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Continental Populations (continental + population)
Selected AbstractsAn unusual distribution of the kdr gene among populations of Anopheles gambiae on the island of Bioko, Equatorial GuineaINSECT MOLECULAR BIOLOGY, Issue 6 2005L. J. Reimer Abstract In West Africa, Anopheles gambiae exists in discrete subpopulations known as the M and S molecular forms. Although these forms occur in sympatry, pyrethroid knock-down resistance (kdr) is strongly associated with the S molecular form. On the island of Bioko, Equatorial Guinea we found high frequencies of the kdr mutation in M form individuals (55.8%) and a complete absence of kdr in the S form. We also report the absence of the kdr allele in M and S specimens from the harbour town of Tiko in Cameroon, representing the nearest continental population to Bioko. The kdr allele had previously been reported as absent in populations of An. gambiae on Bioko. Contrary to earlier reports, sequencing of intron-1 of this sodium channel gene revealed no fixed differences between M form resistant and susceptible individuals. The mutation may have recently arisen independently in the M form on Bioko due to recent and intensive pyrethroid application. [source] A Signal for Independent Coastal and Continental histories among North American wolvesMOLECULAR ECOLOGY, Issue 4 2005BYRON V. WECKWORTH Abstract Relatively little genetic variation has been uncovered in surveys across North American wolf populations. Pacific Northwest coastal wolves, in particular, have never been analysed. With an emphasis on coastal Alaska wolf populations, variation at 11 microsatellite loci was assessed. Coastal wolf populations were distinctive from continental wolves and high levels of diversity were found within this isolated and relatively small geographical region. Significant genetic structure within southeast Alaska relative to other populations in the Pacific Northwest, and lack of significant correlation between genetic and geographical distances suggest that differentiation of southeast Alaska wolves may be caused by barriers to gene flow, rather than isolation by distance. Morphological research also suggests that coastal wolves differ from continental populations. A series of studies of other mammals in the region also has uncovered distinctive evolutionary histories and high levels of endemism along the Pacific coast. Divergence of these coastal wolves is consistent with the unique phylogeographical history of the biota of this region and re-emphasizes the need for continued exploration of this biota to lay a framework for thoughtful management of southeast Alaska. [source] Development of six microsatellite loci for black mangrove (Avicennia germinans)MOLECULAR ECOLOGY RESOURCES, Issue 3 2006IVANIA CERÓN-SOUZA Abstract We developed six new microsatellite loci for the black mangrove (Avicennia germinans), an important member of wetland communities worldwide. Loci showed moderate to high polymorphism and a survey of four locations [Puerto Rico (Jobos Bay and Luquillo), Mexico, French Guyana] revealed clear regional (and local) population structure. All populations were genetically distinct and the two continental populations showed much higher diversity than the two insular Puerto Rican locations. These loci complement those recently published by Nettel et al. (2005) and promise to be valuable for characterizing local and regional population dynamics in the black mangrove. [source] Isolation and characterization of microsatellite markers in Pterocarpus officinalis Jacq.MOLECULAR ECOLOGY RESOURCES, Issue 2 2006FÉLIX MULLER Abstract The leguminous Pterocarpus officinalis Jacq. is one of the dominant freshwater wetland tree species in the Caribbean basin. Anthromorphic factors threaten to reduce its population. In order to investigate the genetic diversity and structure of this species, we developed eight pairs of primers for nuclear microsatellites. One hundred ninety-one individuals were analysed within nine Caribbean and continental populations. These loci were polymorphic in all the populations, with four to 20 alleles per locus. Significant Hardy,Weinberg deviation was detected and was interpreted as a result of Wahlund effect. These loci constitute a powerful tool to investigate the genetic patterns within populations of the swamp species P. officinalis. [source] The biosynthesis of Juvenile Hormone, its degradation and titres in females of the true armyworm: a comparison of migratory and non-migratory populationsPHYSIOLOGICAL ENTOMOLOGY, Issue 2 2000Jeremy N. McNeil Summary In a previous study [McNeil et al. (1996) Archives of Insect Biochemistry and Physiology, 32, 575,584], patterns of sexual maturation and Juvenile Hormone (JH) biosynthesis were compared in virgin females from migratory (North American) and non-migratory (Azorean) populations of the true armyworm moth, Pseudaletia unipuncta Haworth (Lepidoptera: Noctuidae). Sexual maturation occurred at a significantly earlier age after emergence in the non-migrant population, and the rates of biosynthesis of JH in vitro suggested that lower titres of JH may be required to initiate the onset of calling behaviour (pheromone emission) and ovarian development in Azorean females. To examine the physiological differences in the reproductive biology of migratory and non-migratory populations in greater detail, the haemolymph titres of JH and JH esterase activity were compared in virgin females as a function of age. In addition, the effects of mating on JH biosynthesis in vitro, JH titres, JH esterase activity and egg production were measured in the two populations. As expected, JH titres rose more rapidly after emergence in Azorean females than in their North American counterparts but, contrary to our prediction, the maximum levels were also higher in the non-migrant population. Activity of JH esterase was much higher in Azorean females on the day of emergence. However, by the second day both populations had similar activity levels (about 17 nmol JH/min/ml) and exhibited a similar age-related decline in subsequent days. Mating did not affect the rate of JH biosynthesis in vitro but resulted in a significant increase in the titres of JH in the haemolymph of both populations. The maximum titre (a five-fold increase) occurred within 24 h of mating in Azorean females. In North American individuals the increase was greater (seven-fold) but did not occur until 48 h after mating. No difference in the activity of JH esterase was observed between mated and virgin North American females. By contrast, while there was an age-related decline in the activity of JH esterase in mated Azorean females, as seen in both North American groups, activity levels in virgin females remained constant with age. In all females, mating resulted in a significant increase in egg production within 24 h. The Azores is a volcanic archipelago, so these non-migratory populations were probably founded by immigrants originating from migratory continental populations. It is clear from our results that the change from a life history that includes migration to a non-migratory one involved more than just a temporal shift in the timing of the production of JH. Furthermore, the interpopulation differences in titres of JH and mating-induced changes reported here cannot be fully explained by the observed differences in the patterns of activity of JH esterase and JH biosynthesis in vitro. [source] X-chromosome lineages and the settlement of the AmericasAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009Stephane Bourgeois Abstract Most genetic studies on the origins of Native Americans have examined data from mtDNA and Y-chromosome DNA. To complement these studies and to broaden our understanding of the origin of Native American populations, we present an analysis of 1,873 X-chromosomes representing Native American (n = 438) and other continental populations (n = 1,435). We genotyped 36 polymorphic sites, forming an informative haplotype within an 8-kb DNA segment spanning exon 44 of the dystrophin gene. The data reveal continuity from a common Eurasian ancestry between Europeans, Siberians, and Native Americans. However, the loss of two haplotypes frequent in Eurasia (18.8 and 7%) and the rise in frequency of a third haplotype rare elsewhere, indicate a major population bottleneck in the peopling of the Americas. Although genetic drift appears to have played a greater role in the genetic differentiation of Native Americans than in the latitudinally distributed Eurasians, we also observe a signal of a differentiated ancestry of southern and northern populations that cannot be simply explained by the serial southward dilution of genetic diversity. It is possible that the distribution of X-chromosome lineages reflects the genetic structure of the population of Beringia, itself issued from founder effects and a source of subsequent southern colonization(s). Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] | ||||||||||||||||||||||