Aedes albopictus in Sardinia: reappearance or widespread colonization?

The Asian tiger mosquito Aedes albopictus (Skuse, 1894) was first discovered in the South of Sardinia in October 1994, in a tyre depot not far from Cagliari-Elmas airport. Insecticide treatment was thought to have successfully eradicated the mosquito, but in 1996 and 1997 new breeding sites were discovered, a few at some distance from the first. More recently two sites have been reported in the heart of the city of Cagliari. It is not known whether the mosquito has spread from the first breeding place discovered, where treatment may not have been definitive, or whether they have been newly introduced. The recent sighting of Ae. albopictus in Olbia in the Northeast of the island tends to suggest the latter. Cagliari and Olbia are actually Sardinia's two largest sea ports of entry.     

Lutzomyia longipalpis in Brazil: a complex or a single species? A mini-review

Lutzomyia longipalpis is the main vector of Leishmania infantum chagasi, the causative agent of American visceral leishmaniasis (AVL). Although there is strong evidence that Lu. longipalpis is a species complex, not all data concerning populations from Brazil support this hypothesis. The issue is still somewhat controversial for this large part of Lu. longipalpis distribution range even though that it is the Latin American region contributing to most of the cases of AVL. In this mini-review we consider in detail the current data for the Brazilian populations and conclude that Lu. longipalpis is a complex of incipient vector species with a complexity similar to Anopheles gambiae s.s. in Africa.     

Is a single or double arm technique more advantageous in triple jumping?

Triple jumpers employ either an asymmetrical ‘single-arm’ action or symmetrical ‘double-arm’ action in the takeoff of each phase of the jump. This study investigated which technique is more beneficial in each phase using computer simulation. Kinematic data were obtained from an entire triple jump using a Vicon automatic motion capture system. A planar 13-segment torque-driven subject-specific computer simulation model was evaluated by varying torque generator activation timings using a genetic algorithm in order to match performance data. The matching produced a close agreement between simulation and performance, with differences of 3.8%, 2.7%, and 3.1% for the hop, step, and jump phases, respectively. Each phase was optimised for jump distance and an increase in jump distance beyond the matched simulations of 3.3%, 11.1%, and 8.2% was obtained for the hop, step, and jump, respectively. The optimised technique used symmetrical shoulder flexion whereas the triple jumper had used an asymmetrical arm technique. This arm action put the leg extensors into slower concentric conditions allowing greater extensor torques to be produced. The main increases in work came at the joints of the stance leg but the largest increases in angular impulse came at the shoulder joints, indicating the importance of both measures when assessing the impact of individual joint actions on changes in technique. Possible benefits of the double-arm technique include: cushioning the stance leg during impact; raising the centre of mass of the body at takeoff; facilitating an increase in kinetic energy at takeoff; allowing a re-orientation of the body during flight.     

Signaling in the plant cytosol: cysteine or sulfide?

Cysteine (Cys) is the first organic compound containing reduced sulfur that is synthesized in the last stage of plant photosynthetic assimilation of sulfate. It is a very important metabolite not only because it is crucial for the structure, function and regulation of proteins but also because it is the precursor molecule of an enormous number of sulfur-containing metabolites essential for plant health and development. The biosynthesis of Cys is accomplished by the sequential reaction of serine acetyltransferase (SAT) and O-acetylserine(thiol)synthase (OASTL). In Arabidopsis thaliana, the analysis of specific mutants of members of the SAT and OASTL families has demonstrated that the cytosol is the compartment where the bulk of Cys synthesis takes place and that the cytosolic OASTL enzyme OAS-A1 is the responsible enzyme. Another member of the OASTL family is DES1, a novel l-cysteine desulfhydrase that catalyzes the desulfuration of Cys to produce sulfide, thus acting in a manner opposite to that of OAS-A1. Detailed studies of the oas-a1 and des1 null mutants have revealed the involvement of the DES1 and OAS-A1 proteins in coordinate regulation of Cys homeostasis and the generation of sulfide in the cytosol for signaling purposes. Thus, the levels of Cys in the cytosol strongly affect plant responses to both abiotic and biotic stress conditions, while sulfide specifically generated from the degradation of Cys negatively regulates autophagy induced in different situations. In conclusion, modulation of the levels of Cys and sulfide is likely critical for plant performance.     

