The British Species of the Plagiothecium denticulatum–P. silvaticum Group

Abstract

Anomodon viticulosus was subjected to several different patterns of alternating wet and dry periods, and assimilation was measured at intervals over 49 days. Short periods of desiccation intercalated between 6-day moist periods had little effect on subsequent performance. Short moist periods breaking otherwise continuous desiccation had a very pronounced effect in mitigating desiccation damage. The results provide some evidence for a fairly slight, but probably cumulative, specific deleterious effect of drying and remoistening.     

The Birth and Life of Species–Cultures

Evolution and life phenomena can be understood as results of history, i.e., as outcomes of cohabitation and collective memory of populations of autonomous entities (individuals) across many generations and vast extent of time. Hence, evolution of distinct lineages of life can be considered as isomorphic with that of cultures. I argue here that cultures and culture-like systems – human culture, natural languages, and life forms – always draw from history, memory, experience, internal dynamics, etc., transforming themselves creatively into new patterns, never foreseen before. This is possible thanks to the fact that all forms of life are descendants of life. Ontogeny and speciation in various lineages draw from continuous re-interpretation of conservative genetic/generic “texts”, as well as from changes of the interpretative process itself. The result is continuous appearances of new lineages-cultures and/or communities-cultures, in a semiotic process of re-interpretation and inventing new ways of living. The topic is developed here on the backgrounds of ideas presented by R. A. Rappaport in “Ritual and religion in the making of humanity” and J. Flegr in “Frozen evolution”.     

The 1989 James A. F. Stevenson memorial lecture. The knee jerk: still an enigma?

This is a wide-ranging review of muscle proprioceptors, intended primarily for the nonspecialist. It emphasizes how much more they are concerned with, than just the production of the knee jerk; it concentrates on principle rather than documenting detail and cites selectively. The main topics covered are the effect of deafferentation, position sense, the proprioceptors themselves, the control of the muscle spindle by the CNS, and spinal and long-latency "stretch" reflexes. The emphasis is on human work. The knee jerk itself is seen as a "physiological artefact," resulting from a mode of stimulation that does not occur in life, with the normal function of its underlying circuitry still under debate.     

Chemical Composition of Hypericum rumeliacum Boiss. Essential Oil. A New Chemotype of This Pharmacologically Valuable Species?

Analysis by GC and GC/MS of the essential‐oil samples obtained from dry above‐ground parts of Hypericum rumeliacum Boiss . (collected in the flowering and fruit‐forming vegetative stages) allowed the identification of 212 components in total, comprising ≥97.8% of the total oil composition. In the flowering phase, the major identified volatile compounds were undecane (6.6%), dodecanal (10.8%), and germacrene D (14.1%), whereas α‐pinene (7.3%), β‐pinene (26.1%), (Z)‐β‐ocimene (8.5%), (E)‐β‐ocimene (10.2%), bicyclogermacrene (7.7%), and germacrene D (15.1%) were dominant in the fruit‐forming phase. Some of the minor constituents found in the studied oil samples (e.g., a homologous series of four 6‐alkyl‐5,6‐dihydro‐2H‐pyran‐2‐ones, i.e., massoia dodeca‐, trideca‐, tetradeca‐, and hexadecalactones) have a restricted occurrence in the Plant Kingdom, and their presence in Hypericum L. spp. has not been previously reported. The chemical compositions of the herein studied additional 34 oils obtained from selected Hypericum taxa were compared using multivariate statistical analysis (agglomerative hierarchical cluster analysis and principal component analysis). The results of these statistical analyses could not be used to either confirm or discard the existence of different H. rumeliacum chemotypes. However, they have implied that the volatile profile of this plant species is determined by the stage of its phenological development.     

Presidential Address—Some Reflections On The Nature Of Species

Background: Variation in the distribution and abundance of woody plants as consequence of disturbances such as fire may be explained by lineage age.

Aims: We tested whether lowland tropical tree lineages that colonise secondary forests are more late-diverging than clades from old-growth forests, and whether tree phylogenetic beta diversity from old-growth to secondary forests is higher in burned than non-burned secondary forests.

