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Isolated Populations (isolated + population)
Kinds of Isolated Populations Selected AbstractsClimatic adaptation in an isolated and genetically impoverished amphibian populationECOGRAPHY, Issue 4 2010Germán Orizaola The capacity of populations to respond adaptively to environmental change is essential for their persistence. Isolated populations often harbour reduced genetic variation, which is predicted to decrease adaptive potential, and can be detrimental under the current scenarios of global change. In this study, we examined climatic adaptation in larval life history traits in the pool frog Rana lessonae along a latitudinal gradient across the northern distribution area of the species, paying special attention to the isolated and genetically impoverished fringe populations in central Sweden. Larvae from eight populations within three geographic areas (Poland, Latvia and Sweden) were reared under three temperatures (19, 22 and 26°C) in a common garden laboratory experiment. We found clear evidence for latitudinal adaptation in R. lessonae populations, larvae from higher latitudes growing and developing faster than low-latitude ones. Larvae from the Swedish populations were able to compensate for the effects of cooler temperatures and a shorter growth season with genetically higher growth and development rates (i.e. countergradient variation) in the two higher temperature treatments, but there was no difference among the populations at the lowest temperature treatment, which is likely to be close to the temperature limiting growth in R. lessonae. Our results demonstrate that isolated and genetically impoverished populations can be locally adapted, and identify the Swedish fringe populations as a significant conservation unit adapted to the northern environmental conditions. [source] Do male and female black-backed woodpeckers respond differently to gaps in habitat?EVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 3 2010Jennifer C. Pierson Abstract We used population- and individual-based genetic approaches to assess barriers to movement in black-backed woodpeckers (Picoides arcticus), a fire-specialist that mainly occupies the boreal forest in North America. We tested if male and female woodpeckers exhibited the same movement patterns using both spatially implicit and explicit genetic analyses to define population structure and movement patterns of both sexes among populations. Three genetic groups were identified, a large, genetically continuous population that spans from the Rocky Mountains to Quebec, a small isolated population in South Dakota and a separate population in the western portion of their distribution (Oregon). Patterns of genetic diversity suggest extensive gene flow mediated by both males and females within the continuous boreal forest. However, male-mediated gene flow is the main form of connectivity between the continuously distributed group and the smaller populations of South Dakota and Oregon that are separated by large areas of unforested habitat, which apparently serves as a barrier to movement of female woodpeckers. [source] A haplotype of the catalase gene confers an increased risk of essential hypertension in Chinese Han,HUMAN MUTATION, Issue 3 2010Zhimin Wang Abstract Our previous study in an isolated population showed an association between a genetic variant in the catalase gene (CAT) and essential hypertension (EH). This study indicates that three variants in the promoter and 5,-UTR region of CAT are predominant in Chinese Han, and they form two major haplotypes. A case,control study showed that the CATH2 haplotype confers susceptibility to EH (Pgenotype=0.0017, and Pallilc=0.00078). Subjects bearing CATH1/CATH2 and CATH2/CATH2 genotypes demonstrated a higher susceptibility to EH than CATH1/CATH1 homozygotes, with odds ratios of 1.474 and 1.625, respectively. Also, CATH1/CATH1 individuals had a later-onset age (P=0.015). Expression analysis using luciferase reporter vectors indicated that the CATH1 haplotype showed a lower transcriptional activity than the haplotype CATH2 (P<0.05 in all four cell lines), and we observed similar results in the endogenous allelic expression ratios of CATH1/CATH2 in cell lines. In contrast, most CATH1 haplotypes showed a higher transcription level than CATH2 haplotypes (10 out of 11 or 90.9%) in blood from normal individuals (P<0.01). We therefore hypothesize that CATH1 and CATH2 may play alternating roles at different level of oxidative stress. Hum Mutat 31:272,278, 2010. © 2009 Wiley-Liss, Inc. [source] Population trends of Rooks Corvus frugilegus in Spain and the importance of refuse tipsIBIS, Issue 1 2008PEDRO P. OLEA Anthropogenic food from refuse tips can affect population dynamics in birds, especially gulls, but the evidence is mostly circumstantial. We combine analyses of long-term population data and natural experiments to show a positive effect of refuse tips on the growth of the Spanish breeding population of Rooks Corvus frugilegus. In this isolated population of around 2000 breeding pairs, monitored since 1976, birds in colonies less than 10 km from tips fed largely on refuse, particularly during periods of lowest natural food availability. Three lines of evidence support the hypothesis that the supply of refuse influenced breeding numbers, suggesting that this population is limited by food: 1) between 1976 and 2003, the two population nuclei that had access to tips increased 2.1 and 3.7 times more than that without a tip nearby; 2) annual colony growth between 1996 and 2003 was strongly correlated with the availability of tips when other potentially important variables were taken into account; 3) the number of breeding pairs in refuse-foraging colonies declined rapidly after the closure of the local tip and recovered only when a supply of refuse was restored. The effect of tips on colony growth was stronger when the availability of natural foraging habitat around the colonies was low, suggesting that anthropogenic food acts as a buffer against shortage of natural food. Artificial food supplementation may be an effective tool to increase the breeding population of target species, especially those facing a reduction of their foraging habitats. The potential effects on bird species of Directive 1999/31/CE, which is enforcing a massive closure of tips in Europe, are discussed. [source] A model of bovine tuberculosis in the badger Melesmeles: an evaluation of control strategiesJOURNAL OF APPLIED ECOLOGY, Issue 3 2001G.C. Smith Summary 1,An individual-based stochastic simulation model was used to investigate the control of bovine tuberculosis (TB) in the European badger Meles meles. Nearly all population and epidemiological parameters were derived from one study site, and the transmission of TB from badgers to cattle was included. The latter is an essential step if reactive badger control strategies are to be modelled. 