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General Pattern (general + pattern)
Selected AbstractsMultivariate and geometric morphometrics in the analysis of sexual dimorphism variation in Podarcis lizardsJOURNAL OF MORPHOLOGY, Issue 2 2007Antigoni Kaliontzopoulou Abstract Podarcis bocagei and P. carbonelli are two closely related lacertid species, very similar morphologically and ecologically. We investigated sexual dimorphism patterns presented by both species in allopatry and in sympatry. Sexual size and shape dimorphism patterns were analyzed using both multivariate and geometric morphometric techniques. Multivariate morphometrics revealed a marked sexual dimorphism in both species,males being larger with more robust habitus and females presenting a longer trunk. General patterns of sexual size dimorphism are not modified in sympatry, although there is evidence for some morphological change in male head size. The application of geometric morphometrics offered a more detailed image of head shape and revealed that males present a more developed tympanic area than do females, while females have a more rounded head. Differences in the degree of sexual shape dimorphism were detected in sympatry, but no consistent patterns were observed. From the results of the study, and based on previous knowledge on the populations studied, we conclude that the morphological differences observed are probably not caused by exploitative competition between the species, but rather appear attributable to the modification of the relative influence of sexual and natural selection on both sexes. J. Morphol., 2007. © 2007 Wiley-Liss, Inc. [source] Mediator reflections on practice: Connecting select demographics and preferred orientationsCONFLICT RESOLUTION QUARTERLY, Issue 4 2003Margaret S. Herrman This article uses several indicators of a mediator's orientation: (1) his or her goals, (2) focus on the process of mediation, (3) perceptions of personal strengths, (4) the signals that tell him or her that a mediation is working, and (5) his or her preferred outcome. We examine how select demographic and practice characteristics,sex, experience as a mediator, professional background, and organizational context,relate to orientations. The characteristics of sex and professional background significantly modify the general pattern in ways that confirm assumptions common in the literatures on negotiation and mediation. [source] Transforming growth factor-beta 1, 2, 3 and receptor type I and II in diabetic foot ulcersDIABETIC MEDICINE, Issue 6 2002E. B. Jude Abstract Aims To study the distribution of transforming growth factor-beta (TGF-,) 1, 2 and 3, and TGF-, receptor types I and II in diabetic foot ulcers, diabetic skin and normal skin by immunohistochemistry, immunofluorescence and Western blotting. We also compared the TGF-,s with those of chronic venous ulcers. Methods Skin biopsies were obtained from the leg or the foot of non-diabetic and diabetic subjects, and from the edge of diabetic foot ulcers and chronic venous ulcers. Distribution (by immunofluorescence and immunocytochemistry) of TGF-, 1, 2 and 3 and TGF-, receptors (RI and RII) was done by staining 8-µm skin sections using appropriate antibodies. Protein levels of TGF-, were measured by Western blot analysis. Results TGF-,3 expression was increased in the epithelium at the edge of diabetic foot ulcers, being more intense than diabetic and normal skin (P = 0.03, 0.02, respectively), as was its expression in venous ulcers compared with normal skin. However, TGF-,1 expression was not increased in diabetic foot ulcers and chronic venous ulcers, and was comparable to diabetic and normal skin. There was also no increase for the receptors in diabetic foot ulcers. Conclusion The lack of TGF-,1 up-regulation in both diabetic foot ulcers and venous ulcers may explain the impaired healing in these chronic wounds, and could represent a general pattern for chronicity. [source] A shortening of the manus precedes the attenuation of other wing-bone elements in the evolution of flightlessness in birdsACTA ZOOLOGICA, Issue 1 2010R. L. Nudds Abstract Nudds, R. L. and Slove Davidson, J. 2010. A shortening of the manus precedes the attenuation of other wing-bone elements in the evolution of flightlessness in birds. ,Acta Zoologica (Stockholm) 91: 115,122 This is the first study to present evidence for a general pattern of wing-bone attenuation during the early stages of the evolution of flightlessness. A comparative analysis using phylogenetic independent contrasts showed that in families that contain both flighted (volant) and flightless species, the volant species have shorter wings and total-arm (humerus + ulna + manus) lengths relative to their body masses than the species within their wholly volant sister families. A shortening of the manus may typify the early stages of the evolution of flightlessness, with the humerus and ulna attenuating later, perhaps because of their role in maintaining the position of the aerodynamically important alula. A shorter wing relative to body mass was not the result of the inverse (i.e. heavier body mass relative to wing length) because mean body masses of volant members of flightless families were similar to or lower than those of their wholly volant sister families. Despite finding a common trend in the wing morphologies of volant members of flightless families, it seems unlikely that a general model of selection pressures driving the evolution of flightlessness exists. At the very least, a dichotomy between those birds that have lost the ability to fly in order to gain the ability to swim and terrestrial forms, may persist. [source] Male-biased size dimorphism in ichneumonine wasps (Hymenoptera: Ichneumonidae) , the role of sexual selection for large male sizeECOLOGICAL ENTOMOLOGY, Issue 3 2005Tiit Teder Abstract., 1.,Sexual differences in body size are expected to evolve when selection on female and male sizes favours different optima. 2.,Insects have typically female-biased size dimorphism that is usually explained by the strong fecundity advantage of larger size in females. However, numerous exceptions to this general pattern have led to the search for selective pressures favouring larger size in males. 3.,In this study, the benefits of large size were investigated in males of four species of ichneumonine wasps, a species-rich group of parasitoids, many representatives of which exhibit male-biased size dimorphism. 4.,Mating behaviour of all ichneumonine wasps are characterised by pre-copulatory struggles, in the course of which males attempt to override female reluctance to mate. A series of laboratory trials was conducted to study the determinants of male mating success. 