Methods: We sampled tree communities in old-growth forests and in secondary forests with distinct disturbance histories (burned and unburned). We calculated mean family age in each plot, and tested for differences among forest types using ANOVA. A phylogenetic fuzzy-weighting procedure was employed to generate a matrix describing the abundance of tree clades per plot, which was then analysed using a principal coordinate analysis.

Results: Most clades found in old-growth forests were underrepresented in secondary forests, which have been heavily colonised by a single species from a young lineage that is not found in old-growth forests. Phylogenetic beta diversity was higher between unburned secondary forests and old-growth forests than between burned secondary forests and old-growth forests.

Conclusions: The capacity of Neotropical trees to colonise secondary forests and persist after fire disturbance may be related to the age of distinct lineages.     

The New Species Concept in Dermatophytes—a Polyphasic Approach

The dermatophytes are among the most frequently observed organisms in biomedicine, yet there has never been stability in the taxonomy, identification and naming of the approximately 25 pathogenic species involved. Since the identification of these species is often epidemiologically and ethically important, the difficulties in dermatophyte identification are a fruitful topic for modern molecular biological investigation, done in tandem with renewed investigation of phenotypic characters. Molecular phylogenetic analyses such as multilocus sequence typing have had to be tailored to accommodate differing the mechanisms of speciation that have produced the dermatophytes that are commonly seen today. Even so, some biotypes that were unambiguously considered species in the past, based on profound differences in morphology and pattern of infection, appear consistently not to be distinct species in modern molecular analyses. Most notable among these are the cosmopolitan bane of nails and feet, Trichophyton rubrum, and the endemic African agent of childhood tinea capitis, Trichophyton soudanense, which are effectively inseparable in all analyses. The molecular data require some reinterpretation of results seen in conventional phenotypic tests, but in most cases, phylogenetic insight is readily integrated with current laboratory testing procedures.     

The Nest’s Tale. A reply to Richard Dawkins

If temperature does not vary from one generation from to the next but its value is crucial for the development of particular phenotypic characteristics, a long-term change in its value may trigger major evolutionary changes of the organism. If a bird's nest maintains the critical temperature, then a statement that the bird is the nest's way of making another nest is as helpful as accounts couched in terms of genes' intentions. However, the language of intentions rests on different evidence and assumptions from causal language and the languages are not interchangeable. Understanding ontogeny in causal terms requires explanations that are made as simple as possible but not so simple that they become completely unrealistic.     

Are Trade-Offs Among Species’ Ecological Interactions Scale Dependent? A Test Using Pitcher-Plant Inquiline Species

Trade-offs among species' ecological interactions is a pervasive explanation for species coexistence. The traits associated with trade-offs are typically measured to mechanistically explain species coexistence at a single spatial scale. However, species potentially interact at multiple scales and this may be reflected in the traits among coexisting species. I quantified species' ecological traits associated with the trade-offs expected at both local (competitive ability and predator tolerance) and regional (competitive ability and colonization rate) community scales. The most common species (four protozoa and a rotifer) from the middle trophic level of a pitcher plant (Sarracenia purpurea) inquiline community were used to link species traits to previously observed patterns of species diversity and abundance. Traits associated with trade-offs (competitive ability, predator tolerance, and colonization rate) and other ecological traits (size, growth rate, and carrying capacity) were measured for each of the focal species. Traits were correlated with one another with a negative relationship indicative of a trade-off. Protozoan and rotifer species exhibited a negative relationship between competitive ability and predator tolerance, indicative of coexistence at the local community scale. There was no relationship between competitive ability and colonization rate. Size, growth rate, and carrying capacity were correlated with each other and the trade-off traits: Size was related to both competitive ability and predator tolerance, but growth rate and carrying capacity were correlated with predator tolerance. When partial correlations were conducted controlling for size, growth rate and carrying capacity, the trade-offs largely disappeared. These results imply that body size is the trait that provides the basis for ecological interactions and trade-offs. Altogether, this study showed that the examination of species' traits in the context of coexistence at different scales can contribute to our understanding of the mechanisms underlying community structure.     

