Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Mapping population”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36Linked to original sources
PubMed2001

Construction of a genetic linkage map of the model legume Lotus japonicus using an intraspecific F2 population.

Among leguminous plants, the model legume Lotus japonicus (Regel) Larsen has many biological and genetic advantages. We have developed a genetic linkage map of L. japonicus based on amplified fragment length polymorphism (AFLP), simple sequence repeat polymorphism (SSRP) and derived cleaved amplified polymorphic sequence (dCAPS). The F2 mapping population used was derived from a cross between two L. japonicus accessions Gifu B-129 and Miyakojima MG-20. These parental accessions showed remarkable cytological differences, particularly with respect to size and morphology of chromosomes 1 and 2. Using fluorescence in situ hybridization (FISH) with BAC clones from Gifu B-129 and TAC (Transformation-competent Artificial Chromosome) clones from Miyakojima MG-20, a reciprocal translocation was found to be responsible for the cytological differences between chromosomes 1 and 2. The borders of the translocations were identified by FISH and by alignment toward the L. filicaulis x L. japonicus Gifu B-129 linkage map. The markers from the main translocated region were located on linkage groups 1 and 2 of the two accessions, Gifu B-129 and Miyakojima MG-20, respectively. The framework of the linkage map was constructed based on codominant markers, and then dominant markers were integrated separately in each linkage group of the parents. The resulting linkage groups correspond to the six pairs of chromosomes of L. japonicus and consist of 287 markers with 487.3 cM length in Gifu B-129 and 277 markers with 481.6 cM length in Miyakojima MG-20. The map and marker information is available through the World Wide Web at http://www.kazusa.or.jp/lotus/.

Chromosome Mapping↗
PubMed2003

Genome mapping of the orange blotch colour pattern in cichlid fishes.

The dramatic variation of cichlid fish colour pattern is thought to function in mate choice, evolve by sexual selection, and contribute to explosive speciation. Here, we combine linkage mapping and population genetic analyses to identify a single region of the cichlid genome responsible for the orange blotch (OB) colour phenotype. In each analysis, OB is tightly linked to the c-ski1 gene. Additionally, we use comparative mapping information from the Takifugu rubripes and human genomes to suggest positional candidate loci for OB. Our work should engender a more comprehensive understanding of the molecular ecology of OB and its role in cichlid speciation. Moreover, we have assembled the components of a method to focus upon the genetic basis of evolutionarily and ecologically significant phenotypes.

Animals↗
PubMed2001

Genetic basis for co-adaptive gene complexes in rice (Oryza sativa L.) landraces.

One hundred and twenty-two AFLP markers were mapped using an IR64 x Azucena rice doubled-haploid (DH) population. The distribution of these mapped markers was monitored across a set of 48 diverse landraces of rice. Strong statistical associations were observed between 960 of the 7381 possible pairs of markers across the diverse material. These 960 strongly associated pairs of markers mapped to the same chromosomes in only 111 cases. The remaining 849 pairs were the result of association between markers found on different chromosomes. More than 21% of these genetically unlinked but strongly associated markers are not randomly distributed across the genome but instead occupy blocks of DNA on different rice chromosomes. Amongst associated blocks, there has clearly been maintenance of combinations of marker alleles across very diverse germplasm. Analyses have also revealed that markers are found in association with performance for each of four quantitative traits in both the diverse landrace material and a DH mapping population. It is proposed that the present data provide strong evidence for the co-adaptation of geographically distinct landraces and that this has resulted over time in the maintenance of 'adaptive gene complexes' involving agronomically important quantitative traits.

Adaptation, Biological↗
PubMed2002

Resistance gene analogues of chickpea ( Cicer arietinum L.): isolation, genetic mapping and association with a Fusarium resistance gene cluster.

