Adaptive introgression of a visual preference gene

Visual preferences are important drivers of mate choice and sexual selection, but little is known of how they evolve at the genetic level. In this study, we took advantage of the diversity of bright warning patterns displayed by Heliconius butterflies, which are also used during mate choice. Combining behavioral, population genomic, and expression analyses, we show that two Heliconius species have evolved the same preferences for red patterns by exchanging genetic material through hybridization. Neural expression of regucalcin1 correlates with visual preference across populations, and disruption of regucalcin1 with CRISPR-Cas9 impairs courtship toward conspecific females, providing a direct link between gene and behavior. Our results support a role for hybridization during behavioral evolution and show how visually guided behaviors contributing to adaptation and speciation are encoded within the genome.

Divergent warning patterns influence male and female mating behaviours in a tropical butterfly

Traits under divergent ecological selection that also function during mating can be important in maintaining species boundaries. Few studies have considered mutual mate choice, where both males and females base mating decisions on the same trait. Wing colouration in Heliconius butterflies evolved as a warning signal but also functions as a mating cue. We investigated the contribution of visual preference to assortative mating in an aposematic butterfly Heliconius cydno in the context of reproductive isolation with its sympatric, visually distinct relative Heliconius melpomene. Heliconius cydno have conspicuous white bands on their forewings, whereas those of H. melpomene are red in colour. We predicted that both sexes of H. cydno contributed to assortative mating by exhibiting visual preference towards conspecific wing colouration. We analysed published and new data from preference experiments, in which males were presented with conspecific and H. melpomene females. We also recorded female responses and mating outcomes in choice experiments, involving conspecific males with either the original white or artificially painted red forewing bands. Both sexes of H. cydno responded more positively towards the conspecific colouration, and males strongly preferred females of its own colours. In contrast, male colouration did not predict mating outcomes in female choice experiments. As courtships are initiated by males in butterflies, our findings suggest that female visual preference might be of secondary importance in H. cydno. Our data also suggest that the contribution of visual preference to reproductive isolation might be unequal between H. cydno and its sympatric relative H. melpomene.

Genetics and the Evolution of Prezygotic Isolation

The significance of prezygotic isolation for speciation has been recognized at least since the Modern Synthesis. However, fundamental questions remain. For example, how are genetic associations between traits that contribute to prezygotic isolation maintained? What is the source of genetic variation underlying the evolution of these traits? And how do prezygotic barriers affect patterns of gene flow? We address these questions by reviewing genetic features shared across plants and animals that influence prezygotic isolation. Emerging technologies increasingly enable the identification and functional characterization of the genes involved, allowing us to test established theoretical expectations. Embedding these genes in their developmental context will allow further predictions about what constrains the evolution of prezygotic isolation. Ongoing improvements in statistical and computational tools will reveal how pre- and postzygotic isolation may differ in how they influence gene flow across the genome. Finally, we highlight opportunities for progress by combining theory with appropriate data.

Parallel shifts in flight-height associated with altitude across incipient Heliconius species

Vertical gradients in microclimate, resource availability, and interspecific interactions are thought to underly stratification patterns in tropical insect communities. However, only a few studies have explored the adaptive significance of vertical space use during the early stages of reproductive isolation. We analysed flight-height variation across speciation events in Heliconius butterflies, representing parallel colonizations of high-altitude forest. We measured flight-height in wild H. erato venus and H. chestertonii, parapatric lowland and mountain specialists, respectively, and found that H. chestertonii consistently flies at a lower height. By comparing our data to previously published results for the ecologically equivalent H. e. cyrbia (lowland) and H. himera (high altitude), we found that the species flying closest to the ground are those that recently colonized high-altitude forests. We show that these repeated trends largely result from shared patterns of ecological selection producing parallel trait-shifts in H. himera and H. chestertonii. Although our results imply a signature of local adaptation, we did not find an association between resource distribution and flight-height in H. e. venus and H. chestertonii. We discuss how this pattern may be explained by variations in forest structure and microclimate. Overall, our findings underscore the importance of behavioural adjustments during early divergence mediated by altitude-shifts.

The Sensory Ecology of Speciation

In this work, we explore the potential influence of sensory ecology on speciation, including but not limited to the concept of sensory drive, which concerns the coevolution of signals and sensory systems with the local environment. The sensory environment can influence individual fitness in a variety of ways, thereby affecting the evolution of both pre- and postmating reproductive isolation. Previous work focused on sensory drive has undoubtedly advanced the field, but we argue that it may have also narrowed our understanding of the broader influence of the sensory ecology on speciation. Moreover, the clearest examples of sensory drive are largely limited to aquatic organisms, which may skew the influence of contributing factors. We review the evidence for sensory drive across environmental conditions, and in this context discuss the importance of more generalized effects of sensory ecology on adaptive behavioral divergence. Finally, we consider the potential of rapid environmental change to influence reproductive barriers related to sensory ecologies. Our synthesis shows the importance of sensory conditions for local adaptation and divergence in a range of behavioral contexts and extends our understanding of the interplay between sensory ecology and speciation.

Quantifying visual acuity in Heliconius butterflies

Heliconius butterflies are well-known for their colourful wing patterns, which advertise distastefulness to potential predators and are used during mate choice. However, the relative importance of different aspects of these signals will depend on the visual abilities of Heliconius and their predators. Previous studies have investigated colour sensitivity and neural anatomy, but visual acuity (the ability to perceive detail) has not been studied in these butterflies. Here, we provide the first estimate of visual acuity in Heliconius: from a behavioural optomotor assay, we found that mean visual acuity = 0.49 cycles-per-degree (cpd), with higher acuity in males than females. We also examined eye morphology and report more ommatidia in male eyes. Finally, we estimated how visual acuity affects Heliconius visual perception compared to a potential avian predator. Whereas the bird predator maintained high resolving power, Heliconius lost the ability to resolve detail at greater distances, though colours may remain salient. These results will inform future studies of Heliconius wing pattern evolution, as well as other aspects in these highly visual butterflies, which have emerged as an important system in studies of adaptation and speciation.