2,The model appeared to underestimate slightly the rate of population recovery following widespread culling. This may have been due to simulating an isolated population with no immigration and no compensatory increase in fecundity. This should not affect the relative efficacy of each control strategy, but does require further investigation. 3,Of the historical methods of badger control, gassing and the ,clean ring' strategies were the most effective at reducing disease prevalence in the badger and cattle herd breakdown rates. These results agree with those of earlier models. 4,The proactive badger removal operation as part of the current field trial should cause a dramatic decrease in the number of cattle herd breakdowns, but also has the greatest effect on the badger population size. 5,The proactive use of a live test to detect TB, followed by vaccination, appears to reduce substantially cattle herd breakdowns and disease prevalence in the badger. 6,Three combined control strategies gave the best initial reduction in cattle herd breakdown rate and disease prevalence in the badger: (i) a proactive cull followed by reactive test and cull; (ii) a continued vaccination and proactive test and cull; and (iii) a continuous proactive test and cull. 7,The results of simulation models suggest that badger vaccination is a very good method of TB control. This is at odds with simple models and requires further investigation. [source] Mitochondrial DNA variation of an isolated population of the Adriatic brook lamprey Lampetra zanandreai (Agnatha: Petromyzontidae): phylogeographic and phylogenetic inferencesJOURNAL OF FISH BIOLOGY, Issue 9 2009V. Caputo Two mitochondrial genes were examined to compare an isolated population of the Adriatic brook lamprey Lampetra zanandreai in central Italy with other populations in the species range (Po plain) and with parasitic and freshwater lampreys. A single haplotype, identical to one in a Venetian sample, was found in 10 individuals from the isolated population. The reduced variability is consistent with a history of dispersal after the Pleistocene expansion of the Po basin. The results support the hypothesis of an origin of L. zanandreai and L. fluviatilis,L. planeri from a common anadromous ancestor. [source] Breeding structure of an isolated cactophilic Drosophila population on a sandstone table hillJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2002E. M. Moraes Abstract The effect of host cacti on the breeding structure of an isolated population of cactophilic Drosophila gouveai was studied. A comparison was made, using F statistics, of the allozyme frequencies at 11 loci among temporal samples of the adult population and six samples of progeny obtained from individual rotting cactus cladodes. The population appears to be structured by the cacti, forming breeding groups, and approximately four individuals contribute gametes to the progeny of each cladode. This D. gouveai population had a low degree of heterozygosity, compared with mean values for most Drosophila species, however it was within the range of values reported for other cactophilic Drosophila. Zusammenfassung Ziel der Untersuchung der Paarungsstruktur einer isolierten Population der kaktophilen Spezies Drosophila gouveai war die Bestimmung des Strukturniveaus in Abhängigkeit von den jeweiligen Wirtskakteen. Vergleiche der Allozymfrequenzen wurden mittels F-Statistik an elf Loci der Gesamptpopulation durchgeführt, von der zu verschiedenen Zeitpunkten Proben genommen wurden, und an sechs Loci der Nachwuchsgenerationen, die sich in isolierten, verrottenden Kakteenkladodien entwickelten. Die Ergebnisse zeigen, dass die Populationin Bezug auf die Kakteen in Form von Paarungsgruppen strukturiert ist, und dass zum Nachwuchs innerhalb einzelner Kladodien jeweils circa vier Individuen Gameten beitragen. Die geschätzten Heterozygotiegrade wurden mit bereits publizierten Werten anderer kaktophiler und mit nicht-kaktophilen Drosophila -Arten verglichen. Dieser Vergleich zeigte, dass der niedrige Heterozygotiegrad der D.gouveai Population mit den Werten anderer kaktophiler Arten übereinstimmt. [source] CURRENT STATUS AND CONSERVATION NEEDS OF DUGONGS IN SOUTHERN JAPANMARINE MAMMAL SCIENCE, Issue 3 2007Miki Shirakihara Abstract We conducted aerial surveys of dugongs (Dugong dugon) using the line-transect method and snorkeling surveys of dugong feeding trails in 1998 and 1999 around Okinawa Island (26°30,N, 128°00,E) and the Sakishima Islands, southern Japan. A total of ten dugongs were sighted and feeding trails were confirmed in the sea grass beds off the east coast of Okinawa Island. In the Sakishima Islands, however, no dugongs were observed, and there was no evidence of feeding trails despite the existence of apparently suitable sea grass beds for feeding. The results of these surveys and other available information suggest that Okinawan dugongs represent a small, geographically isolated population. Our sightings of dugongs during the daytime, offshore of sea grass beds where feeding trails were recorded, suggest that Okinawan dugongs principally feed at night when human activities are limited. Survival of this remnant dugong population is threatened by habitat degradation and occasional entanglement mortality in fishing nets. [source] Genetic and morphological evolution following a founder event in the dark-eyed junco, Junco hyemalis thurberiMOLECULAR ECOLOGY, Issue 3 2004C. A. Rasner Abstract An isolated population of dark-eyed juncos, Junco hyemalis, became established on the campus of the University of California at San Diego (UCSD), probably in the early 1980s. It now numbers about 70 breeding pairs. Populations across the entire natural range of the subspecies J. h. thurberi are weakly differentiated from each other at five microsatellite loci (FST = 0.01). The UCSD population is significantly different from these populations, the closest of which is 70 km away. It has 88% of the genetic heterozygosity and 63% of the allelic richness of populations in the montane range of the subspecies, consistent with a harmonic mean effective population size of 32 (but with 95% confidence limits from four to > 70) over the eight generations since founding. Results suggest a moderate bottleneck in the early establishment phase but with more than seven effective founders. Individuals in the UCSD population have shorter wings and tails than those in the nearby mountains and a common garden experiment indicates that the morphological differences are genetically based. The moderate effective population size is not sufficient for the observed morphological differences to have evolved as a consequence of genetic drift, indicating a major role for selection subsequent to the founding of the UCSD population. [source] Landscape scale genetic