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Environmental Perturbations (environmental + perturbation)
Selected AbstractsSize compensation in moth larvae: attention to larval instarsPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2010TOOMAS ESPERK Environmental perturbations such as starvation and poor diet often prevent animals from attaining their optimal sizes. When the perturbation has a transient character, compensatory responses are expected in terms of faster growth or a prolonged developmental period. In the case of insect larvae, details of such responses are insufficiently known at the proximate level. Attention to responses at the level of particular larval instars should promote an understanding of insect developmental plasticity also in a more general context. To provide an instar-specific analysis of compensatory growth, larvae of the moth Orgyia antiqua (L.) are reared on inferior diet during one larval instar. Responses in growth parameters are recorded in the course of the manipulated instars, as well as at the level of the entire larval period. The negative relationship between development time and size in response to the inferior food quality, typical of the entire larval periods, is also observed within the manipulated instars taken separately. The manipulated larvae remain smaller than the larvae of the control group (significant in males only), even by the end of the subsequent instar during which all individuals are provided with superior host. In males, close to full size compensation by the time of pupation is achieved only by means of adding an extra larval instar. The inability of larvae to fully compensate during one and even two instars is considered as an indication of the presence of constraints on the within-instar growth pattern. An alternative, adaptational explanation for the incomplete compensation could be based on the cost of prolonged development period. Given the ecological context of the species' life history, such an explanation appears less likely. [source] Elevated atmospheric CO2 affects soil microbial diversity associated with trembling aspenENVIRONMENTAL MICROBIOLOGY, Issue 4 2008Celine Lesaulnier Summary The effects of elevated atmospheric CO2 (560 p.p.m.) and subsequent plant responses on the soil microbial community composition associated with trembling aspen was assessed through the classification of 6996 complete ribosomal DNA sequences amplified from the Rhinelander WI free-air CO2 and O3 enrichment (FACE) experiments microbial community metagenome. This in-depth comparative analysis provides an unprecedented, detailed and deep branching profile of population changes incurred as a response to this environmental perturbation. Total bacterial and eukaryotic abundance does not change; however, an increase in heterotrophic decomposers and ectomycorrhizal fungi is observed. Nitrate reducers of the domain bacteria and archaea, of the phylum Crenarchaea, potentially implicated in ammonium oxidation, significantly decreased with elevated CO2. These changes in soil biota are evidence for altered interactions between trembling aspen and the microorganisms in its surrounding soil, and support the theory that greater plant detritus production under elevated CO2 significantly alters soil microbial community composition. [source] The delicate balance between male and female sex determining pathways: potential for disruption of early steps in sexual developmentINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 2 2010P. Koopman Summary Testes and ovaries develop from the same primordial structures, the genital ridges, in the mammalian foetus. Male development depends critically on the correct functioning of the Y-linked testis-determining gene, Sry. However, Sry is highly vulnerable to mutation, and so does not provide a very robust sex-determining mechanism. Both in testes and in ovaries, proper gonadal development involves co-ordinated regulation of the bipotential fates of a number of different cell lineages, and is dependent on intercellular signalling mechanisms. If either the testicular or ovarian pathway stalls in the early stages, mechanisms operate to engage the alternative pathway. For these reasons, the early steps in mammalian sexual development are vulnerable to genetic and environmental perturbation, and represent possible points of action of endocrine disrupting compounds. [source] Viral infections as potential triggers of type 1 diabetesDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 3 2007Nienke van der Werf Abstract During the last decades, the incidence of type 1 diabetes (T1D) has increased significantly, reaching percentages of 3% annually worldwide. This increase suggests that besides genetical factors environmental perturbations (including viral infections) are also involved in the pathogenesis of T1D. T1D has been associated with viral infections including