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Stable Population (stable + population)
Selected AbstractsALLEE EFFECT AND SELF-FERTILIZATION IN HERMAPHRODITES: REPRODUCTIVE ASSURANCE IN DEMOGRAPHICALLY STABLE POPULATIONSEVOLUTION, Issue 12 2004Pierre-Olivier Cheptou Abstract The fact that selfing increases seed set (reproductive assurance) has often been put forward as an important selective force for the evolution of selfing. However, the role of reproductive assurance in hermaphroditic populations is far from being clear because of a lack of theoretical work. Here, I propose a theoretical model that analyzes selffertilization in the presence of reproductive assurance. Because reproductive assurance directly influences the per capita growth rate, I developed an explicit demographic model for partial selfers in the presence of reproductive assurance, specifically when outcrossing is limited by the possibility of pollen transfer (Allee effect). Mating system parameters are derived as a function of the underlying demographical parameters. The functional link between population demography and mating system parameters (reproductive assurance, selfing rate) can be characterized. The demographic model permits the analysis of the evolution of self-fertilization in stable populations when reproductive assurance occurs. The model reveals some counterintuitive results such as the fact that increasing the fraction of selfed ovules can, in certain circumstances, increase the fraction of outcrossed ovules. Moreover, I demonstrate that reproductive assurance per se cannot account for the evolution of stable mixed selfing rates. Also, the model reveals that the extinction of outcrossing populations depends on small changes in population density (ecological perturbations), while the transition from outcrossing to selfing can, in certain cases, lead the population to extinction (evolutionary suicide). More generally, this paper highlights the fact that self-fertilization affects both the dynamics of individuals and the dynamics of selfing genes in hermaphroditic populations. [source] Winter energetics of Virginia opossums Didelphis virginiana and implications for the species' northern distributional limitECOGRAPHY, Issue 6 2005L. Leann KandaArticle first published online: 27 SEP 200 While climatic limitations are widely recognized as primary factors determining the distributions of many species, the physiological link between climate and species' persistence is poorly understood. The Virginia opossum Didelphis virginiana is a species for which winter energetics have been evaluated and a northern geographical limit has been hypothesized. Expansion of opossum populations beyond this limit, however, suggests that a previous winter energetics model requires modification. I update this energetics model by incorporating random foraging success to estimate the probability of opossum survival under varying winter temperature regimes. Estimation of opossum "success" for winters in Amherst, Massachusetts, since 1926 showed that juvenile females, the key breeding component of the population, would survive at a rate high enough to maintain a stable population in only 4 of the 77 yr. The model correctly predicted the fate of 13 of 14 opossums monitored in the Amherst area during the winters of 2000,2003. The current energetics model does not correctly predict autumn weight gain, but it does accurately estimate opossum winter survival. However, the model predicts that opossums should be winter-limited in areas such as Amherst, Massachusetts, where in fact they are well established. This discrepancy may be explained in three ways: weather station data do not adequately reflect available microclimates, opossums show high levels of flexibility in cold-weather foraging behavior, and most likely, humans provide food and shelter that mitigate the effect of winter. [source] Retroviral labeling of Schwann cells: In vitro characterization and in vivo transplantation to improve peripheral nerve regenerationGLIA, Issue 1 2001Afshin Mosahebi Abstract Transplantation of Schwann cells (SCs) is a promising treatment modality to improve neuronal regeneration. Identification of the transplanted cells is an important step when studying the development of this method. Genetic labeling is the most stable and reliable method of cell identification, but it is still unclear whether it has deleterious effect on SC characteristics. Our aim was to achieve a stable population of SCs transduced with the lacZ gene at a high frequency using a retroviral vector in vitro, and to follow the labeled SC in vitro to assess their viability and phenotypic marker expression. Furthermore, we transplanted lacZ -labeled SCs in a conduit to repair peripheral nerve to investigate their effect on nerve regeneration in vivo. Rat