effects of habitat fragmentation on a high gene flow species: Speyeria idalia (Nymphalidae)MOLECULAR ECOLOGY, Issue 1 2003Barry L. Williams Abstract Detection of the genetic effects of recent habitat fragmentation in natural populations can be a difficult task, especially for high gene flow species. Previous analyses of mitochondrial DNA data from across the current range of Speyeria idalia indicated that the species exhibited high levels of gene flow among populations, with the exception of an isolated population in the eastern portion of its range. However, some populations are found on isolated habitat patches, which were recently separated from one another by large expanses of uninhabitable terrain, in the form of row crop agriculture. The goal of this study was to compare levels of genetic differentiation and diversity among populations found in relatively continuous habitat to populations in both recently and historically isolated habitat. Four microsatellite loci were used to genotype over 300 individuals from five populations in continuous habitat, five populations in recently fragmented habitat, and one historically isolated population. Results from the historically isolated population were concordant with previous analyses and suggest significant differentiation. Also, microsatellite data were consistent with the genetic effects of habitat fragmentation for the recently isolated populations, in the form of increased differentiation and decreased genetic diversity when compared to nonfragmented populations. These results suggest that given the appropriate control populations, microsatellite markers can be used to detect the effects of recent habitat fragmentation in natural populations, even at a large geographical scale in high gene flow species. [source] PERMANENT GENETIC RESOURCES: Development of polymorphic microsatellite loci for the endangered Topeka shiner, Notropis topekaMOLECULAR ECOLOGY RESOURCES, Issue 2 2008CYNTHIA M. ANDERSON Abstract We have developed a set of eight polymorphic microsatellite markers for the endangered Topeka shiner, Notropis topeka. Allelic diversity at each of these loci was assessed in a single isolated population from eastern South Dakota, USA. The allelic diversity ranged from four to 15 alleles. These are the first microsatellite markers to be reported for this species. These markers are being used in a more thorough study of the population structure throughout the remaining range of this species. [source] Variable microsatellite loci isolated from the azure damselfly, Coenagrion puella (L.) (Zygoptera; Coenagrionidae)MOLECULAR ECOLOGY RESOURCES, Issue 5 2007CHRIS D. LOWE Abstract We isolated and characterized 10 polymorphic microsatellite loci from the azure damselfly Coenagrion puella (Zygoptera; Coenagrionidae) as part of a study assessing reproductive success and genetic structure in an isolated population of this species. Levels of genetic diversity were assessed in 50 individuals collected from Queen Elizabeth Country Park, Hampshire, UK. The number of alleles per microsatellite loci ranged from three to 22 and the observed and expected heterozygosities varied between 0.26 and 0.84 and between 0.23 and 0.91, respectively. Two loci showed significant (P < 0.05) heterozygote deficits, likely because of null (non-amplifying) alleles; one pair of loci was in linkage disequilibrium. [source] Polymorphic microsatellite markers, isolated using a simple enrichment procedure, in the threatened smooth snake (Coronella austriaca)MOLECULAR ECOLOGY RESOURCES, Issue 1 2005J. M. BOND Abstract The smooth snake, Coronella austriaca, is particularly rare within the UK and little is known about the genetic variability within the species. Here we report the isolation of 16 polymorphic microsatellite markers in the smooth snake, using a simple enrichment procedure. Despite screening individuals from a potentially isolated population, levels of polymorphism were high. These microsatellite markers will prove very useful in investigating population parameters, which will lead to effective conservation and management plans for this rare species. [source] Restless legs syndrome: Epidemiological and clinicogenetic study in a South Tyrolean population isolateMOVEMENT DISORDERS, Issue 8 2006Florian D. Vogl MSc Abstract Genetic contributions to restless legs syndrome (RLS) have been consistently recognized from population and family studies. To determine the clinical and genetic features of RLS in a population isolate and explore linkage to three previously described susceptibility loci on chromosomes 12q, 14q, and 9p, respectively, an isolated population in the South Tyrolean Alps was identified and 530 adults participated in the study. Using a two-step strategy, 47 patients with idiopathic RLS were ascertained. The prevalence in the population was 8.9%. Twenty-eight patients (59.6%) had at least one affected first-degree relative and were classified as hereditary cases. In a single extended pedigree, linkage to known RLS loci was investigated specifying autosomal dominant and recessive models; parametric and nonparametric multipoint linkage scores were computed. None of the calculated linkage scores was suggestive of linkage between RLS and any of the three investigated loci. This study was conducted in a population isolate providing for a homogeneous genetic and environmental background. The absence of a suggestive linkage signal at the three known RLS susceptibility loci is indicative of further locus heterogeneity of this frequent disorder and encourages further studies to unveil the genetic causes of RLS. © 2006 Movement Disorder Society [source] ORIGINAL ARTICLE: Characterization of Cytokine Production by Human Term Placenta Macrophages In VitroAMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 6 2008Oleg Pavlov Problem, Macrophages are apparently the only immune cells within placenta villi, yet functions of these cells remain obscure. It has been postulated that placental macrophages accomplish regulatory roles at the fetal,maternal interface by means of wide variety of secreted cytokines. We attempt to analyze the patterns of cytokine production in an isolated population of placental macrophages. Method of study, Macrophages were obtained from term placentas in the absence of spontaneous labor. The basal and lipopolysaccharide (LPS)-stimulated levels of intracellular cytokines were detected by flow cytometry. The basal cytokine secretion was determined by BDÔCytometry Bead Array (BD Biosciences, San Diego, CA, USA). Results, Intracellular IL-1,, IL-1,, IL-6, and TNF, were detected in 31, 27, 4, and 3% CD68+ cells, respectively. Stimulation with LPS increased the proportions of cytokine-producing CD68+ cells to 48, 50, 28, and 49%, respectively. Under basal conditions, levels of released TNF, and IL-6, respectively, were 20- and 25-fold higher when