enteroviruses, rubella, mumps, rotavirus, parvovirus and cytomegalovirus (CMV). Although correlations between clinical presentation with T1D and the occurrence of a viral infection that precedes the development of overt disease have been recognized, causalities between viruses and the diabetogenic process are still elusive and difficult to prove in humans. The use of experimental animal models is therefore indispensable, and indeed more insight in the mechanism by which viruses can modulate diabetogenesis has been provided by studies in rodent models for T1D such as the biobreeding (BB) rat, nonobese diabetic (NOD) mouse or specific transgenic mouse strains. Data from experimental animals as well as in vitro studies indicate that various viruses are clearly able to modulate the development of T1D via different mechanisms, including direct ,-cell lysis, bystander activation of autoreactive T cells, loss of regulatory T cells and molecular mimicry. Data obtained in rodents and in vitro systems have improved our insight in the possible role of viral infections in the pathogenesis of human T1D. Future studies will hopefully reveal which human viruses are causally involved in the induction of T1D and this knowledge may provide directions on how to deal with viral infections in diabetes-susceptible individuals in order to delay or even prevent the diabetogenic process. Copyright © 2007 John Wiley & Sons, Ltd. [source] Effects of environmental perturbations on abundance of subarctic plants after three, seven and ten years of treatmentsECOGRAPHY, Issue 1 2001Enrico Graglia Analyses of changes in vegetation were carried out after three, seven and ten years of fertilizer addition, warming and light attenuation in two subarctic, alpine dwarf shrub heaths. One site was just above the tree line, at ca 450 m a.s.l., and the other at a much colder fell-field at ca 1150 m altitude. The aim was to investigate how the treatments affected the abundance of different species and growth forms over time, including examinations of transient changes. Grasses, which increased in abundance by fertilizer addition, and cryptogams, which, by contrast, decreased by fertilizer addition and warming, were the most sensitive functional groups to the treatments at both sites. Nutrient addition exerted a stronger and more consistent effect than both shading and warming. Warming at the fell-field had slightly greater effect than at the warmer tree line with an increase in deciduous shrubs. The decreased abundance of mosses and lichens to fertilizer addition and/or warming was most likely an indirect treatment effect, caused by competition through increased abundance and overgrowth of grasses. Such changes in species composition are likely to alter decomposition rates and the water and energy exchange at the soil surface. We observed few, if any, transient effects of declining responses during the 10 yr of treatments. Instead, there were many cumulative effects of the treatments for all functional groups and many interactions between time and treatment, suggesting that once a change in community composition is triggered, it will continue with unchanged or accelerated rate for a long period of time. [source] Running to stand still: adaptation and the response of plants to rapid climate changeECOLOGY LETTERS, Issue 9 2005Alistair S. Jump Abstract Climate is a potent selective force in natural populations, yet the importance of adaptation in the response of plant species to past climate change has been questioned. As many species are unlikely to migrate fast enough to track the rapidly changing climate of the future, adaptation must play an increasingly important role in their response. In this paper we review recent work that has documented climate-related genetic diversity within populations or on the microgeographical scale. We then describe studies that have looked at the potential evolutionary responses of plant populations to future climate change. We argue that in fragmented landscapes, rapid climate change has the potential to overwhelm the capacity for adaptation in many plant populations and dramatically alter their genetic composition. The consequences are likely to include unpredictable changes in the presence and abundance of species within communities and a reduction in their ability to resist and recover from further environmental perturbations, such as pest and disease outbreaks and extreme climatic events. Overall, a range-wide increase in extinction risk is likely to result. We call for further research into understanding the causes and consequences of the maintenance and loss of climate-related genetic diversity within populations. [source] Impact of Environmental Disturbance on the Stability and Benefits of Individual Status within Dominance HierarchiesETHOLOGY, Issue 5 2006Lynne U. Sneddon Changes in environmental conditions affect social interactions and thus may modify an individual's competitive ability