Resistance gene analogues (RGAs) of Cicer were isolated by different PCR approaches and mapped in an inter-specific cross segregating for fusarium wilt by RFLP and CAPS analysis. Initially, two pairs of degenerate primers targeting sequences encoded at nucleotide-binding sites (NBS), which are conserved in plant disease resistance genes such as RPS2, L6 and N, were selected for amplification. Cloning and sequence analysis of amplified products from C. arietinum DNA revealed eight different RGAs. Additionally, five RGAs were identified after characterisation of the presumptive RGA alleles from C. reticulatum. Therefore, a total of 13 different RGAs were isolated from Cicer and classified through pair-wise comparison into nine distinct classes with sequence similarities below a 68% amino acid identity threshold. Sequence comparison of seven RGA alleles of C. arietinum and C. reticulatum revealed polymorphisms in four RGAs with identical numbers of synonymous and non-synonymous substitutions. An NlaIII site, unique in the RGA-A allele of C. arietinum, was exploited for CAPS analysis. Genomic organisation and map position of the NBS-LRR candidate resistance genes was probed by RFLP analysis. Both single-copy as well as multi-copy sequence families were present for the selected RGAs, which represented eight different classes. Five RGAs were mapped in an inter-specific population segregating for three race-specific Fusarium resistances. All RGAs mapped to four of the previously established eight linkage groups for chickpea. Two NBS-LRR clusters were identified that could not be resolved in our mapping population. One of these clusters, which is characterised by RFLP probe CaRGA-D, mapped to the linkage group harbouring two of three Fusarium resistance genes characterised in the inter-specific population. Our study provides a starting point for the characterisation and genetic mapping of candidate resistance genes in Cicer that is useful for marker-assisted selection and as a pool for resistance genes of Cicer.

Journal Article↗
PubMed1998

A New Method for Estimating Model Parameters for Multinomial Data.

A new procedure for estimating the parameters of a scientific model is described, and the method is applied and illustrated for the class of experiments with multinominal data structure. The procedure is referred to as the method of population-parameter mapping, and it has a number of novel and advantageous features. The method is a variation of a standard Bayesian analysis. However, instead of directly developing a posterior distribution for the model parameters, this procedure first characterizes the population proportions for the multinomial cells. Random samples are then drawn from the posterior distribution for these proportions, and these samples are mapped to the parameters of the scientific model. This method leads naturally to a definition of model identifiability, and leads to a direct probability estimate of the coherence of the scientific model. Moreover, the new procedure can circumvent the problem of dealing with computationally difficult integrals that frequently occur with Bayesian analyses of complex multinomial models. The method is illustrated by means of several memory measurement models as well as a signal-detection model. Copyright 1998 Academic Press.

Journal Article↗
PubMed1994

Map-based cloning in crop plants. Tomato as a model system: I. Genetic and physical mapping of jointless.

A map-based cloning scheme is being used to isolate the jointless (j) gene of tomato. The jointless locus is defined by a single recessive mutation that completely suppresses the formation of the fruit and flower pedicel and peduncle abscission zone jointless was mapped in an F2 population of an interspecific cross between Lycopersicon esculentum and Lycopersicon pennellii to a 7.1 cM interval between two restriction fragment length polymorphism (RFLP) markers TG523 and TG194. Isogenic DNA pools were then constructed from a subset of the mapping population and screened with 800 random decamers for random amplification of polymorphic DNA (RAPD) polymorphisms. Five new RAPD markers were isolated and mapped to chromosome 11, two of which were mapped within the targeted interval. One marker, RPD158, was mapped 1.5 cM to the opposite side of jointless relative to TG523 and thus narrowed the interval between the closest flanking markers to 3.0 cM. Physical mapping by pulse-field gel electrophoresis using TG523 and RPD158 as probes demonstrated that both markers hybridize to a common 600 kb SmaI restriction fragment. This provided an estimate of 200 kb/cM for the relationship between physical and genetic distances in the region of chromosome 11 containing the j locus. The combined results provide evidence for the feasibility of the next step toward isolation of the jointless gene by map-based cloning--a chromosome walk or jump to jointless.

Base Sequence↗
PubMed2006

Genetic mapping of seed shape in three populations of recombinant inbred lines of soybean (Glycine max L. Merr.).

Round soybean seeds are sought-after for food-type soybean. Also the genetic control of seed geometry is of scientific interest. The objectives of this study were to estimate heritability and map quantitative trait loci (QTLs) responsible for seed shape traits. Three densely mapped recombinant inbred populations each with 192 segregants were used, Minsoy x Archer, Minsoy x Noir1, and Noir1 x Archer. A two rep two location experiment was conducted in Los Andes, Chile, and East Lansing, MI, USA. Seed height (SH), width (SW), length (SL), and seed volume (SV) as width x height x length were measured to determine seed shape. Heritability was estimated by variance component analysis. A total of 19 significant QTLs (LOD >or= 3.7) in ten linkage groups (LG) were detected for all the traits. Only one QTL was stable across populations and environments and six were stable in at least two populations in both environments. The amount of phenotypic variation explained by a single QTL varied from 7.5% for SH, to 18.5% for SW and at least 30% of the genetic variation for the traits is controlled by four QTL or less. All traits were highly correlated with each other in all populations with values ranging from 0.5 to 0.9, except for SL and SW that were not significantly correlated or had a low correlation in all populations. Narrow sense heritabilities for all traits ranged from 0.42 to 0.88. We note that LG u9, u11, and u14 are hot points of the genome for QTLs for various traits. The number and genomic distribution of the QTLs confirms the complex genetic control of seed shape. Transgressive segregation was observed for all traits suggesting that careful selection of parents with similar phenotypes but different genotypes using molecular markers can result in desirable transgressive segregants.