compared with IL-1, while IL-10 was secreted in small but detectable amounts. When a secretory activity was estimated for cytokine-producing cells, the secretion rate for TNF, and IL-6 overwhelmingly surpassed that for IL-1, (TNF,:IL-6:IL-1, ratio was 192:145:1). Conclusion, These results suggest functional heterogeneity of the placental macrophage population and contribute to the elucidation of regulatory roles of these cells in gestation. [source] Population genetic structure of rock ptarmigan in the ,sky islands' of French Pyrenees: implications for conservationANIMAL CONSERVATION, Issue 2 2009N. Bech Abstract Expected consequences of global warming include habitat reduction in many cool climate species. Rock ptarmigan is a Holarctic grouse that inhabits arctic and alpine tundra. In Europe, the Pyrenean ptarmigan inhabits the southern edge of the species' range and since the last glacial maximum its habitat has been severely fragmented and is restricted to high-alpine zones or ,sky islands'. A recent study of rock ptarmigan population genetic in Europe found that the Pyrenean ptarmigan had very low genetic diversity compared with that found in the Alps and Scandinavia. Habitat fragmentation and reduced genetic diversity raises concerns about the viability of ptarmigan populations in the Pyrenees. However, information on population structuring and gene flow across the Pyrenees, which is essential for designing a sound management plan, is absent. In this study, we use seven microsatellites and mitochondrial control region sequences to investigate genetic variation and differentiation among five localities across the Pyrenees. Our analyses reveal the presence of genetic differentiation among all five localities and a significant isolation-by-distance effect that is likely the result of short dispersal distances and high natal and breeding philopatry of Pyrenean ptarmigan coupled with severe habitat fragmentation. Furthermore, analysis of molecular variance, principal component analysis and Bayesian analysis of genetic structuring identified the greatest amount of differentiation between the eastern and main parts of the Pyrenean chain separated by the Sègre Valley. Our data also show that the Canigou massif may host an isolated population and requires special conservation attention. We propose a management plan which includes the translocation of birds. If a sky island structure affects genetic divergence in rock ptarmigan, it may also affect the genetic structure of other sky island species having low dispersal abilities. [source] Landscape linkages and conservation planning for the black bear in west-central FloridaANIMAL CONSERVATION, Issue 1 2004Jeffery L. Larkin The Greater Chassahowitzka black bear population is the smallest documented in North America with fewer than 20 individuals. Its future depends on landscape linkages with other bear populations that are separated by denatured habitat. We used a Geographic Information System (GIS) to identify potential landscape linkages between this isolated population and six others in Florida. Pathway lengths ranged from 60,194 km with varying potentials for facilitating black bear dispersal. Each pathway incorporated 35,88% conservation land and encountered at least 11 dispersal bottlenecks. Even pathways that incorporated extensive conservation land encountered bottlenecks that make these linkages potentially unviable. All six pathways, however, passed through ,95% core black bear habitat. Thus, the infrastructure for a conservation network is still largely intact. The Suwannee pathway provides the best opportunity to restore connectivity between the Greater Chassahowitzka Ecosystem (GCE) and a southward colonising bear population in the Big Bend region. However, intensification of development poses an immediate threat to maintaining connectivity between the GCE and other bear populations in Florida. Through immediate strategic planning and active conservation and restoration measures, many of the generated pathways can provide long-term connectivity. Least-cost path analyses can aid in the conservation of wide-ranging animals by providing managers with a science-based, empirically derived blueprint of potential landscape linkages. [source] An INSIG2 Polymorphism Affects Glucose Homeostasis in Sardinian Obese Children and AdolescentsANNALS OF HUMAN GENETICS, Issue 5 2010Patrizia Zavattari Summary Allelic variants of a single nucleotide polymorphism (SNP), rs7566605, located approximately 10 kb upstream of the INSIG2 gene have been found in association with body weight and with other clinical features related to obesity in some populations but not in others. Our objective was to test the association of this SNP in obese children and adolescents from the genetically isolated population of Sardinia. We tested the association of rs7566605 with body mass index (BMI) and with serum glucose and insulin concentrations and a surrogate measure of insulin resistance (HOMA-IR) in a cohort of 747 Sardinian obese children and adolescents. A case control analysis was performed using 548 ethnically-matched healthy controls. Allelic frequencies of the SNP were similar between patients and controls. Mean glucose and insulin concentration and mean HOMA-IR values were significantly higher in patients carrying the CC genotype than in the CG and GG carriers. In the patients with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT), allele C was significantly more frequent than in controls. Although INSIG2 polymorphisms do not consistently associate with BMI, the observation of an association with glucose concentration would support a role for this gene in the metabolic complications of obesity. [source] MQScore_SNP Software for Multipoint Parametric Linkage Analysis of Quantitative Traits in Large PedigreesANNALS OF HUMAN GENETICS, Issue 3 2010Tatiana I. Axenovich Summary We describe software for multipoint parametric linkage analysis of quantitative traits using information about SNP genotypes. A mixed model of major gene and polygene inheritance is implemented in this software. Implementation of several algorithms to avoid computational underflow and decrease running time permits application of our software to the analysis of very large pedigrees collected in human genetically isolated populations. We tested our software by performing linkage analysis of adult height in a large pedigree from a Dutch isolated population. Three significant and four suggestive loci were identified with the help of our programs, whereas variance-component-based linkage analysis, which requires the pedigree fragmentation, demonstrated only three suggestive peaks. The software package MQScore_SNP is available at http://mga.bionet.nsc.ru/soft/index.html. [source] Conservation genetics of the endangered depressed river mussel, Pseudanodonta complanata, using amplified fragment length polymorphism (AFLP) markersAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 5 2010Richard Skidmore Abstract 1.Genetic analysis is increasingly recognized as a key tool for understanding demography, and is particularly useful for describing patterns of gene flow between putative populations. Most effort has been directed towards vertebrate systems, where any one study often benefits from marker development in related species. The greater diversity of invertebrate taxa presents a challenge, but amplified fragment length polymorphism (AFLP) markers offer a solution, yielding high levels of polymorphism and no prior knowledge of a species' genome. 