Coevolution between slave-making ants and their hosts: host specificity and geographical variation.

We explored the impact of a slave-making ant, Protomognathus americanus, on two of its hosts, Leptothorax longispinosus and L. ambiguus. We showed that, on average, slave-maker colonies conduct raids on 2.7 L. longispinosus and 1.4 L. ambiguus nests in a single year. The more common host, L. longispinosus, survives raiding and colony-founding events in a third of the cases, but the less common host rarely survives attacks from the slave-makers. We compare our results, collected in Vermont, to a study conducted in New York where the slave-maker pressure is much stronger. Our results suggest that in Vermont the slave-maker has a sparing strategy when raiding L. longispinosus, but not when raiding L. ambiguus. Thus coevolution between slave-making ants and their hosts shows host specificity and geographical variation.

Proximate and ultimate control of sex ratios in Myrmica brevispinosa colonies.

The literature on sex ratio evolution in ant colonies is dominated by inclusive fitness arguments. In general, genetic theory makes good predictions about sexual investment in ant populations, but understanding colony-level variance in sex investment ratios has proven more difficult. Recently, however, more studies have addressed ecological factors that influence colony-level sex investment ratios. Food availability, in particular, has been manipulated because larval nutrition influences female caste determination, thus implying that resource availability should be of critical importance for colony sex investment ratios. However, results from food supplementation experiments are equivocal, and it is clear that ant colony response to food supplementation is dependent on the ecological background of the population. We presented field colonies of the ant Myrmica brevispinosa with two food types (proteins and carbohydrates), and assessed their relative impact on colony-level sex investment ratios. We show that colonies receiving carbohydrate enhancement invested in more female sexuals and produced more female-biased sex allocation ratios than protein-fed or control colonies. Thus, our study is the first, to our knowledge, to demonstrate that sex ratios in social insect colonies might be sensitive to resource quality. Male investment was not influenced by food treatment, but was positively correlated with colony size. Therefore, the shift in sex ratios in our study must have been mediated through nutritional influences on female caste determination rather than male brood elimination. We also used our data to evaluate evidence for sex ratio compensation by queenright colonies in response to male production by workers from orphaned colonies.

Coevolution in host-parasite systems: behavioural strategies of slave-making ants and their hosts.

Recently, avian brood parasites and their hosts have emerged as model systems for the study of host-parasite coevolution. However, empirical studies of the highly analogous social parasites, which use the workers of another eusocial species to raise their own young, have never explicitly examined the dynamics of these systems from a coevolutionary perspective. Here, we demonstrate interpopulational variation in behavioural interactions between a socially parasitic slave-maker ant and its host that is consistent with the expectations of host-parasite coevolution. Parasite pressure, as inferred by the size, abundance and raiding frequency of Protomognathus americanus colonies, was highest in a New York population of the host Leptothorax longispinosus and lowest in a West Virginia population. As host-parasite coevolutionary theory would predict, we found that the slave-makers and the hosts from New York were more effective at raiding and defending against raiders, respectively, than were conspecifics from the West Virginia population. Some of these variations in efficacy were brought about by apparently simple shifts in behaviour. These results demonstrate that defence mechanisms against social parasites can evolve, and they give the first indications of the existence of a coevolutionary arms race between a social parasite and its host.

Colony structure of a slavemaking ant. I. Intracolony relatedness, worker reproduction, and polydomy.

Colony and population structure of the obligate slavemaker ant Protomognathus americanus was analyzed via four nuclear microsatellite loci and mitochondrial DNA (mtDNA) markers. Colonies of P. americanus usually contain a single queen, and here we show that she is singly inseminated. Nestmate workers are generally full sisters and their relatedness does not deviate from the expected value of 0.75. Even though colonies were strictly monogynous, we were able to infer that colony takeover by related queens was common and queen replacement by unrelated queens was rare. Polydomy is widespread, with neighboring nests having the same genetic composition. Although we found no evidence of population viscosity or inbreeding from nuclear markers, mtDNA markers provided evidence for small-scale genetic structuring. Haplotype structuring and takeover by related queens suggest philopatry of newly mated queens. In this species, workers reproduce in queenright and queenless nests and worker reproduction accounts for more than 70% of all males. Although sex-ratio theory points to slavemaking ants as important systems for studying queen-worker conflict, our results indicate no basis for such conflict in P. americanus, because extensive worker reproduction generates shifts in relatedness values. Rather, the dual effects of independent polydomous nest units and local resource competition among queens produce male-biased allocation ratios in this species.

Colony structure of a slavemaking ant. II. Frequency of slave raids and impact on the host population.