within a social group. We subjected three-spined sticklebacks, Gasterosteus aculeatus, housed in groups of four individuals, to environmental perturbations to assess the impact on dominance hierarchy stability. Hierarchy stability decreased during increased turbulence or lowered water levels (,simulated drought') whereas control hierarchies became more stable in a constant environment. The dominant individual either became more aggressive and remained dominant during the environmental manipulation or was usurped by a lower rank member. Only simulated drought affected rates of aggression where levels of aggression were higher after the water level was dropped which may be the result of an increased encounter rate in these conditions. When there were large size differences between the group members, the dominant individual performed the greatest amount of aggression and ate the largest proportion of food and there was little aggressive behaviour from the lower ranks. In groups of similar-sized individuals, aggression was much higher. The benefit of being dominant was to gain weight over the experimental period whereas ranks 2 and 3 lost weight. The lowest rank, 4, actually gained weight over the experimental period. This study suggests that it would benefit an individual to be dominant, highly aggressive and gain weight or be submissive, avoid aggressive interactions and, by sneakily obtaining access to food, also gain weight. Altering environmental conditions has a profound effect on social behaviour in this study. [source] ORIGINAL ARTICLE: Big dams and salmon evolution: changes in thermal regimes and their potential evolutionary consequencesEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 2 2008Michael J. Angilletta Jr Abstract Dams designed for hydropower and other purposes alter the environments of many economically important fishes, including Chinook salmon (Oncorhynchus tshawytscha). We estimated that dams on the Rogue River, the Willamette River, the Cowlitz River, and Fall Creek decreased water temperatures during summer and increased water temperatures during fall and winter. These thermal changes undoubtedly impact the behavior, physiology, and life histories of Chinook salmon. For example, relatively high temperatures during the fall and winter should speed growth and development, leading to early emergence of fry. Evolutionary theory provides tools to predict selective pressures and genetic responses caused by this environmental warming. Here, we illustrate this point by conducting a sensitivity analysis of the fitness consequences of thermal changes caused by dams, mediated by the thermal sensitivity of embryonic development. Based on our model, we predict Chinook salmon likely suffered a decrease in mean fitness after the construction of a dam in the Rogue River. Nevertheless, these demographic impacts might have resulted in strong selection for compensatory strategies, such as delayed spawning by adults or slowed development by embryos. Because the thermal effects of dams vary throughout the year, we predict dams impacted late spawners more than early spawners. Similar analyses could shed light on the evolutionary consequences of other environmental perturbations and their interactions. [source] Environmental ,loopholes' and fish population dynamics: comparative pattern recognition with focus on El Niño effects in the PacificFISHERIES OCEANOGRAPHY, Issue 4-5 2003Andrew Bakun Abstract A process of comparative pattern recognition is undertaken for the purpose of garnering insights into the mechanisms underlying some currently puzzling conundrums in fishery resource ecology. These include (a) out-of-phase oscillations between anchovies and sardines, (b) the remarkable fish productivity of the Peru,Humboldt marine ecosystem, (c) sardine population increases in the eastern Pacific during El Niños, (d) basin-wide synchronies in large-amplitude abundance variations, (e) characteristic spawning of large tuna species in poorly productive areas, (f) contrary trends in Pacific tropical tuna abundance during the 1970s and early 1980s. It is found that each of the items appears to become less enigmatic when the conceptual focus shifts from conventional trophodynamics to the idea that ,loopholes' in the fields of biological controls (i.e. of predators of early life stages), produced by poor ocean productivity or by disruptive environmental perturbations, may in fact lead to remarkable reproductive success. Implications include the following: (1) El Niño, rather than being an unmitigated disaster for Peruvian fisheries, may in the long run be a prime reason for the remarkable fishery productivity of the Peru,Humboldt large marine ecosystem. (2) Globally-teleconnected climatic trends or shifts might produce globally-coherent population expansions even when local environmental expressions may be quite different. (3) It may be unreasonable to expect any management