2.AFLP markers have been used to analyse an unusual metapopulation of an invertebrate, the endangered freshwater mussel, Pseudanodonta complanata, sampled from river systems across the UK. This was done to assess the extent to which individual river systems were genetically isolated from one another. 3.The results show patterns of weak genetic differentiation across the UK, with one hydrologically isolated population in the south west showing clear genetic differentiation from the rest of the country. However, the UK population as a whole exhibits significant isolation by distance, particularly when one population subject to fish stocking is removed, this population probably being seeded with mussel glochidia larvae which use fish as vectors. Genetic estimates of inbreeding reveal a complicated pattern in which inbreeding peaks at intermediate densities. High-density populations may be genetically diverse due to their size, while the lowest density populations may represent transient groups of emigrants from other, larger populations. 4.The findings show that limited gene flow does exist between some but not all river systems. The isolation of the south-west population indicates that dispersal is variable and should not be assumed to be present. Waterways that remain hydrologically isolated may require special attention in conservation programmes as they can harbour genetically distinct populations. The balance between river management activities and conservation priorities therefore needs careful consideration. Copyright © 2010 John Wiley & Sons, Ltd. [source] Description, biology and conservation of a new species of Australian tree frog (Amphibia: Anura: Hylidae: Litoria) and an assessment of the remaining populations of Litoria genimaculata Horst, 1883: systematic and conservation implications of an unusual speciation eventBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2007CONRAD J. HOSKIN The Australian populations of the green-eyed tree frog Litoria genimaculata consist of a northern and southern genetic lineage that meet in a mosaic contact zone comprising two independent areas of contact: one where the main ranges of the lineages overlap, and the second where a population of the southern lineage is isolated within the range of the northern lineage. A recent study failed to find significant reproductive isolation between the main ranges of the two lineages, despite deep genetic divergence, partial postzygotic isolation, and call differences. The study did, however, demonstrate rapid phenotypic divergence and speciation of the isolated population of the southern lineage from both the parapatric northern lineage and from the allopatric, but genetically similar, main range of the southern lineage. Herein, the isolated population of the southern lineage is described as a distinct species, Litoria myola sp. nov., whereas the remainder of the southern lineage and the northern lineage are retained as a single, paraphyletic species, Litoria genimaculata. Resolving this unusual systematic situation demonstrates the value of using multiple lines of evidence in delimiting species. Litoria myola sp. nov. has a very small distribution and population size and warrants a Critically Endangered listing (B1, 2) under IUCN criteria. Threats and management recommendations are outlined, and the conservation of hybrid zones as areas of evolutionary novelty is discussed. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 549,563. [source] The occurrence of dominant spinocerebellar ataxias among 251 Finnish ataxia patients and the role of predisposing large normal alleles in a genetically isolated populationACTA NEUROLOGICA SCANDINAVICA, Issue 3 2005V. Juvonen Objectives,,, Frequency and distribution of dominant ataxias caused by dynamic mutations may vary in different populations, which has been explained on the basis of relative frequency of predisposing normal alleles. The aim of the study was to evaluate the occurrence of spinocerebellar ataxias (SCAs) and dentatorubral-pallidoluysian atrophy (DRPLA) in Finland, and to investigate the role of predisposing normal alleles in a genetically homogenous population. Material and methods,,, Mutation analyses for SCA1, 2, 3, 6, 7, 8, 10, 12, 17, and DRPLA and frataxin genes were performed for 251 unrelated Finnish patients who presented with progressive ataxia disorder. Results,,, Expansions of SCA1, SCA2, SCA6, SCA7, SCA8, and SCA17 genes were detected in 2, 1, 1, 7, 22, and 1 patients, respectively. Altogether, 39 and 7% of dominant and sporadic SCA patients, respectively, harboured expansions at some of the investigated loci. Normal variation, collected from 477 to 502 chromosomes at each disease loci, revealed that Finns were different from the Japanese but largely similar to other Caucasians. Conclusions,,, Lack of SCA3 and excess of SCA8 are characteristic to the Finnish population. Homozygosity for the SCA8 expansion increases penetrance. Frequencies of large normal alleles at the SCA loci predict poorly prevalence of the respective diseases in Finland. Prioritization in DNA testing, based on ethnic origin and geographical location, is recommendable in Finland, and analogous approach may be applied to other countries as well. [source] Quantifying Plant Population Persistence in Human-Dominated LandscapesCONSERVATION BIOLOGY, Issue 4 2008DAWN M. LAWSON Base de Datos de la Diversidad Natural de California; conservación de plantas; crecimiento de la población; especies en peligro; paisajes urbanos Abstract:,We assessed population performance of rare plants across a gradient from rural to urban landscapes and evaluated 2 hypotheses central to strategic conservation planning: (1) population performance declines with increasing human dominance and (2) small populations perform poorly relative to larger ones. Assessing these hypotheses is critical to strategic conservation planning. The current conservation paradigm adheres to the well-established ecology theory that small isolated populations, particularly those in human-dominated landscapes, are the least likely to succeed over the long term. Consequently, conservation planning has strongly favored large, remote targets for protection. This