Oviposition behavior is not affected by ultraviolet light in a butterfly with sexually-dimorphic expression of a UV-sensitive opsin

Animal vision is important for mediating multiple complex behaviors. In Heliconius butterflies, vision guides fundamental behaviors such as oviposition, foraging, and mate choice. Color vision in Heliconius involves ultraviolet (UV), blue and long-wavelength-sensitive photoreceptors (opsins). Additionally, Heliconius possess a duplicated UV opsin, and its expression varies widely within the genus. In Heliconius erato, opsin expression is sexually dimorphic; only females express both UV-sensitive opsins, enabling UV wavelength discrimination. However, the selective pressures responsible for sex-specific differences in opsin expression and visual perception remain unresolved. Female Heliconius invest heavily in finding suitable hostplants for oviposition, a behavior heavily dependent on visual cues. Here, we tested the hypothesis that UV vision is important for oviposition in H. erato and Heliconius himera females by manipulating the availability of UV in behavioral experiments under natural conditions. Our results indicate that UV does not influence the number of oviposition attempts or eggs laid, and the hostplant, Passiflora punctata, does not reflect UV wavelengths. Models of H. erato female vision suggest only minimal stimulation of the UV opsins. Overall, these findings suggest that UV wavelengths do not directly affect the ability of Heliconius females to find suitable oviposition sites. Alternatively, UV discrimination could be used in the context of foraging or mate choice, but this remains to be tested.

Parallel evolution of behaviour, physiology and life history associated with altitudinal shifts in forest type in Heliconius butterflies

Parallel evolution of morphological traits is widely reported, providing evidence for the role of local conditions in driving adaptive divergence. Comparatively, fewer studies have tested for parallelism in behaviour, and it is less clear to what extent heritable behavioural shifts contribute to adaptive divergence. We exploit repeated incipient speciation across altitudinal gradients to explore behaviour and physiology in Heliconius butterflies adapted to high-elevation. We performed common garden experiments with H. chestertonii, a high-altitude specialist from the Colombian Cordillera Occidental, and H. erato venus, a low-elevation proxy for the ancestral population, and compared our results to existing data for an equivalent Ecuadorian taxa-pair. Using broad-scale climatic data, we show that both pairs diverge across similar ecological gradients, confirmed using localised data loggers in the ranges of H. chestertonii and H. e. venus. We further show that H. chestertonii and H. e. venus have divergent activity patterns, attributable to different responses to microclimate, and life histories. Finally, we provide evidence for parallelism in these traits with H. himera and H. e. cyrbia. We propose that this is a result of selection associated with independent colonisations of high-altitude forests, emphasising the importance of heritable behavioural and physiological adaptations during population divergence and speciation.

Does sexual conflict contribute to the evolution of novel warning patterns?

Why warning patterns are so diverse is an enduring evolutionary puzzle. Because predators associate particular patterns with unpleasant experiences, an individual's predation risk should decrease as the local density of its warning pattern increases, promoting pattern monomorphism. Distasteful Heliconius butterflies are known for their diversity of warning patterns. Here, we explore whether interlocus sexual conflict can contribute to their diversification. Male Heliconius use warning patterns as mating cues, but mated females may suffer costs if this leads to disturbance, favouring novel patterns. Using simulations, we show that under our model conditions drift alone is unlikely to cause pattern diversification, but that sexual conflict can assist such a process. We also find that genetic architecture influences the evolution of male preferences, which track changes in warning pattern due to sexual selection. When male attraction imposes costs on females, this affects the speed at which novel pattern alleles increase. In two experiments, females laid fewer eggs with males present. However, although males in one experiment showed less interest in females with manipulated patterns, we found no evidence that female colouration mitigates sex-specific costs. Overall, male attraction to conspecific warning patterns may impose an unrecognized cost on Heliconius females, but further work is required to determine this experimentally.

Evolution of physical linkage between loci controlling ecological traits and mating preferences

Coupling of multiple barriers to gene-flow, such as divergent local adaptation and reproductive isolation, facilitates speciation. However, alleles at loci that contribute to barrier effects can be dissociated by recombination. Models of linkage between diverging alleles often consider elements that reduce recombination, such as chromosomal inversions and alleles that modify recombination rate between existing loci. In contrast, here, we consider the evolution of linkage due to the close proximity of loci on the same chromosome. Examples of such physical linkage exist in several species, but in other cases, strong associations are maintained without physical linkage. We use an individual-based model to study the conditions under which the physical linkage between loci controlling ecological traits and mating preferences might be expected to evolve. We modelled a single locus controlling an ecological trait that acts also as a mating cue. Mating preferences are controlled by multiple loci, formed by mutations that are randomly placed in the "genome", within varying distances from the ecological trait locus, allowing us to examine which genomic architectures spread across the population. Our model reveals that stronger physical linkage is favoured when mating preferences and selection are weaker. Under such conditions mating among divergent phenotypes is more frequent, and matching ecological trait and mating preference alleles are more likely to become dissociated by recombination, favouring the evolution of genetic linkage. While most theoretical studies on clustering of divergent loci focus on how physical linkage influences speciation, we show how physical linkage itself can arise, establishing conditions that can favour speciation.

Light environment influences mating behaviours during the early stages of divergence in tropical butterflies

Speciation is facilitated when traits under divergent selection also act as mating cues. Fluctuations in sensory conditions can alter signal perception independently of adaptation to the broader sensory environment, but how this fine-scale variation may constrain or promote behavioural isolation has received little attention. The warning patterns of Heliconius butterflies are under selection for aposematism and act as mating cues. Using computer vision, we extracted behavioural data from 1481 h of video footage, for 387 individuals. We show that the putative hybrid species H. heurippa and its close relative H. timareta linaresi differ in their response to divergent warning patterns, but that these differences are strengthened with increased local illuminance. Trials with live individuals reveal low-level assortative mating that is sufficiently explained by differences in visual attraction. Finally, results from hybrid butterflies are consistent with linkage between a major warning pattern gene and the corresponding behaviour, though the differences in behaviour we observe are unlikely to cause rapid reproductive isolation as predicted under a model of hybrid trait speciation. Overall, our results reveal that the contribution of ecological mating cues to reproductive isolation may depend on the immediate sensory conditions during which they are displayed to conspecifics.

A novel terpene synthase controls differences in anti-aphrodisiac pheromone production between closely related Heliconius butterflies

Plants and insects often use the same compounds for chemical communication, but not much is known about the genetics of convergent evolution of chemical signals. The terpene (E)-β-ocimene is a common component of floral scent and is also used by the butterfly Heliconius melpomene as an anti-aphrodisiac pheromone. While the biosynthesis of terpenes has been described in plants and microorganisms, few terpene synthases (TPSs) have been identified in insects. Here, we study the recent divergence of 2 species, H. melpomene and Heliconius cydno, which differ in the presence of (E)-β-ocimene; combining linkage mapping, gene expression, and functional analyses, we identify 2 novel TPSs. Furthermore, we demonstrate that one, HmelOS, is able to synthesise (E)-β-ocimene in vitro. We find no evidence for TPS activity in HcydOS (HmelOS ortholog of H. cydno), suggesting that the loss of (E)-β-ocimene in this species is the result of coding, not regulatory, differences. The TPS enzymes we discovered are unrelated to previously described plant and insect TPSs, demonstrating that chemical convergence has independent evolutionary origins.

