共找到 20 条结果
Under brief consideration is the uses of presumptions, as a kind of a priori judgments, in phylogenetics in light of their critics by Pesenko (2005). It is shown that the concept of presumption is fully compatible with the hypothetic-deductive argumentation scheme allowing to realize the parsimony principle in its epistemic interpretation. System of phylogenetic presumptions deserves future development in the framework of construing phylogenetics as a kind of the informal axiomatics.
Under brief consideration is the problem of primary or secondary status of the judgments about taxa relative to the judgments about characters in the biological classifications. The following formal definition of taxonomic system (classification) TS is provided: TS = BT[T, C(t), R(t), R(c), R(tc)], where BT is a biological theory constituting content-wise background of the system, T is a set of taxa, C(t) is a set of taxonomic characters, R(t) is a set of relationships among taxa (similarity, kinship, etc.), R(c) is a set of relationships among characters (homology, etc.), and R(tc) is a set of correspondences among taxa and characters. The latter correspondences may be complete or incomplete. At ontological level, there two basical traditions exist in biological systematics regarding R(tc) according to which the biological diversity is patterned either as a set of groups of organisms (taxa) or as a set of their properties (characters). In the first case, taxon is "primary" relative to character (in cladistics); in its opposite, character is "primary" relative to taxon (in scholasticism, classical typology, classical phylogenetics). At epistemological level, incompleteness of the taxon-character correspondence makes classificatory procedure iterative and taxonomic diagnoses context-dependent. The interative nature of classificatory procedure makes the "primary" or "secondary" status of both taxa and characters relative and alternating. This makes it necessary to introduces a kind of uncertainty relation in biological systematics which means impossibility of simultaneous definition of both extensional and intentional parameters of the taxonomic system at each step of classificatory iterations.
The use of differential statistics to test for treatment effect with data from experiments where either treatments were not replicated (though samples may be) or replicates are not statistically independent leads to serious methodological problem. This problem, discovered by Hurbert (1984), is called pseudoreplication. Due to unknown reasons, pseudoreplication issue was completely overlooked by the Russian ecologists, in spite of the fact that the international scientific community is aware of pseudoreplication for almost twenty years. As the result, up to 47% of the experimental ecological papers, published in six Russian academic journals (Botanicheskij zhurnal, Ekologia, Izvestija RAN Ser. Biol., Lesovedenie, Zhurnal Obshchei Biologii, Zooligicheskij zhurnal) in 1998-2001, are pseudoreplicated; this proportion is nearly twice as high as the proportion of pseudoreplicated studies in international journals during 1960-1980, e.g. before the problem was discovered by Hurlbert (1984). This situation is alarming, especially because a substantial part of pseudoreplication arise from incorrect use of statistics, not from incorrect designing of experiments. By using several examples from the recent papers of Russian ecologists I shortly review the situations where pseudoreplication may occur and discuss some aspects of the experimental design, which are critical for correct processing and interpretation of ecological data.
The problem of continuality versus discreteness of vegetation cover ("biocoenotic cover"--more generally) was the object of heated debates for at least hundred years. The ideas of continuality have been spread in the USSR in the 1970-80s but later the adherents of other approach, that focused on the discreteness of vegetation became more active. The author discussed the views of one of them, A.I. Kafanov (2005), published recently in "Zhurnal Obshchei Biologii". It is claimed that pluralistic approach that is characteristic for present ecology makes unnecessary the search for universal law of relationship between continuum and discreteness of biocoenotic cover. This relationship depends on the particular character of biocoenotic cover and the scale of study.
Using successional system of Stachyo sylvaticae-Tilietum cordatae association as a case study, the possibilities are considered of applying syntaxonomy as developed on the basis of floristic classification principles. Characteristics of restorative successions on cut-over lands have been analysed at strong and weak disturbance of soil cover as well as in plantings of coenotically weak species Pinus sylvestris and coenotically strong species Picea obovata. High self-restoring potential of the association studied is emphasised.