methodologies to be able to keep the fish populations of highly climatically-perturbed systems such as the Peruvian LME always at stable high levels; an alternative approach, for example, might be to take optimal advantage of the transient opportunities afforded by the high fish productivity of such inherently erratic systems. [source] Stoichiometric impacts of increased carbon dioxide on a planktonic herbivoreGLOBAL CHANGE BIOLOGY, Issue 6 2003JOTARO URABE Abstract The partial pressure of carbon dioxide (pCO2) in lake ecosystems varies over four orders of magnitude and is affected by local and global environmental perturbations associated with both natural and anthropogenic processes. Little is known, however, about how changes in pCO2 extend into the function and structure of food webs in freshwater ecosystems. To fill this gap, we performed laboratory experiments using the ecologically important planktonic herbivore Daphnia and its algal prey under a natural range of pCO2 with low light and phosphorus supplies. The experiment showed that increased pCO2 stimulated algal growth but reduced algal P : C ratio. When feeding on algae grown under high pCO2, herbivore growth decreased regardless of algal abundance. Thus, high CO2 -raised algae were poor food for Daphnia. Short-term experimental supplementation of PO4 raised the P content of the high CO2 -raised algae and improved Daphnia growth, indicating that low Daphnia growth rates under high pCO2 conditions were due to lowered P content in the algal food. These results suggest that, in freshwater ecosystems with low nutrient supplies, natural processes as well as anthropogenic perturbations resulting in increased pCO2 enhance algal production but reduce energy and mass transfer efficiency to herbivores by decreasing algal nutritional quality. [source] Molecular relaxation and metalloenzyme active site modelingINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2002James W. Whittaker Abstract Metalloenzymes represent a broad class of important biomolecules containing an essential metal ion cofactor in their catalytic active sites, forming biologic metal complexes that perform a wide range of important functions: activation of small molecules (O2, N2, H2, CO), atom transfer chemistry, and the control of oxidation equivalents. The structures of many metalloenzyme active sites have been defined by X-ray crystallography, revealing transition metal ions in unique low-symmetry environments. These bioinorganic complexes present significant challenges for computational studies aimed at going beyond crystal structures to develop a detailed understanding of the catalytic mechanisms. Considerable progress has been made in the theoretical characterization of these sites in recent years, supported by the availability of efficient computational tools, in particular density functional methods. However, the ultimate success of a theoretical model depends on a number of factors independent of the specific computational method used, including the quality of the initial structural data, the identification of important environmental perturbations and constraints, and experimental validation of theoretical predictions. We explore these issues in detail and illustrate the effects of molecular relaxation in calculations of two metalloenzymes, manganese superoxide dismutase and galactose oxidase. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 [source] How environmental stress affects density dependence and carrying capacity in a marine copepodJOURNAL OF APPLIED ECOLOGY, Issue 3 2000Richard M. Sibly Summary 1.,Management of the effects of stress on populations , for instance in ecotoxicology , requires understanding of the effects of stressors on populations and communities. Attention to date has too rarely been directed to relevant ecological endpoints, such as carrying capacity and density dependence. Established procedures are instead based on measuring the Life Tables of individual organisms exposed to differing concentrations of a pollutant at low population density, but this approach does not take into account population effects that may occur through interactions between individuals. Here we introduce an approach that allows direct measurement of the effects of stressors on carrying capacity and density dependence. 2.,Using the marine copepod Tisbe battagliai Volkmann-Rocco, we report replicated experiments establishing the effects of 100 µg L,1 pentachlorophenol (PCP) in combination with varying diet and food concentrations. Population density was measured as population biomass in 10 mL volumes. Diet was either the alga Isochrysis galbana Parke (here designated ,poor diet') or a mix of two algal species (I. galbana and Rhodomonas reticulata Novarino: ,good diet'). Each was given at three food concentrations (520, 1300 and 3250 µgC L,1), selected on the basis that at low population density these cover the range between limited and maximal population growth. 