Geographic Location Of Populations Research Articles

Morphological variability decreases in populations living in less suitable environments and close to the range edges

AbstractAimGeographical range expansion depends on ecological and evolutionary processes that may hamper local adaptations in populations living at range edges by constraining phenotypic variability. This study investigates the spatial patterns of the intraspecific variability of skull traits throughout the geographical range of a marsupial from the Brazilian Atlantic Forest. We aimed to answer whether the distance from the range edge and the environmental suitability explain the geographical variation of morphological variability of the species.LocationAtlantic Forest, Brazil.TaxonMarmosops incanus (Didelphimorphia, Didelphidae).MethodsWe analysed adult specimens deposited in the main biological collections in southeastern Brazil. The morphological variability extent and integration within populations were characterised by 13 linear measures of the skull, using a multivariate approach. Environmental suitability for the species' occurrence was estimated by ecological niche models, using climate variables and vegetation productivity as predictors and three different modelling methods. Distance from the range edge was calculated based on the minimum linear distance between populations and the closest range limit. We fitted linear regressions and selected the best models that explained the spatial variation of morphological variability based on the Akaike information criterion.ResultsThe extent of morphological variability of M. incanus is positively correlated with morphological integration and increases with local environmental suitability and distance from the range edges. However, the relationship between morphological variability and environmental suitability depends on the niche modelling method.Main ConclusionsUnfavourable environmental conditions constrain morphological variability within populations of the Gray slender opossum and may hamper local adaptation in peripheral populations living in less suitable environments. In addition to environmental conditions, geographical location of populations also plays an important role in phenotypic variability among populations. We stress the boundary effect of the species range on local adaptation of peripheral populations and its possible consequences for the range expansion dynamics.

Cross-mapping medical records to NANDA-I to identify nursing diagnoses in a vulnerable population.

To assess the association between vulnerable populations and nursing care needs, using NANDA-I diagnostics, in the population of the Canary Islands, Spain. Nursing social epidemiology study. Cross Mapping of Medical Records to NANDA-I to Identify Nursing Diagnoses in a Population usinga medical, epidemiological follow-up study of a cohort of 7,190 people. The level of vulnerability of the participants was assigned, among those who were also assigned nursing diagnoses, using the "ICE index" to calculate the expected associations. The most prevalent nursing diagnosis in our sample was Sedentary lifestyle (60.5%), followed by Ineffective health self-management (33.8%) and Risk-prone health behaviour (28.7%). Significant differences were found by sex, age group and social class, with the nursing diagnoses included in the study being more prevalent among the most socio-economically disadvantaged social class. The cross-mapping method is useful to generate diagnostic information in terms of care needs, using the NANDA-I classification. The expected associations between high social vulnerability and care needs have been verified in a comprehensive and representative sample of the Canarian population (Spain). From an epidemiological perspective, identifying nursing diagnoses at the population level allows us to find the most prevalent needs in the different community groups and to focus appropriate nursing interventions for their implementation and impact assessment.

Population Variability of Almond-Leaved Willow (Salix triandra L.) Based on the Leaf Morphometry: Isolation by Distance and Environment Explain Phenotypic Diversity

Almond-leaved willow (Salix triandra L., Salicaceae) is a dioecious shrub, rarely a small tree that grows under various environmental conditions. We examined the population structure of 12 populations of almond-leaved willow using nine leaf morphological traits and specific leaf area. Populations were selected from a range of habitats, from continental to the sub-Mediterranean zone, to examine the influence of environmental conditions (climate and altitude) and geographic distance on leaf variability. Significant differences were confirmed among all populations for all traits, with significant correlations between geographic location of populations and morphological traits, and between environmental conditions and morphological traits. Large-leaved populations were found in continental and sub-Mediterranean climates, while small-leaved populations were found in higher elevations and smaller karstic rivers. In addition, populations from floodplains showed greater variability than populations from the karstic habitats, indicating a positive influence of lowland habitats and possible underlying differences in gene pool size. In conclusion, we found that environmental conditions and geographical distances in addition to genetic drift, are the main influences on the variability in almond-leaved willow, with the species showing a high level of plasticity and adaptation to local environmental conditions.

