What is an ‘extant’ type specimen? Problems arising from naming mammalian species‐group taxa without preserved types

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To follow or not? How animals in fusion–fission societies handle conflicting information during group decision‐making

When group members possess differing information about the environment, they may disagree on the best movement decision. Such conflicts result in group break‐ups, and are therefore a fundamental driver of fusion–fission group dynamics. Yet, a paucity of empirical work hampers our understanding of how adaptive evolution has shaped plasticity in collective behaviours that promote and maintain fusion–fission dynamics. Using movement data from GPS‐collared bison, we found that individuals constantly associated with other animals possessing different spatial knowledge, and both personal and conspecific information influenced an individual's patch choice decisions. During conflict situations, bison used group familiarity coupled with their knowledge of local foraging options and recently sampled resource quality when deciding to follow or leave a group – a tactic that led to energy‐rewarding movements. Natural selection has shaped collective behaviours for coping with social conflicts and resource heterogeneity, which maintain fusion–fission dynamics and play an essential role in animal distribution.     

Are Normal‐Weight Americans Over‐Fat?

Data from National Health and Nutrition Examination Surveys (NHANES) 1999-2004 have recently shown the percent body fat of American adults. Average American men and women have ~28 and 40% body fat. When categorized by BMI and age, the data also show high percent body fat values, particularly in lower BMI categories. These data should make one reflect on the health status of Americans in all BMI categories and the use of these data for public health recommendations.     

The α‐sheet: A missing‐in‐action secondary structure?

The α-sheet has been speculated to play a role as a toxic conformer in amyloid diseases. However, except for relatively short fragments, its detection has remained elusive. Here, we present molecular dynamics simulations that support the existence of the α-sheet as a stable, metastable, or long-lived secondary structure in polyglutamine and, to a lesser extent, in polyasparagine aggregates.     

Is there safety‐in‐numbers for prey?

The abundance of prey affects the rate of predation, but little consensus exists on whether this enhances or reduces per capita mortality. Studies of aggregating prey in marine habitats generally emphasise that the probability of predation of any individual is the reciprocal of the number of prey within a school. A field experiment tested the alternative hypotheses that predation by predatory fish on schooling prey (1) increased with an increase in the number of prey per school and that this caused (2) survival to be lower in schools with more individuals. The number of prey (juvenile Acanthochromis polyacanthus ) per school was manipulated in replicate treatments with natural densities of large predatory fish (open plots) and treatments without large predatory fish (exclusion cages). Large predatory fish preyed on juveniles in a density-dependent manner and this was the key source of density-dependent mortality in plots open to all predators. There was some suggestion that small predatory fish also prey on juveniles in a density-dependent manner, but this was weak and did not translate into density-dependent mortality of juveniles. It would appear that aggregation of prey may be a successful strategy against predation from some predators, but not always every predator, or all predators in combination.     

Do some deep‐sea,sediment‐dwelling species of harpacticoid copepods have 1000‐km‐scale range sizes?

The range sizes of sediment‐dwelling deep‐sea species are largely unknown. Such knowledge is important because a deep sea composed in large part of species with 100‐km‐scale ranges would be very different from one composed predominantly of species with 1000‐km‐scale ranges. For example, the total species richness would be much greater in the first case than in the second. As a step towards the determination of the distribution of species’ range sizes in the deep sea, we asked whether harpacticoid copepods (Crustacea) on the continental rise in the northeastern Pacific had 1000‐km‐scale range sizes. We chose harpacticoids because they occur widely in deep‐sea sediments and thus are a typical deep‐sea taxon. In addition, they have no pelagic stage in their life history, so they allow a conservative test of hypotheses about species’ range sizes. We used morphology and gene‐sequence data to assign individuals to species. At least 13.3% of the species we studied had 1000‐km‐scale ranges, raising the question of how these species maintain genetic continuity.     

Proteasomal dysfunction induced by 4‐hydroxy‐2,3‐trans‐nonenal,an end‐product of lipid peroxidation: a mechanism contributing to neurodegeneration?

4-Hydroxy-2,3-trans-nonenal (HNE) is a neurotoxic unsaturated aldehyde end-product of lipid peroxidation. The addition of HNE to NT-2 and SK-N-MC cell lines induces apoptosis and we now investigated the time-course of events occurring prior to apoptosis. Treatment of both NT-2 and SK-N-MC cell lines with HNE led to HNE association with the proteasome, increased levels of protein carbonyls and ubiquitinated proteins, and decreased proteasomal function. There was also decreased metabolic activity, cytochrome c release and activation of caspase 3, followed by apoptotic changes including chromatin condensation, cell shrinkage and DNA fragmentation and laddering. Overexpression of mutant superoxide dismutase 1 proteins associated with amyotrophic lateral sclerosis decreased proteasomal activities in the absence of HNE and accelerated the apoptosis induced by HNE. By contrast, overexpression of wild-type superoxide dismutase 1 did not affect basal levels of proteasomal activity. The data suggest that accumulation of ubiquitinated proteins and impairment of proteasomal function are important events in HNE toxicity. We propose that the proteasomal system is a significant target of HNE neurotoxicity in a wide range of neurodegenerative diseases, especially if abnormal proteins are being expressed.     