Plants and insects often use the same compounds for chemical communication, but little is known about the convergent evolution of such chemical signals. This study identifies a novel terpene synthase involved in production of an anti-aphrodisiac pheromone by the butterfly Heliconius melpomene. This enzyme is unrelated to other insect terpene synthases, providing evidence that the ability to synthesise terpenes has arisen multiple times independently within the insects.

Clustering of loci controlling species differences in male chemical bouquets of sympatric Heliconius butterflies

The degree to which loci promoting reproductive isolation cluster in the genome-that is, the genetic architecture of reproductive isolation-can influence the tempo and mode of speciation. Tight linkage between these loci can facilitate speciation in the face of gene flow. Pheromones play a role in reproductive isolation in many Lepidoptera species, and the role of endogenously produced compounds as secondary metabolites decreases the likelihood of pleiotropy associated with many barrier loci. Heliconius butterflies use male sex pheromones to both court females (aphrodisiac wing pheromones) and ward off male courtship (male-transferred antiaphrodisiac genital pheromones), and it is likely that these compounds play a role in reproductive isolation between Heliconius species. Using a set of backcross hybrids between H. melpomene and H. cydno, we investigated the genetic architecture of putative male pheromone compound production. We found a set of 40 significant quantitative trait loci (QTL) representing 33 potential pheromone compounds. QTL clustered significantly on two chromosomes, chromosome 8 for genital compounds and chromosome 20 for wing compounds, and chromosome 20 was enriched for potential pheromone biosynthesis genes. There was minimal overlap between pheromone QTL and known QTL for mate choice and color pattern. Nonetheless, we did detect linkage between a QTL for wing androconial area and optix, a color pattern locus known to play a role in reproductive isolation in these species. This tight clustering of putative pheromone loci might contribute to coincident reproductive isolating barriers, facilitating speciation despite ongoing gene flow.

Visual mate preference evolution during butterfly speciation is linked to neural processing genes

Many animal species remain separate not because their individuals fail to produce viable hybrids but because they "choose" not to mate. However, we still know very little of the genetic mechanisms underlying changes in these mate preference behaviours. Heliconius butterflies display bright warning patterns, which they also use to recognize conspecifics. Here, we couple QTL for divergence in visual preference behaviours with population genomic and gene expression analyses of neural tissue (central brain, optic lobes and ommatidia) across development in two sympatric Heliconius species. Within a region containing 200 genes, we identify five genes that are strongly associated with divergent visual preferences. Three of these have previously been implicated in key components of neural signalling (specifically an ionotropic glutamate receptor and two regucalcins), and overall our candidates suggest shifts in behaviour involve changes in visual integration or processing. This would allow preference evolution without altering perception of the wider environment.

Species specificity and intraspecific variation in the chemical profiles of Heliconius butterflies across a large geographic range

In many animals, mate choice is important for the maintenance of reproductive isolation between species. Traits important for mate choice and behavioral isolation are predicted to be under strong stabilizing selection within species; however, such traits can also exhibit variation at the population level driven by neutral and adaptive evolutionary processes. Here, we describe patterns of divergence among androconial and genital chemical profiles at inter- and intraspecific levels in mimetic Heliconius butterflies. Most variation in chemical bouquets was found between species, but there were also quantitative differences at the population level. We found a strong correlation between interspecific chemical and genetic divergence, but this correlation varied in intraspecific comparisons. We identified "indicator" compounds characteristic of particular species that included compounds already known to elicit a behavioral response, suggesting an approach for identification of candidate compounds for future behavioral studies in novel systems. Overall, the strong signal of species identity suggests a role for these compounds in species recognition, but with additional potentially neutral variation at the population level.

Hybridization and transgressive exploration of colour pattern and wing morphology in Heliconius butterflies

Hybridization can generate novel phenotypes distinct from those of parental lineages, a phenomenon known as transgressive trait variation. Transgressive phenotypes might negatively or positively affect hybrid fitness, and increase available variation. Closely related species of Heliconius butterflies regularly produce hybrids in nature, and hybridization is thought to play a role in the diversification of novel wing colour patterns despite strong stabilizing selection due to interspecific mimicry. Here, we studied wing phenotypes in first- and second-generation hybrids produced by controlled crosses between either two co-mimetic species of Heliconius or between two nonmimetic species. We quantified wing size, shape and colour pattern variation and asked whether hybrids displayed transgressive wing phenotypes. Discrete traits underlain by major-effect loci, such as the presence or absence of colour patches, generate novel phenotypes. For quantitative traits, such as wing shape or subtle colour pattern characters, hybrids only exceed the parental range in specific dimensions of the morphological space. Overall, our study addresses some of the challenges in defining and measuring phenotypic transgression for multivariate traits and our data suggest that the extent to which transgressive trait variation in hybrids contributes to phenotypic diversity depends on the complexity and the genetic architecture of the traits.

A major locus controls a biologically active pheromone component in Heliconius melpomene

Understanding the production, response, and genetics of signals used in mate choice can inform our understanding of the evolution of both intraspecific mate choice and reproductive isolation. Sex pheromones are important for courtship and mate choice in many insects, but we know relatively little of their role in butterflies. The butterfly Heliconius melpomene uses a complex blend of wing androconial compounds during courtship. Electroantennography in H. melpomene and its close relative Heliconius cydno showed that responses to androconial extracts were not species specific. Females of both species responded equally strongly to extracts of both species, suggesting conservation of peripheral nervous system elements across the two species. Individual blend components provoked little to no response, with the exception of octadecanal, a major component of the H. melpomene blend. Supplementing octadecanal on the wings of octadecanal-rich H. melpomene males led to an increase in the time until mating, demonstrating the bioactivity of octadecanal in Heliconius. Using quantitative trait locus (QTL) mapping, we identified a single locus on chromosome 20 responsible for 41% of the parental species' difference in octadecanal production. This QTL does not overlap with any of the major wing color or mate choice loci, nor does it overlap with known regions of elevated or reduced FST . A set of 16 candidate fatty acid biosynthesis genes lies underneath the QTL. Pheromones in Heliconius carry information relevant for mate choice and are under simple genetic control, suggesting they could be important during speciation.