Developmental processes of cnidarians, the basal metazoan representatives, possess extremely high regulative ability. It is known that any isolated fragment of the freshwater polyp hydra's body can regenerate an intact animal. Moreover, in many cnidarian species, suspension of single dissociated cells can form aggregates, which regenerate normal body plan of polyp or medusa. This process can be considered as an extreme case of regeneration. The development of cell reaggregates of Hydra is a conventional experimental system to study the physical basis of morphogenesis. Investigations of the cnidarians' reaggregate development help to clarify basic rules and mechanisms of the metazoan body plan formation and the role of self-organization in the metazoan early development. In this review, we summarize the data revealed by dissociation - reaggregation experiments performed on the representatives of different cnidarian taxa. We also analyze the data on the morphogenetic and molecular basis of the reaggregate development from randomly organized group of cells to cnidarian-specific body plan.
Starting from 2009, monitoring studies of swamp regimes have been conducted at the swampland station located in the north-eastern Altai. Here, we present the results of biological activity (indices of microorganisms abundance, respirometric indicator, catalase activity) in peat deposits of eutrophic (Turochak) and mesotrophic (Kutyushskoye) swamps during 2012-2013 vegetation periods with different levels of marsh water and oxidation-reduction conditions.
Data are presented on the dynamics of phytomass and primary production of the undershrub-sphagnum bog. Comparison of productivity parameters in sites with unimpaired and bumt-out vegetation is used as a method of analysis of the phytocenosis functioning during its 6-year recovery after a fire. Net primary production varied from 4.9 to 9.6 tons/ha • yr in the unimpaired bog site and from 5.3 to 15.1 tons/ha • yr in the burnt-out one. By the end of the fifth year of recovery, the phytocenosis fully compensated the loss of carbon due to the fire, mainly at the expense of roots production. Recurrent fires have a result of more profound changes in phytomass structure and reduction of primary production.
New analytical method is used to estimate hydrodynamic forces produced by dolphin's flukes. A mathematical model is proposed that describes dolphin's flukes as a flat rigid rectangular wing whose pitch axis location varies, heaving and pitching amplitudes are sufficiently large, and the phase angle shift for the combined oscillations can change arbitrarily. The dolphin's flukes kinematic parameters are obtained and used to estimate hydrodynamic forces.
Processed are 57596 dated series of tree-rings width (TRW ) from the International Tree-ring Data Bank. The results obtained indicate that: 1. The TRW is strongly correlated with tree age. Periods of cambium activity are strictly dependent on the age of the trees. Therefore, there is a strong correlation between TRW and periods of radial growth. It is suggested that synchronization of the periods of radial growth in the first 150 years of trees life with cycles of climatic factors leads to increase in TRW . 2. Satisfactory coincidence between latitudinal profiles of TRW , on the one hand, and climatic and biological indicators, on the other hand, is observed. Latitudinal profile of TRW gets its form under the influence of climate and assimilating mass productivity. 3. Latitudinal change of the TRW in the Cretaceous had a pronounced displacement of a maximum from equator toward 30 °NL. Growth gain of Cretaceous gymnosperms was about twice higher than that of modern trees. Such asymmetry of paleolatitudinal profile of TRW sharply distinguishes it from modern latitudinal profiles that follow climatic parameters.
Considered are the interactions within food chains that allow to refine the mechanisms of selective prey taking, which is important for better understanding of the evolutionary role of predation. By use of greyhounds, the hunting by wild canids is modelled for the purpose of repeated reproduction of searching for, chasing, and taking off the prey. It is found out that parameters of chasing (i.e., speed, distance, duration) are important for hunting but not determinative. There can be a high actual selectivity determined by prey conditions and, at the same time, low success of chasing. The mechanisms of recognition of potential prey availability or unavailability are analyzed. The data are presented that indicate that superficial microflora can be considered as a common marker of various, deviations in the state of a prey. Unlike stabilizing selection, which preserves separate traits, selection by predation stabilizes the phenotype as a whole.