and human SCs were cultured and transduced with an MFG lacZ nls marker gene, achieving a transduction rate of 80% and 70%, respectively. Rat SCs were kept in culture for 27 weeks and examined every 4 weeks for expression of lacZ, viability, and phenotypic marker expression of GFAP, p75, MHC I and II. Throughout this period, transduced rat SCs remained viable and continued to proliferate. The proportion of cells expressing lacZ dropped only by 10% and the expression of phenotypic markers remained stable. Transduced human SCs were followed up for 4 weeks in culture. They proliferated and continued to express the lacZ gene and phenotypic marker expression of GFAP and p75 was preserved. Primary culture of transduced rat SCs were transplanted, syngeneically, in a conduit to bridge a 10 mm gap in sciatic nerve and the grafts were examined after 3 weeks for the presence and participation of labeled SCs and for axonal regeneration distance. Transplanted transduced rat SCs were clearly identified, taking part in the regeneration process and enhancing the axonal regeneration rate by 100% (at the optimal concentration) compared to conduits without SCs. Thus, retroviral introduction of lacZ gene has no deleterious effect on SCs in vitro and these SCs take part and enhance nerve regeneration in vivo. GLIA 34:8,17, 2001. © 2001 Wiley-Liss, Inc. [source] Breeding biology and breeding success of the Lesser Grey Shrike Lanius minor in a stable and dense populationIBIS, Issue 2 2000ANTON KRISTIN The Lesser Grey Shrike Lanius minor is highly endangered throughout Europe, having declined markedly in abundance and range. Long-term changes in climate and agricultural practices have been identified as the main reasons for its decline. To determine which factors influence short-term changes in breeding success, we examined several aspects of its breeding biology. Our investigation revealed that our study area bears a large and stable population of this species. In 1996 and 1997, we recorded 84 and 77 breeding pairs in an area of 20 km2, with an average of 4.20 and 3.85 pairs/km2 respectively. Data on breeding density, clutch size and fledging success from 1989 to 1997 (excluding 1992) indicate a stable breeding population with a constant high breeding success. Reproductive success declined through the season, mainly through seasonal variation in clutch size rather than chick mortality. However, breeding success was generally high (69% and 79% of the nests produced chicks], with low hatching failure and few nest losses. The main cause of breeding failure was nest predation (at least 50% of nest losses), mainly by magpies (at least 66% of depredated nests). Although in this population the Lesser Grey Shrike tends to aggregate in clusters, breeding density had no obvious effect on breeding success and nest predation. [source] Surveillance and measuring trends of stroke in Japan: The Takashima Stroke Registry (1988 , present)INTERNATIONAL JOURNAL OF STROKE, Issue 2 2007Yoshikuni Kita This stroke registry is a population-based, prospective, observational study whose objective is to monitor trends in the incidence and case-fatality of stroke in Japan. Takashima County is located in the rural area of the Shiga prefecture in central Japan, having a stable population of approximately 54,000. It is a farming community with similar cultural values and standards of living throughout the region. The population has remained fairly stable during the 16-year study period. 1750 stroke cases (men 937 and women 813) were registered during 1988,2002. The average ages of the men and women patients were 69.4 and 74.4 years respectively. Stroke diagnostic criteria are established for the Monitoring System for Cardiovascular Disease commissioned by the Ministry of Health and Welfare, Japan. These criteria were based on WHO-MONICA project. Takashima registry system was planned to capture all the cases in the study area by covering all the hospitals of the county. To ensure that eligible patients hospitalized outside the county were not omitted, registration procedures were also conducted at three high-level medical facilities within the Shiga region but outside the county. Due to the high rate of computed tomography use in Japan the identification of stroke cases within the study area is almost complete and stroke diagnosis and classification are accurately recorded. [source] How to test different density-dependent fecundity hypotheses in an increasing or stable populationJOURNAL OF ANIMAL ECOLOGY, Issue 1 2006MIGUEL FERRER Summary 1We report on a simulation study of increasing and stable populations working under two different hypotheses of density dependence of fecundity: the habitat heterogeneity hypothesis (HHH) and the individual adjustment hypothesis (IAH). Our aim is to find critical differences between the two regulatory hypotheses in natural populations. 