The parasite pressure exerted by the slavemaker ant Protomognathus americanus on its host species Leptothorax longispinosus was analyzed demographically and genetically. The origin of slaves found in colonies of the obligate slavemaker was examined with nuclear and mitochondrial DNA markers to make inferences about the frequency and severity of slave raids. Relatedness of enslaved L. longispinosus workers in the same nest was very low, and our data suggest that, on average, each slavemaker nest raids six host colonies per season. Therefore, the influence of slavemaker species on their hosts is much stronger than simple numerical ratios suggest. We also found that slave relatedness was higher in small than in large slavemaker nests; thus, larger nests wield a much stronger influence on the host. We estimated that in the study population, on average, a host nest has a 50% chance of being attacked by a slavemaker colony per year. Free-living Leptothorax colonies in the vicinity of slavemaker nests did not represent the source of slaves working in P. americanus colonies, which suggests that raided nests either do not survive or migrate after being raided. Colony composition and intranest relatedness of free-living L. longispinosus colonies differed markedly between areas with slavemakers and those that are parasite-free. In the presence of slavemakers, host colonies were less likely to be polygynous and had fewer workers and a higher relatedness among worker brood. Host nests with slavemaker neighbors allocated more resources into sexuals, possibly caused by these shifts in nest demography. Finally, enslaved Leptothorax workers in P. americanus nests appeared to be less efficient than their counterparts in free-living colonies. Thus, slavemakers exert a much stronger impact on their hosts than had previously been suspected and represent an unique system to study parasite-host coevolution.

Conflict over sex allocation drives conflict over reproductive allocation in perennial social insect colonies.

Queen-worker conflict in the social Hymenoptera has become a cornerstone of sex-ratio theory. Extending that theory to conflict over life-history decisions, however, has proven controversial. Pamilo first proposed that queen-worker conflict over reproductive allocation should be important in perennial, social insect colonies, but Bourke and Chan have questioned the generality of that claim. Here, we reexamine this problem for the simplest case of a monogynous and monandrous hymenopteran society by relaxing assumptions of Pamilo's model. In populations with monomorphic sex ratios, queens and workers agree on allocation to growth versus reproduction. However, variation in sex allocation across colonies can induce queen-worker conflict over reproductive allocation; the former is a necessary condition for the latter. We explore how conflict over reproductive allocation depends on the population-wide sex ratio, the survivorship probabilities for existing colonies, and the likelihood of establishing new colonies. We then test our theory for two ant species, each with two years of data. We find considerable support for our contention of queen-worker conflict over reproductive allocation and suggest how future studies should be structured to explore this conflict further.

Perspective: evolution's struggle for existence in America's public schools.

The ongoing creation-evolution controversy in North America thrives on the widespread special creationist beliefs of a significant portion of the public. Creation science supports a literal interpretation of the Judeo-Christian Bible, an earth that is no more than 10.000 years old and created ex nihilo in six days by a monotheistic God, with no new kinds arising since the period of creation, and with a single flood of staggering force shaping layers of rocks and trapping the organisms fossilized within them. Despite decisions in numerous court cases that specifically exclude creationism and creation science from primary and secondary biology classes in America's public schools, creationists now work locally to minimize or remove evolution from science teaching standards. The nationally organized movement to resist the teaching of evolution has proven highly effective, influencing state and district school boards in addition to individual teachers and schools. Thus, if teaching about evolution and the nature of science is to survive in America's primary and secondary schools, scientists must likewise work with teachers and reach out to state and local school boards. In this perspective we outline the typical creationist arguments we encounter from students, teachers, school board members, and neighbors. We explain briefly how knowledge of both microevolution and macroevolution is important in medicine, agriculture, and biotechnology. We describe a science education controversy that arose within our own school district, how we responded, and what we learned from it. Finally, we argue that even modest outreach efforts to science teachers will be richly repaid.

Microsatellite analysis reveals deletion of a large region at chromosome 8p in conventional renal cell carcinoma.

Loss of heterozygosity (LOH) at chromosome 8p is associated with the progression of conventional (non-papillary) renal cell carcinomas (RCC). To determine the tumor suppressor gene locus, we carried out a deletion mapping of chromosome 8p at 10 microsatellite loci in 96 RCCs. LOH occurred in 32% of the tumors. The smallest overlapping region of deletion at chromosome 8p11.2-p23.1 corresponds to approximately 34-cM genetic distance. No small interstitial deletion was seen.

The genetics of renal tumors in end-stage renal failure differs from those occurring in the general population.