Male pheromone composition depends on larval but not adult diet in Heliconius melpomene

1. Condition-dependent traits can act as honest signals of mate quality, with fitter individuals being able to display preferred phenotypes. Nutrition is known to be an important determinant of individual condition, with diet known to affect many secondary sexual traits. 2. In Heliconius butterflies, male chemical signalling plays an important role in female mate choice. Potential male sex pheromone components have been identified previously, although it is unclear what information they convey to the female. 3. In the present study, the effect of diet on androconial and genital compound production is tested in male Heliconius melpomene rosina. To manipulate larval diet, larvae are reared on three different Passiflora host plants: Passiflora menispermifolia, the preferred host plant, Passiflora vitifolia and Passiflora platyloba. To manipulate adult diet, adult butterflies are reared with and without access to pollen, a key component of their diet. 4. No evidence is found to suggest that adult pollen consumption affects compound production in the first 10 days after eclosion. There is also a strong overlap in the chemical profiles of individuals reared on different larval host plants. The most abundant compounds produced by the butterflies do not differ between host plant groups. However, some compounds found in small amounts differ both qualitatively and quantitatively. Some of these compounds are predicted to be of plant origin and the others synthesised by the butterfly. Further electrophysiological and behavioural experiments will be needed to determine the biological significance of these differences.

Genetic dissection of assortative mating behavior

The evolution of new species is made easier when traits under divergent ecological selection are also mating cues. Such ecological mating cues are now considered more common than previously thought, but we still know little about the genetic changes underlying their evolution or more generally about the genetic basis for assortative mating behaviors. Both tight physical linkage and the existence of large-effect preference loci will strengthen genetic associations between behavioral and ecological barriers, promoting the evolution of assortative mating. The warning patterns of Heliconius melpomene and H. cydno are under disruptive selection due to increased predation of nonmimetic hybrids and are used during mate recognition. We carried out a genome-wide quantitative trait locus (QTL) analysis of preference behaviors between these species and showed that divergent male preference has a simple genetic basis. We identify three QTLs that together explain a large proportion (approximately 60%) of the difference in preference behavior observed between the parental species. One of these QTLs is just 1.2 (0-4.8) centiMorgans (cM) from the major color pattern gene optix, and, individually, all three have a large effect on the preference phenotype. Genomic divergence between H. cydno and H. melpomene is high but broadly heterogenous, and admixture is reduced at the preference-optix color pattern locus but not the other preference QTLs. The simple genetic architecture we reveal will facilitate the evolution and maintenance of new species despite ongoing gene flow by coupling behavioral and ecological aspects of reproductive isolation.

What shapes the continuum of reproductive isolation? Lessons from Heliconius butterflies

The process by which species evolve can be illuminated by investigating barriers that limit gene flow between taxa. Recent radiations, such as Heliconius butterflies, offer the opportunity to compare isolation between pairs of taxa at different stages of ecological, geographical, and phylogenetic divergence. Here, we report a comparative analysis of existing and novel data in order to quantify the strength and direction of isolating barriers within a well-studied clade of Heliconius Our results highlight that increased divergence is associated with the accumulation of stronger and more numerous barriers to gene flow. Wing pattern is both under natural selection for Müllerian mimicry and involved in mate choice, and therefore underlies several isolating barriers. However, pairs which share a similar wing pattern also display strong reproductive isolation mediated by traits other than wing pattern. This suggests that, while wing pattern is a key factor for early stages of divergence, it may become facultative at later stages of divergence. Additional factors including habitat partitioning, hybrid sterility, and chemically mediated mate choice are associated with complete speciation. Therefore, although most previous work has emphasized the role of wing pattern, our comparative results highlight that speciation is a multi-dimensional process, whose completion is stabilized by many factors.

Male sex pheromone components in Heliconius butterflies released by the androconia affect female choice

Sex-specific pheromones are known to play an important role in butterfly courtship, and may influence both individual reproductive success and reproductive isolation between species. Extensive ecological, behavioural and genetic studies of Heliconius butterflies have made a substantial contribution to our understanding of speciation. Male pheromones, although long suspected to play an important role, have received relatively little attention in this genus. Here, we combine morphological, chemical and behavioural analyses of male pheromones in the Neotropical butterfly Heliconius melpomene. First, we identify putative androconia that are specialized brush-like scales that lie within the shiny grey region of the male hindwing. We then describe putative male sex pheromone compounds, which are largely confined to the androconial region of the hindwing of mature males, but are absent in immature males and females. Finally, behavioural choice experiments reveal that females of H. melpomene, H. erato and H. timareta strongly discriminate against conspecific males which have their androconial region experimentally blocked. As well as demonstrating the importance of chemical signalling for female mate choice in Heliconius butterflies, the results describe structures involved in release of the pheromone and a list of potential male sex pheromone compounds.

Differential effects of air conditioning type on residential endotoxin levels in a semi-arid climate

Residential endotoxin exposure is associated with protective and pathogenic health outcomes. Evaporative coolers, an energy-efficient type of air conditioner used in dry climates, are a potential source of indoor endotoxins; however, this association is largely unstudied. We collected settled dust biannually from four locations in homes with evaporative coolers (n=18) and central air conditioners (n=22) in Utah County, Utah (USA), during winter (Jan-Apr) and summer (Aug-Sept), 2014. Dust samples (n=281) were analyzed by the Limulus amebocyte lysate test. Housing factors were measured by survey, and indoor temperature and relative humidity measures were collected during both seasons. Endotoxin concentrations (EU/mg) were significantly higher in homes with evaporative coolers from mattress and bedroom floor samples during both seasons. Endotoxin surface loads (EU/m² ) were significantly higher in homes with evaporative coolers from mattress and bedroom floor samples during both seasons and in upholstered furniture during winter. For the nine significant season-by-location comparisons, EU/mg and EU/m² were approximately three to six times greater in homes using evaporative coolers. A plausible explanation for these findings is that evaporative coolers serve as a reservoir and distribution system for Gram-negative bacteria or their cell wall components in homes.

No evidence for maintenance of a sympatric Heliconius species barrier by chromosomal inversions

Mechanisms that suppress recombination are known to help maintain species barriers by preventing the breakup of coadapted gene combinations. The sympatric butterfly species Heliconius melpomene and Heliconius cydno are separated by many strong barriers, but the species still hybridize infrequently in the wild, and around 40% of the genome is influenced by introgression. We tested the hypothesis that genetic barriers between the species are maintained by inversions or other mechanisms that reduce between-species recombination rate. We constructed fine-scale recombination maps for Panamanian populations of both species and their hybrids to directly measure recombination rate within and between species, and generated long sequence reads to detect inversions. We find no evidence for a systematic reduction in recombination rates in F1 hybrids, and also no evidence for inversions longer than 50 kb that might be involved in generating or maintaining species barriers. This suggests that mechanisms leading to global or local reduction in recombination do not play a significant role in the maintenance of species barriers between H. melpomene and H. cydno.

