All species are important,but some species are more important than others

Foundation species control biodiversity and ecosystem processes, but are difficult to identify. In this issue of the Journal of Vegetation Science, Elumeeva et al. show that Festuca varia and Nardus stricta act as foundation species in the Caucasus’ alpine. This paper augments the piecemeal literature on foundation species while highlighting the need for more comprehensive approaches to their identification and conservation.     

Psychrotolerant species from the Bacillus cereus group are not necessarily Bacillus weihenstephanensis

Twenty-six strains of Bacillus cereus from different sources were determined to be either mesophilic or psychrotrophic by growth at 6 and 42 degrees C. The strains were also screened by two polymerase chain reaction (PCR) methods designed to discriminate between mesophilic and psychrotrophic types. Seventeen of the 26 strains were able to grow at 6 degrees C, but only four conformed to the new psychrotolerant species Bacillus weihenstephanensis. Among the 26 strains were two which caused outbreaks of food poisoning in Norway, and three others that were isolated from food suspected of causing illness. The presence of the gene components encoding production of enterotoxins Nhe, Hbl, EntT and a recently described cytotoxin K was determined by PCR. All the strains possessed genes for at least one of these toxins, and 19 of the 26 strains were cytotoxic in a Vero cell assay. We conclude that there are psychrotrophic B. cereus strains which cannot be classified as B. weihenstephanensis, and that intermediate forms between the two species exist. No correlation between cytotoxicity and the growth temperature of the strains was found.     

Periodic stimuli are more successful than randomly spaced ones for inducing development inDictyostelium discoideum

Aggregation in the cellular slime moldDictyostelium discoideum is due to chemotaxis. The chemoattractant, cyclic AMP, is synthesised and released periodically by the cells. Externally applied periodic pulses of cyclic AMP can also induce differentiation in this organism. The present work examines the role of periodicityper se in cyclic AMP-mediated stimulation of cell differentiation. For this purpose we use Agip53, aDictyostelium mutant which does not develop beyond the vegetative state but can be made to aggregate and differentiate by reiterated applications of cyclic AMP. Importantly, Agip53 cells do not make or release any cyclic AMP themselves even in response to an increase in extracellular cyclic AMP. A comparison of the relative efficiencies of periodic and aperiodic stimulation shows that whereas the two patterns of stimulation are equally effective in inducing the formation of EDTA-stable cell contacts, periodic stimuli are significantly superior for inducing terminal differentiation. This suggests that there must be molecular pathways which can only function when stimulation occurs at regular intervals.     

Sympatric sister species in rodents are more chromosomally differentiated than allopatric ones: implications for the role of chromosomal rearrangements in speciation

A meta‐analysis approach was used to test for chromosomal speciation in rodents. Forty‐one pairs of sister species, identified in the two most species‐rich rodent families (Cricetidae and Muridae), were used as phylogenetically independent data points, each resulting from a speciation event. About 30% of sister species have an identical karyotype. There was a significant difference in the number of chromosomal differences between sympatric and allopatric sister species, compatible with a direct role of chromosomal rearrangements in speciation.     

Common alien plants are more competitive than rare natives but not than common natives

Success of alien plants is often attributed to high competitive ability. However, not all aliens become dominant, and not all natives are vulnerable to competitive exclusion. Here, we quantified competitive outcomes and their determinants, using response‐surface experiments, in 48 pairs of native and naturalised alien annuals that are common or rare in Germany. Overall, aliens were not more competitive than natives. However, common aliens (invasive) were, despite strong limitation by intraspecific competition, more competitive than rare natives. This is because alien species had higher intrinsic growth rates than natives, and common species had higher intrinsic growth rates than rare ones. Strength of interspecific competition was not related to status or commonness. Our work highlights the importance of including commonness in understanding invasion success. It suggests that variation among species in intrinsic growth rates is more important in competitive outcomes than inter‐ or intraspecific competition, and thus contributes to invasion success and rarity.     

