The Evolution and Consequences of Sex-Specific Reproductive Variance

Natural selection favors alleles that increase the number of offspring produced by their carriers. But in a world that is inherently uncertain within generations, selection also favors alleles that reduce the variance in the number of offspring produced. If previous studies have established this principle, they have largely ignored fundamental aspects of sexual reproduction and therefore how selection on sex-specific reproductive variance operates. To study the evolution and consequences of sex-specific reproductive variance, we present a population-genetic model of phenotypic evolution in a dioecious population that incorporates previously neglected components of reproductive variance. First, we derive the probability of fixation for mutations that affect male and/or female reproductive phenotypes under sex-specific selection. We find that even in the simplest scenarios, the direction of selection is altered when reproductive variance is taken into account. In particular, previously unaccounted for covariances between the reproductive outputs of different individuals are expected to play a significant role in determining the direction of selection. Then, the probability of fixation is used to develop a stochastic model of joint male and female phenotypic evolution. We find that sex-specific reproductive variance can be responsible for changes in the course of long-term evolution. Finally, the model is applied to an example of parental-care evolution. Overall, our model allows for the evolutionary analysis of social traits in finite and dioecious populations, where interactions can occur within and between sexes under a realistic scenario of reproduction.     

Field Studies Concerning the Fecundity of Daphnia galeata,its Causes and Consequences

Field studies on a Daphnia galeata population in the mesotrophic man-made lake Saidenbach show that the fecundity of the animals depends on individual size, water temperature and the food supply (absolute quantity, specific food supply, food quality). These different factors are subsumed in the ingestion rate (rate of individual food intake per unit time), which is of an integrative character. The fecundity plotted versus ingestion rate yields a graph with the shape of a saturation curve. Attention is drawn to the consequences in terms of variation in population size.     

Origin and Consequences of the Relationship between Protein Mean and Variance

Cell-to-cell variance in protein levels (noise) is a ubiquitous phenomenon that can increase fitness by generating phenotypic differences within clonal populations of cells. An important challenge is to identify the specific molecular events that control noise. This task is complicated by the strong dependence of a protein''s cell-to-cell variance on its mean expression level through a power-law like relationship (σ²∝μ^1.69). Here, we dissect the nature of this relationship using a stochastic model parameterized with experimentally measured values. This framework naturally recapitulates the power-law like relationship (σ²∝μ^1.6) and accurately predicts protein variance across the yeast proteome (r² = 0.935). Using this model we identified two distinct mechanisms by which protein variance can be increased. Variables that affect promoter activation, such as nucleosome positioning, increase protein variance by changing the exponent of the power-law relationship. In contrast, variables that affect processes downstream of promoter activation, such as mRNA and protein synthesis, increase protein variance in a mean-dependent manner following the power-law. We verified our findings experimentally using an inducible gene expression system in yeast. We conclude that the power-law-like relationship between noise and protein mean is due to the kinetics of promoter activation. Our results provide a framework for understanding how molecular processes shape stochastic variation across the genome.     

Polymorphism of Fecundity Genes (FecB,FecX, and FecG) in the Indian Bonpala Sheep

The 37-kDa laminin receptor precursor/67-kDa laminin receptor (LRP/LR, also known as ribosomal protein SA, RPSA) has been reported to be involved in cancer development and prion internalization. Previous studies have shown that the LRP/LR is expressed in a wide variety of tissues. In particular, expression of LRP/LR mRNA may be closely related to the degree of PrP^Sc propagation. This study presents a detailed investigation of the LRP/LR mRNA expression levels in eleven normal ovine tissues. Using real-time quantitative PCR, the highest LRP/LR expression was found in neocortex (p < 0.05). Slightly lower levels were found in the heart and obex. Intermediate levels were seen in hippocampus, cerebellum, spleen, thalamus, mesenteric lymph node, and the lowest levels were present in liver, kidney, and lung. In general, the LRP/LR mRNA levels were much higher in neuronal tissues than in peripheral tissues. The observation that differences in LRP/LR mRNA expression levels are consistent with the corresponding variation in PrP^Sc accumulation suggests that the 37-kDa/67-kDa laminin receptor may be involved in the regulation of PrP^Sc propagation.     

