Two's Company, Three's a Crowd: Experimental Evaluation of the Evolutionary Maintenance of Trioecy in Mercurialis annua (Euphorbiaceae)

Trioecy is an uncommon sexual system in which males, females, and hermaphrodites co-occur as three clearly different gender classes. The evolutionary stability of trioecy is unclear, but would depend on factors such as hermaphroditic sex allocation and rates of outcrossing vs. selfing. Here, trioecious populations of Mercurialis annua are described for the first time. We examined the frequencies of females, males and hermaphrodites across ten natural populations and evaluated the association between the frequency of females and plant densities. Previous studies have shown that selfing rates in this species are density-dependent and are reduced in the presence of males, which produce substantially more pollen than hermaphrodites. Accordingly, we examined the evolutionary stability of trioecy using an experiment in which we (a) indirectly manipulated selfing rates by altering plant densities and the frequency of males in a fully factorial manner across 20 experimental plots and (b) examined the effect of these manipulations on the frequency of the three sex phenotypes in the next generation of plants. In the parental generation, we measured the seed and pollen allocations of hermaphrodites and compared them with allocations by unisexual plants. In natural populations, females occurred at higher frequencies in denser patches, a finding consistent with our expectations. Under our experimental conditions, however, no combination of plant densities and male frequencies was associated with increased frequencies of females. Our results suggest that the factors that regulate female frequencies in trioecious populations of M. annua are independent of those regulating male frequencies (density), and that the stable co-existence of all three sex phenotypes within populations is unlikely

Creating a Culture for Leading and Performing in the Extreme

By early 2008 in the Iraq War, the positive effects of the U.S. surge had started to become visible in the streets of Baghdad, as shops began to reopen and people again filled the streets.1 Despite these outwardly positive appearances, a sinister undercurrent flowed through the population. Rumors ran rampant in Iraqi military and government circles that the radical cleric Muqtada al-Sadr\u27s Mahdi Army was about to launch an offensive against the government of Prime Minister Nuri al-Maliki, a fellow Shiite, because of Sadr\u27s unhappiness with his waning political influence. In the neighborhood of Zafaraniyah, in Baghdad\u27s southeastern quadrant, Sadrist fighters started to make trouble. The unit responsible for Zafaraniyah had been trained by its commander to act with a great deal of restraint in order to avoid unnecessary civilian deaths. This was in keeping with guidance issued by General David Petraeus, commanding general of the Multi-National Forces-Iraq. The success or failure of Petraeus\u27 strategy of limiting civilian deaths depended solely on the support of the Iraqi people and their perceptions of American and Iraqi forces. What Petraeus was attempting to do on a large scale was to change the organizational culture of both forces. The events of February and March 2008 would put Petraeus\u27 vision and strategy to the test and offer evidence of what happens when old ways of doing business compete with the new. On the second night of what would come to be called the uprising, a fight erupted between a dozen young Sadrist fighters and a platoon of American and Iraqi soldiers in the most troubled neighborhood in Zafaraniyah. The engaged platoon was well trained, had the situation well in hand, and acted with restraint. What unfolded was a textbook example of the tendency of higher headquarters to use available technological innovations regardless of the logic (or illogic) of doing so and in contravention of a subordinate commander\u27s wishes. The battalion watch officer, or battle captain, ran from the tactical operations center (TOC) to the battalion commander\u27s office to notify him of the firefight. The battle captain explained that the brigade headquarters wanted to drop a SOD-pound bomb from an F/A-18 Super Hornet onto the house where it was believed that twelve or so fighters had gone to make a last stand. The brigade TOC was watching the house from several miles away via a live camera feed from an aerial drone. Rushing to the TOC the battalion commander attempted to call off the strike. For God\u27s sake-our job here is to protect the Iraqi people! It\u27s the first sentence in our f--g mission statement! And you want to drop a damned bomb on someone\u27s house?! Every soldier in the TOC broke eye contact. They knew they were wrong. Their error: they got caught up in viewing the action as nothing more than a video game. They failed to assess whether dropping a bomb on an Iraqi house was consistent with the commander\u27s intent to exercise restraint and minimize civilian casualties. Within minutes, the battalion commander was on his way to the scene of the fighting to assess the situation. Almost immediately, he heard the boom of a Hellfire missile striking its target to the east of the commander\u27s location, followed by the staccato report of a string of 30mm shells from the helicopter\u27s main gun. Several minutes later, the commander found the platoon. The two small units and the Iraqi soldiers began fighting their way deep into the neighborhood to find the target house. It appeared that the missile strike had taken the spirit out of the enemy fighters, and friendly forces surrounded the house. They found surprisingly little damage. Fortunately, the Apache helicopter had fired a newly developed missile, specifically designed to limit destruction in urban terrain. Nonetheless, there was still collateral damage to other houses and pools of blood on the ground, along with bloody Iraqi National Police uniforms