The sectional model of system dynamics of regular branches of a tree together, with submodels for initial growth inhibition and inter-verticil branches, has been extended to the range (0, 3) of fractal parameter ц that connects green biomass and a spruce size, В ~ H µ . It is shown that spruce branches of first three orders appear in the subrange of µ (0, 1). Branches of the first order appear at µ ≈ 0.25. Inter-verticil branches appear at µ ≈ 1.4, which may be viewed as a means of spruce adaptation to unstable lighting conditions. The presence of green biomass at µ < 1.0 indicates that it can be represented as a set of photosynthesizing points (hypothetical cyanobacteria) placed in space. Therefore, the fractal properties of the set of points on the line segment have been considered as a model. It is shown that the condition µ < 1.0 can be fulfilled only if the points are arranged in groups. At that, µ is practically independent of groups alignment while depends on the number of groups and the number and type of points distribution within groups. Based on these fractal properties of points alignment within groups along the segment, and the hypothesis of trophic nature of organelles symbio-genesis in eukaryotic cells, an idea of a two-stage mechanism of proto-plants emergence was formulated. The mechanism is manifested through the motion along the trajectory of endosymbiosis, beginning with a fixed number of points in the group and then with an increase in the number of groups, until, in course of evolution, the host of endosymbiosis would create an infrastructure for the supply and inter-group interaction of cyanobacteria. At this stage, µ decreases from 1 to ≈ 0.25. When the infrastructure is created and it becomes possible to increase the number of points in the group, the motion along the trajectory occurs through doubling the number of cyanobacteria in a group. At this stage, µ value increases to 1. At the first stage, motion along such a composite trajectory results in slow growth of the photosynthetic system size, even with an exponential increase in the number of cyanobacteria groups. The size grows rapidly at the second stage, after the limitations on growth of cyanobacteria number within groups are taken off. It should be noted that such an initial growth inhibition occurs also in modern trees, and is reflected in the initial slow increase in the number of the orders of tree's branches.
暂无摘要（点击查看详情）
Using long-term direct observations in a Polytrichum-Myrtillus pine forest, we have constructed and verified a homogeneous Markov chain model for two dominant species (Vaccinium myrtillus and V. vitis-idaed) at the late stages of succession. The sampling design features a large sample size (2000 quadrats) on permanent transects, several re-examinations with the interval of 5 years, and the use of species rooted frequency. As a model of the process under concern, the discrete Markov chain accounts for the following four states: both species being absent on the quadrat, one of them being present alone, and the joint presence of the both; the model time step coincides with the time interval between observations. The model is calibrated on the data of two successive examinations and verified on that of one more examination. All possible transitions between the states are revealed to realize in quadrats for one time interval, as well as the absence of transitions at each state, which results in the complete digraph (directed graph) of transitions. Major model results are obtained by the formulae of finite Markov chain theory: the steady-state square distribution, cyclicity characteristics, and the mean durations of stages in the fine-scale dynamics. As a steady-state (stable) outcome of succession, the distribution among quadrats is expected where 30% of quadrats are occupied by V. myrtillus alone, 11% by V. vitis-idaea alone, both species are present on 18% of quadrats, and 41% of quadrats are 'empty'. This demonstrates a possibility for V. myrtillus and V. vitis-idaea to coexist stably at the latest stages of succession, with the clear predominance of V. myrtillus, yet without competitive exclusion. The quantitative characteristics of cyclicity and the durations of stages in the fine-scale dynamics enable us to estimate the total duration of secondary post-fire succession as about 45 years (to reach a distribution of states that differs less than 5% from the steady-state one). Out of the four states specified, the quadrats with V. vitis-idaea alone persist for the least time (8 years) on the average, while 'empty' ones persist for the greatest time (18 years). Forecasting the dynamics for one model time step forward and comparing the forecast with the real square distribution have revealed the measure of difference to be 5.4%. This illustrates the efficiency of the (time-)homogeneous Markov chain as a short-term forecast tool, yet leaves open the question whether the homogeneity hypothesis be true in the longer term.