Aragonite shells are more ancient than calcite ones in bivalves: new evidence based on omics

Two calcium carbonate crystal polymorphs, aragonite and calcite, are the main inorganic components of mollusk shells. Some fossil evidences suggest that aragonite shell is more ancient than calcite shell for the Bivalvia. But, the molecular biology evidence for the above deduction is absent. In this study, we searched for homologs of bivalve aragonite-related and calcite-related shell proteins in the oyster genome, and found that no homologs of calcite-related shell protein but some homologs of aragonite-related shell proteins in the oyster genome. We explained the results as the new evidence to support that aragonite shells are more ancient than calcite shells in bivalves combined the published biogeological and seawater chemistry data.     

Brown tawny owls moult more flight feathers than grey ones

The mechanisms by which melanin‐based colour polymorphism can evolve and be maintained in wild populations are poorly known. Theory predicts that colour morphs have differential sensitivity to environmental conditions. Recently it has been proposed that colour polymorphism covaries genetically with intrinsic and behavioural properties. Plumage moult is a costly and crucial somatic maintenance function in birds. We used a long‐term data set consisting of 761 observations on 307 individuals captured between 1985 and 2010 to examine differences in partial flight feather moult between grey (pale) and brown (pheomelanic dark) colour morphs of the tawny owl. We find that the brown morph consistently moult more primary flight feathers than the grey morph whereas there is no clear difference between colour morphs in the moulting of secondary feathers. Contrary to expectations, the difference in the number of moulted flight feathers between the morphs was independent of environmental conditions, as quantified by the abundance of prey. We discuss the potential physiological and behavioural causes for and costs of the observed difference in maintenance functions between colour morphs.     

Ancient fossil specimens of extinct species are genetically more distant to an outgroup than extant sister species are

There exists a remarkable correlation between genetic distance as measured by protein or DNA dissimilarity and time of species divergence as inferred from fossil records. This observation has provoked the molecular clock hypothesis. However, data inconsistent with the hypothesis have steadily accumulated in recent years from studies of extant organisms. Here the published DNA and protein sequences from ancient fossil specimens were examined to see if they would support the molecular clock hypothesis. The hypothesis predicts that ancient specimens cannot be genetically more distant to an outgroup than extant sister species are. Also, two distinct ancient specimens cannot be genetically more distant than their extant sister species are. The findings here do not conform to these predictions. Neanderthals are more distant to chimpanzees and gorillas than modern humans are. Dinosaurs are more distant to frogs than extant birds are. Mastodons are more distant to opossums than other placental mammals are. The genetic distance between dinosaurs and mastodons is greater than that between extant birds and mammals. Therefore, while the molecular clock hypothesis is consistent with some data from extant organisms, it has yet to find support from ancient fossils. Far more damaging to the hypothesis than data from extant organisms, which merely question the constancy of mutation rate, the study of ancient fossil organisms here challenges for the first time the fundamental premise of modern evolution theory that genetic distances had always increased with time in the past history of life on Earth.     

Waterpipe smoking: not necessarily less hazardous than cigarette smoking

Context

Cigarette smoking has declined over the last years in modern countries. On the contrary, waterpipe smoking has increased, especially among young people visiting waterpipe bars. Unfortunately, most waterpipe smokers seem to know little about the possible cardiovascular and other health consequences of waterpipe smoking.

Objective

To describe by narrative literature review the known adverse consequences for the human body caused by smoking the waterpipe compared with the consequences of smoking normal cigarettes. Also, to get a picture of public awareness of these consequences as deducted from the literature and a small new survey in the Netherlands.

Results/Conclusions

Tobacco smoking is associated with serious adverse (cardiovascular) health effects, and there is no evidence that these effects are less serious if a waterpipe is used. The increasing use together with the limited amount of awareness and attention for the possible health consequences of smoking the waterpipe is worrisome. Especially considering the increasing acceptance and use of the waterpipe among the youth. Therefore we recommend more systematic research into the possible health hazards of waterpipe smoking. In the meantime education campaigns and materials are needed to raise public awareness on the possible health risks of waterpipe use.     