2Populations under HHH show a strong negative relationship between fecundity and the coefficient of variation of fecundity. We also found a strong negative relationship between fecundity and skewness, demonstrating that, as fecundity decreases, the form of the distribution of brood sizes changes, being more left-skewed due to more territories failing to produce any offspring. 3This strong relationship was found only in the simulations of populations under HHH; whether increasing or stable, and under different ratios of good : poor territories and different population sizes. In contrast, no relationship between mean fecundity and skewness was found among simulations under IAH. 4Populations under IAH also showed a significant relationship between mean fecundity and the coefficient of variation of fecundity, but with a lower slope than in populations under HHH. 5In conclusion, skewness was found to be an adequate critical test that showed significant and strong relationships with mean fecundity only in populations under HHH, whether increasing or stable. This test is useful for species with a discrete distribution of offspring with a small number of integer categories, including most of the bird and mammal species. [source] Ankle eversion torque response to sudden ankle inversion Torque response in unbraced, braced, and pre-activated situationsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2005Lars Konradsen Abstract In 13 young ankle stable subjects, ankle eversion torque and peroneal EMG were simultaneously recorded in response to sudden ankle inversion. The eversion torque response was bi-phasic. The initial development of torque, which was responsible for 30% of the maximal eversion torque response, was observed 135ms after the start of platform rotation and correlated well with the onset of the automatic postural peroneal EMG response. The remaining eversion torque response commenced after 305 ms, strongly correlating with the onset of the peroneal long latency voluntary EMG activity. With the ankle unbraced, 66% of the maximal torque level was reached in 326ms. While braced, the same torque magnitude was reached using 230ms (p < 0.02), and pre-activation of the peroneal muscles allowed the subjects to reach the same level of torque in 89ms (p < 0.0005). Prior to the study, a common reaction pattern to sudden inversion was expected in an ankle stable population, but review of the eversion torque and EMG data from the 13 subjects revealed three different voluntary reaction patterns: 10 subjects showed an efficient activation of evertor muscles; two subjects stiffened their ankles with activation of both in- and evertor muscles; and one subject showed a marginal voluntary activation of the ankle evertors. The results of the study indicate that the reaction to sudden ankle inversion is not solely automatic. The main part of the torque response is voluntarily mediated and inter-individual differences in strategy seem to exist in healthy subjects. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] A Retrospective Look at the Water Resource Management Policies in Nassau County, Long Island, New York,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2008Daniel J. St. Germain Abstract:, The residents of Nassau County Long Island, New York receive all of their potable drinking water from the Upper Glacial, Jameco/Magothy (Magothy), North Shore, and Lloyd aquifers. As the population of Nassau County grew from 1930 to 1970, the demand on the ground-water resources also grew. However, no one was looking at the potential impact of withdrawing up to 180 mgd (7.9 m3/s) by over 50 independent water purveyors. Some coastal community wells on the north and south shores of Nassau County were being impacted by saltwater intrusion. The New York State Legislature formed a commission to look into the water resources in 1972. The commission projected extensive population growth and a corresponding increase in pumping resulting in a projected 93.5 to 123 mgd (4.1 to 5.5 m3/s) deficit by 2000. In 1986, the New York Legislature passed legislation to strengthen the well permit program and also establish a moratorium on new withdrawals from the Lloyd aquifer to protect the coastal community's only remaining supply of drinking water. Over 30 years has passed since the New York Legislature made these population and pumping projections and it is time to take a look at the accuracy of the projections that led to the moratorium. United States Census data shows that the population of Nassau County did not increase but decreased from 1970 to 2000. Records show that pumping in Nassau County was relatively stable fluctuating between 170 and 200 mgd (7.5 to 8.8 m3/s) from 1970 to 2004, well below the projection of 242 to 321 mgd (10.6 to 14.1 m3/s). Therefore, the population and water demand never grew to projected values and the projected threat to the coastal communities has diminished. With a stable population and water demand, its time to take a fresh look at proactive ground-water resource management in Nassau County. One example of proactive ground-water management that is being considered in New Jersey where conditions are similar uses a ground-water flow model to balance ground water withdrawals, an interconnection model to match supply with demand using available interconnections, and a hydraulic model to balance flow in water mains. New Jersey also conducted an interconnection study to look into how systems with excess capacity could be used to balance withdrawals in stressed aquifer areas with withdrawals in unstressed areas. Using these proactive ground-water management tools, ground-water extraction could be balanced across Nassau County to mitigate potential impacts from saltwater intrusion and provide most water purveyors with a redundant supply that could be used during water emergencies. [source] Genetic modification of mesenchymal stem cells to express a single-chain antibody against EGFRvIII on the cell surfaceJOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, Issue 4 2010Irina V. Balyasnikova Abstract Human adult mesenchymal stem cells (hMSCs) are under active investigation as cellular carriers for gene therapy. hMSCs possess natural tropism toward tumours; however, the targeting of hMSCs to specific cell populations within tumours is unexplored. In the case of glioblastoma multiforme (GBM), at least half of the tumours express EGFRvIII on the cell surface, an ideal target for antibody-mediated gene/drug delivery. In this study, we investigated the feasibility of genetically modifying hMSCs to express a single-chain antibody (scFv) to EGFRvIII on their surfaces. Nucleofection was used to transfect hMSCs with cDNA encoding scFv EGFRvIII fused with PDGFR or human B7-1 transmembrane domains. The expression of scFv EGFRvIII on the cell surface was assessed by FACS. A stable population of scFv EGFRvIII-expressing hMSCs was selected, based on antibiotic resistance, and enriched using FACS. We found that nucleofection allows the efficient expression of scFv EGFRvIII on the cell surface of hMSCs. hMSCs transfected with the construct encoding scFv EGFRvIII as a fusion with PDGFRtm showed scFv EGFRvIII expression in up to 86% of cells. Most importantly, human MSCs expressing scFv against EGFRvIII demonstrated enhanced binding to U87-EGFRvIII cells in vitro and significantly increased retention in human U87-EGFRvIII-expressing tumours in vivo. In summary, we provide the first conclusive evidence of genetic modification of hMSCs with a single-chain antibody against an antigen expressed on the surface of tumour cells, thereby opening up a new venue for enhanced delivery of gene therapy applications in the context of malignant brain cancer. Copyright © 2009 John Wiley & Sons, Ltd. [source] Mitochondrial phylogeography of the European sprat (Sprattus sprattus L., Clupeidae) reveals isolated climatically vulnerable populations in the Mediterranean Sea and range expansion in the northeast AtlanticMOLECULAR ECOLOGY, Issue 17 2008P. V. DEBES Abstract We examined the genetic structure of the European sprat (Sprattus sprattus) by means of a 530-bp sequence of the mitochondrial control region from 210 fish originating from seven sampling localities of its distributional range. Phylogeographical analysis of 128 haplotypes showed a phylogenetic separation into two major clades with the Strait of Sicily acting as a barrier to gene flow between them. While no population differentiation was observed based on analysis of molecular variance and net nucleotide differences between samples of the Baltic Sea, the North Sea and the Bay of Biscay nor between the Black Sea and the Bosporus, a strong population differentiation between these samples and two samples from the Mediterranean Sea was found. Further, the biggest genetic distance was observed within the Mediterranean Sea between the populations of the Gulf of Lyon and the Adriatic Sea, indicating genetic isolation of these regions. Low genetic diversities and star-like haplotype networks of both Mediterranean Sea populations point towards recent demographic expansion scenarios after low population size, which is further supported by negative FS values and unimodal mismatch distributions with a low mean. Along the northeast Atlantic coast, a northwards range expansion of a large and stable population can be assumed. The history of a diverse but differentiated Black Sea population remains unknown due to uncertainties in the palaeo-oceanography of this sea. Our genetic data did not confirm the presently used classification into subspecies