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Geographical Variation (geographical + variation)
Selected AbstractsGEOGRAPHICAL VARIATION OF THE PARASITE, PHYLLOBOTHRIUM DELPHINI (CESTODA), IN BALL'S PORPOISE, PHOCOENOIDES DALLI, IN THE NORTHERN NORTH PACIFIC, BERING SEA, AND SEA OF OKHOTSKMARINE MAMMAL SCIENCE, Issue 2 2001William A. Walker Abstract Prevalence of the larval cestode, Phyllobothrium delphini, was estimated from 2,445 Dall's porpoise, Phocoenoides dalli, from the incidental take of the Japanese high seas salmon drift-net fishery in the northwestern North Pacific Ocean, Bering Sea, and a local hand harpoon fishery in the southern Sea of Okhotsk. Prevalence of P. delphini was 22.7% in the northwestern North Pacific Ocean and 1.4% in the Bering Sea. This parasite was not found in the southern Sea of Okhotsk. Geographical differences in the prevalence of P. delphini may be due, at least in part, to regional differences in abundance of elasmobranchs known to feed on marine mammals and suspected as hosts of the parasite. Estimated intensity of infection of individual porpoises by P. delphini was low (estimated mean intensity of 3.5 plerocercoids per animal). This is a low intensity of infection compared to other species of small cetaceans studied and may be due to both differences in regional abundance of elasmobranchs and the comparatively short life span of P. dalli. [source] Threatened Peripheral Populations in Context: Geographical Variation in Population Frequency and Size and Sexual Reproduction in a Clonal Woody ShrubCONSERVATION BIOLOGY, Issue 3 2007SARAH B. YAKIMOWSKI especies en riesgo; límites de distribución; poblaciones periféricas; reproducción sexual; Vaccinium stamineum Abstract:,Geographically peripheral populations of widespread species are often the focus of conservation because they are locally rare within political jurisdictions. Yet the ecology and genetics of these populations are rarely evaluated in a broader geographic context. Most expectations concerning the ecology and evolution of peripheral populations derive from the abundant-center model, which predicts that peripheral populations should be less frequent, smaller, less dense, and have a lower reproductive rate than central populations. We tested these predictions and in doing so evaluated the conservation value of peripheral populations for the clonal shrub Vaccinium stamineum L. (Ericaceae, deerberry), which is listed as threatened in Canada. Based on 51 populations sampled from the center to the northern range limits over 2 years, population frequency and size declined toward the range limit, but ramet density increased. Sexual reproductive output varied widely among populations and between years, with many populations producing very few seeds, but did not decline toward range margins. In fact seed mass increased steadily toward range limit, and this was associated with faster germination and seedling growth, which may be adaptive in seasonal northern environments. Our results did not support the prediction that clonal reproduction is more prevalent in peripheral populations or that it contributed antagonistically to the wide variation in seed production. Peripheral populations of V. stamineum are as productive as central populations and may be locally adapted to northern environments. This emphasizes the importance of a broad geographical perspective for evaluating the ecology, evolution, and conservation of peripheral populations. Resumen:,Las poblaciones geográficamente periféricas de una especie de amplia distribución a menudo son el foco de conservación porque son raras localmente dentro de jurisdicciones políticas. Sin embargo, la ecología y genética de estas poblaciones son evaluadas poco frecuentemente en un contexto geográfico más amplio. La mayoría de las expectaciones relacionadas con la ecología y evolución de las poblaciones periféricas se derivan del modelo centro-abundante, que predice que las poblaciones periféricas son menos frecuentes, más pequeñas, menos densas y menor tasa reproductiva que poblaciones centrales. Probamos estas predicciones y al hacerlo evaluamos el valor de conservación de poblaciones periféricas de una especie de arbusto clonal (Vaccinium stamineum L., Ericaceae), que está enlistada como amenazada en Canadá. Con base en 51 poblaciones muestreadas del centro hacia los límites norteños de su distribución durante 2 años, la frecuencia y tamaño poblacional declinó hacia los límites de su distribución, pero la densidad de rametos aumentó. La reproducción sexual varió ampliamente entre las poblaciones y entre años, con muchas poblaciones produciendo muy pocas semillas, pero no declinó hacia los límites de su distribución. De hecho, la masa de semillas incrementó sostenidamente hacia los límites, y esto se asoció a una acelerada germinación y crecimiento de plántulas, lo cual puede ser adaptativo en ambientes norteños estacionales. Nuestros resultados no sustentaron la predicción de que la reproducción clonal es más prevaleciente en poblaciones periféricas o que contribuye antagónicamente a la amplia variación en la producción de semillas. Las poblaciones periféricas de V. stamineum son tan productivas como las poblaciones centrales y pueden estar adaptadas localmente a ambientes norteños. Esto enfatiza la importancia de una perspectiva geográfica amplia cuando se evalúa la ecología, evolución y conservación de poblaciones periféricas. [source] Geographical Variations in the Nature of Undeclared WorkGEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 3 2004Colin C. Williams Abstract Inspired by a stream of cultural economic geographical thought that has sought to deconstruct the view that monetary transactions are everywhere market-like and profit-motivated, this paper seeks to reread the nature of undeclared work. Conventionally, such work has been seen as epitomising unbridled profit-motivated market-like monetised exchange, and depictions of the geographical variations in its character have distinguished only between various types of profit-motivated informal employment in different area types. Drawing upon detailed empirical evidence from eleven deprived and affluent localities in urban and rural England, however, it is here displayed that universally portraying undeclared work as a form of profit-motivated informal employment over-simplifies and obscures its spatially variable nature and heterogeneous meanings. Although undeclared work in affluent locality types and urban areas is more likely to be market-like and conducted for profit-motivated purposes, undeclared work in deprived locality types and rural areas is revealed to be much more a form of mutual aid conducted for kin, neighbours and friends and embedded in non-market motives. The outcome is not only a refiguring of the geographical variations in the nature of undeclared work but also clear evidence of the need to investigate other mainstream economic spaces so as to explore further the heterogeneous and spatially variable nature of monetised transactions. [source] Geographical variation in the size of body organs in seabirdsFUNCTIONAL ECOLOGY, Issue 3 2000G. M. Hilton Abstract 1.,The size of body organs shows adaptive temporal variation in many animal species. The variation in the size of body organs was examined to see if it is also a component of local adaptation to geographical variation in ecological conditions. 