Ecology and evolution of soil nematode chemotaxis.

Plants influence the behavior of and modify community composition of soil-dwelling organisms through the exudation of organic molecules. Given the chemical complexity of the soil matrix, soil-dwelling organisms have evolved the ability to detect and respond to these cues for successful foraging. A key question is how specific these responses are and how they may evolve. Here, we review and discuss the ecology and evolution of chemotaxis of soil nematodes. Soil nematodes are a group of diverse functional and taxonomic types, which may reveal a variety of responses. We predicted that nematodes of different feeding guilds use host-specific cues for chemotaxis. However, the examination of a comprehensive nematode phylogeny revealed that distantly related nematodes, and nematodes from different feeding guilds, can exploit the same signals for positive orientation. Carbon dioxide (CO(2)), which is ubiquitous in soil and indicates biological activity, is widely used as such a cue. The use of the same signals by a variety of species and species groups suggests that parts of the chemo-sensory machinery have remained highly conserved during the radiation of nematodes. However, besides CO(2), many other chemical compounds, belonging to different chemical classes, have been shown to induce chemotaxis in nematodes. Plants surrounded by a complex nematode community, including beneficial entomopathogenic nematodes, plant-parasitic nematodes, as well as microbial feeders, are thus under diffuse selection for producing specific molecules in the rhizosphere that maximize their fitness. However, it is largely unknown how selection may operate and how belowground signaling may evolve. Given the paucity of data for certain groups of nematodes, future work is needed to better understand the evolutionary mechanisms of communication between plant roots and soil biota.

Hybrid speciation in birds: allopatry more important than ecology?

Hybrid speciation was once thought to be rare in animals, but over the past decade, improved molecular analysis techniques and increased research attention have allowed scientists to uncover many examples. In this issue, two papers (Elgvin et al. 2011; Hermansen et al. 2011) present compelling evidence for the hybrid origin of the Italian sparrow based on nuclear and mitochondrial DNA sequences, microsatellites, and plumage coloration. These studies point to an important role for geographic isolation in the process of hybrid speciation, and provide a starting point for closer examination of the genetic and behavioural mechanisms involved.

Dialyse et écologie: est-il possible de faire mieux à l'avenir [Dialysis and ecology: can we do better in the future?].

Development of dialysis has saved the lives of many patients. However, haemodialysis and peritoneal dialysis are very demanding in resources such as water and electricity, and generate a large amount of waste. In this article, we will review the environmental aspects of dialysis. Different solutions will be discussed, such as recycling of water discharged during reverse osmosis, the integration of solar energy, recycling of waste plastics, and the use of other techniques such as sorbent dialysis. In a world where natural resources are precious and where global warming is a major problem, it is important that not only dialysis, but all branches of medicine become more attentive to ecology.

Vascular dysfunction in children conceived by assisted reproductive technologies: underlying mechanisms and future implications.

Epidemiological studies in humans have demonstrated a relationship between pathological events during fetal development and increased cardiovascular risk later in life and have led to the so called "Fetal programming of cardiovascular disease hypothesis". The recent observation of generalised vascular dysfunction in young apparently healthy children conceived by assisted reproductive technologies (ART) provides a novel and potentially very important example of this hypothesis. This review summarises recent data in ART children demonstrating premature subclinical atherosclerosis in the systemic circulation and pulmonary vascular dysfunction predisposing to exaggerated hypoxia-induced pulmonary hypertension. These problems appear to be related to the ART procedure per se. Studies in ART mice demonstrating premature vascular aging and arterial hypertension further demonstrate the potential of ART to increase cardiovascular risk and have allowed to unravel epigenetic alterations of the eNOS gene as an underpinning mechanism. The roughly 25% shortening of the life span in ART mice challenged with a western style high-fat-diet demonstrates the potential importance of these alterations for the long-term outcome. Given the young age of the ART population, data on cardiovascular endpoints will not be available before 20 to 30 years from now. However, already now cohort studies of the ART population are needed to early detect cardiovascular alterations with the aim to prevent or at least optimally treat cardiovascular complications. Finally, a debate needs to be engaged on the future of ART and the consequences of its exponential growth for public health.

Energy requirements during reproduction and reproductive effort in shrews (Soricidae)

The energy requirements of reproducing and non-reproducing females of three species of Crocidura (C. russula, C. viaria, C. olivieri), and two species of Sorex (S. coronatus, S. minutus) were measured. Members of these two genera show different rates of metabolism and reproductive strategies (extreme altriciality and larger litter size in Sorex). During pregnancy, the daily energy intake (on either an absolute or a mass-specific basis) remained close to the non-reproductive value in all species. The absolute energy intake increased strongly after parturition and was influenced by the litter size. Peak energy intake of lactating females was extremely high, typically between 100% and 200% above the non-reproductive requirements in the Crocidura and about 300% above the non-reproductive intake in the Sorex. The mass-specific daily energy intake was reduced during lactation in the three smaller species but not in C. viaria and C. olivieri. This decrease probably involves the different thermoregulatory abilities and/or basal rate of metabolism of the pups. Average reproductive effort was about 50%, in the Crocidura species and above 150% in the Sorex species. The higher effort in the latter is partly due to a larger litter size. But in addition, extreme altriciality in the Sorex leads to an earlier increase in the energy requirements and thus is an energetically more expensive reproductive mode. The present results support the hypothesis that a higher basal rate of metabolism is associated with a higher reproductive effort in shrews.