The genetics of renal cell tumors (RCT), which occur at a high frequency in patients with end-stage renal failure (ESRF), is not yet known. Using a fluorescence microsatellite assay and comparative genomic hybridization, 18 renal tumors obtained from nine patients with ESRF were analyzed for genetic alterations, which are known to be characteristic of common nonpapillary and papillary RCT in the general population. Deletion of chromosome 3p was detected in six nonpapillary tumors, whereas trisomies of 7 and 17 or 3, 8, and 16 were seen in four of 18 tumors. No alterations were found in four tumors, and another four tumors had unspecific changes. The fragile histidine triad (FHIT) gene is localized at the most common fragile site at chromosome 3p14.2. The FHIT and the p53 tumor suppressor gene are targets of different environmental agents. Because both toxic effect and genomic instability are implicated in the development of renal cysts in ESRF, the alteration of both genes in tumor cells was analyzed. No abnormal expression of the FHIT gene or mutation of the p53 gene were found. This study suggests that the genetics and also the morphology of some of the ESRF RCT differ from those known for RCT in the general population.

Lack of genetic changes at specific genomic sites separates renal oncocytomas from renal cell carcinomas.

Morphological similarities between renal oncocytomas and 'oncocytic' renal cell carcinomas (RCCs) make a differential diagnosis in many cases difficult. A series of 41 renal oncocytomas has been analysed by microsatellite markers from chromosomes 1, 2, 3p, 6q, 8p, 9, 10, 13q, 14q, 17, and 21, alterations of which are known to be involved specifically in non-papillary and chromophobe RCCs. Only eight of the 41 renal oncocytomas showed loss of heterozygosity (LOH). LOH at chromosomes 1 and 14 occurred in four tumours each and at chromosomes 2, 8, and 9 in one tumour each. Combined LOH at chromosomes 1, 9, and 14 and also at chromosomes 1 and 14 occurred in one case each. No LOH was seen at any other genomic sites. The lack of combination of LOH at specific chromosomal sites differentiates renal oncocytomas from other renal cell tumours with overlapping phenotypes. Applying the microsatellite assay described here, the diagnosis can be established within 2 days, from fresh as well as from paraffin-embedded material.

Loss of heterozygosity at chromosomes 8p, 9p, and 14q is associated with stage and grade of non-papillary renal cell carcinomas.

In this study, 105 non-papillary renal cell carcinomas (RCCs) have been examined for allelic loss at the chromosome 8p12-21.1, 9p21, and 14q24.2-qter regions, each by two highly polymorphic microsatellites. Loss of heterozygosity (LOH) was detected at both chromosome 8p and 9p in 33 per cent of the cases and at chromosome 14q in 45 per cent of the tumours. A correlation of variables such as size, grade, and stage of tumours with these specific genetic alterations showed that loss of chromosomes 8p and 9p, and especially loss of chromosome 14q regions, is significantly associated with a higher grade of tumour and the combined LOH at these chromosomal sites with advanced tumour stage. These genetic alterations did not show any correlation with the size of non-papillary RCCs. This study suggests that genetic markers at the above-mentioned chromosomal sites can predict the clinical outcome of non-papillary RCCs.

Detailed microsatellite analysis of chromosome 3p region in non-papillary renal cell carcinomas.

Multiple hemi- and homozygous interstitial deletions at chromosome 3p have been found in different types of cancer, including non-papillary renal cell carcinoma (RCC). To determine the frequency and size of deletions, we have analyzed paired normal and tumor DNA obtained from short-term cultures of 104 non-papillary RCCs with 29 microsatellite markers covering the entire chromosome 3p region. Deletion mapping provided evidence for terminal deletion, with the most distal breakpoint between loci D3S1606 and D3S3666 in 94 cases, whereas constitutional heterozygosity was retained at all loci in 4 RCCs. In 6 cases, interstitial deletions were detected. Deletion mapping detected the smallest overlapping region between loci D3S3666 and D3S1560, which corresponds to an approx. 55 cM genetic distance.

Significance of chromosome arm 14q loss in nonpapillary renal cell carcinomas.

We examined 88 nonpapillary renal cell carcinomas for allelic loss at chromosome arm 14q and correlated the results to size, grade, and stage of these tumors. Fourteen highly polymorphic microsatellite markers on the long arm of chromosome 14 were used for deletion mapping. Loss of heterozygosity (LOH) at the smallest overlapping segment of 14q24.2-qter was seen in 42 of 88 tumors. There was no significant correlation between frequency of 14q LOH and size of tumors (P = 0.11). LOH was frequently seen in grade 2 and 3 tumors (55% and 73%, respectively) and in stage III and IV tumors (53% and 80%, respectively). We found a significant correlation between chromosome arm 14q LOH and nuclear grade (P < 0.001) and stage (P < 0.001) of tumors. These observations indicate the presence of a tumor-suppressor gene at chromosome segment 14q24.2-qter and demonstrate the usefulness of microsatellite analysis for assessing the possible clinical outcome of nonpapillary renal cell carcinomas.