shift in conservation toward ecosystem-based programs and protection of populations within large, remote systems has been at the expense of protection of the rarest of the rare species, the dominant paradigm for conservation driven by the endangered species act. Yet, avoiding conservation of small populations appears to be based more on theoretical understanding and expert opinion than empiricism. We used Natural Heritage data from California in an assessment of population performance of rare plants across a landscape with an urban-rural gradient. Population performance did not decrease in urban settings or for populations that were initially small. Our results are consistent with a pattern of few species extinctions within these landscapes over the past several decades. We conclude that these populations within compromised landscapes can contribute to overall biodiversity conservation. We further argue that conservation planning for biodiversity preservation should allocate relatively more resources to protecting urban-associated plant taxa because they may provide conservation benefit beyond simply protecting isolated populations; they may be useful in building social interest in conservation. Resumen:,Evaluamos el funcionamiento de la población de plantas raras a lo largo de un gradiente de paisajes rurales a urbanos y evaluamos 2 hipótesis centrales para la planificación estratégica de la conservación: (1) declinaciones en el funcionamiento poblacional con el incremento de la dominancia humana y (2) las poblaciones pequeñas funcionan pobremente en relación con las grandes. La evaluación de estas hipótesis es crítica para la planificación estratégica de la conservación. El paradigma actual de la conservación se adhiere a la teoría ecológica bien establecida que propone que las poblaciones pequeñas aisladas, particularmente en paisajes dominados por humanos, tienen menor probabilidad de sobrevivir a largo plazo. Consecuentemente, la planificación de la conservación ha favorecido objetivos grandes y remotos. Este cambio hacia programas de conservación basados en ecosistemas y la protección de poblaciones en sistemas extensos y remotos ha sido a costa de la protección de las especies más raras entre las raras, el paradigma dominante en la conservación conducida por el acta de especies en peligro. No obstante, la evasión de la conservación de poblaciones pequeñas parece estar basada más en entendimiento teórico y en la opinión de expertos que en el empirismo. Utilizamos datos del Patrimonio Natural de California en una evaluación del funcionamiento de plantas raras en un paisaje con un gradiente urbano a rural. El funcionamiento de la población no decreció en sitios urbanos o en poblaciones que eran pequeñas inicialmente. Nuestros resultados son consistentes con un patrón de extinción de especies en estos paisajes en las últimas décadas. Concluimos que estas poblaciones en paisajes comprometidos pueden contribuir a la conservación de la biodiversidad en general. También argumentamos que la planificación de la conservación para la preservación de la biodiversidad debería asignar más recursos para la protección de taxa de plantas asociadas a ambientes urbanos porque pueden proporcionar beneficios de conservación más allá de simplemente proteger poblaciones aisladas; pueden ser útiles para construir el interés social por la conservación. [source] Introduction Strategies Put to the Test: Local Adaptation versus HeterosisCONSERVATION BIOLOGY, Issue 3 2004PHILIPPINE VERGEER exogamia; introducciones multi-fuente; introducciones uni-fuente; Succisa pratensis Abstract:,Plant biodiversity has declined seriously because of both habitat deterioration and habitat fragmentation. As a result, many species have been forced into small, fragmented, and isolated populations and are believed to suffer from higher extinction risks. Genetic reinforcement and the establishment of new populations are now widely used to prevent extinction. However, the genetic background of transplants may seriously affect the long-term success of these populations because increased genetic variation may reduce the risk of inbreeding or lead to better performance by restored heterozygosity levels (heterosis). Introduced transplants, however, may be poorly adapted to the new local conditions. We tested the initial success of alternative introduction strategies. We evaluated the potential for inbreeding, heterosis, and/or local adaptation after introduction of artificial populations of Succisa pratensis. We introduced individuals from local and distant artificial populations that were created from either small or large populations. We created the artificial populations with the same census population size but varying effective population sizes by adjusting the relatedness of individuals. We analyzed the demographic consequences of inbreeding, heterosis, and/or local adaptation of these artificial populations. Reduced performance after selfing was manifested by a reduction in seed production, seed weight, germination, and flowering percentage. Seed production, seed weight, flowering percentage, and number of flowerheads were negatively affected by small population size. Local adaptation increased biomass and flowering percentage for local individuals. Seed weight and seed production exhibited significant heterosis. Our results demonstrate that threatened populations can benefit from introduction and genetic reinforcement of individuals from related populations. Significant differences among the artificial populations for several measured performance components suggest that introduction or reinforcement is best achieved through material from a local population or, when unavailable, from several large populations. Resumen:,La biodiversidad de plantas ha declinado seriamente tanto por el deterioro como la fragmentación de hábitats. Como resultado, muchas especies han sido relegadas a poblaciones pequeñas, fragmentadas y aisladas cuyos riesgos de extinción se piensa que son mayores. El reforzamiento genético y el establecimiento de poblaciones nuevas se utilizan ampliamente en la actualidad para prevenir la extinción. Sin embargo, los antecedentes genéticos de transplantes pueden afectar seriamente el éxito de estas poblaciones a largo plazo debido a que el incremento en la variación genética puede reducir el riesgo de endogamia o puede conducir a un mejor rendimiento por lograr niveles de heterocigosidad restaurados (heterosis). No obstante, los trasplantes introducidos pueden adaptarse deficientemente a las nuevas condiciones locales. Probamos el éxito inicial de estrategias de introducción alternativas. Evaluamos el potencial de endogamia, heterosis y/o adaptación local después de la introducción de poblaciones artificiales de Succisa pratensis. Introdujimos individuos de poblaciones locales y de poblaciones artificiales