Chromosome Mapping↗
PubMed1994

Mapping and computer assisted morphometry and microdensitometry of glucocorticoid receptor immunoreactive neurons and glial cells in the rat central nervous system.

By means of a monoclonal mouse immunoglobulin G2a antibody against the rat liver glucocorticoid receptor and the indirect immunoperoxidase technique, the distribution of glucocorticoid receptors in neuronal and glial cell populations was mapped in the central nervous system of the male rat. The mapping was complemented by computer-assisted morphometric and microdensitometric evaluation of glucocorticoid receptor immunoreactivity in many brain regions. The quantitative analysis allowed us to achieve for the first time an objective characterization of glucocorticoid receptor distribution in the CNS, thus avoiding the ambiguities of previous mapping studies based on subjective evaluations. In addition, a taxonomic analysis of central nervous system regions containing glucocorticoid receptor immunoreactivity was carried out utilizing the quantitative parameters obtained in the morphometric evaluation. Nuclei of neuronal and glial cells containing glucocorticoid receptor immunoreactivity were detected in a widespread, but still highly heterogeneous, fashion in the central nervous system, underlining the view that glucocorticoids can control a large number of central nervous system target cells via effects on gene expression. Many nerve cell populations have been shown to contain substantial amounts of nuclear glucocorticoid receptor immunoreactivity, whereas only a low density of glial cells, in both gray and white matter, show nuclear glucocorticoid receptor immunoreactivity. Thus, in most brain areas, the major target for glucocorticoids appears to be the nerve cells. Interestingly, an inverse correlation was found in the regional density of glucocorticoid receptor-immunoreactive nerve and glial cells, suggesting that glucocorticoids may influence a brain area either via glial cells or, more frequently, via nerve cells. The results on mapping highlight the impact of glucocorticoids in areas both traditionally and not traditionally involved in stress responses. The distribution of glucocorticoid receptor immunoreactivity also emphasizes a role of glucocorticoids in the regulation of the afferent regions of the basal ganglia and the cerebellar cortex, and of both afferent and efferent layers of the cerebral cortex. Glucocorticoid receptor immunoreactivity is widely distributed over the thalamus, probably leading to modulation of activity in the various thalamocortical pathways transmitting inter alia specific sensory information to the cerebral cortex. Many unspecific afferents to the cerebral cortex are potentially regulated by glucocorticoid receptors such as the noradrenaline and 5-hydroxytryptamine afferents, since their nerve cells of origin contain strong glucocorticoid receptor immunoreactivity. Eight brain regions involving sensory, motor and limbic areas were shown to have a similarity with regard to glucocorticoid receptor-immunoreactive parameters at the level of 95%. The density of glucocorticoid receptor-immunoreactive nerve cells appeared to be the main factor in determining such a very high level of similarity. Overall, our results emphasize that glucocorticoids may appropriately tune networks of different areas to obtain optimal integration and in this way improve survival of the animal under challenging conditions.

Adrenalectomy↗
PubMed2002

Evolution after the flood: phylogeography of the desert fish Utah Chub.

The Bonneville Basin and upper Snake River drainage of western North America underwent extensive hydrological changes during the late Pleistocene, potentially influencing the geographic distribution and evolutionary trajectories of aquatic species that occupied this region. To test this hypothesis, I reconstructed the phylogeographic history of the desert fish Utah chub (Gila atraria) by examining 16 populations that span the natural distribution of this species across the Bonneville Basin and upper Snake River. I compared mitochondrial control region sequences (934 bp) among 77 individuals revealing 24 unique haplotypes. Geographic and phylogenetic relationships among haplotypes were explored using parsimony, maximum likelihood, nested clade analysis, and analysis of molecular variance. I found that G. atraria is composed of two distinct clades that represent an early Pleistocene split between the upper Snake River and Bonneville Basin. Within each of these clades, geographic structuring was highly concordant with the hydrological history of late Pleistocene Lake Bonneville and the upper Snake River, suggesting that glacial-induced shifts in climate and unpredictable geological events have played a major role in shaping genetic subdivision among populations. To examine the effects of vicariant events on phenotypic divergence among Utah chub populations, I mapped chub life histories to the control region haplotype network. I found a nonrandom association between haplotypes and life-history phenotypes. These results suggest that historical events responsible for population fragmentation may have also contributed to phenotypic shifts in life histories, both indirectly by limiting gene flow among populations and directly by altering the selective environments where populations persisted.