2.,Major body organs were measured in five species of Icelandic seabirds, sampled from two areas where birds experience slightly different ecological conditions. Between-area differences in ecological conditions were consistent among the study species, allowing tests of the generality of ecological effects on organ size. 3.,All major body organs showed geographical size variation. Livers and kidneys were larger in locations where daily energy expenditure was expected to be higher; small intestines were heavier where food was of lower energy density; stomachs were heavier where food was less digestible; heart and flight muscle were larger where flight costs were greater. 4.,It is concluded that adaptive variation in organ size may be an important means by which animals optimize exploitation of their local environment, and may be a proximate factor in intraspecific life-history and metabolic variations between geographically separate populations. [source] Geographical variation in predictive seedling emergence in a perennial desert grassJOURNAL OF ECOLOGY, Issue 1 2000Steven E. Smith Summary 1,Mechanisms that link germination and emergence to environmental cues associated with seedling success (predictive germination) would be expected to evolve when seedlings have a greater mortality risk than seeds, but may be less important in perennial plants than in annual plants. 2,We investigated variation in predictive seedling emergence among divergent populations of a short-lived perennial desert grass, Digitaria californica, from sites that differed in climatic and edaphic factors. This species is native to environments in which the amount and duration of adequate soil moisture may control germination and seedling establishment success. 3,We utilized a special irrigation system that permits application of a range of amounts of water within a single experiment in a glasshouse. Emergence data were subjected to probit and survival analyses to describe differences among the populations in response to applied water. 4,Significant variation in predictive emergence was shown to exist among populations of D. californica when measured as amount of water required for 50% emergence following 3 days of water application, or as time required to achieve this level of emergence. Both climatic and soil characteristics were important with populations that originated from sites with less summer precipitation, and soils with higher water-holding capacity tended to have lower water requirements for emergence. 5,The report demonstrates the existence of subtle variation in predictive emergence among populations of a perennial grass representing a relatively narrow range of ecological amplitude. It also establishes the usefulness of line-source irrigation and probit analysis procedures in studying seedling emergence behaviour. [source] Temperature dependent larval resource allocation shaping adult body size in Drosophila melanogasterJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2003Z. Bochdanovits Abstract Geographical variation in Drosophila melanogaster body size is a long-standing problem of life-history evolution. Adaptation to a cold climate invariably produces large individuals, whereas evolution in tropical regions result in small individuals. The proximate mechanism was suggested to involve thermal evolution of resource processing by the developing larvae. In this study an attempt is made to merge proximate explanations, featuring temperature sensitivity of larval resource processing, and ultimate approaches focusing on adult and pre-adult life-history traits. To address the issue of temperature dependent resource allocation to adult size vs. larval survival, feeding was stopped at several stages during the larval development. Under these conditions of food deprivation, two temperate and two tropical populations reared at high and low temperatures produced different adult body sizes coinciding with different probabilities to reach the adult stage. In all cases a phenotypic trade-off between larval survival and adult size was observed. However, the underlying pattern of larval resource allocation differed between the geographical populations. In the temperate populations larval age but not weight predicted survival. Temperate larvae did not invest accumulated resources in survival, instead they preserved larval biomass to benefit adult weight. In other words, larvae from temperate populations failed to re-allocate accumulated resources to facilitate their survival. A low percentage of the larvae survived to adulthood but produced relatively large flies. Conversely, in tropical populations larval weight but not age determined the probability to reach adulthood. Tropical larvae did not invest in adult size, but facilitated their own survival. Most larvae succeeded in pupating but then produced small adults. The underlying physiological mechanism seemed to be an evolved difference in the accessibility of glycogen reserves as a result of thermal adaptation. At low rearing temperatures and in the temperate populations, glycogen levels tended to correlate positively with adult size but negatively with pupation probability. The data presented here offer an explanation of geographical variation in body size by showing that thermal evolution of resource allocation, specifically the ability to access glycogen storage, is the proximate mechanism responsible for the life-history trade-off between larval survival and adult size. [source] Changing aetiology of liver dysfunction in the new generation of a hepatitis B and C-endemic area: cross-sectional studies on adolescents born in the first 10 years after universal hepatitis B vaccinationLIVER INTERNATIONAL, Issue 9 2008Jung-Ta Kao Abstract Background/Aim: Geographical variation in viral hepatitis infection complicates various levels of liver diseases. This study elucidates the