The gene cortex controls mimicry and crypsis in butterflies and moths

The wing patterns of butterflies and moths (Lepidoptera) are diverse and striking examples of evolutionary diversification by natural selection1,2. Lepidopteran wing colour patterns are a key innovation, consisting of arrays of coloured scales. We still lack a general understanding of how these patterns are controlled and if there is any commonality across the 160,000 moth and 17,000 butterfly species. Here, we identify a gene, cortex, through fine-scale mapping using population genomics and gene expression analyses, which regulates pattern switches in multiple species across the mimetic radiation in Heliconius butterflies. cortex belongs to a fast evolving subfamily of the otherwise highly conserved fizzy family of cell cycle regulators3, suggesting that it most likely regulates pigmentation patterning through regulation of scale cell development. In parallel with findings in the peppered moth (Biston betularia)4, our results suggest that this mechanism is common within Lepidoptera and that cortex has become a major target for natural selection acting on colour and pattern variation in this group of insects.

The diversification of Heliconius butterflies: what have we learned in 150 years?

Research into Heliconius butterflies has made a significant contribution to evolutionary biology. Here, we review our understanding of the diversification of these butterflies, covering recent advances and a vast foundation of earlier work. Whereas no single group of organisms can be sufficient for understanding life's diversity, after years of intensive study, research into Heliconius has addressed a wide variety of evolutionary questions. We first discuss evidence for widespread gene flow between Heliconius species and what this reveals about the nature of species. We then address the evolution and diversity of warning patterns, both as the target of selection and with respect to their underlying genetic basis. The identification of major genes involved in mimetic shifts, and homology at these loci between distantly related taxa, has revealed a surprising predictability in the genetic basis of evolution. In the final sections, we consider the evolution of warning patterns, and Heliconius diversity more generally, within a broader context of ecological and sexual selection. We consider how different traits and modes of selection can interact and influence the evolution of reproductive isolation.

Divergent warning patterns contribute to assortative mating between incipient Heliconius species

Theoretical models suggest that traits under divergent ecological selection, which also contribute to assortative mating, will facilitate speciation with gene flow. Evidence for these so-called "magic traits" now exists across a range of taxa. However, their importance during speciation will depend on the extent to which they contribute to reproductive isolation. Addressing this requires experiments to determine the exact cues involved as well as estimates of assortative mating in the wild. Heliconius butterflies are well known for their diversity of bright warning color patterns, and their amenability to experimental manipulation has provided an excellent opportunity to test their role in reproductive isolation. Here, we reveal that divergent color patterns contribute to mate recognition between the incipient species Heliconius himera and H. erato, a taxon pair for which assortative mating by color pattern has been demonstrated among wild individuals: First, we demonstrate that males are more likely to attempt to mate conspecific females; second, we show that males are more likely to approach pinned females that share their own warning pattern. These data are valuable as these taxa likely represent the early stages of speciation, but unusually also allow comparisons with rates of interbreeding between divergent ecologically relevant phenotypes measured in the wild.

Ecological and genetic factors influencing the transition between host-use strategies in sympatric Heliconius butterflies

Shifts in host-plant use by phytophagous insects have played a central role in their diversification. Evolving host-use strategies will reflect a trade-off between selection pressures. The ecological niche of herbivorous insects is partitioned along several dimensions, and if populations remain in contact, recombination will break down associations between relevant loci. As such, genetic architecture can profoundly affect the coordinated divergence of traits and subsequently the ability to exploit novel habitats. The closely related species Heliconius cydno and H. melpomene differ in mimetic colour pattern, habitat and host-plant use. We investigate the selection pressures and genetic basis underlying host-use differences in these two species. Host-plant surveys reveal that H. melpomene specializes on a single species of Passiflora. This is also true for the majority of other Heliconius species in secondary growth forest at our study site, as expected under a model of interspecific competition. In contrast, H. cydno, which uses closed-forest habitats where both Heliconius and Passiflora are less common, appears not to be restricted by competition and uses a broad selection of the available Passiflora. However, other selection pressures are likely involved, and field experiments reveal that early larval survival of both butterfly species is highest on Passiflora menispermifolia, but most markedly so for H. melpomene, the specialist on that host. Finally, we demonstrate an association between host-plant acceptance and colour pattern amongst interspecific hybrids, suggesting that major loci underlying these important ecological traits are physically linked in the genome. Together, our results reveal ecological and genetic associations between shifts in habitat, host use and mimetic colour pattern that have likely facilitated both speciation and coexistence.

Disruptive ecological selection on a mating cue

Adaptation to divergent ecological niches can result in speciation. Traits subject to disruptive selection that also contribute to non-random mating will facilitate speciation with gene flow. Such 'magic' or 'multiple-effect' traits may be widespread and important for generating biodiversity, but strong empirical evidence is still lacking. Although there is evidence that putative ecological traits are indeed involved in assortative mating, evidence that these same traits are under divergent selection is considerably weaker. Heliconius butterfly wing patterns are subject to positive frequency-dependent selection by predators, owing to aposematism and Müllerian mimicry, and divergent colour patterns are used by closely related species to recognize potential mates. The amenability of colour patterns to experimental manipulation, independent of other traits, presents an excellent opportunity to test their role during speciation. We conducted field experiments with artificial butterflies, designed to match natural butterflies with respect to avian vision. These were complemented with enclosure trials with live birds and real butterflies. Our experiments showed that hybrid colour-pattern phenotypes are attacked more frequently than parental forms. For the first time, we demonstrate disruptive ecological selection on a trait that also acts as a mating cue.

Mate preference across the speciation continuum in a clade of mimetic butterflies

Premating behavioral isolation is increasingly recognized as an important part of ecological speciation, where divergent natural selection causes the evolution of reproductive barriers. A number of studies have now demonstrated that traits under divergent natural selection also affect mate preferences. However, studies of single species pairs only capture a snapshot of the speciation process, making it difficult to assess the role of mate preferences throughout the entire process. Heliconius butterflies are well known for their brightly colored mimetic warning patterns, and previous studies have shown that these patterns are also used as mate recognition cues. Here, we present mate preference data for four pairs of sister taxa, representing different stages of divergence, which together allow us to compare diverging mate preferences across the continuum of Heliconius speciation. Using a novel Bayesian approach, our results support a model of ecological speciation in which strong premating isolation arises early, but continues to increase throughout the continuum from polymorphic populations through to "good," sympatric ecologically divergent species.

Factors associated with attrition and success in a worksite wellness telephonic health coaching program

OBJECTIVES

This study identifies factors associated with attrition and improvements in body mass index (BMI) in a telephonic health coaching program.

METHODS

A cohort study design was used with 6,129 employees aged 21-88 years, enrolled in telephonic health coaching sometime during 2002 through 2008.