Origin and outcome of multiple pregnancies in Bern, Switzerland, 1995-2006 and the current proposal of the Swiss parliament to revise the Swiss law of reproductive medicine: Switzerland quo vadis?

INTRODUCTION: Infertility treatments are a major source of the increase in multiple pregnancies (MPs). AIMS: The aims of the present study were (1.) to investigate the origin and maternal/neonatal outcomes of MP and (2.) to review the different measures that can be adopted to reduce these serious complications. METHODS: The study included all women with multiple births between 1 January 1995 and 31 December 2006 at the University Hospital of Bern, Switzerland. The outcomes associated with the various origins of MP (natural conception, ovarian stimulation [OS] ‒ in-vitro fertilisation [IVF-ICSI]) were analysed using a multinomial logistic regression model. An analysis of the Swiss law on reproductive medicine and its current proposed revision, as well as a literature review using Pubmed, was carried out. RESULTS: A total of 592 MP were registered, 91% (n = 537) resulted in live births. There was significantly more neonatal/maternal morbidity in MP after OS compared with natural conception and even with the IVF-ICSI group. With a policy of elective single embryo transfer (eSET), twin rates after IVF-ICSI can be reduced to <5% and triplets to <1%. CONCLUSIONS: After OS, more triplets are found and the outcome of MP is worse. MP is known to be associated with morbidity, mortality, and economic and social risks. To counteract these complications (1.) better training for physicians performing OS should be encouraged and (2.) the Swiss law on reproductive medicine needs to be changed, with the introduction of eSET policies. This would lead to a dramatic decrease in neonatal and maternal morbidity/mortality as well as significant cost reductions for the Swiss healthcare system.

Individual reproductive success and effective population size in the greater white-toothed shrew Crocidura russula.

In order to investigate the determinants of effective population size in the socially monogamous Crocidura russula, the reproductive output of 44 individuals was estimated through genetic assignment methods. The individual variance in breeding success turned out to be surprisingly high, mostly because the males were markedly less monogamous than expected from previous behavioural data. Males paired simultaneously with up to four females and polygynous males had significantly more offspring than monogamous ones. The variance in female reproductive success also exceeded that of a Poisson distribution (though to a lesser extent), partly because females paired with multiply mated males weaned significantly more offspring. Polyandry also occurred occasionally, but only sequentially (i.e. without multiple paternity of litters). Estimates of the effective to census size ratio were ca. 0.60, which excluded the mating system as a potential explanation for the high genetic variance found in this shrew's populations. Our data suggest that gene flow from the neighbourhood (up to one-third of the total recruitment) is the most likely cause of the high levels of genetic diversity observed in this shrew's subpopulations.

Linking life-history traits, ecology, and niche breadth evolution in north american eriogonoids (polygonaceae).

Abstract Macroevolutionary and microevolutionary studies provide complementary explanations of the processes shaping the evolution of niche breadth. Macroevolutionary approaches scrutinize factors such as the temporal and spatial environmental heterogeneities that drive differentiation among species. Microevolutionary studies, in contrast, focus on the processes that affect intraspecific variability. We combine these perspectives by using macroevolutionary models in a comparative study of intraspecific variability. We address potential differences in rates of evolution of niche breadth and position in annual and perennial plants of the Eriogonoideae subfamily of the Polygonaceae. We anticipated higher rates of evolution in annuals than in perennials owing to differences in generation time that are paralleled by rates of molecular evolution. Instead, we found that perennial eriogonoid species present greater environmental tolerance (wider climate niche) than annual species. Niche breadth of perennial species has evolved two to four times faster than in annuals, while niche optimum has diversified more rapidly among annual species than among perennials. Niche breadth and average elevation of species are correlated. Moreover, niche breadth increases more rapidly with mean species elevation in perennials than in annuals. Our results suggest that both environmental gradients and life-history strategy influence rates and patterns of niche breadth evolution.

Male reproductive success and multiple paternity in wild, low-density populations of the adder (Vipera berus).

We studied for the first time the occurrence of multiple paternity, male reproductive success, and neonate survival in wild, low-density adder (Vipera berus) populations using 13 microsatellite loci. Paternity was assigned for 15 clutches, collected during 3 years. Our data demonstrated that multiple paternity can occur at a high level (69%) in natural populations of V. berus, even if the density of adults is low. The high proportion of multiple sired clutches was comparable to the proportion observed in captive populations. Male reproductive success significantly increased with body length, and only the largest males successfully sired entire clutches. Finally, no relationship was detected between the number of fathers per clutch and neonate survival. These results suggest that multiple matings could be beneficial in populations with high level of inbreeding or low male fecundity.

Estimating the basic reproductive number from viral sequence data.