5.,A tendency was found for larger males as well as those in better condition to be more successful in achieving copulations. Size dimorphism of the species studied, mostly male-biased in hind tibia length but female-biased in body weight, indicates that sexual selection in males favours longer bodies and appendages rather than larger weight. 6.,The qualitative similarity of the mating patterns suggests that sexual selection cannot completely explain the considerable among-species differences in sexual size dimorphism. 7.,The present study cautions against using various size indices as equivalents for calculating sexual size dimorphism. 8.,It is suggested that female reluctance in ichneumonine wasps functions as a mechanism of female mate assessment. [source] Invasive aliens and sampling biasECOLOGY LETTERS, Issue 4 2003Andrew M. Simons Abstract Two hypotheses have been proposed to explain the observation of increased vigour of invasive alien plants in their nonindigenous ranges: phenotypic plasticity, and the post-invasion evolution of increased competitive ability (EICA). Here I specify how a general pattern of increased vigour may result from sampling bias. Ignoring failed invasions can account for the illusion of increased vigour over a broad range of assumptions. Plasticity and EICA need not be viewed as explanations for a general pattern of increased vigour even if they are the mechanisms underlying every occurrence. [source] Dual enantioselective effect of the insecticide bifenthrin on locomotor behavior and development in embryonic,larval zebrafishENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2010Meiqing Jin Abstract Bifenthrin (BF) is a synthetic pyrethroid that targets the nervous system of insects and may have adverse effects on the behavior and development of nontarget organisms. However, no reports have been issued on the effects of different enantiomers on locomotor behavior for synthetic pyrethroids (SPs) in zebrafish, and whether locomotor activity is associated with the developmental toxicities remains unclear. In this study, enantioselectivity of BF (1S and 1R) on the acute locomotor activity and developmental toxicities of embryonic,larval zebrafish were first evaluated. The results indicated that 1R -BF was more toxic, causing morphological impairments, with a 96-h median effective concentration (EC50) of 226,µg/L for pericardial edema and 145,µg/L for curved body axis. Administration of 20,µg/L of one enantiomer of BF had differential effects on the locomotor activity of zebrafish larvae at 4 d postfertilization (dpf) under alternating light and dark conditions. Larvae treated with 1R -BF were not sensitive to the alteration of light to dark, and the locomotor activities were reduced to a level similar to that observed in light, which otherwise increased rapidly and markedly. However, 1S -BF did not alter the general pattern of zebrafish response to the light or dark compared with the control. The results demonstrated that the differential effects on development might have contributed to the enantioselectivity in the locomotor activity. The consistency of enantioselectivity with insecticidal activity may also indicate a common mode of action. Furthermore, 1R -BF accelerated the spontaneous movement and hatching process, whereas 1S -BF seemed to be inhibitory. The results suggest the need to link behavioral changes to developmental toxicities in order to achieve more comprehensive health risk assessments of chiral pesticides. Environ. Toxicol. Chem. 2010;29:1561,1567. © 2010 SETAC [source] Hormesis: Why it is important to toxicology and toxicologists,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2008Edward J. Calabrese Abstract This article provides a comprehensive review of hormesis, a dose-response concept that is characterized by a low-dose stimulation and a high-dose inhibition. The article traces the historical foundations of hormesis, its quantitative features and mechanistic foundations, and its risk assessment implications. The article indicates that the hormetic dose response is the most fundamental dose response, significantly outcompeting other leading dose-response models in large-scale, head-to-head evaluations. The hormetic dose response is highly generalizable, being independent of biological model, endpoint measured, chemical class, and interindividual variability. Hormesis also provides a framework for the study and assessment of chemical mixtures, incorporating the concept of additivity and synergism. Because the hormetic biphasic dose response represents a general pattern of biological responsiveness, it is expected that it will become progressively more significant within toxicological evaluation and risk assessment practices as well as have numerous biomedical applications. [source] EXTREME SELECTION ON SIZE IN THE EARLY LIVES OF FISHEVOLUTION, Issue 8 2010Kestrel O. Perez Although fitness typically increases with body size and selection gradients on size are generally positive, much of this information comes from terrestrial taxa. In the early life history of fish, there is evidence of selection both for and against larger size, leaving open the question of whether the general pattern for terrestrial taxa is valid for fish. We reviewed studies of size-dependent survival in the early life history of fish and obtained estimates of standardized selection differentials from 40 studies. We found that 77% of estimated selection differentials favored larger size and that the strength of selection was more than five times that seen in terrestrial taxa. Selection decreased with study period duration and initial length, and disruptive selection occurred significantly more frequently than stabilizing selection. Contrary to expectations from Bergmann's rule, selection on size did not increase with latitude. [source] UNDERSTANDING TRADITIONALIST OPPOSITION TO MODERNIZATION: NARRATIVE PRODUCTION IN A NORWEGIAN MOUNTAIN CONFLICTGEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 1 2008Tor A. Benjaminsen ABSTRACT. In Gausdal, a mountainous community in southern Norway, a conflict involving dogsledding has dominated local politics during the past two decades. In order to understand local protests against this activity, in this article we apply discourse analysis within the evolving approach of political ecology. In this way, we also aim at contributing to the emerging trend of bringing political ecology "home". To many people, dogsledding appears as an environmentally friendly outdoor recreation activity as well