing gene flow among populations within Guam reveals a genetic mosaic, probably more typical of cycads than previously assumed. Contiguous cycad populations in the north of Guam had higher self-recruitment rates compared to fragmented populations in the south, with no substantial connection between them except for one population. Guam's genetic mosaic may be explained by the influence of forest continuity, seed size, edaphic differences, and human transport of cycads. Also important are the extent of synchrony among flushes of reproductive female seed-bearing sporophylls and restricted pollen movement by an obligate mutualist and generalist insects. An NADH EST-locus under positive selection may reflect pressure from edaphic differences across Guam. This and three other loci are ideal candidates for ecological genomic studies. Given this species' vulnerability due to the recent introduction of the cycad aulacaspis scale, we also identify priority populations for ex situ conservation, and provide a genetic baseline for understanding the effects of invasive species on cycads in the Western Pacific, and islands in general. [source] | ||||||||||||||||||||||||||||||||||||||||