Creating a Culture for Leading and Performing in the Extreme

By early 2008 in the Iraq War, the positive effects of the U.S. surge had started to become visible in the streets of Baghdad, as shops began to reopen and people again filled the streets.1 Despite these outwardly positive appearances, a sinister undercurrent flowed through the population. Rumors ran rampant in Iraqi military and government circles that the radical cleric Muqtada al-Sadr\u27s Mahdi Army was about to launch an offensive against the government of Prime Minister Nuri al-Maliki, a fellow Shiite, because of Sadr\u27s unhappiness with his waning political influence. In the neighborhood of Zafaraniyah, in Baghdad\u27s southeastern quadrant, Sadrist fighters started to make trouble. The unit responsible for Zafaraniyah had been trained by its commander to act with a great deal of restraint in order to avoid unnecessary civilian deaths. This was in keeping with guidance issued by General David Petraeus, commanding general of the Multi-National Forces-Iraq. The success or failure of Petraeus\u27 strategy of limiting civilian deaths depended solely on the support of the Iraqi people and their perceptions of American and Iraqi forces. What Petraeus was attempting to do on a large scale was to change the organizational culture of both forces. The events of February and March 2008 would put Petraeus\u27 vision and strategy to the test and offer evidence of what happens when old ways of doing business compete with the new. On the second night of what would come to be called the uprising, a fight erupted between a dozen young Sadrist fighters and a platoon of American and Iraqi soldiers in the most troubled neighborhood in Zafaraniyah. The engaged platoon was well trained, had the situation well in hand, and acted with restraint. What unfolded was a textbook example of the tendency of higher headquarters to use available technological innovations regardless of the logic (or illogic) of doing so and in contravention of a subordinate commander\u27s wishes. The battalion watch officer, or battle captain, ran from the tactical operations center (TOC) to the battalion commander\u27s office to notify him of the firefight. The battle captain explained that the brigade headquarters wanted to drop a SOD-pound bomb from an F/A-18 Super Hornet onto the house where it was believed that twelve or so fighters had gone to make a last stand. The brigade TOC was watching the house from several miles away via a live camera feed from an aerial drone. Rushing to the TOC the battalion commander attempted to call off the strike. For God\u27s sake-our job here is to protect the Iraqi people! It\u27s the first sentence in our f--g mission statement! And you want to drop a damned bomb on someone\u27s house?! Every soldier in the TOC broke eye contact. They knew they were wrong. Their error: they got caught up in viewing the action as nothing more than a video game. They failed to assess whether dropping a bomb on an Iraqi house was consistent with the commander\u27s intent to exercise restraint and minimize civilian casualties. Within minutes, the battalion commander was on his way to the scene of the fighting to assess the situation. Almost immediately, he heard the boom of a Hellfire missile striking its target to the east of the commander\u27s location, followed by the staccato report of a string of 30mm shells from the helicopter\u27s main gun. Several minutes later, the commander found the platoon. The two small units and the Iraqi soldiers began fighting their way deep into the neighborhood to find the target house. It appeared that the missile strike had taken the spirit out of the enemy fighters, and friendly forces surrounded the house. They found surprisingly little damage. Fortunately, the Apache helicopter had fired a newly developed missile, specifically designed to limit destruction in urban terrain. Nonetheless, there was still collateral damage to other houses and pools of blood on the ground, along with bloody Iraqi National Police uniforms

Sex-Differential Herbivory in Androdioecious Mercurialis annua

Males of plants with separate sexes are often more prone to attack by herbivores than females. A common explanation for this pattern is that individuals with a greater male function suffer more from herbivory because they grow more quickly, drawing more heavily on resources for growth that might otherwise be allocated to defence. Here, we test this ‘faster-sex’ hypothesis in a species in which males in fact grow more slowly than hermaphrodites, the wind-pollinated annual herb Mercurialis annua. We expected greater herbivory in the faster-growing hermaphrodites. In contrast, we found that males, the slower sex, were significantly more heavily eaten by snails than hermaphrodites. Our results thus reject the faster-sex hypothesis and point to the importance of a trade-off between defence and reproduction rather than growth