A stochastic model of migrations on a lattice and with discrete time is considered. It is assumed that space is homogenous with respect to its properties and during one time step every individual (independently of local population numbers) can migrate to nearest nodes of lattice with equal probabilities. It is also assumed that population size remains constant during certain time interval of computer experiments. The following variants of estimation of encounter rate between individuals are considered: when for the fixed time moments every individual in every node of lattice interacts with all other individuals in the node; when individuals can stay in nodes independently, or can be involved in groups in two, three or four individuals. For each variant of interactions between individuals, average value (with respect to space and time) is computed for various values of population size. The samples obtained were compared with respective functions of classic models of isolated population dynamics: Verhulst model, Gompertz model, Svirezhev model, and theta-logistic model. Parameters of functions were calculated with least square method. Analyses of deviations were performed using Kolmogorov-Smirnov test, Lilliefors test, Shapiro-Wilk test, and other statistical tests. It is shown that from traditional point of view there are no correspondence between the encounter rate and functions describing effects of self-regulatory mechanisms on population dynamics. Best fitting of samples was obtained with Verhulst and theta-logistic models when using the dataset resulted from the situation when every individual in the node interacts with all other individuals.
The refined Markov model of cyclic zoogenic successions caused by beaver (Castor fiber L.) life activity represents a discrete chain of the following six states: flooded forest, swamped forest, pond, grassy swamp, shrubby swamp, and wet forest, which correspond to certain stages of succession. Those stages are defined, and a conceptual scheme of probable transitions between them for one time step is constructed from the knowledge of beaver behaviour in small river floodplains of "Bryanskii Les" Reserve. We calibrated the corresponding matrix of transition probabilities according to the optimization principle: minimizing differences between the model outcome and reality; the model generates a distribution of relative areas corresponding to the stages of succession, that has to be compared to those gained from case studies in the Reserve during 2002-2006. The time step is chosen to equal 2 years, and the first-step data in the sum of differences are given various weights, w (between 0 and 1). The value of w = 0.2 is selected due to its optimality and for some additional reasons. By the formulae of finite homogeneous Markov chain theory, we obtained the main results of the calibrated model, namely, a steady-state distribution of stage areas, indexes of cyclicity, and the mean durations (M(j)) of succession stages. The results of calibration give an objective quantitative nature to the expert knowledge of the course of succession and get a proper interpretation. The 2010 data, which are not involved in the calibration procedure, enabled assessing the quality of prediction by the homogeneous model in short-term (from the 2006 situation): the error of model area distribution relative to the distribution observed in 2010 falls into the range of 9-17%, the best prognosis being given by the least optimal matrices (rejected values of w). This indicates a formally heterogeneous nature of succession processes in time. Thus, the refined version of the homogeneous Markov chain has not eliminated all the contradictions between the model results and expert knowledge, which suggests a further model development towards a "logically inhomogeneous" version or/and refusal to postulate the Markov property in the conceptual scheme of succession.
Epigenetic phenomena are defined as morpho-physiological changes not related to impairments of DNA sequence. The results of our study indicate that a pulsed non-mutagenic thermal stress inflicted on developing ova (pro-embryos) gives rise to positive transgenerational epigenetic changes in the life span of offspring. At that, this effect depends on heterozygosity by lgl-mutation inherited from mothers. In generation Fl, determination of higher survival trait occurs even at early stages of oogenesis. The most pronounced effect is observed when heating is applied to the cells at the earliest stages of pro-embryo development. This study is the first experimental work on modeling the transgenerational aftereffects of pre-zygotic (pro-embryo) stress on offspring survivability and longevity when tumor suppressor lgl is operating. The significance of the results with regard to human epigenetics is discussed.