as a type of adventure tourism that may provide new income opportunities to marginal agricultural communities. Hence, at a first glance, the protests against this activity may be puzzling. Looking for explanations for these protests, this empirical study demonstrates how the opposition to dogsledding may be understood as grounded in four elements of a narrative: (1) environmental values are threatened; (2) traditional economic activities are threatened; (3) outsiders take over the mountain; and (4) local people are powerless. Furthermore, we argue that the narrative is part of what we see as a broader Norwegian "rural traditionalist discourse". This discourse is related to a continued marginalization of rural communities caused by increasing pressure on agriculture to improve its efficiency as well as an "environmentalization" of rural affairs. Thus, the empirical study shows how opposition to dogsledding in a local community is articulated as a narrative that fits into a more general pattern of opposition to rural modernization in Norway as well as internationally. [source] Application of a three-dimensional ray-tracing technique to global P, PP and Pdiff traveltime tomographyGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2001A. Gorbatov Summary A 3-D ray-path tracing algorithm was successfully applied to global P -wave traveltime tomography. The inversion was conducted iteratively using the resultant P -wave velocity model as the initial model for the subsequent iteration. The LSQR method was adopted to solve a large and sparse system of equations. This iteratively linearized inversion with 3-D ray tracing increased wave-speed anomalies, located heterogeneities better and reduced smearing as compared to those derived from a conventional one-step inversion using 1-D ray tracing, although the general pattern of velocity anomalies was similar. A major difference was found in the lowermost mantle, where the departure of a ray path from the great circle path tends to be in general greatest. In particular, a pronounced high-velocity anomaly develops beneath the Indian Ocean, a feature not obvious in the result of 1-D inversion. The final P -wave velocity model was obtained by including reported PP and Pdiff traveltime data. The addition of the PP data sharpened the images and enhanced velocity anomalies in the upper mantle, especially at latitudes above 45° of the Northern Hemisphere. The addition of the Pdiff data sharpened and amplified velocity anomalies in the lowermost mantle in general. [source] Consequences of simultaneous elevation of carbon dioxide and temperature for plant,herbivore interactions: a metaanalysisGLOBAL CHANGE BIOLOGY, Issue 1 2006E. L. ZVEREVA Abstract The effects of elevated carbon dioxide on plant,herbivore interactions have been summarized in a number of narrative reviews and metaanalyses, while accompanying elevation of temperature has not received sufficient attention. The goal of our study is to search, by means of metaanalysis, for a general pattern in responses of herbivores, and plant characteristics important for herbivores, to simultaneous experimental increase of carbon dioxide and temperature (ECET) in comparison with both ambient conditions and responses to elevated CO2 (EC) and temperature (ET) applied separately. Our database includes 42 papers describing studies of 31 plant species and seven herbivore species. Nitrogen concentration and C/N ratio in plants decreased under both EC and ECET treatments, whereas ET had no significant effect. Concentrations of nonstructural carbohydrates and phenolics increased in EC, decreased in ET and did not change in ECET treatments, whereas terpenes did not respond to EC but increased in both ET and ECET; leaf toughness increased in both EC and ECET. Responses of defensive secondary compounds to treatments differed between woody and green tissues as well as between gymnosperm and angiosperm plants. Insect herbivore performance was adversely affected by EC, favoured by ET, and not modified by ECET. Our analysis allowed to distinguish three types of relationships between CO2 and temperature elevation: (1) responses to EC do not depend on temperature (nitrogen, C/N, leaf toughness, phenolics in angiosperm leaves), (2) responses to EC are mitigated by ET (sugars and starch, terpenes in needles of gymnosperms, insect performance) and (3) effects emerge only under ECET (nitrogen in gymnosperms, and phenolics and terpenes in woody tissues). This result indicates that conclusions of CO2 elevation studies cannot be directly extrapolated to a more realistic climate change scenario. The predicted negative effects of CO2 elevation on herbivores are likely to be mitigated by temperature increase. [source] Tidal Effects on Ground Water Discharge Through a Sandy Marine BeachGROUND WATER, Issue 7 2004Daniel W. Urish Tidal fluctuations along the salt water boundary of a sandy beach affect the magnitude, location, timing, and salinity of both subaerial and submarine ground water discharge. Detailed studies of shoreline discharge from an unconfined aquifer at two sites in an embayment on the Cape Cod, Massachusetts, coastline provide insight into the highly dynamic spatial and temporal nature of discharge along sandy beaches affected by the tide. The constantly moving tidal boundary over a sloping beach results in a shoreline-perpendicular discharge zone of 10 to 20 m, with ,35% to 55% of the discharge being submarine discharge. The distribution of fresh ground water through a beach face varies greatly, depending primarily on the tidal cycle and range, the heterogeneous characteristics of the beach sediments, and the beach geometry. The estimated relative volume of discharge varies temporally with tidal fluctuations, with the greatest discharge occurring during early to mid ebbing tide and location of greatest estimated discharge moving seaward during ebbing tide. This is determined using net hydraulic head calculations in monitoring wells set in a shoreline-perpendicular transect in the beach. The salinity of discharge varies temporally from near fresh water values of 1 part per thousand (ppt) to near coastal salt water values of 30 ppt, being saltiest at the start of discharge as the tide ebbs and freshest during a low tide period of ,2 h. Of the discharge volume, ,65% to 85% is estimated to be from salt water that infiltrates during high tide episodes. This study highlights the complexity of the dynamic coastal ground water discharge phenomenon and provides insight into the hydraulic mechanisms involved. While there is a general pattern to sandy beach discharge, comparison of results