Mating dynamics in a nematode with three sexes and its evolutionary implications

Nematodes have diverse reproductive strategies, which make them ideal subjects for comparative studies to address how mating systems evolve. Here we present the sex ratios and mating dynamics of the free-living nematode Rhabditis sp. SB347, in which males, females and hermaphrodites co-exist. The three sexes are produced by both selfing and outcrossing, and females tend to appear early in a mother’s progeny. Males prefer mating with females over hermaphrodites, which our results suggest is related to the female-specific production of the sex pheromones ascr#1 and ascr#9. We discuss the parallels between this system and that of parasitic nematodes that exhibit alternation between uniparental and biparental reproduction

Spoligotyping and Drug Resistance Analysis of Mycobacterium tuberculosis Strains from National Survey in China

BACKGROUND: Tuberculosis (TB), caused by Mycobacterium tuberculosis complex (MTBC), is one of the major causes of death in the world today. Although China has the second largest global case rate of tuberculosis, a systematic study of TB prevalence in China has not been completed. From 2006 to 2007, the base line surveillance of tuberculosis was carried out by Ministry of Health, and more than 4000 representative strains were selected from 31 provinces in China. METHODOLOGY/PRINCIPAL FINDINGS: The aim of the present research was to survey the genotypes of representative Mycobacterium tuberculosis (M. tuberculosis) strains from China using spacer oligonucleotide typing (spoligotyping), and to analyze the relationship between genotype and drug resistance for the first time. A total of 4017 clinical isolates were collected from 2007 to 2008 throughout China. Among those M. tuberculosis isolates, 2500 (62.2%) isolates were Beijing genotypes. The percentage of Beijing genotypes in northern China was higher than in southern China (76.5% vs. 53.2%). Additionally, the frequencies of rifampin-resistant, ofloxacin-resistant and multidrug-resistant isolates were significantly higher in Beijing genotype strains than non-Beijing strains. Furthermore, a novel genotype named "China Southern genotype (CS)" was only isolated from Fujian and Guangdong provinces. Hence, it is very practical to uncover the reason for prevalence of the CS type in southern China. CONCLUSIONS/SIGNIFICANCE: In conclusion, Beijing family genotypes were still the predominant genotype throughout China, which exhibited a greater correlation with rifampin-resistance, ofloxacin-resistance and MDR phenotypes than other TB spoligotypes, and some regions of China showed several unique characters in the distribution of M. tuberculosis genotypes. Our research represents an important contribution for the TB control and research community, which completes broad pictures on drug resistance levels and distribution of M. tuberculosis strain types over China

Genetic Diversity in the SIR Model of Pathogen Evolution

We introduce a model for assessing the levels and patterns of genetic diversity in pathogen populations, whose epidemiology follows a susceptible-infected-recovered model (SIR). We model the population of pathogens as a metapopulation composed of subpopulations (infected hosts), where pathogens replicate and mutate. Hosts transmit pathogens to uninfected hosts. We show that the level of pathogen variation is well predicted by analytical expressions, such that pathogen neutral molecular variation is bounded by the level of infection and increases with the duration of infection. We then introduce selection in the model and study the invasion probability of a new pathogenic strain whose fitness (R0(1+s)) is higher than the fitness of the resident strain (R0). We show that this invasion probability is given by the relative increment in R0 of the new pathogen (s). By analyzing the patterns of genetic diversity in this framework, we identify the molecular signatures during the replacement and compare these with those observed in sequences of influenza A

A first AFLP-based genetic linkage map for brine shrimp Artemia franciscana and its application in mapping the sex locus

We report on the construction of sex-specific linkage maps, the identification of sex-linked markers and the genome size estimation for the brine shrimp Artemia franciscana. Overall, from the analysis of 433 AFLP markers segregating in a 112 full-sib family we identified 21 male and 22 female linkage groups (2n = 42), covering 1,041 and 1,313 cM respectively. Fifteen putatively homologous linkage groups, including the sex linkage groups, were identified between the female and male linkage map. Eight sex-linked AFLP marker alleles were inherited from the female parent, supporting the hypothesis of a WZ-ZZ sex-determining system. The haploid Artemia genome size was estimated to 0.93 Gb by flow cytometry. The produced Artemia linkage maps provide the basis for further fine mapping and exploring of the sex-determining region and are a possible marker resource for mapping genomic loci underlying phenotypic differences among Artemia species