RESULTS

Attrition through 3, 6 and 12 months of follow-up was 13%, 17% and 36%, respectively. Those currently making changes in physical activity or nutrition had the highest BMI (kg/m2), lowest levels of exercise and the poorest overall health at baseline. They were also most likely to continue with health coaching through 12 months. Those not ready to make changes at this time or having maintained an appropriate level of physical activity or nutrition for more than six months were least likely to continue with health coaching through 12 months. They also had the lowest BMI, highest levels of exercise and the best overall health. Among those continuing with health coaching through 12 months, the percent decrease in BMI between baseline and 12 months was: 1.5% for normal weight, 2.7% for overweight, 4.1% for class I & II obesity and 7.2% for class III obesity; 4.3% for high confidence to lose weight, 3.5% for medium confidence to lose weight and 3.1% for low confidence to lose weight; and 3.8% for very good or good general health, 4.5% for average general health and 6.8% for poor/very poor general health.

CONCLUSIONS

Attrition in the telephonic health coaching program is greatest among those least in need of behavior change. Of those who continued in the program, the greatest decrease in BMI occurred in those in greatest need for behavior change.

KEYWORDS

Behavior change, BMI, interactive health coaching, readiness to change, self-efficacy, weight.

Sectors of the Russian economy that would benefit from reduced cigarette sales

BACKGROUND

Cigarette companies argue that tobacco control measures will harm the Russian economy. Research in other countries has refuted this claim.

OBJECTIVE

To identify how current and former smokers would (or did) spend their cigarette money if (or when) they quit smoking.

METHODS

A nationwide face-to-face survey of 1599 participants aged 18 years and older in 128 cities was conducted in Russia during May 2008 by the Russian Levada Analytical Center.

RESULTS

In all, 10% of respondents were former smokers and 33% were current smokers. Respondents indicated that they would spend their cigarette money on selected items if they quit. These items, from most to least common are groceries, recreation, housing, clothing, transportation, healthcare and savings. The ways that cigarette money would be spent in the absence of smoking significantly differed according to smoking status, gender, age, education, income, rural versus urban residency and geographic region.

CONCLUSIONS

Tobacco control may benefit the Russian economy by producing healthier workers and because the money that would have been used for cigarettes would be shifted primarily to groceries, recreation, housing and clothing.

Pervasive genetic associations between traits causing reproductive isolation in Heliconius butterflies

Ecological speciation proceeds through the accumulation of divergent traits that contribute to reproductive isolation, but in the face of gene flow traits that characterize incipient species may become disassociated through recombination. Heliconius butterflies are well known for bright mimetic warning patterns that are also used in mate recognition and cause both pre- and post-mating isolation between divergent taxa. Sympatric sister taxa representing the final stages of speciation, such as Heliconius cydno and Heliconius melpomene, also differ in ecology and hybrid fertility. We examine mate preference and sterility among offspring of crosses between these species and demonstrate the clustering of Mendelian colour pattern loci and behavioural loci that contribute to reproductive isolation. In particular, male preference for red patterns is associated with the locus responsible for the red forewing band. Two further colour pattern loci are associated, respectively, with female mating outcome and hybrid sterility. This genetic architecture in which ‘speciation genes’ are clustered in the genome can facilitate two controversial models of speciation, namely divergence in the face of gene flow and hybrid speciation.

Employee weight management through health coaching

OBJECTIVE

This study will evaluate the effectiveness of an interactive health coaching intervention at lowering weight.

METHODS

The study involved 5405 overweight or obese employees aged 18-85, who entered the program sometime during 2001-2008.

RESULTS

Average body mass index (BMI) significantly decreased from 32.1 at baseline to 31.4 at 3 months, 31.0 at 6 months, and 30.6 at 12 months. Decreasing BMI was more pronounced in older age groups and among women, those using weight loss medication, those with higher BMI, and those with higher motivation and confidence to make behavior changes. When the effects of these variables on the decreasing trend in BMI were simultaneously estimated, only baseline classifications of BMI, health status, and confidence remained significant. Change in BMI through 12 months was -0.7% for those with normal weight, -2.0% for overweight, -3.6% for obese, and -7.1% for morbidly obese individuals at baseline. Among morbidly obese individuals, decrease in BMI through 12 months was -7.6% for those with "high" confidence to lose weight at baseline vs -4.4% for those with low confidence. Better health status at baseline was also related to more pronounced weight loss.

CONCLUSION

Interactive health coaching significantly lowered BMI among participants through 3, 6, and 12 months of follow-up.

Perceived effectiveness of counselling patients about smoking among medical students in Amman, Jordan

We identified the prevalence of smoking and perceived effectiveness of physicians counselling patients about smoking among 340 1st and 4th year medical students in Amman, Jordan. Smoking prevalence was 26% for males and 7% for females, similar to that of their peers in the general population. Smokers and male students were less likely to believe it is wrong for physicians to smoke in front of patients or that smoking policy or physician interaction with patients can influence smoking practices. Students believed that physicians can more effectively prevent smoking than influence patients to stop smoking. Student training on how to effectively counsel patients about smoking prevention and cessation is warranted.

The effects of an intensive lifestyle modification program on sleep and stress disorders

BACKGROUND

To determine if a lifestyle change program can modify behavior to reduce sleep and stress disorders.

METHODS

Analyses are based on 2,624 individuals aged 30 to 80 years from the Rockford, Illinois metropolitan area who completed a lifestyle evaluation at baseline and again after four weeks, following participation in a 40-hour educational course given over a four-week period. Participants receive instruction on the importance of making better lifestyle choices related to making long-term improvements in nutrition and physical activity and they learn ways to improve sleep and reduce stress in their lives.

RESULTS

Significant percent decreases were observed in the number experiencing selected sleep or stress disorders from baseline to four weeks later for "sleeps restlessly" (-59%), "suffers from insomnia" (-64%), "feels under pressure" (-37%), "easily emotionally upset" (-52%), and "feels fearful or depressed" (-61%). Experiencing a selected sleep or stress disorder after four weeks among those who had the disorder at baseline was significantly more likely in those not physically active and/or not having lowered their BMI after four weeks. Changes in alcohol consumption and smoking did not significantly contribute to changes in the disorders. Those who failed to lower their coffee/tea use after four weeks were significantly more likely to have a sleep disorder and be easily emotionally upset.

CONCLUSIONS

Changes in lifestyle behaviors after attending an educational program significantly reduced sleep and stress disorders in as little as four weeks, primarily explained by decreasing BMI and/or increasing exercise.

Sit to stand transfer: performance in rising power, transfer time and sway by age and sex in senior athletes

OBJECTIVE

To observe the differences in performance variables of the sit to stand transfer (as measured on the NeuroCom Balance Master) in a population of senior athletes.