Exaggerated male forelegs are not more differentiated than wing morphology in two widespread sister species of black scavenger flies

Sexual selection represents a potent force that can drive rapid population differentiation in traits related to reproductive success. Hence, sexual traits are expected to show greater population divergence than non-sexual traits. We test this prediction by exploring patterns of morphological differentiation of the exaggerated fore femur (a male-specific sexual trait) and the wing (a non-sexual trait) among allopatric and sympatric populations of the widespread sister dung fly species Sepsis neocynipsea and Sepsis cynipsea (Diptera: Sepsidae). While both species occur in Eurasia, S. neocynipsea also abounds in North America, albeit previous studies suggest strong differentiation in morphology, behavior, and mating systems. To evaluate the degree of differentiation expected under neutrality between S. cynipsea, European S. neocynipsea, and North American S. neocynipsea, we genotyped 30 populations at nine microsatellite markers, revealing almost equal differentiation between and minor differentiation among geographic populations within the three lineages. Landmark-based analysis of 18 populations reared at constant 18 and 24°C in a laboratory common garden revealed moderate temperature-dependent phenotypic plasticity and significant heritable differentiation in size and shape of male forelegs and wings among iso-female lines of the three lineages. Following the biological species concept, there was weaker differentiation between cross-continental populations of S. neocynipsea relative to S. cynipsea, and more fore femur differentiation between the two species in sympatry versus allopatry (presumably due to character displacement). Contrary to expectation, wing morphology showed as much shape differentiation between evolutionary independent lineages as fore femora, providing no evidence for faster diversification of traits primarily engaged in mating.     

Protein-protein interactions more conserved within species than across species

Experimental high-throughput studies of protein-protein interactions are beginning to provide enough data for comprehensive computational studies. Today, about ten large data sets, each with thousands of interacting pairs, coarsely sample the interactions in fly, human, worm, and yeast. Another about 55,000 pairs of interacting proteins have been identified by more careful, detailed biochemical experiments. Most interactions are experimentally observed in prokaryotes and simple eukaryotes; very few interactions are observed in higher eukaryotes such as mammals. It is commonly assumed that pathways in mammals can be inferred through homology to model organisms, e.g. the experimental observation that two yeast proteins interact is transferred to infer that the two corresponding proteins in human also interact. Two pairs for which the interaction is conserved are often described as interologs. The goal of this investigation was a large-scale comprehensive analysis of such inferences, i.e. of the evolutionary conservation of interologs. Here, we introduced a novel score for measuring the overlap between protein-protein interaction data sets. This measure appeared to reflect the overall quality of the data and was the basis for our two surprising results from our large-scale analysis. Firstly, homology-based inferences of physical protein-protein interactions appeared far less successful than expected. In fact, such inferences were accurate only for extremely high levels of sequence similarity. Secondly, and most surprisingly, the identification of interacting partners through sequence similarity was significantly more reliable for protein pairs within the same organism than for pairs between species. Our analysis underlined that the discrepancies between different datasets are large, even when using the same type of experiment on the same organism. This reality considerably constrains the power of homology-based transfer of interactions. In particular, the experimental probing of interactions in distant model organisms has to be undertaken with some caution. More comprehensive images of protein-protein networks will require the combination of many high-throughput methods, including in silico inferences and predictions. http://www.rostlab.org/results/2006/ppi_homology/     

Mistletoe species richness patterns are influenced more by host geographic range than nitrogen content

Mistletoes are hemiparasites that access water and nutrients from their hosts. Previous studies have suggested that host genera with high nitrogen are parasitized by more mistletoe species but these studies failed to take into account phylogenetic relationships among host genera. Our main question was whether more mistletoe species parasitize host genera with high nitrogen content when phylogenetic relationships were controlled. We also asked whether patterns in mistletoe parasitism were related to host geographic range size, host fruit type and host spinescence. Overall, we found no difference between conventional and phylogenetically controlled analyses. We also found no evidence for higher mistletoe species richness on host genera with high nitrogen, fleshy fruits or spinescence. However, similar to findings for animal parasites, we found that host genera with large geographic range had higher mistletoe species richness. This is likely because a greater number of mistletoe species will encounter hosts that have a greater geographic distribution. Mistletoe studies frequently assume that nitrogen status drives patterns in mistletoe parasitism but our study suggests that macroecological patterns in mistletoe assemblages are primarily determined by host geographic range.