Phenoptosis,another specialized neologism,or the mark of a widespread revolution?

The classical approach of evolutionism is based on the concept of the survival of the fittest individuals. More and more data indicate that natural selection often acts with supra-individual mechanisms favoring genes and actions harmful for the individual. The most striking type of cases is when an individual kills himself or his offspring by actions genetically determined or favored. The neologism “phenoptosis” describes these events and implicates that they are not evolutionary anomalies but physiological phenomena determined by natural selection. The most important and familiar kind of phenoptosis, the “slow phenoptosis” or aging, which is currently considered an inevitable and scarcely changeable event, is transformed by this different interpretation into a function, in principle modifiable and manageable. Perhaps, the neologism “phenoptosis” will represent, together with the term supra-individual selection, the mark of a vital enrichment of evolutionism, conceived in broader terms of which the individual selection is just a particular case, and will be referred to as the brand and the standard for the start of a new era.     

Do anthropogenic corridors homogenize plant communities at a local scale? A case studied in Tenerife (Canary Islands)

Biological homogenization is defined as a process that occurs when native species are replaced by common and dominant exotic species or due to depletion and expansion of native species, reducing the beta diversity between areas or habitats. Islands are particularly vulnerable to plant invasion, and as a consequence, homogenization is a process that can become faster and more intense in islands than in continental areas. We recorded vascular plant species composition in roadside communities along a strong altitudinal gradient using plots beside the road and at two distances from the road (0–50 and 50–100 m). We analyzed the results separately for each group of plots with a Detrended Correspondence Analysis (DCA) including and excluding exotic species. The results revealed that where exotic species were most abundant, i.e., at the road edge, they can create an effect of floristic homogenization where three similar roads are compared. At a distance of >50 m from the road, where exotic species are less frequent, this effect has already disappeared, indicating that it is a local phenomenon, closely related to the highly disturbed roadside environment. Furthermore, floristic homogenization seems to be more important at higher altitudes (>1000 m), probably related to higher diversity in native plant communities and lower levels of human disturbances. Roads allow humans to reach relatively remote and sometimes well-conserved areas, and, at the same time, facilitate the spread of exotic plants and the most common native species which can locally create floristic homogenization in roadside communities on this oceanic island. A deeper understanding of the effects of these anthropogenic corridors at the local and regional scales is therefore required to integrate road planning and management with the aim of conserving the value of the natural areas.     

More plant biomass results in more offspring production in annuals,or does it?

Competitive ability in plants has been previously measured almost exclusively in terms of traits related to growth (biomass) or plant size. In this study, however, we used a multi‐species competition experiment with six annuals to measure relative competitive ability in terms of reproductive output, i.e. the number of offspring produced for the next generation. Under greenhouse conditions, plants of each species were started in pots from germinating seeds and were grown singly (free of competition) and at high density in both monocultures and in mixtures with all study species. Several traits traditionally regarded as determinants of competitive ability in plants were recorded for each species grown singly, including: seed mass, germination time, early growth rate and potential plant size (biomass and height). Under competition, several traits were recorded as indicators of relative performance in both monocultures and mixtures, including: biomass of survivors, total number of survivors, number of reproductive survivors, and reproductive output (total seed production) of the survivors. As expected, species that grew to a larger biomass in isolation had higher seed production in isolation. However, none of the traditional plant growth/size‐related traits, measured either in isolation or under competition, could predict between species variation in reproductive output under competition in either monocultures or mixtures. In mixtures, 97% of this variation in reproductive output could be explained by between‐species variation in the number of reproductive survivors. The results indicate that traits measured on plants grown singly may be poor predictors of reproductive output under competition, and that species’ rank order of competitive ability in terms of the biomass of survivors may bear no relationship to their rank order in terms of the number of offspring produced by these survivors. This has important implications for the interpretation of mechanisms of species coexistence and community assembly within vegetation.     

Increasing melanism along a latitudinal gradient in a widespread amphibian: local adaptation,ontogenic or environmental plasticity?