METHOD

A convenience sample of 173 subjects aged 50 years and older. Data were obtained from voluntary participation in a health fair offered at the annual Huntsman World Senior Games in St George, Utah, USA. All sit to stand tests were performed on the NeuroCom Balance Master. The measured parameters were weight transfer time (WTT), rising power (force exerted to rise), and centre of gravity sway (COG sway) during the rising phase.

RESULTS

A significant difference was found between stratified age groups (50-64 and 65+ years) on rising power. There was also a sex difference in rising power. No significant differences were found in weight transfer time or COG sway.

CONCLUSION

While rising power decreases with increasing age in senior athletes, WTT and COG sway remain similar regardless of age or sex. The maintenance of these other two variables (WTT and COG sway) may be attributable to physical activity and/or participation in sport.

Trends in tobacco smoking among adolescents in Lyon, France

To provide information that may promote more effective cancer prevention, we identified factors associated with regular smoking among adolescents in Lyon, France. School grades where these factors began to influence regular smoking were also identified. Seven consecutive cross-sectional anonymous surveys were conducted in three public schools, beginning in grade 6ème (average age 11.5 years) in 1993 and ending in grade Terminale (average age 17.4 years) in 1999. All classes in each respective grade were surveyed, with 3650 completed questionnaires for all years combined. Prevalence of current regular smoking is presented according to school grade for 17 variables identified as significantly related to regular smoking in a multivariate logistic regression analysis. Important factors associated with regular smoking were identified as early as grade 6ème and included not viewing the taking care of one's health as important, not eating breakfast regularly, associating with groups where smoking occurs, having a best friend who smokes, and having a brother and/or sister who smokes. Not regularly reading was first associated with an increased risk of regular smoking in grade 5ème. Not living with both parents, alcohol drinking, episodes of drunkenness, illicit drug use, and sexual relationships were positively associated with regular smoking in the middle and later grades, when these questions were first asked. Not playing sports and not playing with computers were initially associated with an increased risk of regular smoking in grade 3ème.

Demographics and health-related factors of men receiving prostate-specific antigen screening in Utah

BACKGROUND

Identifying who is pursuing prostate-specific antigen (PSA) screening for prostate cancer is prerequisite to effectively influencing participation in PSA screening and educating people about potential screening implications and personal risk. This paper describes the relationship between select demographic and health-related factors with PSA screening.

METHODS

Analysis was based on 1,293 men age 40 years or older who responded to a cross-sectional random telephone survey involving 12 health districts in the state of Utah from June 1 to August 31, 1996. Independent variables were current age, race, marital status, education, household income, medical insurance, level of physical activity, intake of fruits and vegetables, receipt of psychiatric help, religious preference, church attendance, general health status, and employment.

RESULTS

Forty-eight percent of respondents reported having had a PSA in the past year. PSA screening in the previous year significantly increased and leveled off with age: 23.9% for ages 40-49, 51.4% for ages 50-59, 67.4% for ages 60-69, and 67.0% for ages 70+. After adjusting for age, only marital status and medical insurance were significantly related to PSA screening, with medical insurance having the largest effect. Approximately 50.6% married men and 33.5% unmarried men had a PSA in the past year. Percentages for insured and uninsured men were 49.4 and 16.6%, respectively.

CONCLUSION

A substantial portion of elderly men, particularly those who are married and medically insured, have had a PSA test in the past year. This information makes it possible to more effectively influence participation in PSA screening and educate people about potential screening implications and personal risk.

Measuring the public health burden of cancer in the United States through lifetime and age-conditional risk estimates

PURPOSE

Effects of an aging population in the United States on lifetime and age-conditional risk estimates of developing site-specific cancers are identified and the potential role these statistics play in monitoring disease burden discussed.

METHODS

Risk estimates were derived by applying cross-sectional population-based incidence rates of cancer and mortality rates from other causes to a hypothetical cohort. The cohort was aged through a double decrement life table to determine the expected proportion of the population that would develop the disease.

RESULTS

Despite black men having higher invasive cancer incidence rates than white men, and black and white women having similar rates, because of the better life expectancy among whites lifetime risk estimates of developing cancer are higher for whites than blacks: 45.5% in white men, 40.4% in black men, 39.2% in white women, and 32.4% in black women based on 1995-97 data. White men experience higher 10-year cancer risk than black men in only bladder cancer, non-Hodgkin's lymphomas (NHL), and leukemia. White women tended to show a greater risk than black women for cancers of the breast, corpus uteri, ovary, NHL, and leukemia. For both whites and blacks, the 10-year risk of lung cancer ranks first among men aged 40, ranks second to prostate cancer for men aged 50, 60, and 70, and ranks second to breast cancer for women aged 40, 50, 60, and 70.

CONCLUSIONS

Lifetime and age-conditional risk measures reflect both changes in the disease incidence rates and age distribution over calendar time such that they are useful for monitoring the disease burden in the population. Even if cancer rates remain stable or fall, it is possible for the cancer burden, as reflected by lifetime and age-conditional risk estimates, to increase due to the aging population.

Religious preference, church activity, and physical exercise

BACKGROUND

Utah has the highest percentage of physically active adults in the United States. It also has a high percentage of religiously active people. About 90% of the adult population has a religious preference and 62% of those individuals attend church weekly. This study evaluates the relationship between religious preference, church attendance, and physical activity.

METHODS

Analysis is based on 6,188 adult respondents ages 18 years and older to a cross-sectional random telephone survey involving 12 health districts in the state of Utah from June 1 to August 31, 1996.

RESULTS

Within religious groups, those attending church weekly were more likely to exercise than individuals attending church less than weekly. About 70% of Utah consists of members of the Church of Jesus Christ of Latter-day Saints (LDS). LDS attending church less than weekly were least physically active in Utah. The percentages of those exercising vigorously at least 20 min three times per week were 52.3% (LDS who attend church weekly), 44.5% (LDS who attend church less than weekly), 57.6% (non-LDS who attend church weekly), 54.3% (non-LDS who attend church less than weekly), and 53.1% (no religious preference) (P = 0.0070). When adjustment was made for age, smoking status, education, marital status, and general health, differences in exercise between church activity levels within religious groups became insignificant. Smoking and general health have the greatest influences on the relationship between religious preference, church attendance, and exercise. LDS were significantly less physically active than non-LDS in the adjusted model.

CONCLUSIONS

Although differential smoking levels and general health status explained differences between church activity levels within religious groups, lower levels of exercise among LDS versus non-LDS could not be explained and require further study.

