Identifying regions of the Drosophila melanogaster genome that have been recent targets of positive Darwinian selection will provide evidence for adaptations that have helped this species to colonize temperate habitats. We have begun a search for such genomic regions by analyzing multiple loci (about 250) dispersed across the X chromosome in a putatively ancestral population from East Africa and a derived European population. For both populations we found evidence for past changes in population size. We estimated that a major bottleneck associated with the colonization of Europe occurred about 3,500-16,000 years ago. We also found that while this bottleneck can account for most of the reduction in variation observed in the European sample, there is a deficit of polymorphism in some genomic regions that cannot be explained by demography alone.
It has been hypothesized that the ratio of X-linked to autosomal sequence diversity is influenced by unequal sex ratios in Drosophila melanogaster populations. We conducted a genome scan of single nucleotide polymorphism (SNP) of 378 autosomal loci in a derived European population and of a subset of 53 loci in an ancestral African population. On the basis of these data and our already available X-linked data, we used a coalescent-based maximum-likelihood method to estimate sex ratios and demographic histories simultaneously for both populations. We confirm our previous findings that the African population experienced a population size expansion while the European population suffered a population size bottleneck. Our analysis also indicates that the female population size in Africa is larger than or equal to the male population size. In contrast, the European population shows a huge excess of males. This unequal sex ratio and the bottleneck alone, however, cannot account for the overly strong decrease of X-linked diversity in the European population (compared to the reduction on the autosome). The patterns of the frequency spectrum and the levels of linkage disequilibrium observed in Europe suggest that, in addition, positive selection must have acted in the derived population. I N recent years genomic scans of DNA sequence variation using single nucleotide polymorphisms (SNPs) have been performed for multiple species. These studies became possible by the availability of full genome sequences, and data are now available from a variety of organisms such as Drosophila melanogaster (Glinka et al. 2003;Orengo and Aguadé 2004;Ometto et al. 2005), humans (Akey et al. 2004), and Arabidopsis thaliana (Schmid et al. 2005). These data sets provide useful tools to address questions such as estimating population sizes and demographic histories of a species. One of the main conclusions of the work performed on D. melanogaster was that demographic events are major factors in shaping the patterns of DNA polymorphism (e.g., Andolfatto 2001; Glinka et al. 2003;Haddrill et al. 2005b). D. melanogaster is thought to have originated in sub-Saharan Africa and to have only relatively recently (10,000-15,000 years ago) colonized the rest of the world (David and Capy 1988;Lachaise et al. 1988). Populations that reside in the ancestral species range show signatures of population size expansion (Glinka et al. 2003;Pool and Aquadro 2006), while derived populations have polymorphism patterns compatible with population size bottlenecks (e.g., Andolfatto 2001;Glinka et al. 2003). Theoretical studies have since utilized the data obtained from genome scans to estimate the parameters of these demographic events (Haddrill et al. 2005b;Li and Stephan 2006).The aforementioned SNP-based genome scans in D. melanogaster were performed solely for noncoding regions on the X chromosome. This leaves us virtually ignorant about noncoding autosomal variation on a chromosomal scale. In general, data quantifying the amount of autosomal variation based ...
Association studies have identified dozens of genetic variants linked to training responses and sport-related traits. However, no intervention studies utilizing the idea of personalised training based on athlete's genetic profile have been conducted. Here we propose an algorithm that allows achieving greater results in response to high- or low-intensity resistance training programs by predicting athlete's potential for the development of power and endurance qualities with the panel of 15 performance-associated gene polymorphisms. To develop and validate such an algorithm we performed two studies in independent cohorts of male athletes (study 1: athletes from different sports (n = 28); study 2: soccer players (n = 39)). In both studies athletes completed an eight-week high- or low-intensity resistance training program, which either matched or mismatched their individual genotype. Two variables of explosive power and aerobic fitness, as measured by the countermovement jump (CMJ) and aerobic 3-min cycle test (Aero3) were assessed pre and post 8 weeks of resistance training. In study 1, the athletes from the matched groups (i.e. high-intensity trained with power genotype or low-intensity trained with endurance genotype) significantly increased results in CMJ (P = 0.0005) and Aero3 (P = 0.0004). Whereas, athletes from the mismatched group (i.e. high-intensity trained with endurance genotype or low-intensity trained with power genotype) demonstrated non-significant improvements in CMJ (P = 0.175) and less prominent results in Aero3 (P = 0.0134). In study 2, soccer players from the matched group also demonstrated significantly greater (P < 0.0001) performance changes in both tests compared to the mismatched group. Among non- or low responders of both studies, 82% of athletes (both for CMJ and Aero3) were from the mismatched group (P < 0.0001). Our results indicate that matching the individual's genotype with the appropriate training modality leads to more effective resistance training. The developed algorithm may be used to guide individualised resistance-training interventions.
Shade tolerance, plastic phenotypic response to light and sensitivity to photoinhibition were studied in holly (Ilex aquifolium L.) seedlings transported from the field to a greenhouse and in adult trees in the field. All plants were growing in, or originated from, continental Mediterranean sites in central Spain. Seedlings tolerated moderate but not deep shade. Mortality was high and growth reduced in 1% sunlight. Survival was maximal in 12% sunlight and minimal in full sunlight, although the relative growth rate of the seedlings surviving in high light was similar to that of plants in moderate shade. Maximum photochemical efficiency at predawn was significantly lower in sun plants than in shade plants in the field, revealing chronic photoinhibition that was most pronounced in winter. Plasticity in response to available light varied according to the variable studied, being low for photosynthetic capacity and stomatal conductance, and high for specific leaf area, root:shoot ratio and leaf area ratio, particularly in seedlings. Differences in water relations and hydraulic features between sun and shade plants in the field were marginal. High water potential at the turgor loss point of field-grown plants suggested that holly is sensitive to drought during both the seedling and the adult stage. Low relative growth rates in both high and low light with low physiological plasticity in response to light indicate the existence of a stress-tolerance mechanism. We conclude that holly is a facultative understory plant in areas of oceanic and relatively mild climate, but an obligate understory plant in dry continental areas such as the study site. The impact of abandonment of traditional management practices and climate change on these Mediterranean populations is discussed.
A scan of the X chromosome of a European Drosophila melanogaster population revealed evidence for the recent action of positive directional selection at individual loci. In this study we analyze one such region that showed no polymorphism in the genome scan (located in cytological division 2C10-2E1). We detect a 60.5-kb stretch of DNA encompassing the genes ph-d, ph-p, CG3835, bcn92, Pgd, wapl, and Cyp4d1, which almost completely lacks variation in the European sample. Loci flanking this region show a skewed frequency spectrum at segregating sites, strong haplotype structure, and high levels of linkage disequilibrium. Neutrality tests reveal that these data are unlikely under both the neutral equilibrium model and the simple bottleneck scenarios. In contrast, newly developed maximum-likelihood ratio tests suggest that strong selection has acted recently on the region under investigation, causing a selective sweep. Evidence that this sweep may have originated in an ancestral population in Africa is presented.
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