Dominant climate influences on North American bird distributions

Aim Geographic distributions of species are constrained by several factors acting at different scales, with climate assumed to be a major determinant at broad extents. Recent studies, however, have challenged this statement and indicated that climate may not dominate among the factors governing geographic distributions of species. Here, we argue that these results are misleading due to the lack of consideration of the geographic area that has been accessible to the species. Location North America. Methods We generated null distributions for 75 North American endemic and 19 non‐endemic bird species. For each species, climatic envelopes of observed and null distributions were modelled using neural networks and generalized linear models, and seven climatic predictors. Values of the area under the receiver–operating characteristic curve (AUC) based on models of observed distributions were compared with corresponding AUC values for the null distributions. Results More than 82% of the endemic species showed AUC higher for the observed than for the null distributions, while 63% of the non‐endemic species showed such a pattern. Main conclusions We demonstrate a dominant climatic signal in shaping North American bird distributions. Our results attest to the importance of climate in determining species distributions and support the use of climate‐envelope models for estimating potential distributional areas at the appropriate spatial scales.     

Anthropogenic disturbances and plant biodiversity in forests of Uttaranchal,central Himalaya

Eight forest types varying in disturbance frequencies were identified along an elevational gradient in Uttaranchal, central Himalaya. Low elevation forests were close to human habitation and had high disturbance frequency, while high elevation forests were situated far from the human habitation and had low disturbance. The dominant tree species at low elevation were Pinus roxburghii and Quercus leucotrichophora, while Q. floribunda and Q. semecarpifolia dominated the high elevation forests. Pyracantha crenulata was the shrub present in all the forests except in Q. semecarpifolia forest and Anaphalis contorta, a herb species, was present in all the forests. Disturbance decreased the dominance of single species and increased the plant biodiversity by mixing species of different successional status. Species richness and diversity for all the vegetation layers were higher in low elevation–high disturbance forests. Mean tree density decreased from high to moderate and increased in low disturbance. The shrub density decreased from high to low disturbance while the reverse occured for herbs. High proportion of early successional species in disturbed forests indicated that disturbance induces succession. The mean number of young individuals increasing from high to low disturbance indicates that disturbance adversely affects regeneration. But, however, the high number of young individuals of Coriaria nepalensis, a small non-leguminous nitrogen fixing tree, in disturbed forests shows that the forest is regenerating. This species could be helpful in the re-establishment of original vegetation through triggering the regeneration of these forests. High elevation–low disturbed forests separated from low elevation–high disturbed forests. Forest type and elevation may have more influence on tree richness while shrub and herb richness may be more sensitive to disturbance and forest types.     

Oligodendrocyte Precursor Cells Modulate the Neuronal Network by Activity-Dependent Ectodomain Cleavage of Glial NG2

The role of glia in modulating neuronal network activity is an important question. Oligodendrocyte precursor cells (OPC) characteristically express the transmembrane proteoglycan nerve-glia antigen 2 (NG2) and are unique glial cells receiving synaptic input from neurons. The development of NG2+ OPC into myelinating oligodendrocytes has been well studied, yet the retention of a large population of synapse-bearing OPC in the adult brain poses the question as to additional functional roles of OPC in the neuronal network. Here we report that activity-dependent processing of NG2 by OPC-expressed secretases functionally regulates the neuronal network. NG2 cleavage by the α-secretase ADAM10 yields an ectodomain present in the extracellular matrix and a C-terminal fragment that is subsequently further processed by the γ-secretase to release an intracellular domain. ADAM10-dependent NG2 ectodomain cleavage and release (shedding) in acute brain slices or isolated OPC is increased by distinct activity-increasing stimuli. Lack of NG2 expression in OPC (NG2-knockout mice), or pharmacological inhibition of NG2 ectodomain shedding in wild-type OPC, results in a striking reduction of N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation (LTP) in pyramidal neurons of the somatosensory cortex and alterations in the subunit composition of their α-amino-3-hydroxy-5-methyl-4-isoxazolepr opionicacid (AMPA) receptors. In NG2-knockout mice these neurons exhibit diminished AMPA and NMDA receptor-dependent current amplitudes; strikingly AMPA receptor currents can be rescued by application of conserved LNS protein domains of the NG2 ectodomain. Furthermore, NG2-knockout mice exhibit altered behavior in tests measuring sensorimotor function. These results demonstrate for the first time a bidirectional cross-talk between OPC and the surrounding neuronal network and demonstrate a novel physiological role for OPC in regulating information processing at neuronal synapses.     