Specific genetic changes of diagnostic importance in chromophobe renal cell carcinomas.

The histologic diagnosis of chromophobe renal cell carcinomas is often uncertain because of phenotype overlap among different types of kidney cancers. Recently, in a novel genetic classification of renal cell tumors, a combination of monosomies of chromosomes 1, 2, 3, 6, 10, 13, 17, and 21 have been suggested to have a diagnostic value for this unique type of tumor. Therefore, we have analyzed fresh and paraffin-embedded tissues obtained from 42 chromophobe renal cell carcinomas for allelic losses at the above-mentioned chromosomal regions by employing microsatellite markers. Loss of chromosomes 1, 2, 6, 10, 13, and 17 was detected in between 75% and 95% of tumors, and loss of chromosome 21 was observed in 54% of cases. All but one tumor showed a combination of monosomies at the specific chromosomes. Thus, applying the set of microsatellite markers used in this study, a PCR-based diagnosis of chromophobe renal cell carcinomas could be established within 1 to 2 days. The general applicability of this approach to fresh and paraffin-embedded tissues allows a correct genetic characterization in all cases where a diagnosis based on histopathology remains uncertain.

Ankyrin-1 mutations are a major cause of dominant and recessive hereditary spherocytosis.

Hereditary spherocytosis (HS) is the most common inherited haemolytic anaemia in Northern Europeans. The primary molecular defects reside in the red blood cell (RBC) membrane, particularly in proteins that link the membrane skeleton to the overlying lipid bilayer and its integral membrane constituents. Ankyrin-1 is the predominant linker molecule. It attaches spectrin, the major skeletal protein, to the cytoplasmic domain of band 3, the RBC anion exchanger. Two-thirds of patients with HS have combined spectrin and ankyrin-1 deficiency; deficiency of band 3 occurs in about 15 to 20% (ref.1). These data suggest that ankyrin-1 or band 3 defects may be common in HS. To test this we screened all 42 coding exons plus the 5' untranslated/promoter region of ankyrin-1 and the 19 coding exons of band 3 in 46 HS families. Twelve ankyrin-1 mutations and five band 3 mutations were identified. Missense mutations and a mutation in the putative ankyrin-1 promoter were common in recessive HS. In contrast, ankyrin-1 and band 3 frameshift and nonsense null mutations prevailed in dominant HS. Increased accumulation of the normal protein product partially compensated for the ankyrin-1 or band 3 defects in some of these null mutations. Our findings indicate that ankyrin-1 mutations are a major cause of dominant and recessive HS (approximately 35 to 65%), that band 3 mutations are less common (approximately 15 to 25%), and that the severity of HS is modified by factors other than the primary gene defect.

Promoter analysis of the bovine gene for seminalplasmin.

In this study we mapped the transcriptional initiation site of the gene for seminalplasmin (SAP) by primer extension analysis, situated 125 nucleotides upstream of the translational initiation site of the SAP-specific mRNA. We showed that the TATA-box in position -30 of the SAP gene is part of a functional promoter. A 280 bp region of the 5'-flanking region exerted a strong positive effect on promoter activity. In this region we identified consensus sequences for the transcriptional control elements AP1, AP2, PEA3 and GATA.

When the physician leaves the patient: predictors of satisfaction with the transfer of care in a primary care clinic.

OBJECTIVE: To identify independent predictors of patients' satisfaction with transfer of their care from a departing to a new resident physician. DESIGN: A self-administered questionnaire completed by consecutive patients following up after transfer of their care, and by a randomly selected 50% of patients not returning within three months after transfer. SETTING: An internal medicine clinic in a teaching hospital. PATIENTS: Questionnaires were completed by 376 patients: 237 returning to clinic and 139 (91%) of 152 randomly selected patients who had not returned. Mean age of the patients was 65 years, 52% were men, and they had come to the clinic for a median of four years. RESULTS: 57% of the patients were satisfied with the transfer process, 25% were neutral, and 18% expressed frank dissatisfaction. Of nine variables significantly associated with satisfaction by univariate analysis, stepwise multiple regression identified five independent predictors. Personal notification of the patient by the departing physician was the most powerful determinant, explaining 41% of the variability in satisfaction. Other predictors were whether patients believed their physicians had done everything possible to facilitate transfer, whether the departing physician had provided opportunity for discussion of the transfer, whether this discussion was considered sufficient, and patients' impressions of the institution. CONCLUSIONS: Most of the predictors identified can be influenced by physician behavior, suggesting that physicians should personally notify patients of their departure and provide an opportunity for discussion. This could significantly improve patient satisfaction with the transfer process and, as previous studies suggest, translate into greater compliance with medications and follow-up.