Genetic variability of Araucaria angustifolia in the Argentinean Parana Forest and implications for management and conservation

Genetic variability of Araucaria angustifolia populations in Argentina was moderate-to-low and reduced by logging. Some studied populations and the plantation are valuable gene pools for conservation and management. The main forces shaping genetic variability of woody species in fragmented forest are the geographical distribution and demographic history of populations. We conducted molecular analyses to evaluate how these factors have affected Araucaria angustifolia genetic variability in the Argentinean Parana Forest and to identify valuable gene pools for conservation and management purposes. Using 706 polymorphic AFLP (Amplified Fragment Length Polymorphism) markers, we analyzed nine native populations with different logging history and one plantation (312 individuals) of an uncertain origin. Average genetic diversity for the native populations was moderate-to-low (He = 0.128) in accordance with their marginal location within Araucaria’s range. In general, genetic diversity of populations decreases from east to west with increasing distances from the main area of species distribution on southern Brazil. Logging may have been responsible for further reduction of genetic variability in the more intensely exploited populations of the southern region and in some private fields. The moderate genetic differentiation among populations (ΦPT = 0.080) suggests an increase in the genetic structure of remnant populations because of fragmentation. UPGMA and Bayesian analyses agreed with the geographic location of populations. Populations from the southern Provincial Parks at Araucaria’s range edges grouped and differed genetically more from other populations. The highest genetic diversity of the plantation (He = 0.155) suggests that its individuals could have originated from seeds collected from different and/or highly variable sources of Brazil and the northeast of Argentina.

Comparison of ITS, RAPD and ISSR from DNA-based genetic diversity techniques

ITS, RAPD-PCR and ISSR-PCR are most popular DNA-based techniques that are extensively applied in the determination of the genetic diversity of species among populations. However, especially for organisms having high genetic polymorphism, phylogenetic trees drawn from the results of these techniques may be different. For finding a meaningful phylogenetic tree, it should be compared phylogenetic trees obtained from these different techniques with geographic locations of populations. Lichens have a high genetic polymorphism and tolerance against different environmental conditions. In this study, these three DNA-based genetic diversity techniques were compared, using different populations of a lichen species (Xanthoria parietina). X. parietina was especially chosen because of its high genetic diversity in narrow zones. Lichen samples were collected from ten different locations in a narrow transition climate zone Bilecik (Turkey). Statistical analyses of all results were calculated using UPGMA analysis. Phylogenic trees for each technique were drawn and transferred to the Bilecik map for comparative analysis. The results of three techniques allowed us to verify that populations of X. parietina have high genetic variety in a narrow zone. But phylogenetic trees obtained from these results were found to be very different. Our comparative analysis demonstrated that the results of these techniques are not similar and have critical differences. We observed that the ITS method provides more clear data and is more successful in genetic diversity analyses of more asunder populations, in contrast to ISSR-PCR and RAPD-PCR methods.

Applicability of ISSR and DAMD markers for phyto-molecular characterization and association with some important biochemical traits of Dendrobium nobile, an endangered medicinal orchid

Dendrobium nobile is an important medicinal orchid having profound importance in traditional herbal drug preparations and pharmacopeias worldwide. Due to various anthropogenic pressures the natural populations of this important orchid species are presently facing threats of extinction. In the present study, genetic and chemical diversity existing amongst 6 natural populations of D. nobile were assessed using molecular markers, and the influence of genetic factors on its phytochemical activity especially antioxidant potential was determined. Molecular fingerprinting of the orchid taxa was performed using ISSR and DAMD markers along with the estimation of total phenolics, flavonoids and alkaloid contents. Antioxidant activity was also measured using DPPH and FRAP assays which cumulatively revealed a significant level of variability across the sampled populations. The representatives from Sikkim in Northeast India revealed higher phytochemical activity whereas those from Mizoram showed lesser activity. Analysis of molecular variance (AMOVA) revealed that variation amongst the populations was significantly higher than within the populations. The data generated by UPGMA and Bayesian analytical models were compared in order to estimate the genetic relationships amongst the D. nobile germplasm sampled from different geographical areas of Northeast India. Interestingly, identical grouping patterns were exhibited by both the approaches. The results of the present study detected a high degree of existing genetic and phytochemical variation amongst the populations in relation to bioclimatic and geographic locations of populations. Our results strongly establish that the cumulative marker approach could be the best suited for assessing the genetic relationships with high accuracy amongst distinct D. nobile accessions.