Is the Species Flock Concept Operational? The Antarctic Shelf Case

There has been a significant body of literature on species flock definition but not so much about practical means to appraise them. We here apply the five criteria of Eastman and McCune for detecting species flocks in four taxonomic components of the benthic fauna of the Antarctic shelf: teleost fishes, crinoids (feather stars), echinoids (sea urchins) and crustacean arthropods. Practical limitations led us to prioritize the three historical criteria (endemicity, monophyly, species richness) over the two ecological ones (ecological diversity and habitat dominance). We propose a new protocol which includes an iterative fine-tuning of the monophyly and endemicity criteria in order to discover unsuspected flocks. As a result nine « full » species flocks (fulfilling the five criteria) are briefly described. Eight other flocks fit the three historical criteria but need to be further investigated from the ecological point of view (here called « core flocks »). The approach also shows that some candidate taxonomic components are no species flocks at all. The present study contradicts the paradigm that marine species flocks are rare. The hypothesis according to which the Antarctic shelf acts as a species flocks generator is supported, and the approach indicates paths for further ecological studies and may serve as a starting point to investigate the processes leading to flock-like patterning of biodiversity.     

The Metalloprotease Meprin β Generates Amino Terminal-truncated Amyloid β Peptide Species

The amyloid β (Aβ) peptide, which is abundantly found in the brains of patients suffering from Alzheimer disease, is central in the pathogenesis of this disease. Therefore, to understand the processing of the amyloid precursor protein (APP) is of critical importance. Recently, we demonstrated that the metalloprotease meprin β cleaves APP and liberates soluble N-terminal APP (N-APP) fragments. In this work, we present evidence that meprin β can also process APP in a manner reminiscent of β-secretase. We identified cleavage sites of meprin β in the amyloid β sequence of the wild type and Swedish mutant of APP at positions p1 and p2, thereby generating Aβ variants starting at the first or second amino acid residue. We observed even higher kinetic values for meprin β than BACE1 for both the wild type and the Swedish mutant APP form. This enzymatic activity of meprin β on APP and Aβ generation was also observed in the absence of BACE1/2 activity using a β-secretase inhibitor and BACE knock-out cells, indicating that meprin β acts independently of β-secretase.     

A Periodic Droop Model for Two Species Competition in A Chemostat

Both uniform persistence and the existence of periodic coexistence state are established for a periodically forced Droop model on two phytoplankton species competition in a chemostat under some appropriate conditions. Numerical simulations using biological data are presented as well to illustrate the main result. Research supported in part by the NSERC of Canada and the MITACS of Canada.     

A Sea Under Siege – Alien Species in the Mediterranean

Exotic macrophytes, invertebrates and fish are found in most coastal habitats in the Mediterranean Sea. The Mediterranean Sea has been subjected to introductions of non-indigenous species by ship traffic since the opening of interoceanic maritime routes five centuries ago. The Sea, a hub of shipping, is exceptionally susceptible to invaders that arrive in fouling communities or ballast. The Suez Canal has been the largest pathway for the entry of these species: more than 300 Erythrean species – principally molluscs, fish, decapod crustaceans, polychaetes and algae – have become established in the eastern Mediterranean, primarily along the Levantine coasts. Mariculture of nonindigenous shellfish predominates in the northern Mediterranean lagoonar environments. Unrestricted transport of commercially important exotic shellfish has resulted in numerous unintentional introductions of pathogens, parasites and pest species. Some invaders have outcompeted or replaced native species locally, severely reducing biodiversity; some other invaders are so abundant they are exploited commercially. The rate of these biotic invasions has increased in recent decades, and they collectively have significant ecological and economic impacts in the Mediterranean Sea. This revised version was published online in July 2006 with corrections to the Cover Date.     

A.A.Khan教授将来华讲学

美国康乃尔大学种子生理学家A.A.Khan教授,将于今年十月中旬来华,到广州及杭州访问,并在广州举办讲习班,做以下五方面的报告:①应用种子预措施改善幼苗生长与产