changing aetiology of alanine transaminase elevation (ALT levels >40 IU/L) in a previously hepatitis-endemic township. Design/Methods: Five cross-sectional screenings were performed on teenagers born from 1984 to 1993. We examined hepatitis B surface antigen (HBsAg), anti-hepatitis C virus (anti-HCV), ALT and body mass index, and additionally checked hepatitis B envelope antigen (HBeAg) for positive HBsAg and HCV RNA for positive anti-HCV. Teenagers with ALT elevation underwent an ultrasonography examination. Results: This study enrolled 1788 (93.7%) of 1909 students, discovering individual prevalence of HBsAg (6.3%), anti-hepatitis B core (anti-HBc) (15.5%), anti-HCV (2.2%), overweight (22.4%), obesity (12.8%) and ALT >40 IU/L (3.7%). HBsAg and anti-HBc prevalence declined with trends, while obesity increased with trends (P<0.001). Among 66 ALT-elevated teenagers, prevalence percentages of risk factors were HBsAg (22.7%), anti-HCV (1.5%), obesity (45.5%), HBsAg with obesity (7.6%) and anti-HCV with obesity (3.0%). Additionally, obesity showed predominance (85.7%) among aetiologies of teenagers with fatty livers (60.9%). The independently associated factors of ALT elevation included being male (odds ratio, 2.18; 95% confidence interval, 1.21,3.93), HBsAg (4.25; 1.06,17.13), HBeAg (7.24; 1.64,31.9), HCV RNA (29.03; 5.8,145.29) and obesity (16.5; 8.79,30.98). Conclusion: In place of viral hepatitis, obesity is becoming the major aetiology of abnormal liver function among the young generation in a previously hepatitis-endemic area. [source] Geographical variation of genetic and phenotypic traits in the Mexican sailfin mollies, Poecilia velifera and P. petenensisMOLECULAR ECOLOGY, Issue 9 2008S. J. HANKISON Abstract Comparing the patterns of population divergence using both neutral genetic and phenotypic traits provides an opportunity to examine the relative importance of evolutionary mechanisms in shaping population differences. We used microsatellite markers to examine population genetic structure in the Mexican sailfin mollies Poecilia velifera and P. petenensis. We compared patterns of genetic structure and divergence to that in two types of phenotypic traits: morphological characters and mating behaviours. Populations within each species were genetically distinct, and conformed to a model of isolation by distance, with populations within different geographical regions being more genetically similar to one another than were populations from different regions. Bayesian clustering and barrier analyses provided additional support for population separation, especially between geographical regions. In contrast, none of the phenotypic traits showed any type of geographical pattern, and population divergence in these traits was uncorrelated with that found in neutral markers. There was also a weaker pattern of regional differences among geographical regions compared to neutral genetic divergence. These results suggest that while divergence in neutral traits is likely a product of population history and genetic drift, phenotypic divergence is governed by different mechanisms, such as natural and sexual selection, and arises at spatial scales independent from those of neutral markers. [source] Geographical variation in resistance to acetyl-coenzyme A carboxylase-inhibiting herbicides across the range of the arable weed Alopecurus myosuroides (black-grass)NEW PHYTOLOGIST, Issue 4 2010Christophe Délye Summary ,The geographical structure of resistance to herbicides inhibiting acetyl-coenzyme A carboxylase (ACCase) was investigated in the weed Alopecurus myosuroides (black-grass) across its geographical range to gain insight into the process of plant adaptation in response to anthropogenic selective pressures occurring in agricultural ecosystems. ,We analysed 297 populations distributed across six countries in A. myosuroides' main area of occupancy. The frequencies of plants resistant to two broadly used ACCase inhibitors and of seven mutant, resistant ACCase alleles were assessed using bioassays and genotyping, respectively. ,Most of the resistance was not endowed by mutant ACCase alleles. Resistance and ACCase allele distribution patterns were characterized by mosaicism. The prevalence of resistance and of ACCase alleles differed among countries. ,Resistance clearly evolved by redundant evolution of a set of resistance alleles or genes, most of which remain unidentified. Resistance in A. myosuroides was shaped by variation in the herbicide selective pressure at both the individual field level and the national level. [source] Adaptation and ecological differentiation in wheat with special reference to geographical variation of growth habit and Vrn genotypePLANT BREEDING, Issue 2 2001K. Iwaki Abstract Geographical variation of growth habit was studied for 749 landraces from various parts of the world, with special reference to their adaptation and ecogeographical differentiation. The total frequency of spring-type landraces was 49.9%, and varied between localities. Spring-type landraces were frequent in two distinct areas where the average January temperature was either below -7°C or above 4°C, with winter-type landraces in areas from -7°C to 4°C. These results indicated that geographical variation of growth habit is closely related to the degree of winter coldness. An analysis of the Vrn genotype for 216 spring-type landraces demonstrated the uneven distribution of four Vrn genes, with Vrn4 being the least frequent. The adaptive Vrn genotype was different between localities. Genotypes carrying Vrn-A1 and additional Vrn gene(s) were frequent in two distinct areas where the average January temperature was either below -7°C or over 10°C, while genotypes with any of three Vrn genes, except Vrn-A1, adapted to areas with temperatures from 4°C to 10°C. Therefore, it was concluded that the adaptability of wheat landraces differed depending on their growth habit and Vrn genotype, and that ecotypes with different Vrn genotypes were allopatrically distributed as a result of adaptation to different winter temperature. However, the differential distribution of Vrn-B1, Vrn-D1 and Vrn4 could not be explained by their adaptability, and might reflect the polyphyletic origin of common wheat. [source] Geographical variation in an ant,plant interaction correlates with domatia occupancy, local ant diversity, and interlopersBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010MEGHA SHENOY Interactions between potentially mutualistic partners can vary over geographic areas. Myrmecophytes, which are plants harbouring ants, often do not exhibit sufficient intraspecific variability to permit