Selection in Reference to Biological Groups. V. Analysis of Full-Sib Groups

Previous studies in this series have dealt with the consequences of truncation selection operating with respect to random groups within which geno-full-sib group structure. The objective is to compare the results of individual and group selection as these methods operate on populations of random versus typic interaction may exist. The present study deal with a non-random, full-sib groups. In almost all comparisons individual selection is found to be qualitatively and quantitatively superior when used in conjunction with full-sib groups. This is due to the fact that the change in gene frequency for full-sib groups is a function of both direct and associate effects, whereas with random groups it is a function of direct effects only. With regard to group selection the efficiency is invariably superior when selection operates on non-random, full-sib rather than random groups.     

Response to Selection Under Non-Random Mating II. Prediction

A general expression for response to selection appropriate for both random and non-random mating situations is derived and illustrated with full-sibbing.     

A Note on Response to Selection in Non-Random Mating Populations

The selection theory proposed by Muralidharan and Jain (1992a, b; Biom. J. 34 , 147–152, 633–637) was re-examined. Although they concluded that the theory is appropriate for any system of mating, the author showed that it is not applicable to inbreeding populations, which is the most important type of non-random mating.     

Kin Selection in Primate Groups

Altruism poses a problem for evolutionary biologists because natural selection is not expected to favor behaviors that are beneficial to recipients, but costly to actors. The theory of kin selection, first articulated by Hamilton (1964), provides a solution to the problem. Hamilton's well-known rule (br > c) provides a simple algorithm for the evolution of altruism via kin selection. Because kin recognition is a crucial requirement of kin selection, it is important to know whether and how primates can recognize their relatives. While conventional wisdom has been that primates can recognize maternal kin, but not paternal kin, this view is being challenged by new findings. The ability to recognize kin implies that kin selection may shape altruistic behavior in primate groups. I focus on two cases in which kin selection is tightly woven into the fabric of social life. For female baboons, macaques, and vervets maternal kinship is an important axis of social networks, coalitionary activity, and dominance relationships. Detailed studies of the patterning of altruistic interactions within these species illustrate the extent and limits of nepotism in their social lives. Carefully integrated analyses of behavior, demography, and genetics among red howlers provide an independent example of how kin selection shapes social organization and behavior. In red howlers, kin bonds shape the life histories and reproductive performance of both males and female. The two cases demonstrate that kin selection can be a powerful source of altruistic activity within primate groups. However, to fully assess the role of kin selection in primate groups, we need more information about the effects of kinship on the patterning of behavior across the Primates and accurate information about paternal kin relationships.     

A theory of natural selection incorporating interaction among individuals. V. Use of random synchronized groups

In the first paper of the current series, (I), a complex interaction model capable of describing any kind of interaction among individuals was developed. However, selection operating on random groups with regard to this model yielded short- and long-term results which were unbalanced. In subsequent kin-selection papers (II, III, and IV), a systematic analysis demonstrated that use of non-random groups could partially solve the balance problem.The present study is the first of several to employ a different approach to the problem of accommodating interaction. This approach involves changing the life-history model itself in such a way that the fitness components of individuals within groups are synchronized. Synchronization of fitness components produces total fitness values which are symmetrical. In the present study, selection operating on random groups for a model having symmetrical fitness values is evaluated for both balance and efficiency. It is demonstrated that the selection response is balanced and yields short- and long-term optimum results, but under a variety of conditions the efficiency can be low.     

A theory of natural selection incorporating interaction among individuals. VI. Use of non-random synchronized groups

The previous study, (V), in this series approached the problem of accommodating interaction among individuals in a population by considering a life-history model which resulted in the synchronization of fitness components (viability and fecundity) for members within groups of interacting individuals. It was shown that such synchronization resulted in symmetric fitness values, and that selection operating on symmetric fitness values produced optimum short- and long-term results. However, it was also shown that selection operating on the random groups of the model could be inefficient.The present paper demonstrates that use of non-random (related) groups can increase the efficiency of symmetric selection without destroying its short-term balance. The consequences of long-term selection are more complicated and depend on the complexity of the genetic model.     