Can the combination of electrochemical regeneration of NAD+, selectivity of L‐α‐amino‐acid dehydrogenase,and reductive amination of α‐keto‐acid be applied to the inversion of configuration of a L‐α‐amino‐acid?

The inversion of configuration of L‐alanine can be carried out by combining its selective oxidation in the presence of NAD⁺ and L‐alanine dehydrogenase, electrochemical regeneration of the NAD⁺ at a carbon felt anode, and reductive amination of pyruvate, i.e., reduction of its imino derivative at a mercury cathode, the reaction mixture being buffered with concentrated ammonium/ammonia (1.28M / 1.28M). The dehydrogenase exhibits astonishing activity and stability under such extreme conditions of pH and ionic strength. The main drawback of the process is its slowness. At best, the complete inversion of a 10 mM solution of L‐alanine requires 140 h. A careful and detailed quantitative analysis of each of the key steps involved shows that the enzyme catalyzed oxidation is so thermodynamically uphill that it can be driven efficiently to completion only when both the coenzyme regeneration and the pyruvate reduction are very effective. The first condition is easily fulfilled. Under the best conditions, it is the rate of the chemical reaction producing the imine which controls the whole process kinetically. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 101–107, 1999.     

Obesity and triple‐negative‐breast‐cancer: Is apelin a new key target?

Epidemiological studies have shown that obese subjects have an increased risk of developing triple‐negative breast cancer (TNBC) and an overall reduced survival. However, the relation between obesity and TNBC remains difficult to understand. We hypothesize that apelin, an adipokine whose levels are increased in obesity, could be a major factor contributing to both tumour growth and metastatization in TNBC obese patients. We observed that development of obesity under high‐fat diet in TNBC tumour‐bearing mice significantly increased tumour growth. By showing no effect of high‐fat diet in obesity‐resistant mice, we demonstrated the necessity to develop obesity‐related disorders to increase tumour growth. Apelin mRNA expression was also increased in the subcutaneous adipose tissue and tumours of obese mice. We further highlighted that the reproduction of obesity‐related levels of apelin in lean mice led to an increased TNBC growth and brain metastases formation. Finally, injections of the apelinergic antagonist F13A to obese mice significantly reduced TNBC growth, suggesting that apelinergic system interference could be an interesting therapeutic strategy in the context of obesity and TNBC.     

Song and Sperm in Crickets: A Trade‐off between Pre‐ and Post‐copulatory Traits or Phenotype‐Linked Fertility?

When females mate multiply (polyandry) both pre‐ and post‐copulatory sexual selection can occur. Sperm competition theory predicts there should be a trade‐off between investment in attracting mates and investment in ejaculate quality. In contrast, the phenotype‐linked fertility hypothesis predicts a positive relationship should exist between investment in attracting mates and investment in ejaculate quality. Given the need to understand how pre‐ and post‐copulatory sexual selection interacts, we investigated the relationship between secondary sexual traits and ejaculate quality using the European house cricket, Acheta domesticus. Although we found no direct relationship between cricket secondary sexual signals and ejaculate quality, variation in ejaculate quality was dependent on male body weight and mating latency: the lightest males produced twice as many sperm as the heaviest males but took longer to mate with females. Our findings are consistent with current theoretical models of sperm competition. Given light males may have lower mating success than heavy males because females take longer to mate with them in no‐choice tests, light males may be exhibiting an alternative reproductive tactic by providing females with more living sperm. Together, our findings suggest that the fitness of heavy males may depend on pre‐copulatory sexual selection, while the fitness of light males may depend on post‐copulatory fertilization success.     

Male genes: X‐pelled or X‐cluded?

Two recent studies by Parisi et al. and Ranz et al., catalogue sex differences in gene expression across the whole genome of the fruit fly Drosophila melanogaster. Both report striking associations of sex-biased gene expression with the X chromosome. Genes with male-biased expression are depauperate on the X chromosome, whereas genes with female-biased expression show weaker evidence of being in excess. A number of evolutionary hypotheses for the expulsion or exclusion of male-biased genes from the X chromosome have been suggested. None is entirely consistent with the available evidence.     

Always together: mate guarding or predator avoidance as determinants of group cohesion in white‐breasted mesites?