comparative studies of myrmecophytic traits over space or time. Humboldtia brunonis (Fabaceae), a dominant, endemic myrmecophyte of the Indian Western Ghats, is unique in exhibiting considerable variability in myrmecophytic traits, e.g. domatia presence, as well as domatia occupancy and associated ant diversity throughout its geographic range. Although its caulinary domatia are occupied by at least 16 ant species throughout its distribution, young leaves and floral buds producing extrafloral nectar (EFN) are protected by ants from herbivory only in the southernmost region, where Technomyrmex albipes (Dolichoderinae) is the most abundant ant species. The extent of protection by ants was positively related to local species richness of ants and their occupancy of domatia. On the other hand, the highest abundance of interlopers in the domatia, including non-protective ants, the arboreal earthworm Perionyx pullus, and other invertebrates, occurred in sites with the least protection from herbivory by ants. Whereas domatia morphometry did not vary between sites, domatia occupied by protective ants and invertebrate interlopers were longer and broader than empty ones at all sites. The lowest percentage of empty domatia was found at the southernmost site. There was a progressive decline in ant species richness from that found at the sites, to that feeding on H. brunonis EFN, to that occupying domatia, possibly indicating constraints in the interactions with the plants at various levels. Our study of this dominant myrmecophyte emphasizes the impact of local factors such as the availability of suitable ant partners, domatia occupancy, and the presence of interlopers on the emergence of a protection mutualism between ants and plants. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 538,551. [source] Alcohol consumption and liver cirrhosis mortality with and without mention of alcohol,the case of CanadaADDICTION, Issue 9 2003Mats Ramstedt ABSTRACT Aims, To analyse post-war variations in per capita alcohol consumption in relation to gender-specific liver cirrhosis mortality in Canadian provinces and to assess the extent to which alcohol bears a different relation to cirrhosis deaths with mention of alcohol (alcoholic cirrhosis) compared to cirrhosis deaths without mention of alcohol (non-alcoholic cirrhosis). Data and method, Annual liver cirrhosis mortality rates by 5-year age groups were converted into gender-specific and age-adjusted mortality rates. Outcome measures included total cirrhosis,the conventional measure of liver cirrhosis,alcoholic cirrhosis and non-alcoholic cirrhosis. Per capita alcohol consumption was measured by alcohol sales and weighted with a 10-year distributed lag model. A graphical analysis was used to examine the regional relationship and the Box,Jenkins technique for time-series analysis was used to estimate the temporal relationship. Findings, Geographical variations in alcohol consumption corresponded to variations in total liver cirrhosis and particularly alcoholic cirrhosis, whereas non-alcoholic cirrhosis rates were not associated geographically with alcohol consumption. In general, for all provinces, time-series analyses revealed positive and statistically significant effects of changes in alcohol consumption on cirrhosis mortality. In Canada at large, a 1-litre increase in per capita consumption was associated with a 17% increase in male total cirrhosis rates and a 13% increase in female total cirrhosis rates. Alcohol consumption had a stronger impact on alcoholic cirrhosis, which increased by fully 30% per litre increase in alcohol per capita for men and women. Although the effect on the non-alcoholic cirrhosis rate was weaker (12% for men and 7% for women) it was nevertheless statistically significant and suggests that a large proportion of these deaths may actually be alcohol-related. Conclusions, Some well-established findings in alcohol research were confirmed by the Canadian experience: per capita alcohol consumption is related closely to death rates from liver cirrhosis and alcohol-related deaths tend to be under-reported in mortality statistics. [source] Geographical variations of inflammatory bowel disease in France: A study based on national health insurance dataINFLAMMATORY BOWEL DISEASES, Issue 3 2006Virginie Nerich Abstract Background and Aim: A north-south gradient in inflammatory bowel disease (IBD) incidence has been found in Europe and the United States. Its existence is inferred from comparisons of registries that cover only small portions of territories. Several studies suggest that IBD incidence in the north has reached a plateau, whereas in the south it has risen sharply. This evolution tends to reduce the north-south gradient, and it is uncertain whether it still exists. In France, patients with IBD are fully reimbursed for their health expenses by the national health insurance system, which is a potential source of data concerning the incidence of IBD at the national level. The aim of this study was to assess the geographical distribution of Crohn's disease (CD) and ulcerative colitis (UC) in France and to test the north-south gradient hypothesis. Methods: This study was conducted in metropolitan France and included patients to whom IBD reimbursement was newly attributed between January 1, 2000 and December 31, 2002. Data provided relate to age, sex, postcode area of residence, and IBD type. The mapping of geographical distribution of smoothed relative risks (RR) of CD and UC was carried out using a Bayesian approach, taking into account autocorrelation and population size in each département. Results: In the overall population, incidence rates were 8.2 for CD and 7.2 for UC per 100,000 inhabitants. A clear north-south gradient was shown for CD. Départements with the highest smoothed RR were located in the northern third of France. By contrast, the geographical distribution of smoothed RR of UC was homogeneous. Conclusions: This study shows a north-south gradient in France for CD but not for UC. [source] Geographical differences within Finland in the frequency of HLA-DQ genotypes associated with Type 1 diabetes susceptibilityINTERNATIONAL JOURNAL OF IMMUNOGENETICS, Issue 4 2000J. Ilonen Geographical variations in the HLA-DQ genotypes associated with risk for type 1 diabetes were evaluated in Finland. Samples of 280 diabetic children diagnosed in Turku (south-west of the country) and 405 in Oulu (north of the country) were studied as well as a series of 14 096 and 10 016 newborns collected from the same hospitals. There were no major differences in the risk or protection conferred by various HLA-DQB1 genotypes