3.,Carrying capacity increased linearly with food concentration. On the poor diet the increase was 1·2 ,g L,1 for each ,gC L,1 increase in food concentration. On the good diet the increase was 2·3 ,g L,1/,gC L,1 in the absence of PCP, and 1·9 ,g L,1/,gC L,1 with PCP. Maximum carrying capacity was in the region of 60,80 ,g per 10 mL volume. Population growth rate (pgr) decreased linearly with population biomass when the latter was plotted on a logarithmic scale. Increasing biomass reduced pgr by 1·70 week,1 for each unit increase in log10 biomass. Increasing food concentration and improving diet both increased pgr, but did not affect the slope of the density-dependent relationship. Presence or absence of PCP had no effect except that at some higher food concentrations non-PCP populations initially increased faster than PCP populations, and at high concentration on the good diet the effect of density-dependence was decreased in PCP populations. 4.,The results show that a stressor's effects at high population density may differ from its effects at low density, and emphasizes the importance of finding new protocols, such as those introduced here, with which to study the joint effects of a stressor and population density. Managers and researchers of threatened species, harvested species and pest species need to know the joint effects of stressors and population density, in order to be able to predict the effects of stressors on carrying capacity and on the course of recovery from environmental perturbations. [source] Some aspects of the biology of the stargazer mountain catfish, Amphilius uranoscopus (pfeffer); (Siluriformes: Amphiliidae) indigenous to Kenya streamsAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Charles C. Ngugi Abstract A study on some biological parameters of the mountain catfish, Amphilius uranoscopus Pfeffer 1889 (Silurifomes: Amphiliidae), was carried out in the Thego stream on the slopes of Mount Kenya from February to December 2002. Physical and chemical profiles of the Thego show that the water quality parameters is typical of high altitude streams with temperatures rarely exceeding 18°C, DO ranging from 7.9 to 8.2 mg l,1 and relatively high conductivity (97,137 ,S cm,1) typical of perturbed lotic environments. A total of 1010 fish were caught by an electro-fisher, with sizes ranging between 8 and 24 cm fork length. The population structure had a unimodal distribution with maxima at 14,16 cm. The length,weight relationship showed relatively narrow range in the slope ranging from 2.61 in April to 2.98 in February 2002, thereby suggesting isometric growth pattern. The fitted growth pattern of A. uranoscopus showed an asymptotic length (L,) of 28.5 cm and a growth curvature (K) of 0.56 year,1 resulting in an estimated natural mortality coefficient (M) of 0.90 year,1. The Fulton's condition factor (K) was also relatively stable with a peak in April (0.92 ± 0.21) and lowest value in June (0.86 ± 0.10). As A. uranoscopus is not under commercial exploitation, the seemingly depressed population is possibly attributed to the introduced exotic rainbow trout that heavily predates on the species and environmental perturbations arising from changes in land use. The implications of such changes on A. uranoscopus are discussed. Résumé Une étude de certains paramètres du poisson-chat de montagne Amphilius uranoscopus Pfeffer 1889 (Silurifomes: Amphiliidae) a été réalisée dans le courant du Thego, sur les pentes du mont Kenya entre février et décembre 2002. Le profil physique et chimique du Thego montre que les paramètres de la qualité de l'eau sont typiques des cours d'eau de haute altitude, avec une température qui dépasse rarement 18°C, un OD qui varie de 7,9 à 8,2 mg/l, et une conductivité relativement haute (87 à 137 ,S/cm) typique d'environnements lotiques perturbés. Au total, 1 010 poissons ont été capturés au moyen d'une canne électrique, d'une taille allant de 8 à 24 cm de longueur à la fourche. La structure de la population avait une distribution unimodale avec des maxima de 14,16 cm. La relation longueur/poids présente une variation relativement étroite dans la pente, allant de 2,61 en avril à 2,98 en février 2002, ce qui suggère un schéma de croissance isométrique. Le schéma de croissance intégré d'A. uranoscopus montre une longueur asymptotique (L,) de 28,5 cm et une courbure de croissance (K) de 0,56/an, résultant en un coefficient de mortalité naturelle estimé (M) de 0,90/an. Le facteur de condition de Fulton (K) était aussi relativement stable, avec un pic en avril (0,92 ± 0,21) et la valeur la plus basse en juin (0,86 ± 0,10). Puisque A. uranoscopus ne fait pas l'objet d'une exploitation commerciale, la dépression apparente de la population doit peut-être être attribuée à la truite arc-en-ciel, espèce exotique introduite qui se nourrit abondamment de l'espèce, et à des perturbations environnementales