Being a member of a cohesive group can have fitness benefits such as decreased predation risk, increased feeding efficiency as well as enhanced access to social information and mates. However, competition and the risk of parasite transmission exert centrifugal forces on group‐living. Thus, the actual degree of cohesion is expected to vary as a function of the relative importance of several social and ecological factors. White‐breasted mesites Mesitornis variegata are medium‐sized ground‐dwelling birds endemic to the dry deciduous forests of western Madagascar. They live in stable breeding pairs or small family groups, mate monogamously and often form temporary heterospecific associations with canopy‐dwelling bird species that give alarm calls to which mesites respond with anti‐predator behaviours. We investigated the potential effects of predation risk and mate defence on mesite group cohesion by analysing inter‐individual distances of 20 groups as a function of mesite social organization, alarm call events, the size of associated heterospecific flocks, and the adults' reproductive state. Mesite social units were very cohesive, particularly in families, when associated with smaller heterospecific flocks, and after an alarm call event. Adult reproductive state did not influence breeding partners' cohesion. Therefore, the pronounced group cohesion in mesites seems to be mainly a response to the high predation risk typically associated with a terrestrial life‐style, and not to mate‐guarding. However, we suggest that high group cohesion due to predation risk could limit opportunities for solitary extra‐territorial forays to obtain extra‐pair copulations, thereby contributing to a strictly monogamous system in this species.     

Phylogeography of a high‐dispersal New Zealand sea‐star: does upwelling block gene‐flow?

New Zealand's (NZ) geographical isolation, extensive coastline and well-characterized oceanography offer a valuable system for marine biogeographical research. Here we use mtDNA control region sequences in the abundant endemic sea-star Patiriella regularis to test the following literature-based predictions: that coastal upwelling disrupts north-south gene flow and promotes population differentiation (hypothesis 1); and that an invasive Tasmanian population of the species was introduced anthropogenically from southern New Zealand (hypothesis 2). We sequenced 114 samples from 22 geographical locations, including nine sites from North Island, nine from South Island, one from Stewart Island and three from Tasmania. Our analysis of these sequences revealed an abundance of shallow phylogenetic lineages within P. regularis (68 haplotypes, mean divergence 0.9%). We detected significant genetic heterogeneity between pooled samples from northern vs. southern New Zealand (FST = 0.072; P = 0.0002), consistent with the hypothesis that upwelling disrupts gene flow between these regions (hypothesis 1). However, we are currently unable to rule out the alternative hypothesis that Cook Strait represents a barrier to dispersal (North Island vs. South Island; FST = 0.031; P = 0.0467). The detection of significant spatial structure in NZ samples is consistent with restricted gene flow, and the strong structure evident in northern NZ may be facilitated by distinct ocean current systems. Four shared haplotypes and nonsignificant differentiation (FST = 0.025; P = 0.2525) between southern New Zealand and Tasmanian samples is consistent with an anthropogenic origin for the latter population (hypothesis 2).     

MATHEMATICS OF KIN‐ AND GROUP‐SELECTION: FORMALLY EQUIVALENT?

Evolutionary game theory is a general mathematical framework that describes the evolution of social traits. This framework forms the basis of many multilevel selection models and is also frequently used to model evolutionary dynamics on networks. Kin selection, which was initially restricted to describe social interactions between relatives, has also led to a broader mathematical approach, inclusive fitness, that can not only describe social evolution among relatives, but also in group structured populations or on social networks. It turns out that the underlying mathematics of game theory is fundamentally different from the approach of inclusive fitness. Thus, both approaches—evolutionary game theory and inclusive fitness—can be helpful to understand the evolution of social traits in group structured or spatially extended populations.     

ARE RANGE‐SIZE DISTRIBUTIONS CONSISTENT WITH SPECIES‐LEVEL HERITABILITY?

The concept of species-level heritability is widely contested. Because it is most likely to apply to emergent, species-level traits, one of the central discussions has focused on the potential heritability of geographic range size. However, a central argument against range-size heritability has been that it is not compatible with the observed shape of present-day species range-size distributions (SRDs), a claim that has never been tested. To assess this claim, we used forward simulation of range-size evolution in clades with varying degrees of range-size heritability, and compared the output of three different models to the range-size distribution of the South American avifauna. Although there were differences among the models, a moderate-to-high degree of range-size heritability consistently leads to SRDs that were similar to empirical data. These results suggest that range-size heritability can generate realistic SRDs, and may play an important role in shaping observed patterns of range sizes.     

Unsaturated fatty acid‐induced non‐canonical autophagy: unusual? or unappreciated?

The breakdown of cellular components via autophagy is crucial for cellular homeostasis. In this issue of The EMBO Journal, Niso‐Santano et al ( 2015 ) report the important observation that feeding cells with saturated or unsaturated fatty acids triggers mechanistically distinct autophagic responses. Feeding cells saturated fatty acid induced the canonical, BECN1/PI3K‐dependent autophagy pathway. Conversely, the unsaturated fatty acid oleate triggered autophagic responses that were independent of the BECN1/PI3K complex, but that required a functional Golgi system.