between south-western and northern parts of the country when genotypes of children with type 1 diabetes from these two centres were compared with those of newborns, representing the background populations. However, the distribution of various genotypes was different, both in diabetic children and in newborns, when compared between the two regions (P < 0.0001, ,2 test). These differences reflected the allele frequencies in newborn cohorts in which HLA-DQB1*02 and DQB1*0301 were found more often in Turku and DQB1*0302 more often in Oulu (P < 0.0001 for all differences). Similar types of differences were detected when children who were diagnosed as having diabetes during the national ,Childhood Diabetes in Finland' (DiMe) study between the years 1986,1989 were compared according to their residence. The observed differences in genotype and allele frequencies demonstrate the heterogeneity for HLA alleles even in a population that is generally regarded as highly homogeneous. These differences also affect the sensitivity and efficiency of the screening programme used for identifying infants with genetic susceptibility to IDDM in the ongoing Finnish Diabetes Prediction and Prevention Study. [source] Analysis of drug resistance and virulence-factor genotype of Irish Helicobacter pylori strains: is there any relationship between resistance to metronidazole and cagA status?ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 7 2009I. TANEIKE Summary Background,Helicobacter pylori infection is eradicated with antimicrobial agents and drug-resistant strains make successful treatment difficult. Geographical variations in virulence-factor genotype also exist. Aim, To evaluate prevalence of drug resistance and virulence-factor genotype in Irish H. pylori strains and to investigate if there is any relationship between drug resistance and genotype. Methods,Helicobacter pylori strains isolated from 103 patients were examined. Antimicrobial susceptibilities were tested by Etest. The virulence-factor genotypes were determined using PCR. Frequencies of spontaneous metronidazole-resistance were measured in vitro. Results, Metronidazole resistance was present in 37.9% of strains examined. 16.5% of strains were clarithromycin-resistant and resistance to both agents observed was found in 12.6% of strains. 68% of strains were cagA+. The dominant vacA type was s1/m2, followed by s1/m1 and s2/m2. The metronidazole resistance rate in cagA, group was significantly higher than in cagA+ (P = 0.0089). Spontaneous resistance to metronidazole in cagA, occurred in higher frequency when compared with cagA+. Conclusions,cagA+ and vacAs1/m2 type was the dominant genotype in Irish H. pylori strains. Significant rates of metronidazole resistance were observed in cagA, group. cagA, strains tend to acquire metronidazole resistance in vitro. Absence of cagA might be a risk factor in development of metronidazole resistance. [source] Characterization of six microsatellite markers in Trillium camschatcense using a dual-suppression-polymerase chain reaction techniqueMOLECULAR ECOLOGY RESOURCES, Issue 4 2006S. KUBOTA Abstract Trillium camschatcense is a herbaceous perennial plant distributed in Hokkaido and northern Honshu, Japan. Geographical variations in the breeding system (partial selfing or obligate outcrossing) are reported in the populations of Hokkaido. We isolated six polymorphic microsatellite loci from this species. The number of allele per locus ranged from four to 12, whereas the expected heterozygosities ranged from 0.69 to 0.83. These markers may allow further investigations to reveal the evolutionary and ecological processes of mating system in T. camschatcense. [source] A low incidence of Type 1 diabetes between 1977 and 2001 in south-eastern Sweden in areas with high population density and which are more deprivedDIABETIC MEDICINE, Issue 3 2008B.-M. Holmqvist Abstract Aims To explore how socioeconomic factors and population density may contribute to the geographical variation of incidence of Type 1 diabetes in children in south-eastern Sweden. Method All children diagnosed with Type 1 diabetes in south-eastern Sweden during 1977,2001 were defined geographically to their place of residence and were allocated x and y coordinates in the national grid. The population at risk and socioeconomic data were aggregated in 82 000 200-m squares and geocoded likewise. A socioeconomic index was calculated using a signed ,2 method. Rural,urban gradients were defined by overlay analysis in a geographic information system. Results The incidence during the past 25 years has been rising steadily, particularly in the last 6 years. The incidence was highest in areas with a high proportion of small families, of families with a high family income and better education, and this was found both at the time of diagnosis and at the time of birth. In the rural,urban analysis, the lowest incidence was found in the urban area with > 20 000 inhabitants, where there was also a higher frequency of deprivation. Conclusions Our findings indicate that geographical variations in incidence rates of Type 1 diabetes in children are associated with socioeconomic factors and population density, although other contributing factors remain to be explained. [source] Environmental determinants of amphibian and reptile species richness in ChinaECOGRAPHY, Issue 4 2007Hong Qian Understanding the factors that regulate geographical variation in species richness has been one of the fundamental questions in ecology for decades, but our knowledge of the cause of geographical variation in species richness remains poor. This is particularly true for herpetofaunas (including amphibians and reptiles). Here, using correlation and regression analyses, we examine the relationship of herpetofaunal species richness in 245 localities across China with 30 environmental factors, which include nearly all major environmental factors that are considered to explain broad-scale species richness gradients in such theories as ambient energy, water,energy dynamics, productivity, habitat heterogeneity, and climatic stability. We found that the species richness of amphibians and reptiles is moderately to strongly correlated with most of the environmental variables examined, and that the best fit models, which include explanatory variables of temperature, precipitation, net primary productivity, minimum elevation, and range in elevation, explain ca 70% the variance in species richness for both amphibians and reptiles after accounting for sample area. Although water and temperature are important explanatory variables to both amphibians and reptiles, water variables