but are only preliminary in the absence of nuclear genetic analyses. [source] EXPLORING THE IMPORTANCE OF EXCESS FEMALE MORTALITY AND DISCRIMINATION IN "NATALITY" IN EXPLAINING THE "LOWNESS" OF THE SEX RATIO IN INDIATHE DEVELOPING ECONOMIES, Issue 2 2009D. JAYARAJ J16 The beginning of the present century has been marked by a shift in attention from "excess" female mortality to discrimination in natality in explaining the "lowness" of the sex ratio or proportion of women in India's population. Such a shift in focus seemingly suggests that discrimination in intra-family allocation of resources has reduced substantially in India. In this context, an attempt has been made to decompose the observed lowness of the sex ratio in India vis-à-vis that of the stable population into that attributable to: (1) age structure difference, (2) excess female mortality, and (3) abnormalities in sex ratios at birth in India. Estimated contributions by each factor suggest that, as late as 2001, excess female mortality or the lowness of the relative survival advantage of women is the single most important determinant of "missing" women in India. The results also point to the importance of age structure difference, which accounts for a little more than 17% of the lowness of the sex ratio in India in 2001. [source] ALLEE EFFECT AND SELF-FERTILIZATION IN HERMAPHRODITES: REPRODUCTIVE ASSURANCE IN DEMOGRAPHICALLY STABLE POPULATIONSEVOLUTION, Issue 12 2004Pierre-Olivier Cheptou Abstract The fact that selfing increases seed set (reproductive assurance) has often been put forward as an important selective force for the evolution of selfing. However, the role of reproductive assurance in hermaphroditic populations is far from being clear because of a lack of theoretical work. Here, I propose a theoretical model that analyzes selffertilization in the presence of reproductive assurance. Because reproductive assurance directly influences the per capita growth rate, I developed an explicit demographic model for partial selfers in the presence of reproductive assurance, specifically when outcrossing is limited by the possibility of pollen transfer (Allee effect). Mating system parameters are derived as a function of the underlying demographical parameters. The functional link between population demography and mating system parameters (reproductive assurance, selfing rate) can be characterized. The demographic model permits the analysis of the evolution of self-fertilization in stable populations when reproductive assurance occurs. The model reveals some counterintuitive results such as the fact that increasing the fraction of selfed ovules can, in certain circumstances, increase the fraction of outcrossed ovules. Moreover, I demonstrate that reproductive assurance per se cannot account for the evolution of stable mixed selfing rates. Also, the model reveals that the extinction of outcrossing populations depends on small changes in population density (ecological perturbations), while the transition from outcrossing to selfing can, in certain cases, lead the population to extinction (evolutionary suicide). More generally, this paper highlights the fact that self-fertilization affects both the dynamics of individuals and the dynamics of selfing genes in hermaphroditic populations. [source] How to test different density-dependent fecundity hypotheses in an increasing or stable populationJOURNAL OF ANIMAL ECOLOGY, Issue 1 2006MIGUEL FERRER Summary 1We report on a simulation study of increasing and stable populations working under two different hypotheses of density dependence of fecundity: the habitat heterogeneity hypothesis (HHH) and the individual adjustment hypothesis (IAH). Our aim is to find critical differences between the two regulatory hypotheses in natural populations. 2Populations under HHH show a strong negative relationship between fecundity and the coefficient of variation of fecundity. We also found a strong negative relationship between fecundity and skewness, demonstrating that, as fecundity decreases, the form of the distribution of brood sizes changes, being more left-skewed due to more territories failing to produce any offspring. 