Geographic pattern of shell morphology in the endemic freshwater mussel Unio ravoisieri (Bivalvia: Unionidae) from northern Tunisia

Unio ravoisieri is an endemic freshwater mussel inhabiting North Africa rivers. Morphological diversity in U. ravoisieri was examined at eight sites covering the three main drainage systems in northern Tunisia. Variation was assessed using 10 shell measurements in 193 specimens. Univariate and multivariate analyses were applied to test the effects of sex and sites on shell traits. Simple and partial Mantel correlations on external and internal shell traits and geographic locations of populations were performed to test for spatial effects. Our results showed significant differences in shell morphometric characters among locations, but no evidence of sexual size dimorphism. Mantel correlations between geographic and all shell morphometric distances were significant, indicating an isolation-by-distance pattern. However, partial Mantel correlation did not detect a significant correlation between internal and external shell morphometric distances after controlling for geographic distance. The nonparametric Spearman correlations between geographical parameters (latitude, longitude and altitude) and external shell traits, as well as growth index were significant, but no significant relationships were demonstrated for internal traits or for condition index. Assessment of the underlying processes involved in this differentiation is not straightforward, because of the likely complex interaction between genetic and environmental factors.

Assessment of diversity among populations of Rauvolfia serpentina Benth. Ex. Kurtz. from Southern Western Ghats of India, based on chemical profiling, horticultural traits and RAPD analysis

Genetic, morphological and chemical variations of ten natural populations of Rauvolfia serpentina Benth. Ex. Kurtz. from Southern Western Ghats of India were assessed using RAPD markers reserpine content and morphological traits. An estimate of genetic diversity and differentiation between genotypes of breeding germplasm is of key importance for its improvement. Populations were collected from different geographical regions. Data obtained through three different methods were compared and the correlation among them was estimated. Statistical analysis showed significant differences for all horticultural characteristics among the accessions suggesting that selection for relevant characteristics could be possible. Variation in the content of Reserpine ranges from 0.192g/100g (population from Tusharagiri) to 1.312g/100g (population from Aryankavu). A high diversity within population and high genetic differentiation among them based on RAPDs were revealed caused both by habitat fragmentation of the low size of most populations and the low level of gene flow among them. The UPGMA dendrogram and PCA analysis based on reserpine content yielded higher separation among populations indicated specific adaptation of populations into clusters each of them including populations closed to their geographical origin. Genetic, chemical and morphological data were correlated based on Mantel test. Given the high differentiation among populations conservation strategies should take into account genetic diversity and chemical variation levels in relation to bioclimatic and geographic location of populations. Our results also indicate that RAPD approach along with horticultural analysis seemed to be best suited for assessing with high accuracy the genetic relationships among distinct R. serpentina accessions.

Genetic Variability of Hymenoscyphus pseudoalbidus on Ash Leaf Rachises in Leaf Litter of Forest Stands in Poland

Two hundred and thirty cultures of Hymenoscyphus pseudoalbidus were obtained from ascospores created in apothecia on the previous years' ash leaf rachises in the stand floor. Fruiting bodies of the pathogen were collected in four regions of Poland differing by geographical location, the altitude above sea level and climatic conditions. Isolates were identified based on the sequences of ribosomal DNA (ITS1-5.8S-ITS2) and the calmodulin gene. Only the presence of H. pseudoalbidus was identified in the decaying ash stands in Poland; morphologically similar, saprotrophic species of H. albidus was absent. Intrapopulation and interpopulation genetic variability of isolates was determined based on 84 RAMS markers obtained using four primers. Genetic variability of the fungus populations, measured by the Dice coefficient of genetic similarity and the Shannon coefficient of genetic diversity, decreased along with a decrease in the location of isolate collection area above sea level. A significant dependency was shown between intrapopulation genetic variability of isolates and altitude of regions above sea level. The Mantel test excluded existence of dependence between geographical and genetic distance among populations (r = −0.038, P = 0.55). A significant correlation was found between the genetic distances of individuals within populations and locations above sea level. Based on PCA and geographical location of populations, it was shown that populations create four distinct groups. amova showed that a majority of total genetic variability (65.80%) constitutes intrapopulation variability. Variability between populations was high (28.7%), and individual regions had a smallest influence (5.5%) on the level of total variability.