Animals↗
PubMed1975

Changes in a population of dikdik, Madoqua (Rhynchotragus) kirki (Günther 1880).

In 1968/69 a small local population (deme)--11 to 17 animals on 42 ha--of Kirk's Dikdik was studied in the Serengeti area, East Africa. All animals were known individually and all territorial boundaries mapped. The population was revisited in 1972 and all animals and boundaries were recorded anew. 6 animals of 1968 were still present in 1972, 6 had disappeared and 4 were new. 2 territories were still the same, 1 had been divided up between 2 neighbouring ones, 1 had gained 1 ha. In the following summary of the results the generally formulated statements like "Dikdik do" always are short and stand for the specific statements like "the observed Kirk's Dikdik of the Soit ol Modison deme did". 1. Dikdik live in pairs in territories.--2. The young are expelled from the parental territory at the age of 6 to 9 months.--3. They then are able--nearly fully grown, but the horns of the male male only half of their final size--to establish their own pairbond and territory.--4. The female can produce her first young at the age of 15 to 18 months and is reproductive up to at least 6 years.--5. While the reproductive potential is 2/female/year (gestation period 25 weeks), the realized rate of raised animals in 1968/69 was 1/female/year.--6. Average population age lies around 5 years.--7. Maximum physiological age is 10 or more years.--8. The pair bond is independent of the territorial bond and lasts for life.--9. The territorial bond is independent of the pairbond but does not last for life.--10. Strategical lines of the territorial boundaries are marked by dung areas. The families of both territories each use their own places on these areas. The whole family urinates and defaecates together (one after the other) in a ritualized way.--11. The territorial boundaries can shift. The number of dungplaces along a disputed and/or shifting boundary is higher than along an undisputed stable one.--12. Only the male defends the territory and chases off the grown up male young.--13. The female who does not defend the territory is nevertheless bound to it directly, not only by her bond to the male.--14. The most important open question with respect to the social organization is: How is the grown up female young induced to leave the territory? Can there be circumstances when she can stay?

Africa, Eastern↗
PubMed1986

A variant of a descriptive epidemiological study of cancer with the aid of a minicomputer.

The presented method of descriptive epidemiological study with the aid of a computer was designed using the model of an average district with a data file of carcinoma incidence from the period 1975-1983. The method is based on processing the statistical characteristics of a data file and on their evaluation. Plotting the coordinates of the communities and of the boundaries of the district constitutes the frame for the construction of maps. The population is divided into age groups of 5 years, incidence is standardized with respect to the age standard of the district. The selection of boundaries (isolines) of zones in the maps is based on the evaluation of the distribution of incidences and on the relative number of inhabitants in communities classified according to the standardized values. The application of the study to the work of centers for clinical oncology is discussed.

Carcinoma↗
PubMed2006

An evaluation of the performance of tag SNPs derived from HapMap in a Caucasian population.

The Haplotype Map (HapMap) project recently generated genotype data for more than 1 million single-nucleotide polymorphisms (SNPs) in four population samples. The main application of the data is in the selection of tag single-nucleotide polymorphisms (tSNPs) to use in association studies. The usefulness of this selection process needs to be verified in populations outside those used for the HapMap project. In addition, it is not known how well the data represent the general population, as only 90-120 chromosomes were used for each population and since the genotyped SNPs were selected so as to have high frequencies. In this study, we analyzed more than 1,000 individuals from Estonia. The population of this northern European country has been influenced by many different waves of migrations from Europe and Russia. We genotyped 1,536 randomly selected SNPs from two 500-kbp ENCODE regions on Chromosome 2. We observed that the tSNPs selected from the CEPH (Centre d'Etude du Polymorphisme Humain) from Utah (CEU) HapMap samples (derived from US residents with northern and western European ancestry) captured most of the variation in the Estonia sample. (Between 90% and 95% of the SNPs with a minor allele frequency of more than 5% have an r2 of at least 0.8 with one of the CEU tSNPs.) Using the reverse approach, tags selected from the Estonia sample could almost equally well describe the CEU sample. Finally, we observed that the sample size, the allelic frequency, and the SNP density in the dataset used to select the tags each have important effects on the tagging performance. Overall, our study supports the use of HapMap data in other Caucasian populations, but the SNP density and the bias towards high-frequency SNPs have to be taken into account when designing association studies.