explain more variance in amphibian species richness than in reptile species richness whereas temperature variables explain more variance in reptile species richness than in amphibian species richness, which is consistent with different physiological requirements of the two groups of organisms. [source] The implications of different species concepts for describing biodiversity patterns and assessing conservation needs for African birdsECOGRAPHY, Issue 5 2005Shaun Dillon It has been suggested that switching from the widely used Biological Species Concept to a Phylogenetic Species Concept, would result in the appearance of hitherto neglected patterns of endemism. The problem has mainly been analyzed with respect to endemic taxa and for rather limited geographical regions, but will here be analysed for the entire resident avifauna of sub-Saharan Africa. A database of African bird distributions was re-edited to create two new datasets representing 1572 biological species and 2098 phylogenetic species. Species richness patterns were virtually identical with the two taxonomies, and only subtle changes were found in the geographical variation in range-size rarity sum. However, there were some differences in the most range-restricted species, with increased complexity of long-recognized centres of endemism. Overall, then, the large-scale biogeographic patterns are robust to changes in species concepts. This reflects the aggregated nature of endemism, with certain areas acting as "species pumps" and large intervening areas being characterised by a predominance of widespread species which distribute themselves in accordance with contemporary environmental conditions. The percentages of phylogenetic and threatened species captured in a BSC near-minimum set of 64 grid-cells and a PSC near-maximum set, with the same number of grid-cells, are very similar. [source] Latitudinal gradients in diversity: real patterns and random modelsECOGRAPHY, Issue 3 2001Patricia Koleff Mid-domain models have been argued to provide a default explanation for the best known spatial pattern in biodiversity, namely the latitudinal gradient in species richness. These models assume no environmental gradients, but merely a random latitudinal association between the size and placement of the geographic ranges of species. A mid-domain peak in richness is generated because when the latitudinal extents of species in a given taxonomic group are bounded to north and south, perhaps by a physical constraint such as a continental edge or perhaps by a climatic constraint such as a critical temperature or precipitation threshold, then the number of ways in which ranges can be distributed changes systematically between the bounds. In addition, such models make predictions about latitudinal variation in the latitudinal extents of the distributions of species, and in beta diversity (the spatial turnover in species identities). Here we test how well five mid-domain models predict observed latitudinal patterns of species richness, latitudinal extent and beta diversity in two groups of birds, parrots and woodpeckers, across the New World. Whilst both groups exhibit clear gradients in richness and beta diversity and the general trend in species richness is acceptably predicted (but not accurately, unless substantial empirical information is assumed), the fit of these models is uniformly poor for beta diversity and latitudinal range extent. This suggests either that, at least for these data, as presently formulated mid-domain models are too simplistic, or that in practice the mid-domain effect is not significant in determining geographical variation in diversity. [source] Could the tree diversity pattern in Europe be generated by postglacial dispersal limitation?ECOLOGY LETTERS, Issue 6 2007Jens-Christian Svenning Abstract The relative importance of contemporary climate and history as controls of geographical diversity patterns is intensely debated. A key example is the controversy over the extent to which temperate tree distributions and diversity patterns reflect postglacial dispersal limitation. Here, we focus on Central and Northern Europe, and show that recent estimates of tree migration rates < 100 m year,1 imply that many species have probably not reached equilibrium with climate in this region. We then demonstrate that geographical accessibility from glacial refuges explains 78% of the geographical variation in the region's tree diversity and is a much stronger diversity predictor than climate. Finally, we show that realistic estimates of migration rates can be derived from the observed tree diversity pattern by assuming it to be purely dispersal driven. In conclusion, the tree diversity pattern in Central and Northern Europe could, to a large extent, be a result of postglacial dispersal limitation. [source] Small-scaled geographical variation in life-history traits of the blowfly Calliphora vicina between rural and urban populationsENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2009C. C. Hwang Abstract The impact of the urban heat-island effect, the warming-up of an urban area caused by human activity, on the blowfly Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) was examined at two British sites, 30 km apart. Waterloo in Central London is a highly urbanised built-up area, whereas Box Hill in the county of Surrey is a rural pasture and woodland location. The phenotypic plasticity of 12 C. vicina cultures, originated from single females from each of the two sites, was measured using three developmental characters: adult body size (represented as the length of the cross vein dm-cu of the right wing), development time as accumulated degree-days (ADD), and growth rate (length of dm-cu/ADD), along a constant temperature series of 16, 20, 24, and 28 °C in the laboratory. The blowflies from Box Hill had the same ADD as those from Waterloo, but showed a significantly larger adult size and growth rate at lower temperatures, suggesting the existence of local adaptations that may be caused by the differing levels of urbanisation between the two studied sites. Not surprisingly, a trade-off between adult size and development time was found. Females showed longer development times than males at all four temperatures, indicating they may need to ingest more food as larvae to furnish ovarioles and increase fecundity. However, females had larger adult size than males at 16 and 20 °C but a reverse at 28 °C, suggesting that females may be more cold-adapted than males. [source] Geographical and individual variation in echolocation calls of the intermediate leaf-nosed bat, Hipposideros larvatusETHOLOGY, Issue 8 