Characterization of Culex pipiens Complex (Diptera: Culicidae) Populations in Colorado, USA Using Microsatellites

Mosquitoes such as those in the Culex pipiens complex are important vectors of disease. This study was conducted to genetically characterize Cx. pipiens complex populations in the state of Colorado, USA, and to determine the number of genetic clusters represented by the data. Thirteen populations located among four major river basins were sampled (n = 597 individuals) using a panel of 14 microsatellites. The lowest-elevation sites had the highest Expected Heterozygosity (HE) values (range 0.54–0.65). AMOVA results indicated the presence of statistically significant amounts of variation within each level when populations were analyzed as one group or when they were grouped either by river basin or by their position on the east or west side of the Rocky Mountains. Most pairwise FST values were significant via permutation test (range 0–0.10), with the highest values from comparisons with Lamar, in southeast CO. A neighbor joining tree based on Cavalli–Sforza and Edwards’s chord distances was consistent with the geographic locations of populations, as well as with the AMOVA results. There was a significant isolation by distance effect, and the cluster analysis resolved five groups. Individuals were also assayed with an additional microsatellite marker, Cxpq78, proposed to be monomorphic in Cx. pipiens but polymorphic in the closely related but biologically distinct species Cx. quinquefasciatus. Low frequencies (≤3%) of Cx. quinquefasciatus alleles for this marker were noted, and mostly confined to populations along the Interstate 25 corridor. Pueblo was distinct in that it had 10% Cx. quinquefasciatus alleles, mostly of one allele size. The degree of population genetic structure observed in this study is in contrast with that of Cx. tarsalis, the other major vector of WNV in the western U.S., and likely reflects the two species’ different dispersal strategies.

Chemical and genetic variability of Thymus algeriensis Boiss. et Reut. (Lamiaceae), a North African endemic species

Genetic and essential oil variations from eight Tunisian natural populations of Thymus algeriensis Boiss. et Reut. (Synonym Thymus hirtus Willd. subsp. algeriensis Boiss. et Reut.), a North African endemic species, were assessed using 47 terpenoids and 154 RAPD markers amplified by seven selected primers. Populations were collected from different geographical regions belonging to the sub-humid, upper semi-arid, mean semi-arid, lower semi-arid and upper arid bioclimates. Essential oil composition varied among populations. Five chemotypes according to main compounds have been distinguished: caryophyllene oxide/1,8-cineole/α-pinene, 1,8-cineole/α-pinene, 1,8-cineole/α-pinene/camphor, linalool and thymol chemotypes. A high genetic diversity within population and high genetic differentiation among them, based on RAPDs, were revealed (Hpop=0.303 and GST=0.339) caused both by the habitat fragmentation, the low size of most populations and the low level of gene flow among them. The genetic and chemical structures are in accordance with geography distances indicating isolation by distance. The UPGMA dendrogram and PCA analysis based on volatiles yielded higher separation among populations indicated specific adaptation of populations to the local environments. While the results obtained through RAPDs separated populations into three distinct clusters each of them including populations closed to their geographical origin. Genetic and chemical data were correlated based on Mantel test. Population differentiation performed on the two sets of data was similar to that shown using RAPDs suggesting higher accuracy of these markers. Given the high differentiation among all populations, conservation strategies should take into account genetic diversity and chemical variation levels in relation to bioclimatic and geographic location of populations.

Update: The (often ignored) role of vicariance in evolutionary diversification on oceanic islands

