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Marginal Populations (marginal + population)
Selected AbstractsGenet age in marginal populations of two clonal Carex species in the Siberian ArcticECOGRAPHY, Issue 4 2000Ingibjörg S. Jónsdóttir During a Swedish-Russian expedition to northern Siberia 1994, we sampled two marginal populations of two Carex species at two high arctic sites (C, stans Drej. on Faddeyevsky Island and C. ensifolia V. Krecz ssp. arctisibirica Jurtz. at north-eastern Taymyr Peninsula), both north of previously documented localities in that areas for the two species. These populations were composed of a few distinct patches of ramet colonies, some of them shaped like fairy rings with dead centres. We measured the size of all colonies and collected samples for detailed morphometric analyses of rhizome growth. By using RAPD (random amplified polymorphic DNA) analysis we established that the largest colony at each site consisted of a single genet, based on 41 polymorphic bands amplified with three primers. Pooled samples from each of two additional colonies of C. stans on Faddeyevsky Island were analysed and showed that clones of the same species at the same site were relatively dissimilar (Dice's similarity index 0.26 0,43), We then assumed that each ramet colony represented a single genet. Based on the morphometric data, we developed a deterministic growth model that simulates the clonal growth of these species and enabled estimates of the time since establishment of the genets. The estimated age of the five C. Stans clones varied from 17 to 154 yr and the age of the two C. ensifolia ssp, arctisibirica clones was well over 3000 yr. [source] Range-wide genetic structure in a north-east Asian spruce (Picea jezoensis) determined using nuclear microsatellite markersJOURNAL OF BIOGEOGRAPHY, Issue 5 2009Mineaki Aizawa Abstract Aim, We used microsatellite markers to determine the range-wide genetic structure of Picea jezoensis and to test the hypothesis that the past population history of this widespread cold-temperate spruce has resulted in a low level of genetic variation and in imprints of inbreeding and bottlenecks in isolated marginal populations. Location, The natural range of the three infraspecific taxa of P. jezoensis throughout north-east Asia, including isolated marginal populations. Methods, We analysed a total of 990 individuals across 33 natural populations using four nuclear microsatellite loci. Population genetic structure was assessed by analysing genetic diversity indices for each population, examining clustering (model-based and distance-based) among populations, evaluating signals of recent bottlenecks, and testing for isolation by distance (IBD). Results, The 33 populations were clustered into five groups. The isolated marginal groups of populations (in Kamchatka, Kii in Japan and South Korea) exhibited low levels of allelic richness and gene diversity and a complete or almost complete loss of rare alleles. A recent bottleneck was detected in the populations in Hokkaido across to mid-Sakhalin. The IBD analysis revealed that genetic divergence between populations was higher for populations separated by straits. Main conclusions,Picea jezoensis showed a higher level of genetic differentiation among populations (FST = 0.101) than that observed in the genus Picea in general. This might be attributable to the fact that historically the straits around Japan acted as barriers to the movement of seeds and pollen. The low levels of genetic diversity in the isolated marginal population groups may reflect genetic drift that has occurred after isolation. Evidence of a significant bottleneck between the Hokkaido and mid-Sakhalin populations implies that the cold, dry climate in the late Pleistocene resulted in the decline and contraction of populations, and that there was a subsequent expansion followed by a founder effect when conditions improved. The high polymorphism observed in P. jezoensis nuclear microsatellites revealed cryptic genetic structure that organellar DNA markers failed to identify in a previous study. [source] Tertiary relict trees in a Mediterranean climate: abiotic constraints on the persistence of Prunus lusitanica at the eroding edge of its rangeJOURNAL OF BIOGEOGRAPHY, Issue 8 2008Fernando Pulido Abstract Aim, To investigate the ecophysiological traits allowing persistence of a subtropical relict tree (Prunus lusitanica L.) under a dry Mediterranean climate at the eroding edge of its range. Location, A glasshouse for the study under controlled conditions and two marginal populations located in riparian forests of central Spain and exposed to summer drought, in contrast to subtropical populations that grow in mountain cloud forests. Methods, Two experiments were conducted to assess tolerance to the abiotic conditions found in riparian habitats. In a glasshouse experiment, gas-exchange and light-use parameters were measured to evaluate seedling responses to a factorial combination of irradiance (60%, 10%, 2% and 0.5% full sun) and moisture (well watered control and drought stress). In a parallel field experiment, irradiance and soil moisture were measured as predictors of seedling survival at two sites in which half the seedlings were subjected to a threefold increase in summer precipitation by adding water every 10 days. Results Soil moisture strongly determined survival both in the glasshouse and in the two field sites. In the field, periodic addition of water failed to increase survival. Water-use efficiency (WUE) increased with drought. Seedlings did not tolerate deep shade (2,0.5%) and their performance and survival were better when exposed to moderate (10%) or high (60%) irradiance. The effect of water stress on seedling performance was stronger at moderate irradiance, moderate at high irradiance and negligible at very low light. Seedling size (height and number of leaves) attained after 1 month of experimental treatments