Mating order-dependent female mate choice in the polygynandrous common lizard Lacerta vivipara

Recent studies indicate that directional female mate choice and order-dependent female mate choice importantly contribute to non-random mating patterns. In species where females prefer larger sized males, disentangling different hypotheses leading to non-random mating patterns is especially difficult, given that male size usually correlates with behaviours that may lead to non-random mating (e.g. size-dependent emergence from hibernation, male fighting ability). Here we investigate female mate choice and order-dependent female mate choice in the polygynandrous common lizard (Lacerta vivipara). By sequentially presenting males in random order to females, we exclude non-random mating patterns potentially arising due to intra-sexual selection (e.g. male–male competition), trait-dependent encounter probabilities, trait-dependent conspicuousness, or trait-dependent emergence from hibernation. To test for order-dependent female mate choice we investigate whether the previous mating history affects female choice. We show that body size and body condition of the male with which a female mated for the first time were bigger and better, respectively, than the average body size and body condition of the rejected males. There was a negative correlation between body sizes of first and second copulating males. This indicates that female mate choice is dependent on the previous mating history and it shows that the female’s choice criteria are non-static, i.e. non-directional. Our study therefore suggests that context-dependent female mate choice may not only arise due to genotype-environment interactions, but also due to other female mating strategies, i.e. order-dependent mate choice. Thus context-dependent female mate choice might be more frequent than previously thought.     

Oxidative Damages and Repair in Euglena gracilis Exposed to Ozone. I. SH Groups and Lipids

Malondialdehyde, a product of lipid oxidation, increased graduallywhen Euglena gracilis cells were bubbled with 240 µ1.liter^–1ozone (delivery rate of 1µmolO₃.min^–1) for 120 min.Simultaneously, the sulfhydryl group content decreased by 36%during the treatment, which was mainly due to oxidation of proteinsulfhydryl groups. The molar amount of SH groups oxidized was3 times higher than that of fatty acid oxidized, indicatingthat sulfhydryl groups were more accessible or more easily oxidizedby O₃ than fatty acids. When Euglena cells were allowed to recoverunder autotrophic growth conditions following O₃ treatment,viable cells were incapable of dividing during the first 5 hof the recovery period but regenerated SH groups nearly to thecontrol level. The increase of SH content during this periodpreceded the resumption of cell division and the restorationof normal growth. These results suggest that the regenerationof SH groups by Euglena cells is a part of a mechanism involvedin the repair of oxidative damage caused by ozone and is anessential step for the initiation of cell division. (Received July 20, 1987; Accepted December 14, 1987)     

Multi-scale Inference of Interaction Rules in Animal Groups Using Bayesian Model Selection

Inference of interaction rules of animals moving in groups usually relies on an analysis of large scale system behaviour. Models are tuned through repeated simulation until they match the observed behaviour. More recent work has used the fine scale motions of animals to validate and fit the rules of interaction of animals in groups. Here, we use a Bayesian methodology to compare a variety of models to the collective motion of glass prawns (Paratya australiensis). We show that these exhibit a stereotypical ‘phase transition’, whereby an increase in density leads to the onset of collective motion in one direction. We fit models to this data, which range from: a mean-field model where all prawns interact globally; to a spatial Markovian model where prawns are self-propelled particles influenced only by the current positions and directions of their neighbours; up to non-Markovian models where prawns have ‘memory’ of previous interactions, integrating their experiences over time when deciding to change behaviour. We show that the mean-field model fits the large scale behaviour of the system, but does not capture the observed locality of interactions. Traditional self-propelled particle models fail to capture the fine scale dynamics of the system. The most sophisticated model, the non-Markovian model, provides a good match to the data at both the fine scale and in terms of reproducing global dynamics, while maintaining a biologically plausible perceptual range. We conclude that prawns’ movements are influenced by not just the current direction of nearby conspecifics, but also those encountered in the recent past. Given the simplicity of prawns as a study system our research suggests that self-propelled particle models of collective motion should, if they are to be realistic at multiple biological scales, include memory of previous interactions and other non-Markovian effects.     