2010Tinglei Jiang The cause and significance of variation in echolocation call frequency within hipposiderid bats is not well understood despite an increasing number of allopatric and sympatric examples being documented. We examined variation patterns in the resting frequency (RF) of echolocation calls emitted by the intermediate leaf-nosed bat, Hipposideros larvatus, on a broad geographical scale. Data mining technology and Kruskal,Wallis test both showed substantial variation with a longitudinal pattern in RF in H. larvatus among colonies, and this variation was associated with geographical distance and not body size. In addition, we found that a high degree of variability between individuals was hidden under the geographical variation. The results support an effect of random cultural drift, and challenge the prey detection hypothesis. Moreover, an acoustic difference among local island colonies may be indicative of a vocal dialect. We found that each colony of H. larvatus seems to maintain a ,private bandwidth', which could be used for colony identity and individual communication thus helping individuals and colonies to get a number of fitness benefits. [source] Vocal Discrimination in Mate Guarding Male Australian Sea Lions: Familiarity Breeds ContemptETHOLOGY, Issue 8 2010Marie R. G. Attard The vocal characteristics of a species can be immensely diverse, and can significantly impact animal social interactions. The social structure of a species may vary with geographical variation in call characteristics. The ability of pinnipeds (true seals, fur seals, sea lions and walrus) to distinguish between conspecifics may assist male reproductive strategies, particularly mate acquisition. We assessed the ability of mate guarding Australian sea lion (Neophoca cinerea) males to discriminate local from foreign males' barks recorded from a geographically distant breeding colony. Bark characteristics were significantly different between colonies, with barks produced by males from the Lewis Island breeding colony higher pitched and longer in both duration and interval duration than barks produced by males on Kangaroo Island. Mate guarding males displayed inter-colony discrimination of barks, with a significantly stronger response to barks from local males than to those of males from a colony approx. 180 km away. Local males' barks were apparently considered a greater threat than barks from unfamiliar males. We propose that discrimination of acoustic characteristics may facilitate reproductive isolation in this species that may lead to an ethological,acoustic barrier between breeding colonies, and subsequent genetic isolation. [source] ASYMMETRY IN STRUCTURAL DEFENSES: INSIGHTS INTO SELECTIVE PREDATION IN THE WILDEVOLUTION, Issue 9 2003C. A. Bergstrom Abstract Assessment of geographical patterns in fluctuating asymmetry (small, random differences between sides of bilateral characters) among populations shows promise as a tool to resolve the relative biomechanical importance of traits, in addition to being a possible indicator of habitat quality. We used 115 endemic freshwater populations of threespine stickleback (Gasterosteus aculeatus) from Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada, to explore the degree of concordance between geographical variation of asymmetry in a predator defense structure (bony lateral plates) and geographical variation in several indirect measures of predation regime as well as several abiotic habitat variables. We found a geographical cline in the population frequency of lateral plate asymmetries, with reduced asymmetry in the southern clear-water regions of the archipelago characterized by long reaction distances and greater chance of capture by predators, and elevated asymmetry in the northern stained-water regions with poor visibility and low chances of capture. Lateral plate asymmetry was strongly correlated with expression of several defensive armor traits, including total plate numbers among populations, mean cross-sectional diameter of stickleback with the dorsal and pelvic spines erect, and mean degree of overlap between the plates and spine supports. There were no significant correlations between frequency of asymmetric fish and any of our abiotic habitat variables. Stickleback with structural plate asymmetries had fewer trout-induced scars than symmetric fish in the significant majority of populations, and there was a decrease in structural plate asymmetry with age in stained-water habitats, suggesting that trout predators may be selectively removing asymmetric fish in some lakes. This study provides evidence that geographical variation in developmental stability of threespine stickleback, as seen in the frequencies of asymmetry, reflects differences among populations in the importance of structural defenses to fitness rather than differences in habitat quality, and that asymmetry may be a target of selection by predators in wild populations. [source] Geographical variation in the size of body organs in seabirdsFUNCTIONAL ECOLOGY, Issue 3 2000G. M. Hilton Abstract 1.,The size of body organs shows adaptive temporal variation in many animal species. The variation in the size of body organs was examined to see if it is also a component of local adaptation to geographical variation in ecological conditions. 2.,Major body organs were measured in five species of Icelandic seabirds, sampled from two areas where birds experience slightly different ecological conditions. Between-area differences in ecological conditions were consistent among the study species, allowing tests of the generality of ecological effects on organ size. 3.,All major body organs showed geographical size variation. Livers and kidneys were larger in locations where daily energy expenditure was expected to be higher; small intestines were heavier where food was of lower energy density; stomachs were heavier where food was less digestible; heart and flight muscle were larger where flight costs were greater. 