had a positive effect on survival at the end of the summer, hence greater survival was not achieved at the expense of vertical growth. Main conclusions, While studies in Macaronesia have shown that P. lusitanica occupies a wide range of moisture conditions along mountain slopes, it behaves as an obligate riparian species in dry peripheral populations. Intolerance to deep shade and tolerance to moderate and high irradiance allow the species to grow in small and moist gaps, or in treeless river sections. Despite the species' low range filling in marginal, drought-prone regions, long-term persistence might have been achieved through shifts to riparian habitats serving as local refuges. [source] Deceptive Utopias: Violence, Environmentalism, and the Regulation of Multiculturalism in ColombiaLAW & POLICY, Issue 3 2009DIANA BOCAREJO Multiculturalism, constructed as a liberal utopia intended to recognize marginal populations, commonly draws upon deceptive mechanisms that reify the old trope of anthropological "savage slots" (a term borrowed from Trouillot 2003). Such slots configure the relationship between politics and places: the fixation of ethnicity in a territory and the creation of strong frontiers,both physical and symbolic,between grantees and nongrantees of differential citizenships. In the case analyzed in this article, those frontiers reify the distinction between peasants and indigenous peoples; two group categories widely mobilized in the context of indigenous land expansion in the northern region of Colombia (South America). This article explores how an environmental "utopic space" used by state institutions and nongovernmental organizations (NGOs), has turned into a fetish that hides a segment of Colombia's most dramatic reality: the violent context wherein paramilitary threats force small peasant landholders to sell and leave their land. [source] Taxonomic and biogeographical status of guanaco Lama guanicoe (Artiodactyla, Camelidae)MAMMAL REVIEW, Issue 2 2006BENITO A. GONZÁLEZ ABSTRACT 1We review the status of the four currently recognized guanaco Lama guanicoe subspecies, and provide information about their taxonomy and distribution. The success of guanaco in inhabiting open habitats of South America is based mainly on the flexibility of their social behaviour and ecophysiological adaptations to harsh environments. 2Lönnberg described the first subspecies, L. g. cacsilensis, at the beginning of the 20th century. Forty years later Krumbiegel described L. g. voglii, based on skull measurements and pelage colouration. The other two subspecies, L. g. huanacus and L. g. guanicoe, were classified as subspecies by Krumbiegel based on pelage colouration and body size, while maintaining the original Latin names and descriptors. 3Further guanaco populations have been incorporated into each of these subspecies, based on their proximity to the type locality but without attention to the homogeneity of phenotype or habitat and only limited consideration of Bergmann's rule based on scarce skulls. Two alternative geographical ranges were proposed in the middle and towards the end of the 20th century. Discrepancies occur in the geographical range of each subspecies. 4Molecular studies based on mitochondrial DNA cytochrome b sequences recognized only two subspecies: the Peruvian L. guanicoe cacsilensis and the rest of the populations grouped in the clade recognized as L. g. guanicoe. We conclude that the evolutionary biology of L. guanicoe requires a significant revision with respect to biogeography. Phylogeographical data hold particular value in developing conservation strategies, particularly for some of the reduced and marginal populations and/or subspecies and will support IUCN (The World Conservation Union) Red List classification. [source] Phylogeography of Kandelia candel in East Asiatic mangroves based on nucleotide variation of chloroplast and mitochondrial DNAsMOLECULAR ECOLOGY, Issue 11 2001T. Y. Chiang Abstract Vivipary with precocious seedlings in mangrove plants was thought to be a hindrance to long-range dispersal. To examine the extent of seedling dispersal across oceans, we investigated the phylogeny and genetic structure among East Asiatic populations of Kandelia candel based on organelle DNAs. In total, three, 28 and seven haplotypes of the chloroplast DNA (cpDNA) atpB- rbcL spacer, cpDNA trnL- trnF spacer, and mitochondrial DNA (mtDNA) internal transcribed spacer (ITS) were identified, respectively, from 202 individuals. Three data sets suggested consistent phylogenies recovering two differentiated lineages corresponding to geographical regions, i.e. northern South-China-Sea + East-China-Sea region and southern South-China-Sea region (Sarawak). Phylogenetically, the Sarawak population was closely related to the Ranong population of western Peninsula Malaysia instead of other South-China-Sea populations, indicating its possible origin from the Indian Ocean Rim. No geographical subdivision was detected within the northern geographical region. An analysis of molecular variance (amova) revealed low levels of genetic differentiation between and within mainland and island populations (,CT = 0.015, ,SC = 0.037), indicating conspicuous long-distance seedling dispersal across oceans. Significant linkage disequilibrium excluded the possibility of recurrent homoplasious mutations as the major force causing phylogenetic discrepancy between mtDNA and the trnL- trnF spacer within the northern region. Instead, relative ages of alleles contributed to nonrandom chlorotype,mitotype associations and tree inconsistency. Widespread distribution and random associations (,2 = 0.822, P = 0.189) of eight hypothetical ancestral cytotypes indicated the panmixis of populations of the northern geographical region as a whole. In contrast, rare and recently evolved alleles were restricted to marginal populations, revealing some preferential directional migration. [source] | ||||||||||