provoquées par des changements d'utilisation des terres. Les implications de tels changements pour A. uranoscopus sont discutées. [source] Effects of anthropogenic disturbances on the diversity and composition of the butterfly fauna of sites in the Sango Bay and Iriiri areas, Uganda: implications for conservationAFRICAN JOURNAL OF ECOLOGY, Issue 2008Perpetra Akite Abstract In assessing environmental change, butterflies have been proven as replicable indicators of biodiversity and functional integrity that can be monitored at a range of scales. Butterflies have been identified as important bio-indicators for assessing biodiversity and monitoring ecosystem responses to environmental perturbations. The objectives of this study were to determine changes in the butterfly fauna of differing sites in the Sango Bay Area (SBA) and Iriiri (Karamoja) in comparison with data collected 10 years ago, and to investigate the impact of different degrees of habitat disturbance on butterflies. The general butterfly diversity was determined by trapping and sweep netting along transect lines and by random sweeping. The impact of human-induced disturbance was assessed by comparing species richness and composition between the sites and regressing the weighted disturbances against species diversity per site. There was a marked decrease in species diversity and varied species composition between the two studies and between the habitat types. Charcoal burning and grazing had significant negative correlations with diversity within forest sites (r2 = 0.825, P < 0.05), whereas cultivation and tree cutting/logging had significant negative correlations with diversity of open savannas (r2 = 0.718, P < 0.05 and r2 = 0.999, P < 0.05, respectively). [source] Experimental investigation of laser power addition with composite four-mirror cavityLASER PHYSICS LETTERS, Issue 1 2007M. Lei Abstract Beam combination is an effective geometry which can improve laser output power with good beam quality. A new and practical four-mirror cavity configuration is presented to combine the beams intracavity. This close-ended scheme is good at withstanding environmental perturbations and is easier to realize the alignment than the conventional Michelson cavity. The length of each arm can be rather short which makes the cavity more compact in practical implement. With this four-mirror cavity, the output brightness is efficiently improved compared to single F-P cavity laser by combining two Nd:YAG lasers. A single beam output exceeding 3.3 W is achieved in this composite cavity, which has the potential for scaling to much higher output power with high brightness. (© 2007 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Biotic diachroneity during the Ordovician Radiation: evidence from South ChinaLETHAIA, Issue 3 2006Renbin Zhan The Ordovician radiation was one of the most marked and sustained increases in Phanerozoic biodiversification; nevertheless it occurred against a background of minimal global climatic and environmental perturbations. Detailed investigations of the Ordovician successions on the Yangtze Platform of the South China palaeoplate indicate that: (1) the brachiopod ,- and ,-diversity changes are diachronous; (2) macroevolutionary patterns were different across the South China palaeoplate, with the Early Ordovician brachiopod radiation first occurring in normal marine, shallow-water environments and then moving gradually to both nearer-shore and offshore locations; (3) the main contributors to the initial Ordovician brachiopod radiation were the Orthida and Pentamerida; the typical Ordovician brachiopod fauna, dominated by the Orthida and Strophomenida, did not appear until the late Mid Ordovician (Undulograptus austrodentatus Biozone) when the Strophomenida apparently replaced the dominant position of the Pentamerida within the fauna; (4) different ecotypes (e.g., sessile benthos, mobile benthos together with pelagic and planktonic organisms) demonstrate substantially different macroevolutionary patterns. The Ordovician brachiopod radiation of South China was apparently earlier than that suggested by global trends together with the data available from other palaeoplates or terranes, which may be related to its unique palaeogeographic position (peri-Gondwanan terrane gradually moving to equatorial latitudes). [source] Human influences on rates of phenotypic change in wild animal populationsMOLECULAR ECOLOGY, Issue 1 2008ANDREW P. HENDRY Abstract Human activities can expose populations to dramatic environmental perturbations, which may then precipitate adaptive phenotypic change. We ask whether or not phenotypic changes associated with human-disturbed (anthropogenic) contexts are greater than those associated with more ,natural' contexts. Our meta-analysis is based on more than 3000 rates of phenotypic change in 68 ,systems', each representing a given species in a particular geographical area. We find that