distantes que fueron creadas a partir de poblaciones tanto pequeñas como grandes. Las poblaciones artificiales fueron creadas con el mismo tamaño poblacional censal pero variaron en tamaños poblacionales efectivos al ajustar la parentela de los individuos. Analizamos las consecuencias demográficas de la endogamia, heterosis y/o adaptación local de estas poblaciones artificiales. Después de la autofecundación se manifestó una reducción en el rendimiento por reducción en la producción y peso de semillas y en el porcentaje de germinación y floración. La producción y peso de semillas, el porcentaje de floración y el número de botones florales fueron afectados negativamente por el tamaño poblacional pequeño. La adaptación local incrementó la biomasa y el porcentaje de floración en individuos locales. El peso y producción de semillas mostró heterosis significativa. Nuestros resultados demuestran que las poblaciones amenazadas pueden beneficiarse de la introducción y del reforzamiento genético de individuos de poblaciones emparentadas. Las diferencias significativas entre las poblaciones artificiales en varios de los componentes de rendimiento medidos sugiere que la introducción o reforzamiento se logra mejor con material de una población local o, cuando no disponible, con material de varias poblaciones grandes. [source] Performance of Greater Sage-Grouse Models for Conservation Assessment in the Interior Columbia Basin, U.S.A.CONSERVATION BIOLOGY, Issue 5 2002Michael J. Wisdom Consequently, we evaluated the performance of two models designed to assess landscape conditions for Greater Sage-Grouse across 13.6 million ha of sagebrush steppe in the interior Columbia Basin and adjacent portions of the Great Basin of the western United States (referred to as the basin). The first model, the environmental index model, predicted conditions at the scale of the subwatershed (mean size of approximately 7800 ha) based on inputs of habitat density, habitat quality, and effects of human disturbance. Predictions ranged on a continuous scale from 0 for lowest environmental index to 2 for optimal environmental index. The second model, the population outcome model, predicted the composite, range-wide conditions for sage grouse based on the contribution of environmental index values from all subwatersheds and measures of range extent and connectivity. Population outcomes were expressed as five classes (A through E) that represented a gradient from continuous, well-distributed populations (outcome A) to sparse, highly isolated populations with a high likelihood of extirpation (outcome E). To evaluate performance, we predicted environmental index values and population outcome classes in areas currently occupied by sage grouse versus areas where extirpation has occurred. Our a priori expectations were that models should predict substantially worse environmental conditions ( lower environmental index) and a substantially higher probability of extirpation ( lower population outcome class) in extirpated areas. Results for both models met these expectations. For example, a population outcome of class E was predicted for extirpated areas, as opposed to class C for occupied areas. These results suggest that our models provided reliable landscape predictions for the conditions tested. This finding is important for conservation planning in the basin, where the models were used to evaluate management of federal lands for sage grouse. Resumen: Modelos válidos de hábitat y de poblaciones del urogallo (Centrocercus urophasianus) son una necesidad crítica para su manejo debido a la creciente preocupación por la viabilidad de la población. Por lo tanto, evaluamos el funcionamiento de dos modelos diseñados para evaluar las condiciones del paisaje para el urogallo en 13.6 millones de ha de la estepa de artemisa en la Cuenca Columbia Interior y las porciones adyacentes de la Gran Cuenca de los Estados Unidos occidentales (referidos como cuenca). El primer modelo (modelo de índice ambiental) predijo condiciones a escala de la subcuenca (tamaño promedio , 7800 ha) basado en información de la densidad del hábitat, calidad del hábitat y efectos de la perturbación humana. Las predicciones variaron en una escala continua a partir de 0 (el índice ambiental más bajo) a 2 (índice ambiental óptimo). El segundo modelo (modelo del resultado de la población) predijo las condiciones compuestas, de amplio rango, para el urogallo con base en la contribución de los valores de índice ambiental de todas las subcuencas y las medidas de extensión y de conectividad de la pradera. Los resultados de la población fueron expresados en cinco clases (A - E) que representan un gradiente de poblaciones continuas, bien-distribuidas (resultado A) a poblaciones escasas, altamente aisladas con una alta probabilidad de extirpación (resultado E). Para evaluar el funcionamiento, predijimos valores de índice ambiental y resultados de la población en las áreas actualmente ocupadas por urogallos versus áreas donde ha ocurrido la extirpación. Nuestras expectativas a priori eran que los modelos deben predecir condiciones ambientales substancialmente peores (índice ambiental más bajo) y una probabilidad de extirpación sustancialmente mayor (menor resultado de la población) en áreas extirpadas. Los resultados para ambos modelos cumplieron estas expectativas. Por ejemplo, se predijo un resultado de la población de la clase E para áreas extirpadas, en comparación con la clase C para áreas ocupadas. Estos resultados sugieren que nuestros modelos proporcionaron predicciones de paisaje confiables para las condiciones probadas. Este hallazgo es importante para planeación de la conservación de la cuenca, donde los modelos fueron utilizados para evaluar el manejo de terrenos federales para urogallos. [source] Genetic Allee effects on performance, plasticity and developmental stability in a clonal plantECOLOGY LETTERS, Issue 6 2000M. Fischer Negative effects of small population size on fitness, so-called Allee effects, may threaten population persistence even in intact habitat remnants. We studied genotypes of 14 isolated populations of the clonal plant Ranunculus reptans, for which molecular genetic (RAPD-) variability is higher for large than for small populations. In a competition-free greenhouse environment vegetative offspring of genotypes from large populations produced more rosettes and flowers, indicating higher fitness. Within-genotype coefficients of variation in performance traits, indicating developmental instability, were lower for genotypes from populations with higher RAPD-variability. In competition with a taller grass, we found relative reduction in leaf length less pronounced for plants from large populations, suggesting higher adaptive plasticity. Our experimental study of a plant with predominantly vegetative reproduction suggests, that negative genetic