Partitioned prostate cancer prevalence estimates: an informative measure of the disease burden

STUDY OBJECTIVES

Public health burden of disease is often measured using prevalence statistics. Prevalence of invasive prostate cancer in the United States is presented according to age at diagnosis, time from diagnosis, geographical area, and two races (white and black).

DESIGN

Invasive prostate cancer data from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute is used for obtaining prevalence estimates.

MAIN RESULTS

Despite falling prostate cancer incidence rates, the prevalence of this disease continues to rise for both white and black men. Black men diagnosed at ages 60 years and older experience lower levels of prevalence of prostate cancer than white men because of poorer survival and a smaller proportion of black men living to older ages where the disease becomes common. Black men require fewer years of follow up than white men to capture over 99% of prevalent cases (that is, 14 years versus 16 years, respectively). Prevalence estimates in the United States are traditionally based on Connecticut data. On 1 January 1997, United States prostate cancer prevalence estimates based on Connecticut are overestimated for white men and underestimated for black men.

CONCLUSIONS

Partitioned prevalence estimates may provide a more meaningful and informative measure of the disease burden than conventional prevalence estimates. Prostate cancer prevalence estimates based on SEER rather than Connecticut data are better representative of the United States.

Factors associated with no surgery or radiation therapy for invasive cervical cancer in Black and White women

This paper identifies the proportion of invasive cervical cancer cases that do not receive cancer-directed surgery or radiation; assesses the influence of race, stage, age, grade, nodal status, histology, and co-morbid cancer primaries on receipt of treatment; and considers reasons why cancer-directed therapy is not received. We analyzed data for 8,119 patients with invasive cervical cancer from eleven population-based tumor registries in the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute, 1992-96. Approximately 8.03% of Whites and 11.64% of Blacks did not receive surgery or radiation therapy (no therapy). The percentage of cases receiving no therapy were greatest for unstaged cases, and for cases with unknown grade or unknown lymph node status. Adjusted odds of no therapy significantly increased with distant and unstaged disease (vs local stage) and older age (vs 0-39) at diagnosis; unknown grade (vs well differentiated); or unknown lymph node (vs no lymph node) status. Black cases were more likely to be unstaged and unstaged cases are more likely to not receive therapy. Blacks were more likely than Whites not to receive surgery because it was not recommended, contraindicated due to other conditions, or refused. Of cases refusing radiation, 53.85% of Whites and 83.33% of Blacks refused surgery, and of women refusing surgery, 22.58% of Whites and 50% of Blacks refused radiation. Stage, age, grade, and lymph node status directly influence receipt of treatment. Race influences receipt of treatment indirectly through stage. Reasons why therapy was not received (eg, not recommended, refused) differ according to race and stage at diagnosis.

Prevalence corrected hysterectomy rates and probabilities in Utah

PURPOSE

A life table method is used for correcting hysterectomy rates and probabilities for prevalent cases of hysterectomies in the population. Both corrected and conventional hysterectomy rates and probabilities are reported.

METHODS

Hysterectomy prevalence estimates are derived from cross-sectional hysterectomy and mortality using a life table method. Analysis is based on the Utah Hospital Discharge Data Base and State death certificates.

RESULTS

Hysterectomy rates are strongly influenced by age, reaching 150 per 10,000 for ages 45-49 years. The corresponding corrected hysterectomy rate is 196. Differences between the corrected and uncorrected cause-specific hysterectomy rates tend to be most pronounced at their peaks, particularly later in life where the prevalence of hysterectomy is greatest. Probability of hysterectomy approaches slightly above 35% over the life span, whereas the corrected hysterectomy probability approaches 43%. Probability of hysterectomy in the next 10 years is 12.9% for women aged 35 years and 11.7% for women aged 45 years. Corresponding corrected hysterectomy probabilities are 14.3 and 15.1. Higher prevalence of hysterectomy in later ages explains the reverse in magnitude of the rates when the correction is applied to the hysterectomy rates.

CONCLUSIONS

Conventional hysterectomy rates are underestimated, particularly in older age groups. A prevalence correction of the rates and probabilities is necessary to fully understand the potential health related consequences and impact of this medical procedure in the population.

The relationship of perceived age and sales of tobacco and alcohol to underage customers

The ability of store clerks to estimate the age of their customers is critical in preventing illegal sales of tobacco and alcohol to underage individuals. To avoid illegal sales of tobacco products to minors, the Food and Drug Administration created a policy in 1997 requiring store clerks to request identification of anyone perceived to be underage 27. A similar age standard has not been implemented for alcohol. The purpose of this article is to assess whether age 27 is adequate for minimizing tobacco sales to those under age 18 and whether this age is also a useful standard for minimizing illegal alcohol sales to those under age 21. The analysis is based on age estimates from 49 gas station and convenience store clerks. Each clerk estimated ages of 45 people filmed on video whose actual ages ranged from 15 to 29. T-tests, analysis of variance, contingency tables and logistic regression were used to analyze the data. Store clerks found it more difficult to estimate ages of female customers than male customers. In addition, the store clerks significantly underestimated age of male customers under 18 and of female customers under 21. In contrast, the clerks significantly overestimated age of customers 21 years and older. Among underage customers, the store clerks' age, gender, work experience, education, and training in requesting identification had no influence on ability to judge age, nor did it have a strong influence on whether an underage customer was considered 18 or older or 21 or older. The results suggest that age 27 is adequate for minimizing illegal tobacco sales. Adoption of a similar or slightly older age may be appropriate for minimizing illegal alcohol sales.

Nonaggressive management of White and Black prostate cancer patients in the United States

Appropriate treatment for prostate cancer is controversial because of the lack of information from randomized clinical trials indicating the benefits of one treatment over another. Watchful waiting or conservative management remains an alternative for this disease. This paper assesses the extent to which White and Black prostate cancer patients in the USA choose nonaggressive therapy. Nonaggressive therapy is defined as patients not receiving cancer-directed surgery or radiation, or that undergo a transurethral resection of the prostate (TURP)/simple prostatectomy but no radiation. Of 112,445 prostate cancer patients diagnosed in 1992-1996, 40% Whites and 46% Blacks were not aggressively treated. Approximately 28% Whites and 33% Blacks did not receive cancer-directed surgery or radiation, and 12% Whites and 13% Blacks underwent a TURP/simple prostatectomy but no radiation. Stage, histologic grade and age at diagnosis, race (White and Black), and number of cancer primaries each significantly influence how patients are managed. Black patients are more likely than White patients to forego aggressive therapy, even after adjusting for less preferential stage and histologic grade at diagnosis, as well as differences in age and number of cancer primaries. Explanations for this result deserve further consideration. Prostate Cancer and Prostatic Diseases (2000) 3, 94-99