Fitness in animals correlates with proximity to discontinuities in body mass distributions

Discontinuous structure in landscapes may cause discontinuous, aggregated species body-mass patterns, reflecting the scales of structure available to animal communities within a landscape. Empirical analyses have shown that the location of species within body mass aggregations, which reflect this scale-specific organization, is non-random with regard to several ecological phenomena, including species extinctions. The propensity of declining species to have body masses proximate to discontinuities suggests that transition zones between scaling regimes ultimately decreases the ecological fitness for some species. We test this proposition using vulnerable and unthreatened fish species in Mediterranean streams with differing levels of human impact. We show that the proximity to discontinuities in body mass aggregations (“distance-to-edge”) of more vs. less fit individuals within vulnerable and unthreatened populations differs. Specifically, regression analysis between the scaled mass index, a proxy of animal fitness, and distance-to-edge reveals negative and positive relationships for vulnerable and unthreatened species, respectively. That is, fitness is higher close to discontinuities in vulnerable populations and toward the center of body mass aggregation groups in unthreatened populations. Our results demonstrate the suitability of the discontinuity framework for scrutinizing non-random patterns of environmental impact in populations. Further exploration of the usefulness of this method across other ecosystems and organism groups is warranted.     

The effective size of a natural drosophila subobscura population.

The effective size of a natural Drosophila subobscura population has been computed by drawing together various pieces of ecological information. The value, for both variance and inbreeding effective numbers, is approximately 400. This is largely due to reductions caused by a winter bottleneck and non-random distributions of family sizes. Areas where such estimates might be refined further are pointed out, and the implications of the results are discussed.     

Frequency- and density-dependent sexual selection in natural populations of Galician Littorina saxatilis Olivi

Galician exposed shore populations of the direct developing periwinkle Littorina saxatilis are strikingly polymorphic, with an ornamented and banded upper shore form and a smooth and unbanded lower shore form. Intermediates between the two pure forms occur in a narrow mid shore zone together with the parental forms. We have previously shown that the two pure forms share the same gene pool but that mating between them is non-random. This is due to a non-random microdistribution in the zone of overlap, and also to assortative mating. In this study we present data which show that intermediate (hybrid) females mate less often than pure females in micropatches dominated by either of the pure forms, but not in micropatches in which the two pure forms are equally common. Thus, sexual fitness in intermediate females depends on the frequency of both pure morphs. Furthermore, sexual selection against intermediate females also varies with the densities of snails within each micro patch. The biological mechanisms which may explain this particular reduction of female hybrid fitness are discussed. Assortative mating between the pure morphs is sometimes almost complete, while both morphs do not mate the intermediates assortatively. In the light of this, sexual selection against intermediate females may contribute considerably to restrict gene flow between the pure forms.     

Testing local-scale panmixia provides insights into the cryptic ecology, evolution, and epidemiology of metazoan animal parasites

When every individual has an equal chance of mating with other individuals, the population is classified as panmictic. Amongst metazoan parasites of animals, local-scale panmixia can be disrupted due to not only non-random mating, but also non-random transmission among individual hosts of a single host population or non-random transmission among sympatric host species. Population genetics theory and analyses can be used to test the null hypothesis of panmixia and thus, allow one to draw inferences about parasite population dynamics that are difficult to observe directly. We provide an outline that addresses 3 tiered questions when testing parasite panmixia on local scales: is there greater than 1 parasite population/species, is there genetic subdivision amongst infrapopulations within a host population, and is there asexual reproduction or a non-random mating system? In this review, we highlight the evolutionary significance of non-panmixia on local scales and the genetic patterns that have been used to identify the different factors that may cause or explain deviations from panmixia on a local scale. We also discuss how tests of local-scale panmixia can provide a means to infer parasite population dynamics and epidemiology of medically relevant parasites.     