Alleles↗
PubMed2003

Pattern analysis of human cutaneous mast cell populations by total body surface mapping.

BACKGROUND: Mast cells (MCs), critical effector cells in allergic inflammation and innate immunity to bacteria, are located in large numbers in tissues that interface the external environment, including the skin. However, little is known about the distribution and numbers of human skin MCs. OBJECTIVES: To assess the influence of age, sex and skin region on size and spatial distribution of MC populations in normal human skin. METHODS: Biopsies of healthy skin were obtained from 150 male and female individuals (age range 10-86 years). MCs were quantified and mapped planimetrically by histomorphometry in 15 anatomical sites (abdomen, thorax, lower and upper back, lower and upper arm, lower and upper leg, foot, hand, chin, nose, cheek, forehead, back of head). RESULTS: No differences in skin MC numbers or distribution were found when comparing skin obtained from male or female and from young or old individuals. At all skin sites, regardless of age or sex, MC numbers were highest in the most superficial skin layers where up to 10-fold more MCs were found as compared with the subcutis, which consistently contained the lowest numbers of MCs. Interestingly, MC numbers were highest at peripheral skin sites (maximum: chin and nose) and lowest at central skin sites (minimum: abdomen). Thus, healthy human skin exhibits a proximal/distal and a central/peripheral MC gradient and 'skin MC numbers' may vary by a factor of more than 20, depending on the skin layer and skin site analysed. CONCLUSIONS: These findings support the recently identified role of MCs in the elicitation of protective immune responses against infectious microorganisms. One possible explanation for these unexpected findings is that skin site/layer-specific factors (e.g. the density of nerves or vessels, exposure to ultraviolet irradiation, frequency of minimal trauma) are involved in the regulation of skin MC numbers and distribution.

Adolescent↗
PubMed1995

An introgression line population of Lycopersicon pennellii in the cultivated tomato enables the identification and fine mapping of yield-associated QTL.

Methodologies for mapping of genes underlying quantitative traits have advanced considerably but have not been accompanied by a parallel development of new population structures. We present a novel population consisting of 50 introgression lines (ILs) originating from a cross between the green-fruited species Lycopersicon pennellii and the cultivated tomato (cv M82). Each of the lines contains a single homozygous restriction fragment length polymorphism-defined L. pennellii chromosome segment, and together the lines provide complete coverage of the genome and a set of lines nearly isogenic to M82. A field trial of the ILs and their hybrids revealed at least 23 quantitative trait loci (QTL) for total soluble solids content and 18 for fruit mass; these estimates are twice as high as previously reported estimates based on traditional mapping populations. For finer mapping of a QTL affecting fruit mass, the introgressed segment was recombined into smaller fragments that allowed the identification of three linked loci. At least 16 QTL for plant weight, 22 for percentage green fruit weight, 11 for total yield and 14 for total soluble solids yield were identified. Gene action for fruit and plant characteristics was mainly additive, while overdominance (or pseudo-overdominance) of wild species introgressions was detected for yield.

Breeding↗
PubMed2005

Characterization and comparison of microsatellites derived from repeat-enriched libraries and expressed sequence tags.

The construction of high-density linkage maps for use in identifying loci underlying important traits requires the development of large numbers of polymorphic genetic markers spanning the entire genome at regularly spaced intervals. As part of our efforts to develop markers for rainbow trout (Oncorhynchus mykiss), we performed a comparison of allelic variation between microsatellite markers developed from expressed sequence tag (EST) data and anonymous markers identified from repeat-enriched libraries constructed from genomic DNA. A subset of 70 markers (37 from EST databases and 33 from repeat enriched libraries) was characterized with respect to polymorphism information content (PIC), number of alleles, repeat number, locus duplication within the genome and ability to amplify in other salmonid species. Higher PIC was detected in dinucleotide microsatellites derived from ESTs than anonymous markers (72.7% vs. 54.0%). In contrast, dinucleotide repeat numbers were higher for anonymous microsatellites than for EST derived microsatellites (27.4 vs.18.1). A higher rate of cross-species amplification was observed for EST microsatellites. Approximately half of each marker type was duplicated within the genome. Unlike single-copy markers, amplification of duplicated microsatellites in other salmonids was not correlated to phylogenetic distance. Genomic microsatellites proved more useful than EST derived microsatellites in discriminating among the salmonids. In total, 428 microsatellite markers were developed in this study for mapping and population genetic studies in rainbow trout.