Background  

The thermal benefits of melanism in ectothermic animals are widely recognized, but relatively little is known about population differentiation in the degree of melanism along thermal gradients, and the relative contributions of genetic vs. environmental components into the level of melanism expressed. We investigated variation in the degree of melanism in the common frog (Rana temporaria; an active heliotherm thermoregulator) by comparing the degree of melanism (i) among twelve populations spanning over 1500 km long latitudinal gradient across the Scandinavian Peninsula and (ii) between two populations from latitudinal extremes subjected to larval temperature treatments in a common garden experiment.     

Morphology and permeability transitions in plant mitochondria: Different aspects of the same event?

Plant mitochondria are sensitive organelles affected by changing environmental stressors. Upon heat shock or the presence of reactive oxygen species, plant mitochondria undergo in vivo morphological derangements associated with the extensively characterized opening of the mitochondrial permeability transition pore. Nevertheless, the classic mitochondrial permeability transition is known to be triggered by calcium overload causing mitochondrial swelling and dysfunction. Here we review evidence concerning calcium handling, permeability transition and mitochondrial impairments in plants, supporting the notion that the mitochondrial morphology transition is an in vivo indicator of the permeability transition.     

What is more important for invertebrate colonization in a stream with low-quality litter inputs: exposure time or leaf species?

The objective of this study was to evaluate the influences of detritus from the leaves of different species, and of exposure time on invertebrate colonization of leaves in a shaded Cerrado stream. We hypothesized that the exposure time is the main factor that influences the colonization of leaves by invertebrates. We used leaves of five tree species native to the Brazilian Cerrado: Protium heptaphyllum and Protium brasiliense (Burseraceae), Ocotea sp. (Lauraceae), Myrcia guyanensis (Myrtaceae), and Miconia chartacea (Melastomataceae), which are characterized by their toughness and low-nutritional quality. Litter bags, each containing leaves from one species, were placed in a headwater stream and removed after 7, 15, 30, 60, 90, and 120 days. The dominant taxon was Chironomidae, which comprised ca. 52% of all organisms and ca. 20% of the total biomass. The taxonomic richness of colonizing organisms did not vary among the leaf species. However, the density and biomass of the associated organisms varied differently among the kinds of detritus during the course of the incubation. The collector-gatherers and shredders reached higher densities in the detritus that decomposed more rapidly (Ocotea sp. and M. guyanensis), principally in the more advanced stages of colonization. The collector-filterers reached higher densities in the detritus that decomposed more slowly (P. heptaphyllum, P. brasiliense, and M. chartacea), principally in the initial stages of incubation. A cluster analysis divided the detritus samples of different leaf species according to the exposure time (initial phase: up to 7 days; intermediate phase: 7–30 days; advanced phase: 30–120 days), suggesting some succession in invertebrate colonization, with differences in taxon composition (indicator taxa analysis). These results suggest that regardless of the leaf-detritus species, exposure time was the main factor that influenced the colonization process of aquatic invertebrates.     

Shade-induced changes in the branching pattern of a stoloniferous herb: functional response or allometric effect?

Shade-induced changes in the branching pattern of clonal plants can lead to conspicuous modifications of their growth form and architecture. It has been hypothesized that reduced branching in shade may be an adaptive trait, enabling clonal plants to escape from unfavourable patches in a heterogeneous environment by allocating resources preferentially to the growth of the main axis (i.e. linear expansion), rather than to local proliferation by branching. However, such an adaptionist interpretation may be unjustified if (1) branching frequency is a function of the ontogenetic stage of plants, and if (2) shading slows down the ontogenetic development of plants, thereby delaying branch formation. In this case, architectural differences between sun- and shade-grown individuals, harvested at the same chronological age, may not represent a functional response to changes in light conditions, but may be a by-product of effects of shade on the rate of plant development. To distinguish between these two alternatives, individuals of the stoloniferous herb Potentilla reptans were subjected to three experimental light conditions: a control treatment providing full daylight, and two shade treatments: neutral shade (13% of ambient PPFD; no changes in light spectral composition) and simulated canopy shade (13% PPFD and a reduced red:far-red ratio). Plant development was followed throughout the experiment by daily monitoring primary stolon growth as well as branch and leaf initiation. Biomass and clonal offspring production were measured when plants were harvested. At the end of the experiment shaded plants had produced significantly fewer branches than clones grown in full daylight. In all three treatments, however, initiation of secondary stolons occurred at the same developmental stage of individual ramets. Shading significantly slowed down the ontogenetic development of plants and this resulted in the observed differences in branching patterns between sun- and shade-grown individuals, when compared at the same chronological age. These results hence provide evidence that shade-induced changes in the branching pattern of clonal plants can be due to purely allometric effects. Implications for interpreting architectural changes in terms of functional shade-avoidance responses are discussed. Received: 16 August 1996 / Accepted: December 1996     

Cell division in the CNS: protective response or lethal event in post-mitotic neurons?