from beaches studied at Cape Cod indicates that the temporal and spatial details of the discharge is very site-specific. [source] Long-term snow climate trends of the Swiss Alps (1931,99)INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2003Martin Laternser Abstract The mean snow depth, the duration of continuous snow cover and the number of snowfall days in the Swiss Alps all show very similar trends during the observation period 1931,99: a gradual increase until the early 1980s (with insignificant interruptions during the late 1950s and early 1970s) followed by a statistically significant decrease towards the end of the century. Regional and altitudinal variations are large; high altitudes show only slight changes, and the trends become more pronounced at mid and low altitudes. At any particular time the southern part of the Alps often has different conditions than the north. Shorter snow duration is mainly caused by earlier snow melting in spring than by later first snowfalls in autumn. Trends for heavy snowfall events are somewhat different: at elevations above 1300 m a.s.l. a very weak increasing trend towards heavier snowfalls has persisted since the 1960s, and only low altitudes below 650 m a.s.l. show a marked drop since the early 1980s, indicating that heavy winter precipitation to an increasing degree falls in the form of rain instead of snow. A literature review confirms that, throughout the temperate and subpolar Northern Hemisphere, a similar general pattern of temporal snow variations occurred during the 20th century. Copyright © 2003 Royal Meteorological Society [source] Observed changes in seasons: an overviewINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 14 2002T. H. Sparks Abstract Within the last decade the study of phenology has taken on a new legitimacy in the area of climate change research. A growing literature reveals that a change in the timing of natural events is occurring in a wide range of locations and affecting a wide range of species. Changes in spring have been those most commonly reported, with the emphasis on an advance in spring linked to an increase in temperature. Detection of change in autumn is hampered by a smaller pool of available data, events that are harder to define (such as leaf coloration), and various influencing environmental factors triggering autumnal phases. Despite this, the general pattern may be towards a delay in autumn. Plant, animal and abiotic responses, especially in spring, are quite similar. Thus, it would appear that winter is being squeezed at both ends, and this effect, of increasing the growing season, should become more pronounced in the face of predicted global warming. Copyright © 2002 Royal Meteorological Society. [source] Immigrant Communities and Civil War*INTERNATIONAL MIGRATION REVIEW, Issue 1 2009David D. Laitin This paper explains why international migrants, who face numerous security and cultural threats in their host societies, are almost never implicated in civil war violence. This is quite different from situations of internal migration, which often set off violence that escalates to civil war proportions. The paper first lays out the stark contrast between the political implications of external and internal migration based on data adapted from the Minorities at Risk (MAR) dataset. It then explores the reasons for the low incidence of civil war violence for international migrants through an examination of three cases: Bahrain, which has a large expatriate community without political rights that has been politically quiescent; Estonia, where some 30 percent of the population are disaffected Russian-speakers linked to post-World War II migrations from other republics of the Soviet Union; and Pakistan, where the immigrant Muhajirs are a partial exception to the general pattern outlined in this paper. It concludes with a general statement of the relationship between immigration and rebellion, where the level of grievances is less consequential than the conditions that make insurgency pay off. [source] Molecular systematics of Scaphirhynchinae: an assessment of North American and Central Asian Freshwater Sturgeon SpeciesJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2007C. B. Dillman Summary The sturgeon subfamily Scaphirhynchinae contains two genera of obligate freshwater sturgeon: Scaphirhynchus and Pseudoscaphirhynchus, from North America and Central Asia, respectively. Both genera contain morphologically variable species. A novel data set containing multiple individuals representing four diagnosable morphological variants for two species of Pseudoscaphirhynchus, P. hermanni and P. kaufmanni, was generated. These data were used to test taxonomic hypotheses of monophyly for the subfamily Scaphirhynchinae, monophyly of both Scaphirhynchus and Pseudoscaphirhynchus, monophyly of P. hermanni and P. kaufmanni, and monophyly of the recognized morphological variants. Monophyly of the subfamily Scaphirhynchinae is consistently rejected by all phylogenetic reconstruction methodologies with the molecular character set while monophyly of both river sturgeon genera is robustly supported. The molecular data set also rejects hypotheses of monophyly for sampled species of Pseudoscaphirhynchus as well as monophyly for the recognized intraspecific morphological variants. Interestingly both Scaphirhynchus and Pseudoscaphirhynchus demonstrate the same general pattern in reconstructed topologies; a lack of phylogenetic structure in the clade with respect to recognized diversity. Despite rejection of monophyly for the subfamily Scaphirhynchinae with molecular data, reconstructed hypotheses from morphological character sets consistently support monophyly for this subfamily. Disparities among the data sets, as well as reasons for rejection of monophyly for Scaphirhynchinae and species of Scaphirhynchus and Pseudoscaphirhynchus with molecular characters are examined and a decreased rate of molecular evolution is found to be most consistent with the data. [source] New variants of polar glycopeptidolipids detected in Mycobacterium simiae, including ,habana' strains, as evidenced by electrospray ionization-ion trap-mass spectrometryJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2008L. Mederos Abstract Aims:, To determine the composition of polar glycopeptidolipids (pGPLs) of Mycobacterium simiae and, particularly, those of ,habana' strains, in a search for specific markers given the immunogenic potential of ,habana' TMC 5135 in experimental tuberculosis. Methods and Results:, pGPLs were determined in free lipid extracts using electrospray ionization-ion trap-mass spectrometry (ESI-IT-MS), working in both negative- and positive-ion mode. In the case of TMC 5135, the presence of the previously characterized GPL-II (containing 2,4-di-O-CH3 glucuronic acid as distal sugar in the oligosaccharide antigenic moiety) and GPL-III (containing 4-O-CH3 glucuronic acid as distal sugar) was confirmed using MS/MS and MS/MS/MS approaches. Interestingly, some ,habana' strains presented variants of GPL-II, designated GPL-II,-A and GPL-II,-B. A di-O-CH3 -deoxy-hexose (tentatively, 2,3-di-O-CH3 -fucose) was identified as the penultimate sugar in the oligosaccharide moiety of GPL-II,-A, whereas in GPL-II,-B the penultimate sugar was fucose (tentative identification). On the contrary, the distal sugar of the oligosaccharide chain of pGPLs of Myco. simiae ATCC 25275T was identified as tri-O-CH3 -glucuronic acid (designated GPL-simT -I, with two variants: GPL-simT -I-A and GPL-simT -I-B), O-CH3 -glucuronic acid (designated GPL-simT -II) and di-O-CH3 -glucuronic acid (GPL-II,-A and GPL-II,-B). The penultimate sugar of the oligosaccharide chain of GPL-simT -I-A and GPL-simT -II was identified as di-O-CH3 -deoxy-hexose (tentatively, 2,3-di-O-CH3 fucose), and that of GPL-simT -I-B as deoxy-hexose (tentatively, fucose). In all strains studied, each [M-H], and [M+Na]+ ion was revealed as a mixture of homologous compounds varying in the number of ,O-CH3 groups present in the oligosaccharide moiety and in the length of the fatty acyl linked to the peptide. Conclusions:, The present work indicates that, within a similar general pattern of pGPLs, different strains of Myco. simiae present some variations, so that new compounds (GPL-II,-A, GPL-II,-B, GPL-simT -I-A, GPL-simT -I-B and GPL-simT -II) were defined. Noteworthy was the fact that the ,habana' strains clearly differed from the type strain of Myco. simiae. Significance and Impact of the Study:, The data obtained can be used in the delineation of the ,habana' group of Myco. simiae, including the quality control of the immunogenic strain ,habana' TMC 5135. [source] The fellowship of the hobbit: the fauna surrounding Homo floresiensisJOURNAL OF BIOGEOGRAPHY, Issue 6 2010Hanneke J. M. Meijer Abstract The Late Pleistocene Flores fauna shows a pattern observed on many other islands. It is neither aberrant nor exclusive, but the result of non-random selective forces acting upon an impoverished and disharmonic insular fauna. By comparing the Flores vertebrate fauna with other fossil insular biotas, it is apparent that the evolution of Homo floresiensis is part of a general pattern affecting all the inhabitants of Pleistocene Flores. Vertebrate evolution on Flores appears to have been characterized by phylogenetic continuity, low species richness and a disharmonic fauna. All three aspects stem from the isolated position of the island and have resulted in the distinct morphological characteristics of the Flores fauna. Evidence reviewed herein shows that features exhibited by H. floresiensis, such as small stature, a small brain, relatively long arms, robust lower limbs and long feet, are not unique, but are shared by other insular taxa. Therefore, the evolution of H. floresiensis can be explained by existing models of insular evolution and followed evolutionary pathways similar to those of the other terrestrial vertebrates inhabiting Pleistocene Flores. [source] Thermal tolerance and geographical range size in the Agabus brunneus group of European diving beetles (Coleoptera: Dytiscidae)JOURNAL OF BIOGEOGRAPHY, Issue 2 2008P. Calosi Abstract Aim, Within clades, most taxa are rare, whilst few are common, a general pattern for which the causes remain poorly understood. Here we investigate the relationship between thermal performance (tolerance and acclimation ability) and the size of a species' geographical range for an assemblage of four ecologically similar European diving beetles (the Agabus brunneus group) to examine whether thermal physiology relates to latitudinal range extent, and whether Brown's hypothesis and the environmental variability hypothesis apply to these taxa. Location, Europe. Methods, In order to determine the species tolerances to either low or high temperatures we measured the lethal thermal limits of adults, previously acclimated at one of two temperatures, by means of thermal ramping experiments (± 1°C min,1). These measures of upper and lower thermal tolerances (UTT and LTT respectively) were then used to estimate each species' thermal tolerance range, as total thermal tolerance polygons and marginal UTT and LTT thermal polygons. Results, Overall, widespread species have higher UTTs and lower LTTs than restricted ones. Mean upper lethal limits of the Agabus brunneus group (43 to 46°C), are similar to those of insects living at similar latitudes, whilst mean lower lethal limits (,6 to ,9°C) are relatively high, suggesting that this group is not particularly cold-hardy compared with other mid-temperate-latitude insects. Widespread species possess the largest thermal tolerance ranges and have a relatively symmetrical tolerance to both high and low temperatures, when compared with range-restricted relatives. Over the temperature range employed, adults did not acclimate to either high or low temperatures, contrasting with many insect groups, and suggesting that physiological plasticity has a limited role in shaping distribution. Main conclusions, Absolute thermal niche appears to be a good predictor of latitudinal range, supporting both Brown's hypothesis and the environmental variability hypothesis. Restricted-range species may be more susceptible to the direct effect of climate change than widespread species, notwithstanding the possibility that even ,thermally-hardy', widespread species may be influenced by the indirect effects of climate change such as reduction in habitat availability in Mediterranean areas. [source] Historical biogeography of some river basins in central Mexico evidenced by their goodeine freshwater fishes: a preliminary hypothesis using secondary Brooks parsimony analysisJOURNAL OF BIOGEOGRAPHY, Issue 8 2006Omar Domķnguez-Domķnguez Abstract Aims, Our aim was to uncover and describe patterns of historical biogeography of the main river basins in central Mexico, based on a secondary Brooks parsimony analysis (BPA) of goodeine fishes, and to understand the processes that determine them with respect to the molecular clock of the goodeines and the geological events that have taken place in the region since the Miocene. Location, The region covered in this study includes central Mexico, mostly the so-called Mesa Central of Mexico, an area argued to be a transitional zone