Alleles↗
PubMed2000

Activation of TNF-alpha transcription utilizes distinct MAP kinase pathways in different macrophage populations.

Stimulation of macrophages by lipopolysaccharide (LPS) leads to the rapid activation of MAP kinases (MAPK) and the subsequent induction of cytokine gene expression. We sought to determine whether LPS-inducible cytokine genes were differentially regulated in macrophages derived from different tissues. Our studies revealed that PD98059, an inhibitor of the extracellular-regulated kinase (ERK) pathway, blocked LPS-induced activation of tumor necrosis factor alpha (TNF-alpha) gene expression in a murine cell line derived from alveolar macrophages but not in a nonpulmonary macrophage cell line. These findings were confirmed using primary murine alveolar and peritoneal macrophages. This suggests that the TNF-alpha promoter contains MAPK-dependent and -independent regulatory elements that are used in a cell type-specific manner. We also found that differences in MAPK-regulated signaling were not mediated by NF-KB, LITAF, Egr-1, CREB, or ATF2/ c-Jun. Together, these studies demonstrate that transcriptional activation of the TNF-alpha gene requires the ERK signaling cascade in selected macrophage populations.

Activating Transcription Factor 2↗
PubMed2001

Population genomics: a bridge from evolutionary history to genetic medicine.

Studies of human genetic variation are making contributions in several key areas. Evolutionary genetic studies yield critical clues about the histories of human populations, and they provide substantial support for an African origin of modern humans. The analysis of genetic variation has formed a foundation for DNA-based forensic applications. And, as attention is focused on locating genes underlying complex diseases, it is becoming clear that a better understanding of genetic variation will help to guide gene-mapping efforts. Population genomics, the large-scale comparison of DNA sequences, is now beginning to provide new insights in these areas. We review some of the general patterns of human genetic variation, and we show how our knowledge of these patterns can aid in the mapping and cloning of disease-causing genes.

Evolution, Molecular↗
PubMed1998

Spatial structure, environmental heterogeneity, and population dynamics: analysis of the coupled logistic map.

Spatial extent can have two important consequences for population dynamics: It can generate spatial structure, in which individuals interact more intensely with neighbors than with more distant conspecifics, and it allows for environmental heterogeneity, in which habitat quality varies spatially. Studies of these features are difficult to interpret because the models are complex and sometimes idiosyncratic. Here we analyze one of the simplest possible spatial population models, to understand the mathematical basis for the observed patterns: two patches coupled by dispersal, with dynamics in each patch governed by the logistic map. With suitable choices of parameters, this model can represent spatial structure, environmental heterogeneity, or both in combination. We synthesize previous work and new analyses on this model, with two goals: to provide a comprehensive baseline to aid our understanding of more complex spatial models, and to generate predictions about the effects of spatial structure and environmental heterogeneity on population dynamics. Spatial structure alone can generate positive, negative, or zero spatial correlations between patches when dispersal rates are high, medium, or low relative to the complexity of the local dynamics. It can also lead to quasiperiodicity and hyperchaos, which are not present in the nonspatial model. With density-independent dispersal, spatial structure cannot destabilize equilibria or periodic orbits that would be stable in the absence of space. When densities in the two patches are uncorrelated, the probability that the population in a patch reaches extreme low densities is reduced relative to the same patch in isolation; this "rescue effect" would reduce the probability of metapopulation extinction beyond the simple effect of spreading of risk. Pure environmental heterogeneity always produces positive spatial correlations. The dynamics of the entire population is approximated by a nonspatial model with mean patch characteristics. This approximation worsens as the difference between the patches increases and the dispersal rate decreases: Under extreme conditions, destabilization of equilibria and periodic orbits occurs at mean parameter values lower than those predicted by the mean parameters. Apparent within-patch dynamics are distorted: The local population appears to have the wrong growth parameter and a constant number of immigrants (or emigrants) per generation. Adding environmental heterogeneity to spatial structure increases the occurrence of spatially correlated population dynamics, but the resulting temporal dynamics are more complex than would be predicted by the mean parameter values. The three classes of spatial pattern (positive, negative, and zero correlation), while still mathematically distinct, become increasingly similar phenomenologically.

Animals↗