One-year outcome for patients with a chief complaint of dizziness.

UNLABELLED: OBJECTIVE. To determine the one-year outcome for patients with a chief complaint of dizziness that had persisted at least two weeks. DESIGN: Prospective cohort study. SETTING: Federal teaching hospital. PATIENTS: 100 dizzy patients and 25 control subjects. MEASUREMENTS: The primary outcome was dizziness status (improved or not improved); the secondary outcomes were morbidity and health care utilization. RESULTS: The dizziness resolved for 18 patients, whereas the status improved for 37, stayed the same for 32, and worsened for 11, with two patients lost to follow-up. Thus, 55% of patients whose dizziness had not resolved two weeks after their initial visits improved over the subsequent 12 months. Logistic regression revealed four independent predictors of persistent dizziness at one-year follow-up: dizziness due to psychiatric causes, dysequilibrium, vertigo other than benign positional vertigo, vestibular neuronitis, or migraine (odds ratio, 6.3; 95% CI, 2.1-18.6); daily dizziness (odds ratio, 6.4; 95% CI, 2.0-21.0); dizziness worse with walking (odds ratio, 3.0; 95% CI, 1.1-9.0); and patient had initially feared a serious illness (odds ratio, 0.25; 95% CI, 0.10-0.74). These four factors could be used to classify patients as having either a high (82%), medium (47%), or low (0%) likelihood of improvement at one-year follow-up. One patient died from heart failure, and none developed a serious disease for which dizziness had been a harbinger. Dizziness was not associated with an increased number of clinic visits. CONCLUSIONS: Among patients with a chief complaint of dizziness who are still symptomatic at two-week follow-up, more than half improve within a year. Clinical factors identify patients at higher risk for persistent dizziness.

A controlled trial of a seminar to improve medical student attitudes toward, knowledge about, and use of the medical literature.

OBJECTIVE: To determine whether an interactive seminar could affect medical student knowledge of research design, basic critical appraisal skills, and attitudes toward and clinical use of the medical literature. DESIGN: Controlled, nonrandomized clinical trial. PARTICIPANTS: Third-year clinical clerks (n = 146) during their core medicine clerkship. INTERVENTIONS: Two 90-minute interactive seminars. MEASUREMENTS AND MAIN RESULTS: Pre- and postquestionnaires were used to assess knowledge and attitudes regarding the use of the medical literature among 65 study and 81 control students. Blinded review of write-ups assessed actual use of the medical literature. Overall, 80% of the students subscribed to one or more journals and reported reading three or more journal articles per month. After the intervention, the study students were more likely than the control students to consider: 1) study design important in article selection and 2) use of medical literature critical to patient care decisions. Knowledge scores were significantly improved in the study group (p = 0.0001). The intervention yielded no increase in the actual use of medical literature in patient write-ups over that encouraged by usual clerkship goals. 51% of the study and 48% of the control students cited literature at baseline, and 53% of all the students did so after the intervention. Of these citations, 50% were for journal articles and the remainder were for textbooks. The students infrequently mentioned the quality of the cited literature. CONCLUSIONS: An interactive seminar designed to introduce medical students to critical appraisal improved student knowledge and attitudes but did not increase the actual use of literature in patient write-ups.

Cholesterol-lowering therapy: what patients expect in return.

OBJECTIVE: To assess variability in patients' values and preferences regarding cholesterol-lowering therapy. DESIGN: A descriptive study. Patients currently receiving cholesterol-lowering therapy were interviewed using the time tradeoff and standard reference gamble techniques of utility assessment. SETTING: Internal medicine clinics of a military medical center. PARTICIPANTS: Thirty-five patients, clinically free of coronary disease, receiving cholesterol-lowering therapy for at least three months. RESULTS: When the time tradeoff method was applied, 12 (34%) of the patients indicated that less than one month of additional life would be a fair return for adhering to their current therapy for the rest of their lives, while 13 (37%) patients required more than one additional year of life, and four (11%) required at least five years. By the standard reference gamble method, 18 (51%) patients would not have accepted a risk of one in a thousand of imminent death (in 30 days) in hopes of obtaining a normal life expectancy off therapy, while 14 (40%) would have agreed to a 1% or greater risk in order to avoid therapy. CONCLUSIONS: While many patients apparently expected very little in return for adhering to therapy, many others may not be getting "what they bargained for."