Distribution of different cell types within the rat thymus in the neonatal period of life

Summary This study attempted to define reciprocal positions of cell types within the thymus. Random or non-random contacts between specific cell types were analyzed by means of graph theory. For analysis, thymus blocks were sectioned serially and, then, thymus cells were categorized into types, based on morphological criteria. The distribution of individual cell types within the cortex, cortico-medullary zone and medulla was presented in form of a map. In the analysis, three types of epithelial cell, characteristic of each thymus zone, macrophages, Langerhans-like cells and lymphocytes were found in non-random relations to one another. Moreover, characteristic groups of cells associated with one another were also demonstrated.This study was supported by the Polish Academy of Sciences     

Height discordance in monozygotic females is not attributable to discordant inactivation of X-linked stature determining genes.

We tested the hypothesis that X-linked genes determining stature which are subject to skewed or non-random X-inactivation can account for discordance in height in monozygotic female twins. Height discordant female monozygotic adult twins (20 pairs) were identified from the Australian Twin Registry, employing the selection criteria of proven monozygosity and a measured height discordance of at least 5 cm. Differential X-inactivation was examined in genomic DNA extracted from peripheral lymphocytes by estimating differential methylation of alleles at the polymorphic CAG triplet repeat of the Androgen receptor gene (XAR). There were 17/20 MZ pairs heterozygous at this locus and informative for analysis. Of these, 10/17 both had random X-inactivation, 5/17 showed identical X-inactivation patterns of non random inactivation and 2/17 (12%) showed discordant X-inactivation. There was no relationship between inactivation patterns and self-report chorionicity. We conclude that non-random X-inactivation does not appear to be a major contributor to intra-pair height discordance in female MZ twins.     

Selection in monoculture vs. mixture alters plant metabolic fingerprints

Aims In grassland biodiversity experiments, positive biodiversity effects on primary productivity increase over time. Recent research has shown that differential selection in monoculture and mixed-species communities leads to the rapid emergence of monoculture and mixture types, adapted to their own biotic community. We used eight plant species selected for 8 years in such a biodiversity experiment to test if monoculture and mixture types differed in metabolic profiles using infrared spectroscopy.Methods Fourier transform infrared spectroscopy (FTIR) was used to assess metabolic fingerprints of leaf samples of 10 individuals of each species from either monocultures or mixtures. The FTIR spectra were analyzed using multivariate procedures to assess (i) whether individuals within species could be correctly assigned to monoculture or mixture history based on the spectra alone and (ii) which parts of the spectra drive the group assignment, i.e. which metabolic groups were subject to differential selection in monocultures vs. mixtures.Important findings Plant individuals within each of the eight species could be classified as either from monoculture or mixture selection history based on their FTIR spectra. Different metabolic groups were differentially selected in the different species; some of them may be related to defense of pathogens accumulating more strongly in monocultures than in mixtures. The rapid selection of the monoculture and mixture types within the eight study species could have been due to a sorting-out process based on large initial genetic or epigenetic variation within the species.     

Respondent Driven Sampling: Determinants of Recruitment and a Method to Improve Point Estimation

Introduction

Respondent-driven sampling (RDS) is a variant of a link-tracing design intended for generating unbiased estimates of the composition of hidden populations that typically involves giving participants several coupons to recruit their peers into the study. RDS may generate biased estimates if coupons are distributed non-randomly or if potential recruits present for interview non-randomly. We explore if biases detected in an RDS study were due to either of these mechanisms, and propose and apply weights to reduce bias due to non-random presentation for interview.