rates of phenotypic change are greater in anthropogenic contexts than in natural contexts. This difference may be influenced by phenotypic plasticity , because it was evident for studies of wild-caught individuals (which integrate both genetic and plastic effects) but not for common-garden or quantitative genetic studies (which minimize plastic effects). We also find that phenotypic changes in response to disturbance can be remarkably abrupt, perhaps again because of plasticity. In short, humans are an important agent driving phenotypic change in contemporary populations. Although these changes sometimes have a genetic basis, our analyses suggest a particularly important contribution from phenotypic plasticity. [source] Comparative phylogeography of Ponto-Caspian mysid crustaceans: isolation and exchange among dynamic inland sea basinsMOLECULAR ECOLOGY, Issue 10 2006ASTA AUDZIJONYTE Abstract The distributions of many endemic Ponto-Caspian brackish-water taxa are subdivided among the Black, Azov and Caspian Sea basins and further among river estuaries. Of the two alternative views to explain the distributions, the relict school has claimed Tertiary fragmentation of the once contiguous range by emerging geographical and salinity barriers, whereas the immigration view has suggested recolonization of the westerly populations from the Caspian Sea after extirpation during Late Pleistocene environmental perturbations. A study of mitochondrial (COI) phylogeography of seven mysid crustacean taxa from the genera Limnomysis and Paramysis showed that both scenarios can be valid for different species. Four taxa had distinct lineages related to the major basin subdivision, but the lineage distributions and depths of divergence were not concordant. The data do not support a hypothesis of Late Miocene (10,5 Myr) vicariance; rather, range subdivisions and dispersal from and to the Caspian Sea seem to have occurred at different times throughout the Pleistocene. For example, in Paramysis lacustris each basin had an endemic clade 2,5% diverged from the others, whereas Paramysis kessleri from the southern Caspian and the western Black Sea were nearly identical. Species-specific ecological characteristics such as vagility and salinity tolerance seem to have played important roles in shaping the phylogeographic patterns. The mitochondrial data also suggested recent, human-mediated cryptic invasions of P. lacustris and Limnomysis benedeni from the Caspian to the Sea of Azov basin via the Volga-Don canal. Cryptic species-level subdivisions were recorded in populations attributed to Paramysis baeri, and possibly in P. lacustris. [source] Brief communication: Facial fluctuating asymmetry as a marker of sex differences of the response to phenotypic stressesAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Özener Abstract Fluctuating asymmetry (FA) is thought to increase as a result of environmental perturbations during development. A number of studies involving measures of health and developmental stability other than FA have discussed the presumed increased buffering in females relative to males. But, there is little evidence in the literature on FA to support this hypothesis. This research was conducted to determine the level of difference in terms of facial FA between sexes under different environmental conditions. Group 1 included final year students from three high schools in Yenimahalle, a slum district of Ankara (males: N = 163, mean age = 17.55, sd = 0.50; females: N = 141, mean age = 17.48, sd = 0.38). Group 2 included students with higher socioeconomic background and was composed of final year students from three different private schools located in Cankaya (N = 171, mean age = 17.44, sd = 0.26; females: N = 152, mean age = 17.38, sd = 0.31). Digital images were used to assess the degree of facial asymmetry as measured from eight paired traits and calculated as a composite score. The study shows that the male students had higher facial asymmetry than the female students. However, the present difference reaches a significant level in the low-socioeconomic status group. As a result, it could be inferred that differences in developmental stability between sexes might emerge under stressful conditions. Am J Phys Anthropol 143:321,324, 2010. © 2010 Wiley-Liss, Inc. [source] Demo-genetic analysis of a recovering population of otters in Central SwedenANIMAL CONSERVATION, Issue 6 2008M. Björklund Abstract We performed a demo-genetic population viability analysis on a recovering population of otters Lutra lutra in Central Sweden, using data on population size, survival and genetic data from microsatellites. Population data were obtained from genotyping faeces. At present, the size and genetic variability of the population is increasing. We found that survival to first reproduction was the most crucial demographic parameter, and that even slight changes downward in this parameter, might lead