Genealogical Trees of Scientific Papers

Many results have been obtained when studying scientific papers citations databases in a network perspective. Articles can be ranked according to their current in-degree and their future popularity or citation counts can even be predicted. The dynamical properties of such networks and the observation of the time evolution of their nodes started more recently. This work adopts an evolutionary perspective and proposes an original algorithm for the construction of genealogical trees of scientific papers on the basis of their citation count evolution in time. The fitness of a paper now amounts to its in-degree growing trend and a “dying” paper will suddenly see this trend declining in time. It will give birth and be taken over by some of its most prevalent citing “offspring”. Practically, this might be used to trace the successive published milestones of a research field.     

A Genealogical Interpretation of Principal Components Analysis

Principal components analysis, PCA, is a statistical method commonly used in population genetics to identify structure in the distribution of genetic variation across geographical location and ethnic background. However, while the method is often used to inform about historical demographic processes, little is known about the relationship between fundamental demographic parameters and the projection of samples onto the primary axes. Here I show that for SNP data the projection of samples onto the principal components can be obtained directly from considering the average coalescent times between pairs of haploid genomes. The result provides a framework for interpreting PCA projections in terms of underlying processes, including migration, geographical isolation, and admixture. I also demonstrate a link between PCA and Wright''s f_st and show that SNP ascertainment has a largely simple and predictable effect on the projection of samples. Using examples from human genetics, I discuss the application of these results to empirical data and the implications for inference.     

土耳其斯坦叶螨和截形叶螨生殖力比较

在25±0.5℃的条件下,应用岛屿法观察比较了土耳其斯坦叶螨Tetranychus turkestani和截形叶螨Tetranychus truncatus实验种群的存活率、产卵量,组建了土耳其斯坦叶螨和截形叶螨生殖力表特定年龄生命表,比较了2种群净增殖率(R0)、内禀增长率(γm)、周限增长率(λ)和种群翻倍时间(t)等生殖力参数以及种群增长指数(I).从结果看,截形叶螨的生殖能力和种群增长指数低于土耳其斯坦叶螨.因此,可以判断截形叶螨在新疆部分棉田取代土耳其斯坦叶螨种群爆发成灾,并非其物种本身生殖潜能形成,而是由其它生态因子造成.由于截形叶螨存活时间长于土耳其斯坦叶螨,其一旦进入棉田,则造成更大危害.     

Genealogical data and the biodemography of human longevity

Biodemography of human longevity is an emerging interdisciplinary field of sociobiological research with deep historical roots. Two research questions are examined in this article: (1) What evidence is there for the familial transmission of human longevity?, and (2) what are the effects of parental age at reproduction on offspring longevity, and in particular, are there long-term adverse health consequences associated with the trend toward delayed reproduction? The ability of scientists to conduct biodemographic studies depends not only on merging theoretical and methodological elements from the biological and demographic/actuarial sciences, but unique sources of data and statistical methods must also be developed. In this article we describe how gencalogical data have been used for over a century to explore basic questions about human longevity, and how similar kinds of data now being developed are driving the formation of new testable research hypotheses in the field of biodemography.     

Genealogical inference of closely related species based on microsatellites

Despite their unmatched popularity in many research areas, microsatellites have not yet become a major tool for the inference of genealogical relationships of closely related species. Recent studies have successfully extended the repertoire of microsatellite analysis beyond population genetics and demonstrate that phylogenetic relationships of closely related species can be inferred accurately with fewer loci than previously assumed.     

The Consequences of Being a Gift

The issues of dislocated identity are epitomised in Mary's story. Brought from Papua New Guinea to Australia at a very young age as a ‘gift’, she grew up in a series of foster homes in Adelaide, South Australia. Now, as a teenager, Mary constitutes her identity through her body, emphasising her distinctive physical features, through idealised memories and through representations—photographs, cultural icons and people who ‘look like me’. The self she creates in this way sits uneasily along side another self; the Western adolescent self in trouble with the law, the self who struggles to be ‘one of the boys’ on the streets, one who ‘runs amuck’. This paper explores the process of ‘self-making’, the ‘serious play’ that Mary has employed to constitute her identity through her juggling of and reappropriation of cultural symbols. As a participant in a wider ethnographic study into Australian youth and representation, Mary portrayed the complexities of her growing up between worlds, embedded in neither and desperate to belong to her past.     