Methods

Using data from the total population, and the population to whom recruiters offered their coupons, we explored how age and socioeconomic status were associated with being offered a coupon, and, if offered a coupon, with presenting for interview. Population proportions were estimated by weighting by the assumed inverse probabilities of being offered a coupon (as in existing RDS methods), and also of presentation for interview if offered a coupon by age and socioeconomic status group.

Results

Younger men were under-recruited primarily because they were less likely to be offered coupons. The under-recruitment of higher socioeconomic status men was due in part to them being less likely to present for interview. Consistent with these findings, weighting for non-random presentation for interview by age and socioeconomic status group greatly improved the estimate of the proportion of men in the lowest socioeconomic group, reducing the root-mean-squared error of RDS estimates of socioeconomic status by 38%, but had little effect on estimates for age. The weighting also improved estimates for tribe and religion (reducing root-mean-squared-errors by 19–29%), but had little effect for sexual activity or HIV status.

Conclusions

Data collected from recruiters on the characteristics of men to whom they offered coupons may be used to reduce bias in RDS studies. Further evaluation of this new method is required.     

When do host–parasite interactions drive the evolution of non‐random mating?

Interactions with parasites may promote the evolution of disassortative mating in host populations as a mechanism through which genetically diverse offspring can be produced. This possibility has been confirmed through simulation studies and suggested for some empirical systems in which disassortative mating by disease resistance genotype has been documented. The generality of this phenomenon is unclear, however, because existing theory has considered only a subset of possible genetic and mating scenarios. Here we present results from analytical models that consider a broader range of genetic and mating scenarios and allow the evolution of non-random mating in the parasite as well. Our results confirm results of previous simulation studies, demonstrating that coevolutionary interactions with parasites can indeed lead to the evolution of host disassortative mating. However, our results also show that the conditions under which this occurs are significantly more fickle than previously thought, requiring specific forms of infection genetics and modes of non-random mating that do not generate substantial sexual selection. In cases where such conditions are not met, hosts may evolve random or assortative mating. Our analyses also reveal that coevolutionary interactions with hosts cause the evolution of non-random mating in parasites as well. In some cases, particularly those where mating occurs within groups, we find that assortative mating evolves sufficiently to catalyze sympatric speciation in the interacting species.     

Non-random association of mitotic cells from cultured human lymphocyte suspensions.

By using chromosome markers in two separate cell lines of a human dispermic chimera, it was shown that 4.9% of metaphases in suspensions of PHA-cultured lymphocytes were paired because of non-random factors. A similar amount of metaphase pairing occurred in cultured lymphocytes of normal donors, and evidence from the relative mitotic cycles of the paired cells indicated that some of this pairing was non-random. Such non-random pairing could be a source of bias in cell kinetic and other studies involving metaphase cells in lymphocyte cultures.     

A theory of natural selection incorporating interaction among individuals. II. Use of related groups

The present series of studies attempts to accommodate interaction among individuals in evolutionary theory. The interaction phenomenon is characterized by two dimensions (direct and associate) of gene activity. For optimal selection results, a balance between the two dimensions must occur. In the first paper of the series, it was shown that random interactions resulted in an unbalanced selection response. The expression for gene frequency change involved direct, but not associate, effects. The next three papers of the series (II, III and IV) are designed to explore the possibility that restricting interactions to certain non-random patterns may ameliorate the problem of selection balance.In the present study the interactions are restricted to related individuals in a population that is in Hardy-Weinberg equilibrium. A preliminary analysis in which interactions are restricted to full-sibs is made. This analysis is extended to the more general case in which interactions occur among related individuals of any class whose coefficient of relationship is measured by ‘r’. The classical pairwise interaction results of Hamilton are verified and extended to include interactions among individuals in groups of arbitrary size, n.Restricting interactions to related individuals tends to improve the condition of selection balance. It does this by introducing associate effects into the expression for gene frequency change. The extent to which this is accomplished is a function of the coefficient of relationship (r), and the number of interacting genotypes.