An ecological scenario is proposed for the origin of causative agent of the plague (the bacterium Yersenia pestis) from the clone of pseudotuberculous microbe of the first serotype Y. pseudotuberculosis O:1b. Disclosed are the conditions of gradual intrusion of psychrophile saprozoonosis ancestor into the blood of the primary host, Mongolian tarbagan marmot Marmota sibirica. As an inductor of speciation acted the Sartan cooling that occurred in the end of late Pleistocene under conditions of arid ultra-continental climate in Central Asia. Soil freezing down to the level of hibernating chambers in marmot burrows initiated the transition of marmot flea, Oropsylla silantiewi, larvae to optional hemophagy on the mucous coat inside the mouth cavity of sleeping marmots. In its turn, this promoted the conditions of mass traumatic intrusion of Y pseudotuberculosis into marmots bloodstream from faecal particles getting in their mouth cavity in course of building up a plug in a burrow for hibernating. In marmot populations, the selection of bacteria underwent under conditions of heterothermy with repeated changes of hibernating marmots body temperature within the range of 5-37 degrees C (torpor-euthermy). During the warm season, when pseudotuberculous microbes are totally eliminated from the bloodstream of healthy marmots with body temperature about 37 degrees C, bacteria could survive in fleas' digestive tract in the form of biofilm developing in proventriculus as a so called blockage. Final isolation between ancestral and daughter species was helped by the development of intrapopulation antagonism related with the beginning of full-scale synthesis of bacteriocin pesticin. Population-genetic processes in the "marmot-flea" system have led to a macroevolutionary event, that is, to passage of bacteria in a new ecological niche and adaptive zone that are principally different from those of the ancestor. All the present intraspecies forms of Y. pestis that appeared due to microevolution, have originated with the subspecies Y. pestis tarbagani that has formed in Central Asia during the Sartan cooling.
The problem of species and speciation is considered using as a model the cryptic species of rodents inhabiting the Caucasus, the mountain chain with prominent altitude environmental gradient and insular pattern of mountain habitats. These circumstances open additional possibilities for the choice of species conception (biological or phylogenetic), exploration of ancestry pathways (sympatric or allopatric speciation) of model cryptic species groups, and testing the 'refuge' hypothesis. As model species, sibling-species Sicista from the group 'caucasica' (a group of unstriped birch mice) and representatives of the vole subspecies Terricola (Microtus, Arvicolinae) were used. Based on the new data on karyology, nucleotide sequences of mitochondrial gene cytb, multivariate statistical analysis of odontologic traits, and biogeography of sibling-species Sicista from the group 'caucasica' and voles from subspecies Terricola (Microtus, Arvicolinae), their evolutionary history is reconstructed and applicable species concepts are examined. For the present sibling-species Sicista from the group 'caucasica' the allopatric dispersion is typical, which agrees with the hypothesis of speciation in refuges. The sympatry of Terricola sibling-species in the Caucasus is considered as being secondary, and their phenotypic likeness--as an adaptation to similar environmental conditions. Affirmed coexistence of sibling-species Microtus (Terricola) majori and Microtus (Terricola) daghestanicus in the Caucasus (without their hybridization) supports the biological conception of species. The existence of Sicista allospecies from the group of Caucasian unstriped birch mice is best conformed to the phylogenetic conception. However, the high level of chromosomal differences between sibling-species and, in particular, between extreme variants of common evolutionary line (Sicista kazbegica, Sicista kluchorica) does not contradict the biological conception of species.
Betula pendula and B. pubescens are widespread species inhabiting the forest zone of Russia. At the same time, they are closely related species making up transitional forms. It is believed that their ecological ranges are overlapping to a great extent, although B. pubescens is more hydrophilic than B. pendula and less exigent to sunlight. These data, obtained by means of empirical observations, help to understand the ecology of both birch species but so far are not statistically proved. An analysis of habitat distribution of the two birch species is carried out, and a comparison is performed of their ecological relations with such factors as humidification, trophic status, acidity, illumination, and nitrogen soil richness (graded by D. Tzyganov scales). It is shown that B. pendula and B. pubescens differ significantly with relation to humidification, soil richness, nitrogen concentration, and illumination, while do not differ with relation to acidity. Habitat preferences indicate that B. pubescens is more eurytopic species than B. pendula. Although synecolog-ical ranges of both species overlap, their synecological optima still clearly stand apart.