to a declining population trajectory. Human factors that can affect mortality are traffic, fishing equipment and traps, and we argue that efforts to minimize road kills by means of safe passages as well as careful fishing efforts in streams and lakes would reduce the risk of extinction. In general, even though the population is now growing and has no inbreeding problem, its small abundance could make it vulnerable to chance events and environmental perturbations. [source] The frequency and severity of catastrophic die-offs in vertebratesANIMAL CONSERVATION, Issue 2 2003David H. Reed Rare bouts of extreme environmental perturbations (catastrophes) have been predicted to have a major influence on the probability of extinction. Yet very little information is available on the frequency and severity of catastrophes. Improving the available information concerning catastrophe parameters would allow for an evaluation of their effect and a start towards understanding their causes. We used the Global Population Dynamics Database to determine the frequency and severity of die-offs in 88 species of vertebrates. We define a catastrophe as any 1-year decrease in population size of 50% or greater. The data yielded three findings. (1) The frequency of severe die-offs in vertebrate populations is strongly related to the generation length of the organism. (2) The probability of a severe die-off for a particular population is approximately 14% per generation. (3) The frequency of die-off severity can be modelled as a modified power function with the frequency of die-offs decreasing with increasing magnitude of effect. The distribution is not consistent with catastrophes stemming from environmental sources different than those responsible for smaller fluctuations, but seems to represent the tail of a continuous distribution of environmental perturbations. [source] Perturbation-independent community development in low-temperature anaerobic biological wastewater treatment bioreactorsBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010Pádhraig Madden Abstract The reproducibility and stability of low- temperature anaerobic wastewater treatment systems undergoing transient perturbations was investigated. Three identical anaerobic expanded granular sludge bed-based bioreactors were used to degrade a volatile fatty acid and glucose-based wastewater under sub-ambient (15°C) conditions. The effect of a variety of environmental perturbations on bioreactor performance was assessed by chemical oxygen demand removal. Temporal microbial community development was monitored by denaturation gradient gel electrophoresis (DGGE) of 16S rRNA genes extracted from sludge granules. Methanogenic activity was monitored using specific methanogenic activity assays. Bioreactor performance and microbial population dynamics were each well replicated between both experimental bioreactors and the control bioreactor prior to, and after the implementation of most of the applied perturbations. Gene fingerprinting data indicated that Methanosaeta sp. were the persistent, keystone members of the archaeal community, and likely were pivotal for the physical stability and maintenance of the granular biofilms. Cluster analyses of DGGE data suggested that temporal shifts in microbial community structure were predominantly independent of the applied perturbations. Biotechnol. Bioeng. 2010;105: 79,87. © 2009 Wiley Periodicals, Inc. [source] DNA Microarrays: Experimental Issues, Data Analysis, and Application to Bacterial SystemsBIOTECHNOLOGY PROGRESS, Issue 5 2004Yandi Dharmadi DNA microarrays are currently used to study the transcriptional response of many organisms to genetic and environmental perturbations. Although there is much room for improvement of this technology, its potential has been clearly demonstrated in the past 5 years. The general consensus is that the bottleneck is now located in the processing and analysis of transcriptome data and its use for purposes other than the quantification of changes in gene expression levels. In this article we discuss technological aspects of DNA microarrays, statistical and biological issues pertinent to the design of microarray experiments, and statistical tools for microarray data analysis. A review on applications of DNA microarrays in the study of bacterial systems is presented. Special attention is given to studies in the following areas: (1) bacterial response to environmental changes; (2) gene identification, genome organization, and transcriptional regulation; and (3) genetic and metabolic engineering. Soon, the use of DNA microarray technologies in conjunction with other genome/system-wide analyses (e.g., proteomics, metabolomics, fluxomics, phenomics, etc.) will provide a better assessment of genotype-phenotype relationships in bacteria, which serve as a basis for understanding similar processes in more complex organisms. [source] | |||||||||||||||||||||||||||||||