effects of recent habitat fragmentation, which so far rather were expected in plants with frequent sexual reproduction, are more severe and more common than previously acknowledged. [source] Total population density during the first year of life as a major determinant of lifetime body-length trajectory in marble troutECOLOGY OF FRESHWATER FISH, Issue 4 2008S. Vincenzi Abstract,,, The conditions experienced early in life can strongly influence life-history trajectories in a variety of animal species. Here, we use data from four isolated populations of the endangered stream-dwelling salmonid marble trout (Salmo marmoratus Cuvier 1817) living in the Soca and Idrijca river basins (Slovenia) to explore the influence of the total density experienced during and after the first year of life by marble trout year-classes on body length of marble trout through the lifetime. Analyses were performed by pooling together the stream-specific datasets to cover a wider range of densities. Mean body length of marble trout year-classes through the lifetime (from age 1+ to 5+) was negatively related to total density of marble trout during the first year of life. The relationship between density during the first growth period and body length through the lifetime was well described by negative power curves. Total population density after the first year of life was not correlated with body length, thus suggesting that body growth trajectories are heavily determined early in life. Given size-dependent sexual maturity and egg production in marble trout, the relationship between density early in life and lifetime individual growth may have strong implications in terms of population dynamics and regulation of population size. [source] Hormetic effects of gamma radiation on the stress axis of natural populations of meadow voles (Microtus pennsylvanicus)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2005Rudy Boonstra Abstract We tested the hypothesis that low doses of gamma radiation have beneficial, hormetic effects on the stress axis (the hypothalamic-pituitary-adrenocortical axis) of free-ranging meadow vole populations (Microtus pennsylvanicus). Voles were exposed to chronic gamma radiation from a 137Cs field irradiator. In isolated populations, voles received one of three treatments over a four-year period: Controls (0.19,0.42 ,Gy/h , levels that were 2,5X above background levels [0.1 ,Gy/h] and live-trapped in all years , 1982,1985), low doses (22.6 ,Gy/h , 50,200X background, live-trapped from November 1982,April 1985), or high doses (3,840 ,Gy/h , 40,000X background, live-trapped from November 1983,April 1985). Voles exposed to a low dose had levels of free and total corticosterone that were significantly higher than those in the control or high-dose groups. Differences in response to radiation between the sexes were apparent for maximum corticosterone-binding capacity, with females exposed to low doses having higher binding capacity than control or high-dose females, whereas males exposed to low doses had lower binding capacity than control or high-dose males. Low-dose voles had higher counts of neutrophils than either the controls or high-dose voles; hematocrit was greater in the controls than in irradiated voles. These results indicate that voles display a hormetic response to radiation, wherein low doses of an otherwise harmful agent produce a beneficial effect. The stimulation of the stress axis resulting in the increased secretion of glucocorticoids, which may protect against the excessive actions of the immune and inflammatory responses, may be a key mechanism producing this effect. [source] Multiple sclerosis complexity in selected populations: the challenge of Sardinia, insular Italy1EUROPEAN JOURNAL OF NEUROLOGY, Issue 4 2002S. Sotgiu Several lines of evidence indicate a genetic contribution to multiple sclerosis (MS) both in terms of predisposition to the disease and of immunological mechanisms which are known to play crucial roles in MS pathogenesis. The presence of high- and low-risk areas for MS in neighbouring regions supports the theory that MS predisposition is influenced by a complex interaction of genetic and environmental factors. Therefore, the use of genetically homogeneous and geographically isolated populations becomes an increasing requirement to reduce biasing biological variables. Sardinians fulfil these conditions well because of their different phylogeny from Europeans and the unique selective pressures which shaped their genome. Sardinians display amongst the highest MS prevalence rates world-wide and increasing MS incidence rates over time. Also, MS in Sardinia is linked to distinct human leucocyte antigen (HLA) alleles and associated to different patterns of cytokine production from lymphoid cells of different HLA subtypes. In this context, recent findings and future perspectives on the peculiarities of Sardinian MS concerning genetic, immunological and epidemiological aspects are presented. So far, our results indicate that variations at the level of territorial distribution and HLA-association are present which render MS heterogeneous even in this ethnically homogeneous population. [source] Short exposure to high levels of fluoride induces stage-dependent structural changes in ameloblasts and enamel mineralizationEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2006D. M. Lyaruu We tested the hypothesis that the sensitivity of forming dental enamel to fluoride (F,) is ameloblast developmental stage-dependent and that enamel mineralization disturbances at the surface of fluorotic enamel are caused by damage to late-secretory- and transitional-stage ameloblasts. Four-day-old hamsters received a single intraperitoneal dose of 2.5,20 mg NaF/kg body weight and were examined, 24 h later, by histology and histochemistry. A single dose of ,,5 mg of NaF/kg induced the formation of a hyper- followed by a hypomineralized band in the secretory enamel, without changing the ameloblast structure. At 10 mg of NaF/kg, cystic lesions became apparent under isolated populations of distorted late-secretory- and transitional-stage ameloblasts. Staining with von Kossa stain showed that the enamel under these lesions was hypermineralized. At 20 mg of NaF/kg, cystic lesions containing necrotic cells were also found in the early stages of secretory amelogenesis and were also accompanied with hypermineralization of the enamel surface. We concluded that the sensitivity to F, is ameloblast developmental stage-dependent. Groups of transitional ameloblasts are most sensitive, followed by those at early secretory stages. These data suggest that a F-induced increase in cell death in the transitional-stage ameloblasts accompanies the formation of cystic lesions, which may explain the formation of enamel pits seen clinically in erupted teeth. [source] | |||||||||||||||||||||||||||||||||||||||||||