Characterization of an extracellular keratinase of Trichophyton simii and its role in keratin degradation

The ability of Trichophyton simii HN 50, isolated from the Ghana Bird Sanctuary, Bharatpur, India, to produce extracellular keratinase was studied. Enzyme was produced on a keratin salt broth medium at pH7 and a temperature of 28 ± 1 °C. Enzyme secretion was best at 15 days of incubation. Asparagine and keratin were repressive to enzyme yield in comparison to gelatin. No relationship was observed between enzyme release and biomass. Exogenous sugars suppressed keratinase production in descending order as follows: glucose > mannose > maltose > arabinose > fructose. The enzyme showed ability to degrade all of the 3 keratin substrates. Buffalow skin was best degraded in the absence of glucose while chicken feathers were the least degraded in its presence.This revised version was published online in October 2005 with corrections to the Cover Date.     

Choice of topology estimators in Bayesian phylogenetic analysis

Wheeler WC and Pickett KM (2008. Topology-Bayes versus clade-Bayesin phylogenetic analysis. Mol Biol Evol. 25:447–453.)discuss two ways of summarizing the posterior probability distributionof a Bayesian phylogenetic analysis, which they refer to as"topology-Bayes" and "clade-Bayes." They claim that the clade-Bayesapproach leads to problems such as "exaggerated clade support,inconsistently biased priors, and the impossibility of topologyhypothesis testing," which are not problems for the topology-Bayesapproach. However, their argument for topology-Bayes over clade-Bayesis based on errors in the interpretation of summary statisticsassociated with Bayesian phylogenetic analysis. Although thereis a well-documented difference between the maximum posteriorprobability topology and the majority-rule consensus topology(the established terms for topology-Bayes and clade-Bayes summaries,respectively), both have a place in phylogenetic analysis. Choiceof summarization strategy should be driven by choice of parametersthat need to be estimated versus those to be marginalized giventhe evolutionary questions being asked or hypotheses being tested.     

Molecular insights into development of Trichoderma interfusants for multistress tolerance enhancing antagonism against Sclerotium rolfsii Sacc

The current study aimed at developing diverse Trichoderma fusants for fungicides, drought, and salt tolerance with enhanced antagonistic activity against Sclerotium rolfsii Sacc. Trichoderma virens NBAII Tvs12 (mycoparasitic) and Trichoderma koningii MTCC796 (multistress tolerant) were used as parental strains for development of interspecific protoplast fusants. A total of 36 stable fusants were used for mycoparasitism, fungicides, and abiotic stresses (drought and salt) tolerance. The results revealed 20 homozygous progenies showing characteristics of either one parental strain and 14 heterozygous mutants depicting traits of both parental strains. A novel concept of inhibition coefficient was established using growth-related key parameters that represent the pathogen biology and the biocontrol-related biophysics of Trichoderma fusants. The results indicated a differential inhibition coefficient of the test pathogen and the highest (92.88%) inhibition coefficient of S. rolfsii was observed by interstable fusant Fu21. It also grew better under fungicides and abiotic stress (drought and salt) conditions. The molecular characterization and heterozygosity analysis evidenced the highest observed heterozygosity (0.5441) and gene flow (0.3872) in stable heterozygous Fu21. Principal coordinates analysis exhibited 62.7% of total variability. The ecofriendly heterozygous Trichoderma fusant (Fu21) might be useful for biocontrol of stem rot disease under adverse conditions or as a part of integrated disease management.     

SPART: A versatile and standardized data exchange format for species partition information

A wide range of data types can be used to delimit species and various computer-based tools dedicated to this task are now available. Although these formalized approaches have significantly contributed to increase the objectivity of species delimitation (SD) under different assumptions, they are not routinely used by alpha-taxonomists. One obvious shortcoming is the lack of interoperability among the various independently developed SD programs. Given the frequent incongruences between species partitions inferred by different SD approaches, researchers applying these methods often seek to compare these alternative species partitions to evaluate the robustness of the species boundaries. This procedure is excessively time consuming at present, and the lack of a standard format for species partitions is a major obstacle. Here, we propose a standardized format, SPART, to enable compatibility between different SD tools exporting or importing partitions. This format reports the partitions and describes, for each of them, the assignment of individuals to the “inferred species”. The syntax also allows support values to be optionally reported, as well as original trees and the full command lines used in the respective SD analyses. Two variants of this format are proposed, overall using the same terminology but presenting the data either optimized for human readability (matricial SPART) or in a format in which each partition forms a separate block (SPART.XML). ABGD, DELINEATE, GMYC, PTP and TR2 have already been adapted to output SPART files and a new version of LIMES has been developed to import, export, merge and split them.