comprising several major river drainages from their headwaters at high elevations along the Transmexican Volcanic Belt to the coast of the Gulf of Mexico and the Pacific Ocean. Methods, Based on a previous phylogenetic hypothesis regarding the Goodeidae, we built a data matrix using additive binary coding. First, we conducted a primary BPA to provide general explanations of the historical biogeography of Central Mexico. As ambiguity was found, a secondary BPA was conducted, and some areas were duplicated in order to explain the reticulated history of the area. Area cladograms were obtained by running a parsimony analysis. Instances of vicariance and non-vicariance processes were described with reference to the cladogram obtained from secondary BPA. Results, The study area was divided into 18 discrete regions. Primary BPA produced nine equally parsimonious cladograms with 129 steps, and a consistency index (CI) of 0.574. A strict consensus cladogram shows low resolution among some areas, but other area relationships are consistent. For secondary BPA, five of the 18 regions were duplicated (LEA, COT, AYU, CUT, PAN); one was triplicated (BAL); and one was quadruplicated (AME), suggesting that the pattern of distribution of species in these areas reflects multiple independent events. These areas correspond with the regions exhibiting the highest levels of diversification and the most complex geological history, and those for which river piracy events or basin connections have been proposed. The secondary BPA produced a single most parsimonious cladogram with 118 steps, and a CI of 0.858. This cladogram shows that none of the duplicated areas are nested together, reinforcing the idea of a reticulated history of the areas and not a single vicariant event. Main conclusions, Although our results are preliminary and we cannot establish this as a general pattern, as the BPA is based on a single-taxon cladogram, resolution obtained in the secondary BPA provides some insights regarding the historical biogeography of this group of fishes in river basins of central Mexico. Secondary BPA indicates that the historical biogeography of central Mexico, as shown by their goodeine freshwater fishes, is complex and is a result of a series of vicariant and non-vicariant events such as post-dispersal speciation and post-speciation dispersal. [source] Association of Molecular Variants, Haplotypes, and Linkage Disequilibrium Within the Human Vitamin D-Binding Protein (DBP) Gene With Postmenopausal Bone Mineral Density,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2003Yoichi Ezura Abstract Possible contribution of vitamin D-binding protein (DBP) gene for determination of BMD was tested by characterizing 13 SNPs in 384 adult Japanese women. When the effect of a specific single SNP was tested, five SNPs (,39C>T, IVS1+827C>T, IVS1+1916C>T, IVS1-1154A>G, and IVS11+1097G>C) correlated with BMD significantly at various levels. The chromosomal dosage of one haplotype (T-C-C-G-T-C in ,39C>T, IVS1+827C>T, IVS1+1916C>T, IVS1-1154A>G, D432E, and IVS11+1097G>C) displayed significant correlation with adjusted radial BMD (r = 0.15, p = 0.008; n = 331). Multiple regression analyses revealed a most significant correlation with the combination of IVS1+827C>T and D432E (r2 = 0.029, p = 0.005). These results indicate a complex combined effect of several SNPs within the DBP gene that might underlie susceptibility to low radial BMD and osteoporosis. Introduction: Osteoporosis results from the interplay of multiple environmental and genetic determinants. The gene encoding vitamin D-binding protein (DBP), a key factor for regulating calcium homeostasis through the vitamin D endocrine system, is a probable candidate for conferring susceptibility to osteoporosis. Methods: To test a possible contribution of the DBP gene for determination of bone mineral density (BMD) of adult women, we have characterized 13 single nucleotide polymorphisms (SNPs) within the DBP gene in DNA from 384 adult Japanese women and attempted to correlate specific SNPs with BMD. Results and Conclusions: Sixteen major haplotypes accounted for 80% of the variations, indicating allelic complexity in this genomic region. Pairwise linkage disequilibrium (LD), measured by the D, and r2 statistics, demonstrated a general pattern of decline with increasing distance, but individual LD values within small genomic segments were diverse. Regression analysis for adjusted BMD revealed significant correlation with respect to five of them (,39C>T, IVS1+827C>T, IVS1+1916C>T, IVS1-1154A>G, and IVS11+1097G>C) at various levels. An intronic SNP (IVS11+1097G>C) with the highest significance of association (p = 0.006) showed significant LD with four SNPs located around the first exon (r2 values >0.18, D, > 0.5). A non-synonymous coding SNP, D432E, showed a comparable level of correlation, but it was in a moderate LD only with IVS11+1097G>C. The chromosomal dosage of one haplotype (T-C-C-G-T-C in ,39C>T, IVS1+827C>T, IVS1+1916C>T, IVS1-1154A>G, D432E and IVS11+1097G>C) estimated in each subject displayed significant correlation with adjusted radial BMD (r = 0.15, p = 0.008; n = 331). Furthermore, multiple regression analyses revealed that the most significant correlation was achieved for the combination of IVS1+827C>T and D432E (r2 = 0.029, p = 0.005). These results indicate a complex combined effect of several SNPs within the DBP gene that might underlie susceptibility to low radial BMD and osteoporosis. [source] Valence and extra-valence orbitals in main group and transition metal bondingJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 1 2007C. R. Landis Abstract We address the issue first raised by Maseras and Morokuma with regard to the questionable treatment of empty p-orbitals in the algorithm for natural atomic/bond orbitals (NAOs, NBOs) and associated natural population analysis. We quantify this issue in terms of the numerical error (root-mean-square density deviation) resulting from the two alternative treatments of empty p-sets, leading to distinct NAOs, atomic charges, and idealized Lewis structural representations. Computational application of this criterion to a broad spectrum of main group and transition group species (employing both single- and multi-structure resonance models) reveals the interesting general pattern of (i) relatively insignificant differences for normal-valent species, where a single resonance structure is usually adequate, but (ii) clear superiority of the standard NAO algorithm for hypervalent species, where multi-resonance character is pronounced. These comparisons show how the divisive issue of "valence shell expansion" in transition metal bonding is deeply linked to competing conceptual models of hypervalency (viz., "p-orbital participation" in skeletal hybridization vs. 3c/4e resonance character). The results provide a quantitative measure of superiority both for the standard NAO evaluation of atomic charges as well as the general 3c/4e (A: B-C , A-B :C resonance) picture of main- and transition-group hypervalency. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Effects of patch size and density on flower visitation and seed set of wild plants: a pan-European approachJOURNAL OF ECOLOGY, Issue 1 2010Jens Dauber Summary 1.,Habitat fragmentation can affect pollinator and plant population structure in terms of species composition, abundance, area covered and density of flowering plants. This, in turn, may affect pollinator visitation frequency, pollen deposition, seed set and plant fitness. 2.,A reduction in the quantity of flower visits can be coupled with a reduction in the quality of pollination service and hence the plants' overall reproductive success and long-term survival. Understanding the relationship between plant population size and/or isolation and pollination limitation is of fundamental importance for plant conservation. 3.,We examined flower visitation and seed set of 10 different plant species from five European countries to investigate the general effects of plant populations size and density, both within (patch level) and between populations (population level), on seed set and pollination limitation. 4.,We found evidence that the effects of area and density of flowering plant assemblages were generally more pronounced at the patch level than at the population level. We also found that patch and population level together influenced flower visitation and seed set, and the latter increased with increasing patch area and density, but this effect was only apparent in small populations. 5.,Synthesis. By using an extensive pan-European data set on flower visitation and seed set we have identified a general pattern in the interplay between the attractiveness of flowering plant patches for pollinators and density dependence of flower visitation, and also a strong plant species-specific response to habitat fragmentation effects. This can guide efforts to conserve plant,pollinator interactions, ecosystem functioning and plant fitness in fragmented habitats. [source] Refining the stress-gradient hypothesis for competition and facilitation in plant communitiesJOURNAL OF ECOLOGY, Issue 2 2009Fernando T. Maestre Summary 1The stress-gradient hypothesis (SGH) predicts that the frequency of facilitative and competitive interactions will vary inversely across abiotic stress gradients, with facilitation being more common in conditions of high abiotic stress relative to more benign abiotic conditions. With notable exceptions, most tests of the SGH have studied the interaction between a single pair or a few pairs of species, and thus have evaluated shifts in the magnitude and direction of pair-wise interactions along stress gradients, rather than shifts in the general frequency of interactions. 2The SGH has been supported by numerous studies in many ecosystems, has provided a crucial foundation for studying the interplay between facilitation and competition in plant communities, and has a high heuristic value. However, recent empirical research indicates that factors like the variation among species and the nature of the stress gradient studied add complexity not considered in the SGH, creating an opportunity to extend the SGH's general conceptual framework. 3We suggest that one approach for extending the SGH framework is to differentiate between the original idea of how ,common' interactions might be along stress gradients and the ubiquitous empirical approach of studying shifts in the strength of pair-wise interactions. Furthermore, by explicitly considering the life history of the interacting species (relative tolerance to stress vs. competitive ability) and the characteristics of the stress factor (resource vs. non-resource) we may be able to greatly refine specific predictions relevant to the SGH. 4We propose that the general pattern predicted by the SGH would hold more frequently for some combinations of life histories and stress factor, particularly when the benefactor and beneficiary species are mostly competitive and stress-tolerant, respectively. However, we also predict that other combinations are likely to yield different results. For example, the effect of neighbours can be negative at both ends of the stress gradient when both interacting species have similar ,competitive' or ,stress-tolerant' life histories and the abiotic stress gradient is driven by a resource (e.g. water). 5Synthesis. The extension of the SGH presented here provides specific and testable hypotheses to foster research and helps to reconcile potential discrepancies among previous studies. It represents an important step in incorporating the complexity and species-specificity of potential outcomes into models and theories addressing how plant,plant interactions change along stress gradients. [source] Dispersal limitation may result in the unimodal productivity-diversity relationship: a new explanation for a general patternJOURNAL OF ECOLOGY, Issue 1 2007MEELIS PÄRTEL Summary 1Variation in diversity with habitat productivity has long been a central ecological topic. Plant diversity is mostly highest at intermediate productivity, exhibiting the unimodal (so-called ,hump-back') relationship. This relationship has been explained by both evolutionary and ecological processes, but the potential role of dispersal limitation has not been considered. 2We used European flora data to show that dispersal limitation may contribute to the unimodal productivity-diversity relationship. Species were characterized by their habitat productivity preference and dispersal probability (determined by the number of seeds and the presence of a dispersal syndrome). We calculated average relative dispersal probabilities for species assemblages occurring preferentially in different habitat productivity levels. 3At low productivity levels, species without dispersal syndromes predominate (R2 = 0.89), but at high productivity levels, species with a low number of seeds are common (R2 = 0.89). The total relative dispersal probability, combining both the dispersal probabilities attributable to the number of seeds and to the presence of dispersal syndrome, had a unimodal relationship with habitat productivity (R2 = 0.86). Thus, the unimodal productivity-diversity relationship may arise due to the minimal dispersal limitation of local richness in conditions of moderately low productivity. At very low productivity, the lack of dispersal syndromes may limit dispersal. At high productivity, the low number of seeds may limit dispersal. 