The Consequences of Habitual Knuckle Cracking

Habitual knuckle cracking in children has been considered a cause of arthritis. A survey of a geriatric patient population with a history of knuckle cracking failed to show a correlation between knuckle cracking and degenerative changes of the metacarpal phalangeal joints.     

The Effect of Selection on the Phenotypic Variance

We consider the within-generation changes of phenotypic variance caused by selection w(x) which acts on a quantitative trait x. If before selection the trait has Gaussian distribution, its variance decreases if the second derivative of the logarithm of w(x) is negative for all x, while if it is positive for all x, the variance increases.     

Variance matters: The shape of a datum

In the quantitative analysis of behaviour, choice data are most often plotted and analyzed as logarithmic transforms of ratios of responses and of ratios of reinforcers according to the generalized-matching relation, or its derivatives such as conditional-discrimination models. The relation between log choice ratios and log reinforcer ratios has normally been found using ordinary linear regression, which minimizes the sums of the squares of the y deviations from the fitted line. However, linear regression of this type requires that the log choice data be normally distributed, of equal variance for each log reinforcer ratio, and that the x (log reinforcer ratio) measures be fixed with no variance. We argue that, while log transformed choice data may be normally distributed, log reinforcer ratios do have variance, and because these measures derive from a binomial process, log reinforcer ratio distributions will be non-normal and skewed to more extreme values. These effects result in ordinary linear regression systematically underestimating generalized-matching sensitivity values, and in faulty parameter estimates from non-linear regression to assume hyperbolic and exponential decay processes. They also lead to model comparisons, which assume equal normally distributed error around every data point, being incorrect. We describe an alternative approach that can be used if the variance in choice is measured.     

The Misrepresentation of Anthropology and Its Consequences

Critiques of anthropology from within the discipline and from without have been a major feature of our intellectual life since the late 1960s. The theoretical and empirical bases of cultural and social anthropology have been under attack since the Marxist and New Left critiques of the 1960s to those coming more recently from poststructuralism, postmodernist and literary theory, and postcolonial and cultural studies. As a result, several academic generations have been educated by reading the attacks on the field but rarely dealing with the actual theoretical works and ethnographies of earlier anthropologists. This article deals with several of the most common charges leveled at anthropology, notably that it has regularly and necessarily exoticized "Others," has been ahistorical, and has treated each culture as if it were an isolate, unconnected to any other. It demonstrates how inaccurate and easily falsifiable such claims are and recommends a critical reevaluation of these unexamined and destructive cliches,     

The Causes and Consequences of Color Vision

The ability to see colors is not universal in the animal kingdom. Those animals that can detect differences in the wavelengths of the electromagnetic spectrum glean valuable sensory information about their environment. They use color vision to forage, avoid predators, and find high-quality mates. In the past, the colors that humans could see clouded scientists’ study of animals’ color perception. Leaving that bias behind has led to new insights about how and why the color vision of animals evolved. This paper provides a brief introduction to color vision, the genetics of color vision in humans, what colors other animals see, and how scientists study color vision. We examine the consequences of having color vision, including speciation, loss of olfactory capabilities, and sexual selection.     

Genealogical concordance and the specific status of Peromyscus sejugis

Peromyscus sejugis, a peripheral isolate of Peromyscus maniculatus, is a threatened taxon endemic to 2 small islands in the Sea of Cortés. Although its insularity makes the specific recognition of P. sejugis inherently problematic, resolution of this problem has important conservation implications. To evaluate the specific validity and evolutionary history of P. sejugis, we compared sequence variation (ND3/ND4L/ND4) in mtDNA for both island populations of P. sejugis with that for 8 populations of P. maniculatus from mainland Baja California. Each island population of P. sejugis had a single haplotype (0.7% sequence divergence), whereas 11 different haplotypes (mean sequence divergence = 0.68%) were obtained for the populations of P. maniculatus. The mean sequence divergence between the populations of the 2 species was 2.0%. Nested clade analysis supports the conclusion that P. sejugis is an insular isolate of P. maniculatus from mainland Baja California. Although our analysis confirms a low level of mtDNA divergence between P. sejugis and P. maniculatus from Baja California, the genealogical concordance of morphological, chromosomal, microsatellite, and mtDNA haplotype distinctiveness supports the conclusion that the 2 island populations of P. sejugis constitute independent evolutionarily significant units and together represent a phylogenetic species distinct from the P. maniculatus from Baja California.