4.,It is concluded that adaptive variation in organ size may be an important means by which animals optimize exploitation of their local environment, and may be a proximate factor in intraspecific life-history and metabolic variations between geographically separate populations. [source] Geographical and taxonomic influences on cranial variation in red colobus monkeys (Primates, Colobinae): introducing a new approach to ,morph' monkeysGLOBAL ECOLOGY, Issue 2 2009Andrea Cardini ABSTRACT Aim, To provide accurate but parsimonious quantitative descriptions of clines in cranial form of red colobus, to partition morphological variance into geographical, taxonomic and structured taxonomic components, and to visually summarize clines in multivariate shape data using a method which produces results directly comparable to both univariate studies of geographical variation and standard geometric morphometric visualization of shape differences along vectors. Location, Equatorial Africa. Methods, Sixty-four three-dimensional cranial landmarks were measured on 276 adult red colobus monkeys sampled over their entire distribution. Geometric morphometric methods were applied, and size and shape variables regressed onto geographical coordinates using linear and curvilinear models. Model selection was done using the second-order Akaike information criterion. Components of variation related to geography, taxon or their combined effect were partitioned using partial regresssion. Multivariate trends in clinal shape were summarized using principal components of predictions from regressions, plotting vector scores on maps as for univariate size, and visualizing differences along main axes of clinal shape variation using surface rendering. Results, Significant clinal variation was found in size and shape. Clines were similar in females and males. Trend surface analysis tended to be more accurate and parsimonious than alternative models in predicting morphology based on geography. Cranial form was relatively paedomorphic in East Africa and peramorphic in central Africa. Most taxonomic variation was geographically structured. However, taxonomic differences alone accounted for a larger proportion of total explained variance in shape (up to 40%) than in size (, 20%). Main conclusions, A strong cline explained most of the observed size variation and a significant part of the shape differences of red colobus crania. The pattern of geographical variation was largely similar to that previously reported in vervets, despite different habitat preferences (arboreal versus terrestrial) and a long period since divergence (c. 14,15 Myr). This suggests that some aspects of morphological divergence in both groups may have been influenced by similar environmental, geographical and historical factors. Cranial size is likely to be evolutionarily more labile and thus better reflects the influence of recent environmental changes. Cranial shape could be more resilient to change and thus better reflects phylogenetically informative differences. [source] Dependence of broad-scale geographical variation in fleshy-fruited plant species richness on disperser bird species richnessGLOBAL ECOLOGY, Issue 4 2004Ana L. Márquez ABSTRACT Aim, We analysed the interdependence of avian frugivore- and fruited plant-species richness at the scale of major river basins across Europe, taking into account several environmental factors along different spatial gradients. Location, Continental Europe and the British Isles. Methods, We focused on wintering birds and autumn/winter fruiting plants, and used major river basins as geographical units and Structural Equation Modelling as the principal analytical tool. Results, The statistical influence of disperser species richness on fleshy-fruited plant species richness is roughly double that of the reverse. Broad-scale variation in frugivore richness is more dependent on environmental factors than on fruited plant richness. However, the influence of disperser richness on plant richness is four times higher than the influence of environmental factors. Environmental influences on both birds and plants are greater than purely spatial influences. Main conclusions, Our results are interpreted as indicating that biotic dispersal of fruits strongly affects broad-scale geographical trends of fleshy-fruited plant species richness, whereas richness of fruited plants moderately affects frugivore richness. [source] The Governance of Global Production Networks and Regional Development: A Case Study of Taiwanese PC Production NetworksGROWTH AND CHANGE, Issue 1 2009DANIEL YOU-REN YANG ABSTRACT This article applies a global production networks (GPN) perspective to the trans-border investments of Taiwanese personal computer (PC) companies in the Northern Taiwan, Greater Suzhou and Greater Dongguan regions. The findings of extensive field research are used to illustrate two conceptual arguments. First, we show the on-the-ground complexity of inter-firm governance arrangements within the PC industry, thereby casting doubt upon attempts to reduce notions of governance to simplistic, industry-wide categorisations. Second, by comparing Greater Suzhou and Greater Dongguan, we demonstrate that even within a single production system, there is geographical variation in the nature of the strategic coupling between the GPN and local institutional formations. We argue that conceptualising such geographical and organisational complexity is critical to understanding the regional development potential of GPNs. [source] Gallbladder cancer: a morphological and molecular updateHISTOPATHOLOGY, Issue 2 2009Robert David Goldin Gallbladder cancer (GBC) shows a marked geographical variation in its incidence, with the highest figures being seen in India and Chile and relatively low levels in many Western countries. Risk factors for its development include the presence of gallstones, infection and the presence of an anomalous pancreatobiliary ductal junction. It can arise from either a pathway involving metaplasia or dysplasia or one in which there is a pre-existing adenoma. The former is the more common and, because it is often not associated with a macroscopically recognizable lesion, leads to the recommendation that all gallbladders need to be examined microscopically. Accurate staging of invasive cancers is essential to determine prognosis and treatment, and this requires extensive tumour sampling. A number of genetic alterations have been identified in the preinvasive and invasive stages of GBC and they support the morphological evidence of there being two pathways by which tumours develop. Some of these genetic changes are associated with particular risk factors. For example, cases with anomalous pancreatobiliary ductal junction show a higher frequency of K-ras mutations. Some changes are associated with differences in prognosis. For example, cancers without expression of p21 but with expression for p27 have a better prognosis, whereas those that express c-erb-B2 have a worse one. Work has also been done on identifying clinical, imaging and other factors that indicate that patients have a higher risk of having GBC. This is particularly important in high-incidence areas in which GBC is a significant public health problem. [source] | |||||||||||||||||||||||||||||||||||||