3This strong relationship was found only in the simulations of populations under HHH; whether increasing or stable, and under different ratios of good : poor territories and different population sizes. In contrast, no relationship between mean fecundity and skewness was found among simulations under IAH. 4Populations under IAH also showed a significant relationship between mean fecundity and the coefficient of variation of fecundity, but with a lower slope than in populations under HHH. 5In conclusion, skewness was found to be an adequate critical test that showed significant and strong relationships with mean fecundity only in populations under HHH, whether increasing or stable. This test is useful for species with a discrete distribution of offspring with a small number of integer categories, including most of the bird and mammal species. [source] Hunting for large carnivore conservationJOURNAL OF APPLIED ECOLOGY, Issue 6 2009Adrian Treves Summary 1. Carnivores are difficult to conserve because of direct and indirect competition with people. Public hunts are increasingly proposed to support carnivore conservation. This article reviews scientific evidence for the effectiveness of public hunts of large carnivores in attaining three common policy goals: stable carnivore populations, preventing conflict with carnivores (property damage and competition over game) and building public support for carnivore conservation. 2. Sustainable exploitation of stable wildlife populations has a solid, scientific foundation but the theory and its predictions must be adapted to complex patterns of carnivore behavioural ecology and population dynamics that demand years of landscape-level monitoring to understand fully. 3. A review of the evidence that hunting prevents property damage or reduces competition for game reveals large gaps in our understanding. Reducing the number of large carnivores to protect hunters' quarry species seems straightforward but we still know little about behavioural and ecological responses of the contested prey and sympatric meso-predators. For reducing property damage, the direct effect , numerical reduction in problematic individual carnivores , presents numerous obstacles, whereas the indirect effect , behavioural avoidance of humans by hunted carnivores , holds more promise. 4. Scientific measures of public support for carnivore-hunting policies are almost completely lacking, particularly measures of attitudes among hunters before and after controversial wildlife is designated as legal game species. Moreover, illegal killing of carnivores does not appear to diminish if they are designated as game. 5.Synthesis and applications. Sustainable hunting to maintain stable populations is well understood in theory but complex life histories of carnivores, and behavioural changes of hunters and the carnivores they stalk may result in unsustainable mortality for carnivores. The direct impact of hunting on carnivore damage to property is unclear and even doubtful given the inability or unwillingness of hunters to remove specific individuals selectively. However, hunters may indirectly deter carnivores from people and their property. The assumption that hunters will steward carnivores simply because they have in the past helped conserve other game species requires more study as preliminary results suggest it is incorrect. Policy-makers may achieve support for policy if they mesh utilitarian and preservationist values held by the general public. A number of opposed hypotheses should be disentangled before researchers confidently inform policy on sustainable hunting to prevent conflicts and build public support for carnivore conservation. [source] Natural disturbance and life history: consequences of winterkill on fathead minnow in boreal lakesJOURNAL OF FISH BIOLOGY, Issue 3 2006A. J. Danylchuk Age, growth and reproductive characteristics of fathead minnow Pimephales promelas populations inhabiting four lakes that varied in the extent and frequency of winterkill were studied in the boreal region of western Canada. The lifespan of fathead minnows inhabiting lakes prone to winterkill was 1,2 years shorter than those in less disturbed lakes. In populations prone to winterkill, fish displayed faster growth rates and grew to a larger size-at-age, particularly during the first year of life. Although lower population densities in winterkill lakes probably contributed to this increased growth, adults in these populations tended to spawn earlier in the season than the smaller adults in more stable populations. Fathead minnows in lakes prone to winterkill also matured at an earlier age and allocated a greater proportion of their body mass to gonads than conspecifics in the more benign, stable lakes. These trends are consistent with predictions for organisms in variable, unpredictable environments and, because fathead minnows are tolerant to a wide range of environmental conditions, suggest that variation in life-history traits among populations is probably a product of both selection and phenotypic plasticity. [source] Preferences of the Ponto-Caspian amphipod Dikerogammarus haemobaphes for living zebra musselsJOURNAL OF ZOOLOGY, Issue 3 2009J. Kobak Abstract A Ponto-Caspian amphipod Dikerogammarus haemobaphes has recently invaded European waters. In the recipient area, it encountered Dreissena polymorpha, a habitat-forming bivalve, co-occurring with the gammarids in their native range. We assumed that interspecific