Cell cycle events have been documented to be associated with several human neurodegenerative diseases. This review focuses on two diseases--Alzheimer's disease and ataxia telangiectasia--as well as their mouse models. Cell cycle studies have shown that ectopic expression of cell cycle markers is spatially and regional correlated well with neuronal cell death in both disease conditions. Further evidence of ectopic cell cycling is found in both human diseases and in its mouse models. These findings suggest that loss of cell cycle control represents a common pathological root of disease, which underlies the defects in the affected brain tissues in both human and mouse. Loss of cell cycle control is a unifying hypothesis for inducing neuronal death in CNS. In the disease models we have examined, cell cycle markers appear before the more well-recognized pathological changes and thus could serve as early stress markers--outcome measures for preclinical trials of potential disease therapies. As a marker these events could serve as a new criterion in human pathological diagnosis. The evidence to date is compatible with the requirement for a second "hit" for a neuron to progress cell cycle initiation and DNA replication to death. If this were true, any intervention of blocking 'second' processes might prevent or slow the neuronal cell death in the process of disease. What is not known is whether, in an adult neuron, the cell cycle event is part of the pathology or rather a desperate attempt of a neuron under stress to protect itself.     

Inheritance of the replication complex: a unique or common phenomenon in the control of DNA replication?

Early models of the regulation of initiation of DNA replication by protein complexes predicted that binding of a replication initiator protein to a replicator region is required for initiation of each DNA replication round, since after the initiation event the replication initiator should dissociate from DNA. It was, therefore, assumed that binding of the replication initiator is a signal for triggering DNA replication. However, more recent investigations have revealed that in many replicons this is not the case. Studies on the regulation of the replication of plasmids derived from bacteriophage lambda demonstrated that, once assembled, the replication complex can be inherited by one of the two daughter plasmid copies after each replication round and may function in subsequent replication rounds. Since this DNA-bound protein complex bears information about specific initiation of DNA replication, this phenomenon has been called "protein inheritance." A similar phenomenon has recently been reported for oriJ-based plasmids. Moreover, the current model of the initiation of DNA replication in the yeast Saccharomyces cerevisiae proposes that the origin recognition complex (ORC) remains bound to one copy of the ori sequence (the ARS region) after initiation of DNA replication. Thus, it seems plausible that protein inheritance is not unique for lambda plasmids, but may be a common phenomenon in the control of DNA replication, at least in microbes.     

Genetic differentiation of a critically endangered population of the limpet Patella candei candei d’Orbigny, 1840, in the Canary Islands

The adoption of measures to protect the viability of threatened populations should be supported by empirical data identifying appropriate conservation units and management strategies. The global population of the majorera limpet, P. candei candei d’Orbigny, 1840, is restricted to the Macaronesian islands in the NE Atlantic, including near-to-extinct and healthy populations in Fuerteventura and Selvagens, respectively. The taxonomic position, genetic diversity and intra- and interspecific relationships of these populations are unclear, which is hindering the implementation of a recovery plan for the overexploited majorera limpet on Fuerteventura. In this study, ddRAD-based genome scanning was used to overcome the limitations of mitochondrial DNA-based analysis. As a result, P. candei candei was genetically differentiated from the closely related P. candei crenata for the first time. Moreover, genetic differentiation was detected between P. candei candei samples from Selvagens and Fuerteventura, indicating that translocations from the healthy Selvagens source population are inadvisable. In conclusion, the majorera limpet requires population-specific management focused on the preservation of exceptional genetic diversity with which to face future environmental challenges.

     

Complex multicellularity in fungi: evolutionary convergence,single origin,or both?

