Vol 8, No 5 (2018)

The Cretaceous–Cenozoic history of angiosperms resulted in a certain character of the distribution of the number of taxa belonging to different ranks (number of species and genera within a family, S/G ratio in families, and the number of species within a genus). In most cases, such distributions are satisfactorily described by a power law (a Pareto distribution). In logarithmic coordinates, the power function represents a straight line. Empirical curves coincide with this line fairly well, except for the right part of the graphs (the area of small-sized taxa), where empirical curves noticeably deviate from theoretical ones. This fact means that the volumes of small-sized taxa should be significantly larger to fit the theoretical curves properly. The performed modeling of the S/G ratio in families has shown a satisfactory correspondence between the observed and calculated number of species within a wide iteration range only when the dynamic factor of extinction was applied. An assumption has been made that a differentiated extinction of species took place in the course angiosperm evolution. In this case, the extinction rate should be minimal for genera with a large number of species. On the contrary, a decrease in the number of species per a genus may drastically (by orders) increase the extinction rate. As a result, large-sized genera become larger in size, while small-sized genera become smaller; the frequency distribution of species within genera changes according to the power law. The initial divergence in the number of taxa, which determines their further division into larger and smaller sizes, could be caused by the emergence and expansion of herbs characterized by better functional and adaptive potential.

The role of interspecies competition in the structuring of plant communities remains unclear. The purpose of our study was to test the assumption that the relationship between the degree of numerical dominance (DD) and local species richness may differ in plant communities with high and low interspecies competition intensity. The stands and open communities of the river shoals of the Western Caucasus were used as the object of research. The former were regarded as communities with a high intensity of interspecies competition, the latter were seen as communities structured mainly by the processes of species settlement. The results showed that the average DD values ​​are similar in the areas of these communities having an equal amplitude of variation in the number of individuals (shoots) and the size of the actual (cenotic) species pool. In the stands and communities of shallows there is a negative correlation between DD and species richness, which in both cases is a consequence of a reduction in dominants of the amount of resources and/or space available for other species. At the same time, we did not find any signs of other mechanisms that would be specific for stands or communities of shallows. However, the characteristics of communities with high and low intensity of interspecies competition can be manifested more strongly if we compare the ratio between DD and species richness in relatively large areas.

We have composed a “scale of ontogenesis,” i.e., the sequence of ontogenetic stages, and the life cycle graph (LCG) for Androsace albana, a monocarpic plant species that is considered a short-lived perennial, according to annual observations on permanent sample plots in an alpine lichen heath during the 2009–2016 period. There is only one reproduction event in the LCG, which eliminates any reproductive uncertainty from the data of “identified individuals” type so typical for the former projects with polycarpic species, while the monocarpic cycle excludes any returns from the generative stage to a non-flowering status. The LCG describes the ontogeny through five successive stages: seedlings, juvenile, immature, adult virginal, and generative plants, the generative plants perishing after they have flowered and produced seeds. We have constructed a matrix model of the stage-structured population that corresponds to the LCG; its calibration has reduced to calculating the vital rates directly from the data of one time step, i.e., from the censuses at two successive years of observation. Therefore, the nonautonomous model represents a set of 7 annual matrices, each giving a quantitative measure of how the local population is adapted to its environment as the dominant eigenvalue of the model matrix. Its variations have turned out quite significant from year to year, signifying either a growth or decline of the local population and, in general, its vulnerability to stress factors of the environment. Averaging the annual matrices geometrically over the whole observation period has revealed the tendency to decline and enabled us to extract certain age-specific traits (in years) from the stage-structured model using the technique of virtual absorbing Markov chains and their fundamental matrices. The mean life expectancy at various stages of the A. albana ontogeny has turned out maximal in the adult virginal plants, while the mean age at flowering equal to 13 years has exceeded the horizon of the observation time series, thus proving the technique to be efficient. The model indicates that A. albana plants spend most of their life spans as virginal adults, which characterizes the space holder strategy by Körner (2003), or the delayed-development strategy by Zhukova (1995). The model outcome gives another evidence that the A. albana population is endangered.

This review considers the role that immune inflammatory responses (IIRs) play in tumor development and progression. Intratumoral IIR heterogeneity is presumably due to simultaneous differentiation and activation of certain T helper (Th) subpopulations and macrophages in various loci of the tumor, their phenotypic plasticity, and their antagonism of Th1 and Th2 responses. Evidence is provided to demonstrate that the IIR type in the tumor microenvironment determines the probability of the epithelial–mesenchymal transition (EMT), the emergence of invasive properties in tumor cells, the formation of tumor and premetastatic niches, and chemosensitivity. It is hypothesized that the effect of IIRs on tumor cells depends on the IIR type, which determines the cell and cytokine spectrum in the tumor microenvironment, rather than on the efficiency of specific immune responses to tumor antigens. Lastly, it is assumed that more efficient targets for IIR guidance are not provided by single molecules, but rather by the signaling pathways that can permanently prevent the Th2-type IIRs or suppress inflammatory reactions in the tumor.