interactions between these two species, which could develop during their long-term co-evolution, may affect the gammarid behaviour in novel areas. We examined the gammarid ability to select a habitat containing living mussels and searched for cues used in that selection. We hypothesized that they may respond to such traits of a living mussel as byssal threads, activity (e.g. valve movements, filtration) and/or shell surface properties. We conducted the pairwise habitat-choice experiments in which we offered various objects to single gammarids in the following combinations: (1) living mussels versus empty shells (the general effect of living Dreissena); (2) living mussels versus shells with added byssal threads and shells with byssus versus shells without it (the effect of byssus); (3) living mussels versus shells, both coated with nail varnish to neutralize the shell surface (the effect of mussel activity); (4) varnished versus clean living mussels (the effect of shell surface); (5) varnished versus clean stones (the effect of varnish). We checked the gammarid positions in the experimental tanks after 24 h. The gammarids preferred clean living mussels over clean shells, regardless of the presence of byssal threads under the latter. They responded to the shell surface, exhibiting preferences for clean mussels over varnished individuals. They were neither affected by the presence of byssus nor by mussel activity. The ability to detect and actively select zebra mussel habitats may be beneficial for D. haemobaphes and help it establish stable populations in newly invaded areas. [source] Population genetics of a marine bivalve, Pinctada maxima, throughout the Indo-Australian Archipelago shows differentiation and decreased diversity at range limitsMOLECULAR ECOLOGY, Issue 24 2007CURTIS E. LIND Abstract Intraspecific genetic diversity governs the potential of species to prevail in the face of environmental or ecological challenges; therefore, its protection is critical. The Indo-Australian Archipelago (IAA) is a significant reservoir of the world's marine biodiversity and a region of high conservation priority. Yet, despite indications that the IAA may harbour greater intraspecific variation, multiple-locus genetic diversity data are limited. We investigated microsatellite DNA variation in Pinctada maxima populations from the IAA to elucidate potential factors influencing levels of genetic diversity in the region. Results indicate that genetic diversity decreases as the geographical distance away from central Indonesia increases, and that populations located towards the centre of P. maxima's range are more genetically diverse than those located peripherally (P < 0.01). Significant partitioning of genetic variation was identified (FST = 0.027; RST = 0.023, P < 0.001) and indicates that historical biogeographical episodes or oceanographic factors have shaped present population genetic structure. We propose that the genetic diversity peak in P. maxima populations may be due to (i) an abundance of suitable habitat within the IAA, meaning larger, more temporally stable populations can be maintained and are less likely to encounter genetic bottlenecks; and/or (ii) the close proximity of biogeographical barriers around central Indonesia results in increased genetic diversity in the region because of admixture of genetically divergent populations. We encourage further genetic diversity studies of IAA marine biota to confirm whether this region has a significant role in maintaining intraspecific diversity, which will greatly assist the planning and efficacy of future conservation efforts. [source] The Iron Age in Western Spain (800 BC,AD 50): An OverviewOXFORD JOURNAL OF ARCHAEOLOGY, Issue 1 2000Jseús R. Álvarez-Sanchís Vettonia was one of the most important Celtic regions in Iberia which emerged in the Iron Age. It corresponds largely to western Spain, between the Duero and Tagus valleys. The archaeological evidence indicates that the formation of this ethnic group lay in an historical process whose roots went back to the Late Bronze Age-Early Iron Age, when we begin to find a regular association between the first fortified sites and stable populations. These groups did not consolidate before the second half of the first millennium BC, in parallel with the development of other peoples of the interior of the Iberian Peninsula. This period can be recognized in particular through the spread of the ritual of cremation, ironworking, the adoption of the potter's wheel and the expansion of some settlements oppida which were ultimately to disappear with the Roman conquest. This paper sets out to examine the evolution of the area from an indigenous perspective, examining the process of change before and after the evidence referred to by Greek and Roman writers. [source] | ||||||||||||||||