Complex multicellularity represents the most advanced level of biological organization and it has evolved only a few times: in metazoans, green plants, brown and red algae and fungi. Compared to other lineages, the evolution of multicellularity in fungi follows different principles; both simple and complex multicellularity evolved via unique mechanisms not found in other lineages. Herein we review ecological, palaeontological, developmental and genomic aspects of complex multicellularity in fungi and discuss general principles of the evolution of complex multicellularity in light of its fungal manifestations. Fungi represent the only lineage in which complex multicellularity shows signatures of convergent evolution: it appears 8–11 times in distinct fungal lineages, which show a patchy phylogenetic distribution yet share some of the genetic mechanisms underlying complex multicellular development. To explain the patchy distribution of complex multicellularity across the fungal phylogeny we identify four key observations: the large number of apparently independent complex multicellular clades; the lack of documented phenotypic homology between these clades; the conservation of gene circuits regulating the onset of complex multicellular development; and the existence of clades in which the evolution of complex multicellularity is coupled with limited gene family diversification. We discuss how these patterns and known genetic aspects of fungal development can be reconciled with the genetic theory of convergent evolution to explain the pervasive occurrence of complex multicellularity across the fungal tree of life.     

Abundance and Distribution of Sperm Whales in the Canary Islands: Can Sperm Whales in the Archipelago Sustain the Current Level of Ship-Strike Mortalities?

Sperm whales are present in the Canary Islands year-round, suggesting that the archipelago is an important area for this species in the North Atlantic. However, the area experiences one of the highest reported rates of sperm whale ship-strike in the world. Here we investigate if the number of sperm whales found in the archipelago can sustain the current rate of ship-strike mortality. The results of this study may also have implications for offshore areas where concentrations of sperm whales may coincide with high densities of ship traffic, but where ship-strikes may be undocumented. The absolute abundance of sperm whales in an area of 52933 km², covering the territorial waters of the Canary Islands, was estimated from 2668 km of acoustic line-transect survey using Distance sampling analysis. Data on sperm whale diving and acoustic behaviour, obtained from bio-logging, were used to calculate g(0) = 0.92, this is less than one because of occasional extended periods when whales do not echolocate. This resulted in an absolute abundance estimate of 224 sperm whales (95% log-normal CI 120–418) within the survey area. The recruitment capability of this number of whales, some 2.5 whales per year, is likely to be exceeded by the current ship-strike mortality rate. Furthermore, we found areas of higher whale density within the archipelago, many coincident with those previously described, suggesting that these are important habitats for females and immature animals inhabiting the archipelago. Some of these areas are crossed by active shipping lanes increasing the risk of ship-strikes. Given the philopatry in female sperm whales, replacement of impacted whales might be limited. Therefore, the application of mitigation measures to reduce the ship-strike mortality rate seems essential for the conservation of sperm whales in the Canary Islands.     

The formation of symplasmic domains by plugging of plasmodesmata: a general event in plant morphogenesis?

Summary The plasmodesmal network was examined in multicellular protoplast-derived calluses of the dicotyledonSolanum nigrum which had not yet formed any visible adventitious organs and in globular proembryogenic structures developed from scutellar calluses of the monocotyledonMolinia caerulea. Electron microscopical analyses revealed that both calluses and proembryos consisted of small, undifferentiated cells. The interconnecting plasmodesmata at many cell interfaces were structurally inconspicuous in both systems; in particular cell walls, however, all plasmodesmata were occluded with an osmiophilic, dense material. As the blocking material was obviously located in the microchannels of the plasmodesmal cytoplasmic sleeves, the plugged plasmodesmata can be assumed to be nonfunctional. Thus, selective occlusion of all the plasmodesmata in specific cell walls resulted in the symplasmic disconnection of particular adjacent cells. Complex patterns of symplasmic continuity and discontinuity were established within the developing tissues. Some cells or groups of cells were entirely symplasmically disconnected from the surrounding cells by plugged plasmodesmata and might function as independent domains. However, blockage of plasmodesmata was achieved by the surrounding cells rather than by those cells belonging to the isolated domains. The demarcation of symplasmic domains might be a general prerequisite for differential morphogenesis, since they were found to be established very early in the course of morphogenetic processes.