news and update ISSN 1948‐6596 update The (often ignored) role of vicariance in evolutionary diversifica‐ tion on oceanic islands Elucidating the evolutionary history of diversifying lineages in space and time remains a major chal‐ lenge in biology. The value of islands and island‐ like systems for studying this question has been long recognized by professional and amateur bi‐ ologists alike. First, many islands are young and thus have relatively low species diversity; this natural simplicity makes them easier to study. Second, most islands are geographically isolated, which means that insular lineages are often on an evolutionary track independent of external influ‐ ences from other areas. Finally, if part of an archi‐ pelago, islands can be viewed as replicates or snapshots in time of a natural experiment occur‐ ring at a spatial scale and a temporal scale of which experimental biologists could only dream. The considerable scientific attention devoted to island biotas has resulted in an increasingly com‐ plete picture of the geographical distribution of insular species. In addition, with the more recent advances in genetics and phylogenetics, it is now possible to infer the evolutionary processes re‐ sponsible for generating these observed bio‐ geographical patterns. Indeed, by combining infor‐ mation about the current geographical location of populations or species with a description of their genetic or phylogenetic relationship, it becomes possible to reconstruct the evolutionary history of diversifying lineages in their specific geographical contexts, a key step in evaluating the relative im‐ portance of determinism and contingency in evo‐ lutionary diversification (Losos and Ricklefs 2009). However, despite the relative simplicity of island systems, the study of their diversifying line‐ ages poses its own set of challenges. First, al‐ though island biogeographical studies often as‐ sume that islands are fixed in time and space, they are rather dynamic entities that might change in size, location, elevation, etc. over time. Oceanic islands in particular go through a series of predict‐ able “life” stages that are likely to influence their carrying capacity via changes in island area, topog‐ raphy, etc. (Whittaker et al. 2008). Furthermore, over time, geological forces combined with sea‐ level changes might create or eliminate land con‐ nections between islands, which could facilitate or hinder the dispersal and colonization of the geo‐ graphical areas involved. Second, island biotas often are at greater risk of extinction. This greater risk stems from a combination of factors. Impor‐ tantly, island species have limited ranges and as‐ sociated smaller population sizes, and they also are more susceptible to changes in their environ‐ ment caused by introduced species or habitat de‐ struction by human activities. Extinction events are difficult to detect and, if ignored, might lead researchers to draw erroneous conclusions from the observed patterns of biodiversity. Finally, not necessarily specific to island systems, the evolu‐ tionary history of any diversifying lineage might be blurred by human‐mediated dispersal. This effect is exacerbated on islands where dispersal can be quite limited between islands, and where humans might artificially increase the rates and/or modify the trajectories of organisms’ natural dispersal. These three sources of variation—island dynamics, extinction, and introduction—most of‐ ten are ignored, or in the best‐case scenario sim‐ ply assumed to add noise to the diversification patterns observed. However, in a recent study of giant Galapagos tortoises, Poulakakis et al. (2012) tackled these three challenges by incorporating information about the dynamic geography of Galapagos, genetic data from extinct species, and information regarding human‐based dispersal of individuals in this group of species – highlighting their influence on the diversification patterns ob‐ served and reaching a better understanding of the diversification process in this lineage. In their study, Poulakakis and colleagues integrated DNA data from all known extinct and extant species, past information about inter‐island dispersal of giant tortoises by humans, and newly available data on the dynamics of the islands themselves. Overall this results in an updated and more com‐ prehensive picture of the diversification patterns © 2012 the authors; journal compilation © 2012 The International Biogeography Society — frontiers of biogeography 3.4, 2012

Changes of leaf morphology in Betula pendula roth and B. pubescens Ehrh. along a zonal-climatic transect in the Urals and Western Siberia

Leaf size, shape, and parameters of venation in Betula pendula and B. pubescens have been studied along a 1600-km latitudinal zonal transect in the Urals and Western Siberia. The results show that leaf size and venation density depend on the geographic location of population, with these parameters in the two species changing in opposite directions along the transect. In its northern part (forest tundra-southern taiga), B. pubescens shows a positive correlation of leaf area with long-term-average air temperature, while this correlation in B. pendula is negative. In the southern part, correlations of leaf size with long-term average precipitation in the two species are also opposite in sign. Parameters of leaf shape in both species depend mainly on weather conditions in the current year rather than on long-term average climatic parameters. The conclusion is drawn that B. pendula and B. pubescens have different mechanisms of structural adaptation of leaves to climate and weather conditions that are based on changes in leaf size and shape.

Population differences in allele frequencies at the OLR1 locus may suggest geographic disparities in cardiovascular risk events

Background: Several studies have demonstrated a link between cardiovascular disease (CVD) susceptibility and the genetic background of populations.Endothelial activation and dysfunction induced by oxidized low-density lipoprotein (ox-LDL) is one of the key steps in the initiation of atherosclerosis. The oxidized low density lipoprotein (lectin-like) receptor 1 (OLR1) gene is the main receptor of ox-LDL. We have previously characterized two polymorphisms (rs3736235 and rs11053646) associated with the risk for coronary artery disease (CAD) and acute myocardial infarction (AMI).Aim: Given their clinical significance, it is of interest to know the distribution of these variants in populations from different continents.Subjects and methods: A total of 1229 individuals from 17 different African, Asian and European populations was genotyped for the two considered markers.Results: The high frequencies of ancestral alleles in South-Saharan populations is concordant with the African origin of our species. The results highlight that African populations are closer to Asians, and clearly separated from the Europeans.Conclusion: The results confirm significant genetic structuring among populations and suggest a possible basis for varying susceptibility to CVD among groups correlated with the geographical location of populations linked with the migrations out of Africa, or with different lifestyle.