Epidemiological processes leave a fingerprint in the pattern of genetic structure of virus populations. Here, we provide a new method to infer epidemiological parameters directly from viral sequence data. The method is based on phylogenetic analysis using a birth-death model (BDM) rather than the commonly used coalescent as the model for the epidemiological transmission of the pathogen. Using the BDM has the advantage that transmission and death rates are estimated independently and therefore enables for the first time the estimation of the basic reproductive number of the pathogen using only sequence data, without further assumptions like the average duration of infection. We apply the method to genetic data of the HIV-1 epidemic in Switzerland.

On metapopulation resistance to drift and extinction.

The spatial configuration of metapopulations (numbers, sizes, and localization of patches) affects their ability to resist demographic extinction and genetic drift, but sometimes with opposite effects. Small and isolated patches, for instance, contribute marginally to demography but may play a large role in genetics by maintaining a sizeable amount of genetic variance among demes. In source-sink systems, similarly, connectivity may be beneficial in terms of effective size, but detrimental in terms of survival, by lowering the reproductive value of source populations. How to reconcile these opposite effects? Here we propose an analytical framework that integrates fixation time (ability to resist genetic drift) and extinction time (ability to resist demographic extinction) into a single index of resistance, measuring the ability of a metapopulation to maintain its demo-genetic integrity. We then illustrate with numerical examples how conflicting demands may be resolved.

Stable isotope ecology of Miocene large mammals from Sandelzhausen, southern Germany

The carbon, oxygen, and strontium isotope composition of enamel from teeth of large Miocene herbivorous mammals from Sandelzhausen (MN5, late Early/early Middle Miocene) in the North Alpine foreland basin, were analyzed to infer diet and habitat. The mean enamel delta(13)C value of -11.4 +/- 1.0% (n = 53) for the nine taxa analyzed (including proboscideans, cervids, suids, chalicotheres, equids, rhinocerotids) indicates a pure C(3) plant diet for all mammals. (87)Sr/(86)Sr ratios of similar to 0.710 higher than those from teeth of the western Molasse Basin (0.708-0.709) seem to indicate preferential feeding of the mammals in the northeastern Molasse Basin. The sympatric herbivores have different mean delta(13)C and delta(18)O values which support diet partitioning and/or use of different habitats within a C(3) plant ecosystem. Especially the three sympatric rhinoceroses Plesiaceratherium fahlbuschi, Lartetotherium sansaniense, and Prosantorhinus germanicus show clear partitioning of plants and/or habitats. The palaeomerycid Germanomeryx fahlbuschi was a canopy folivore in moderately closed environments whereas Metaschizotherium bavaricum (Chalicotheriidae) and P. germanicus (Rhinocerotidae) were browsers in more closed forest environments. The horse Anchitherium aurelianense was probably a more generalized feeder than assumed from its dental morphology. The forest hog Hyotherium soemmeringi has the highest delta(13)C and lowest delta(18)O value of all analyzed taxa, possibly related to a frugivorous diet. Most taxa were water-dependent browsers that record meteoric water delta(18)O values of about -5.6 +/- 0.7% Vienna Standard Mean Ocean Water (VSMOW). Using a modern-day mean annual air temperature (MAT)-delta(18)OH(2)O relation a MAT of 19.3 +/- 1.5 degrees C can be reconstructed for Sandelzhausen. A Gomphotherium subtapiroideum tusk serially sampled for delta(18)O values does not record a clear pattern of seasonality. Thus most taxa were C(3) browsers in a forested and humid floodplain environment in the Molasse Basin, which experienced a warm-temperate to subtropical climate and possibly low seasonality.

No evidence that within-group male relatedness reduces harm to females in Drosophila.

Conflict between males and females over whether, when, and how often to mate often leads to the evolution of sexually antagonistic interactions that reduce female reproductive success. Because the offspring of relatives contribute to inclusive fitness, high relatedness between rival males might be expected to reduce competition and result in the evolution of reduced harm to females. A recent study investigated this possibility in Drosophila melanogaster and concluded that groups of brothers cause less harm to females than groups of unrelated males, attributing the effect to kin selection. That study did not control for the rearing environment of males, rendering the results impossible to interpret in the context of kin selection. Here, we conducted a similar experiment while manipulating whether males developed with kin prior to being placed with females. We found no difference between related and unrelated males in the harm caused to females when males were reared separately. In contrast, when related males developed and emerged together before the experiment, female reproductive output was higher. Our results show that relatedness among males is insufficient to reduce harm to females, while a shared rearing environment - resulting in males similar to or familiar with one another - is necessary to generate this pattern.

Alternative life-histories in a socially polymorphic ant

Social organisms vary greatly in the number of breeders per group; yet, the causes and consequences of this variation remain poorly known. Here, we show that variation in social structure is tightly linked with changes in several fundamental life-history traits within one population of ants. Multiple-queen colonies of Formica selysi were much more populous than single-queen ones. They also occurred in areas of higher nest density, had longer colony lifespan, produced smaller queens that presumably disperse less, and invested less in reproductive individuals relative to workers. These multiple changes in life histories are consistent with a shift in the mode of colony foundation and the degree of philopatry of queens. They may also provide various fitness benefits to members of multiple-queen colonies and are likely to play a central role in the evolution and maintenance of polymorphic social structures.