Fractured lives : a memoir

Includes abstract.Includes bibliographical references (leaves 264-265).Fractured Lives is a non-fiction work. Part autobiography, part history, part social comment and part war story, it covers a 15 year period, from the early 1980’s to the mid 1990’s when I was making documentaries about the wars taking place in the Southern African region. The films were not about Africa or war, so much as about the effect of war on people’s lives, especially those of women and children. Fractured Lives draws on the experience of making the films, using the stories of people who appear in them. It is my view of what we experienced during those journeys and I drive the narrative, although it is more about the people and places I was filming than about me. I have called it Fractured Lives because the lives of many people I filmed were destroyed almost beyond understanding

Fluctuating selection models and Mcdonald-Kreitman type analyses

It is likely that the strength of selection acting upon a mutation varies through time due to changes in the environment. However, most population genetic theory assumes that the strength of selection remains constant. Here we investigate the consequences of fluctuating selection pressures on the quantification of adaptive evolution using McDonald-Kreitman (MK) style approaches. In agreement with previous work, we show that fluctuating selection can generate evidence of adaptive evolution even when the expected strength of selection on a mutation is zero. However, we also find that the mutations, which contribute to both polymorphism and divergence tend, on average, to be positively selected during their lifetime, under fluctuating selection models. This is because mutations that fluctuate, by chance, to positive selected values, tend to reach higher frequencies in the population than those that fluctuate towards negative values. Hence the evidence of positive adaptive evolution detected under a fluctuating selection model by MK type approaches is genuine since fixed mutations tend to be advantageous on average during their lifetime. Never-the-less we show that methods tend to underestimate the rate of adaptive evolution when selection fluctuates

The Effect of Variation in the Effective Population Size on the Rate of Adaptive Molecular Evolution in Eukaryotes

The role of adaptation is a fundamental question in molecular evolution. Theory predicts that species with large effective population sizes should undergo a higher rate of adaptive evolution than species with low effective population sizes if adaptation is limited by the supply of mutations. Previous analyses have appeared to support this conjecture because estimates of the proportion of nonsynonymous substitutions fixed by adaptive evolution, α, tend to be higher in species with large N(e). However, α is a function of both the number of advantageous and effectively neutral substitutions, either of which might depend on N(e). Here, we investigate the relationship between N(e) and ω(a), the rate of adaptive evolution relative to the rate of neutral evolution, using nucleotide polymorphism and divergence data from 13 independent pairs of eukaryotic species. We find a highly significant positive correlation between ω(a) and N(e). We also find some evidence that the rate of adaptive evolution varies between groups of organisms for a given N(e). The correlation between ω(a) and N(e) does not appear to be an artifact of demographic change or selection on synonymous codon use. Our results suggest that adaptation is to some extent limited by the supply of mutations and that at least some adaptation depends on newly occurring mutations rather than on standing genetic variation. Finally, we show that the proportion of nearly neutral nonadaptive substitutions declines with increasing N(e). The low rate of adaptive evolution and the high proportion of effectively neutral substitution in species with small N(e) are expected to combine to make it difficult to detect adaptive molecular evolution in species with small N(e)

Determinants of the efficacy of natural selection on coding and noncoding variability in two passerine species

Population genetic theory predicts that selection should be more effective when the effective population size (Ne) is larger, and that the efficacy of selection should correlate positively with recombination rate. Here, we analyzed the genomes of ten great tits and ten zebra finches. Nucleotide diversity at 4-fold degenerate sites indicates that zebra finches have a 2.83-fold larger Ne. We obtained clear evidence that purifying selection is more effective in zebra finches. The proportion of substitutions at 0-fold degenerate sites fixed by positive selection (α) is high in both species (great tit 48%; zebra finch 64%) and is significantly higher in zebra finches. When α was estimated on GC-conservative changes (i.e., between A and T and between G and C), the estimates reduced in both species (great tit 22%; zebra finch 53%). A theoretical model presented herein suggests that failing to control for the effects of GC-biased gene conversion (gBGC) is potentially a contributor to the overestimation of α, and that this effect cannot be alleviated by first fitting a demographic model to neutral variants. We present the first estimates in birds for α in the untranslated regions, and found evidence for substantial adaptive changes. Finally, although purifying selection is stronger in high-recombination regions, we obtained mixed evidence for α increasing with recombination rate, especially after accounting for gBGC. These results highlight that it is important to consider the potential confounding effects of gBGC when quantifying selection and that our understanding of what determines the efficacy of selection is incomplete

Fractured Lives

Fractured Lives is a memoir of one woman?s experiences as a documentary filmmaker covering the wars in southern Africa during the 1980s and 1990s. Part autobiography, part history, part social commentary and part war story, it offers a female perspective on a traditionally male subject. Growing up in South Africa in a politically active family, Toni went to Britain as an exile in 1965 in the wake of the famous Rivonia Trial, and in the years to follow, became a filmmaker. Despite constant difficulties fighting for funding and commissions from television broadcasters, and the prejudices of working in a male-dominated industry, Toni made several remarkable films in Mozambique and Angola. These bear witness to the silent victims of war, particularly the women and children. Fractured Lives paints the changing landscape of southern Africa: Namibian independence and the end of the war in Mozambique bring hope ? but also despondency. Yet there is also the possibility of redemption, of building new lives for the victims of war. In its final chapters, Fractured Lives traces the power of survival and the opportunities for new beginnings. Fractured Lives concludes with Toni?s return to South Africa after nearly three decades in exile. However, the joy following the demise of apartheid is tempered by the poignancy of returning to a place that for so long had existed in her dreams alone and the realization that home will forever lie somewhere else