Boundaries and clines in the West Eurasian Y‐chromosome landscape: Insights from the European part of Russia

Previous studies of Y chromosome variation have revealed that western Europe, the Volga-Ural region, and the Caucasus differ dramatically with respect to Y-SNP haplogroup composition. The European part of Russia is situated in between these three regions; to determine if these differences reflect clines or boundaries in the Y-chromosome landscape, we analyzed 12 Y-SNPs in 545 males from 12 populations from the European part of Russia. The majority of Russian Y chromosomes (from 74% to 94%) belong to three Y chromosomal lineages [I-M170, R1a1-M17, and N3-TAT] that are also frequent in the rest of east Europe, north Europe, and/or in the Volga-Ural region. We find significant but low correlations between haplogroup frequencies and the geographic location of populations, suggesting gradual change in the Y chromosome gene pool across western Eurasia. However, we also find some significant boundaries between populations, suggesting that both isolation and migration have influenced the Y chromosome landscape.

Isozyme markers and volatiles in Tunisian Rosmarinus officinalis L. (Lamiaceae): A comparative analysis of population structure

Genetic and essential oil variations from 14 Tunisian natural populations of Rosmarinus officinalis L. were assessed using eight isozymes and 25 terpenoids. Isozymes were revealed by 13% gel electrophoresis. Volatiles were analysed by GC and GC–MS. Populations were collected from different regions belonging to sub-humid, upper semi-arid and upper arid bioclimates. A high genetic diversity within population was revealed by isozymes due to the species mating system and the large size of populations before fragmentation. Cluster constructed using Nei's genetic distances showed mainly bioclimatic related population groupings. A high differentiation among populations and ecological groups was observed. Essential oil composition varied among populations. Volatiles of the sub-humid and the upper semi-arid populations located in regions of Cap Bon and Tunisian Dorsal were rich in 1,8-cineole, while populations from the upper arid bioclimate (Matmata regions) were characterized by high amounts of camphor. Genetic and chemical data were highly correlated. Population differentiation performed on the two sets of data was similar to those shown using isozyme and terpenoids matrices separately. Conservation strategies should take into account genetic diversity and chemical variation levels in relation to bioclimatic and geographic location of populations.

Genetic differentiation and trade among populations of peach palm ( Bactris gasipaes Kunth) in the Peruvian Amazon-implications for genetic resource management.

Peach palm ( Bactris gasipaes Kunth) is cultivated for fruit and 'heart of palm', and is an important component of agroforestry systems in the Peruvian Amazon. In this study, AFLP was used to compare genetic diversity among domesticated populations along the Paranapura and Cuiparillo rivers, which are managed by indigenous and colonist farming communities, respectively. Gene diversity was 0.2629 for the populations in indigenous communities and 0.2534 in colonist communities. Genetic differentiation among populations ( G(st)) was 0.0377-0.0416 ( P<0.01) among populations along both rivers. There was no relation between genetic differentiation and the geographical location of populations along the rivers. Since natural seed dispersal by birds and rodents is thought to occur only across relatively short distances (100-200 m), it is likely that exchange of material by farmers and commercial traders is responsible for most of the 'long-distance' (over more than 20 km) gene flow among populations along the two rivers studied. This exchange of material may be important to counteract the effects of selection as well as genetic drift in small groups of trees in farmers' fields, much as in a metapopulation, and may account for the weak genetic differentiation between the two rivers ( G(st)=0.0249, P<0.01). A comparison with samples from other landraces in Peru and Brazil showed the existence of an isolation-by-distance structure up to 3,000 km, consistent with gene flow on a regional scale, likely mediated by trade in the Amazon Basin. Results are discussed with regard to practical implications for the management of genetic resources with farming communities.

Genetic differentiation and relationship between genetic and geographical distance in Danish sea trout (Salmo trutta L.) populations

Twenty-four samples of anadromous brown trout from four river systems/geographical regions were studied by PCR-RFLP analysis of the ND-1 and ND-5/6 regions of the mitochondrial genome. A total of 14 haplotypes was observed, and these could be divided into three phylogenetic groups. Populations within river systems/regions tended to be more closely related to each other than to populations from other river systems/regions. Also, a significant correlation was observed between geographical and genetic distances between populations. These results contrast with results from other studies of mainly resident and landlocked populations, where no correspondence was observed between genetic relationships and geographical location of populations. Gene flow connecting anadromous populations is probably the reason for the observed isolation-by-distance patterns, whereas in isolated resident and landlocked trout populations drift leads to random genetic divergence of populations. Tests for nonrandom geographical distribution of phylogenetic groups of haplotypes showed that drift and gene flow are probably the predominant factors affecting the distribution of haplotypes. There were, however, also some indications of clines in frequencies of phylogenetic groups of haplotypes.