4Consequently, in conditions where species pool size and biotic interactions do not vary along productivity gradients, the variation in dispersal probabilities with productivity alone can produce unimodal relationships between diversity and productivity. Thus, dispersal limitation may contribute to the observed diversity pattern and ecosystem functioning to a greater extent than usually assumed. [source] Cope's rule in cryptodiran turtles: do the body sizes of extant species reflect a trend of phyletic size increase?JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2006D. S. MOEN Abstract Cope's rule of phyletic size increase is questioned as a general pattern of body size evolution. Most studies of Cope's rule have examined trends in the paleontological record. However, neontological approaches are now possible due to the development of model-based comparative methods, as well as the availability of an abundance of phylogenetic data. I examined whether the phylogenetic distribution of body sizes in extant cryptodiran turtles is consistent with Cope's rule. To do this, I examined body size evolution in each of six major clades of cryptodiran turtles and also across the whole tree of cryptodirans (n = 201 taxa). Extant cryptodiran turtles do not appear to follow Cope's rule, as no clade showed a significant phyletic body size trend. Previous analyses in other extant vertebrates have also found no evidence for phyletic size increase, which is in contrast to the paleontological data that support the rule in a number of extinct vertebrate taxa. [source] Indirect evidence from DNA sequence diversity for genetic degeneration of the Y-chromosome in dioecious species of the plant Silene: the SlY4/SlX4 and DD44-X/DD44-Y gene pairsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2005V. LAPORTE Abstract The action of natural selection is expected to reduce the effective population size of a nonrecombining chromosome, and this is thought to be the chief factor leading to genetic degeneration of Y-chromosomes, which cease recombining during their evolution from ordinary chromosomes. Low effective population size of Y chromosomes can be tested by studying DNA sequence diversity of Y-linked genes. In the dioecious plant, Silene latifolia, which has sex chromosomes, one comparison (SlX1 vs. SlY1) indeed finds lower Y diversity compared with the homologous X-linked gene, and one Y-linked gene with no X-linked homologue has lower species-wide diversity than a homologous autosomal copy (SlAp3Y vs. SlAp3A). To test whether this is a general pattern for Y-linked genes, we studied two further recently described X and Y homologous gene pairs in samples from several populations of S. latifolia and S. dioica. Diversity is reduced for both Y-linked genes, compared with their X-linked homologues. Our new data are analysed to show that the low Y effective size cannot be explained by different levels of gene flow for the X vs. the Y chromosomes, either between populations or between these closely related species. Thus, all four Y-linked genes that have now been studied in these plants (the two studied here, and two previously studied genes, have low diversity). This supports other evidence for an ongoing degeneration process in these species. [source] Disentangling the role of MHC-dependent ,good genes' and ,compatible genes' in mate-choice decisions of three-spined sticklebacks Gasterosteus aculeatus under semi-natural conditionsJOURNAL OF FISH BIOLOGY, Issue 8 2009T. L. Lenz To investigate and disentangle the role of major histocompatibility complex (MHC)-based ,good genes' and ,compatible genes' in mate choice, three-spined sticklebacks Gasterosteus aculeatus with specific MHC IIB genotypes were allowed to reproduce in an outdoor enclosure system. Here, fish were protected from predators but encountered their natural parasites. Mate choice for an intermediate genetic distance between parental MHC genotypes was observed, which would result in intermediate diversity in the offspring, but no mate choice based on good genes was found under the current semi-natural conditions. Investigation of immunological variables revealed that the less-specific innate immune system was more active in individuals with a genetically more divergent MHC allele repertoire. This suggests the need to compensate for an MHC-diminished T-cell repertoire and potentially explains the observed mate choice for intermediate MHC genetic distance. The present findings support a general pattern of mate choice for intermediate MHC diversity (i.e. compatible genes). In addition, the potentially dynamic role of MHC good genes in mate choice under different parasite pressures is discussed in the light of present and previous results. [source] Spatial synchrony of planthopper species with contrasting outbreak behaviourAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2008Mariano P. Grilli Abstract 1,We studied the synchrony of two sympatric delphacids species with different outbreak behaviours over a range of 250 km in Argentina. 2,The spatial synchrony in the dynamics of Delphacodes kuscheli and Toya propinqua was quantified by collecting individuals of both species simultaneously at three sampling heights: ground, 1.5 m and 6 m above the ground. Synchrony between paired sampling sites separated by increasing distances was estimated using a nonparametric covariance function. 3,A significant difference was found between the spatial synchrony of the species studied. Delphacodes kuscheli individuals collected at 6 m above the ground showed consistent spatial synchrony over long distances with correlation values declining by 40%. Population dynamics showed declining synchrony as site separation increased. Toya propinqua populations did not show this pattern. This species had a lower mean regional synchrony at at 6 m above the ground, but their ground height synchrony was greater than that observed for D. kuscheli. 4,One possible synchronizing mechanism is seasonality and the dispersal strategies of each species. The main host plants of D. kuscheli are winter cereals sown as pasture for cattle grazing and the synchrony of the crop may affect the general pattern of dispersing individuals of this species. The lack of synchrony observed in T. propinqua populations was probably due to the wider host range of this species. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||