Том 6, № 5 (2016)

Polyvariant ontogeny (PVO) gets a visual expression in the life cycle graphs (LCGs) for Calamagrostis woodreeds as a variety of pathways for individual plants to develop through many of their states, which are distinguishable by the ontogenetic stage and chronological age (in years). PVO is recognized as the basic mechanism of adaptation in local populations of grasses to their environments, while a quantitative measure of adaptation is found by constructing a matrix model for the double-structured population, calibrating its matrix of vital rates from empirical data, and calculating the dominant eigenvalue λ₁. This approach encounters an obstacle typical for grasses: while the rates of aging and ontogenetic transitions can be determined from field data mainly by the morphology of aboveground parts of the plant, the rates of vegetative propagation can be reliably determined only from digging up the belowground rhizome system, i.e., by destroying the sample plot (“reproductive uncertainty”). Therefore, the former (nondestructive) calibrations of matrix models were, to an extent, subjective, resulting in correspondingly subjective estimations. A novel method to overcome the reproductive uncertainty makes use of the maximization hypothesis: the uncertain rates are such that λ₁ attains its maximal possible value under the given conditions. To test the hypothesis, we have conducted a field study by a new technique with a model species, the woodreed Calamagrostis epigeios (L.) Roth, which vegetatively reproduces in a meadow phytocenosis and a spruce forest clearance. Excavating the whole system of ramets with their rhizomes and analyzing the parent–offspring links in laboratory, we have gained (in addition to the former data on the local population structures and ontogenetic transitions) a new kind of data to calculate the status-specific rates of reproduction. The novel calibration method has enabled us to find an exact range of λ₁ values, i.e., the true quantitative bounds of adaptation for a given local population. Obtained under the reproductive uncertainty and maximality hypothesis, the values of λ₁ have turned out to be close to the upper bounds of the ranges, thus verifying the hypothesis. The study has discovered some generative subsidiary plants that sprout from the rhizomes of maternal ramets without entering the virginal stage. As a result, the LCG is enriched with new reproductive pathways, and there are new (not yet published) situations, in which λ₁ fails in its accuracy as a measuring tool of comparative plant demography. We propose a general method to adjust the adaptation measure in this kind of situation.

Reciprocal transplantations of turf pieces have been conducted in alpine plant communities of the northwestern Caucasus. The changes in floristic richness and successional rates have been registered for 25 years. The study objects were plant communities located in a toposequence from ridges to deep depressions along the gradients of an increase in the snow cover thickness and a decrease in the growth season: alpine lichen heaths (ALHs), Festuca varia grasslands (FVGs), Geranium–Hedysarum meadows (GHMs), and snow bed communities (SBCs). The results of the study confirm the hypothesis about the approach of the floristic richness of transplanted pieces to that of the background acceptor community. It is shown that variability reduces during succession if turf pieces from different communities are transplanted into a common community. In particular, this is obvious in the case of SBCs, where the floristic richness of turf pieces transplanted from ALHs and GHMs has been noticeably reduced. The results also show that the more different are the donor and acceptor communities, the higher is the rate of their changing. However, the assumption of a higher succession rate in more productive communities has not been confirmed. On the contrary, the communities with initially low productivity changed more rapidly than those with high productivity. It is found that turf pieces transplanted to upper plots of the toposequence have a higher rate of alteration in comparison with those transplanted to lower plots, which may be related to the longer growth season, which indicates a more prolonged period of high functional activity, and, hence, more time for the effects of competition, seed transfer, etc. In general, the rate of succession decreases as the time since the moment of transplantation increases, especially in communities with low productivity.

A new modification of the previously designed individual-based simulation model of population dynamics of a mass pelagic species, Daphnia longispina is presented. The model describes a population as an ordered list of individuals with specific sets of traits. For each individual, its energy traits are calculated, and the probabilities of different outcomes are assigned or calculated for various life situations. This variant significantly differs from the previous chemosignal blocks that modify Daphnia behavior. After receiving a chemical signal (predator kairomones or sex pheromones), adult Daphnia of the model population can avoid predation with a certain probability by diel vertical migrations and can increase the efficiency of sexual reproduction through the active search for a sexual partner. Simulation experiments in which the ability to detect different chemical signals was excluded, sequentially or in combination, were used to investigate the role of chemoreception in the population dynamics and the seasonal adaptations of planktonic crustaceans. For the first time, a quantitative estimate for the role of such information has been obtained as the ratio between the annual production levels of model populations that possess or lack the ability to perceive chemical signals of predators and mating partners. According to the present version of the model, chemoreception increased the annual production of the model population by 1.5 times. Thus, biological information is a significant factor enabling individual hydrobiont populations to fine-tune their adaptations to the particular environmental conditions of a given aquatic habitat.

Geese (Anser) and brants (Branta) are important elements of Arctic ecosystems, which attract the interest of biologists around the world. Due to this interest, a great amount of empirical data has been accumulated, including detailed descriptions of the morphology, nesting characteristics, trophic ecology, behavior, migrations, population geography, and other features of Arctic geese and brants. The extent of their range along the Arctic coast of Eurasia largely depends on population size. Therefore, all of the factors influencing population size also indirectly affect the range extent. Geese and brants species significantly differ in population size, range extent, and tendencies in their changes over time. We compared the available data in order to find out what, in which way, and to what extent determines the population size and range extent in geese and brants. The main contribution to a reduction in population size is made by extermination at nesting sites and along the flyways and the lack of food at overwintering sites. The species that do not use cultivated plants in winter are small population size. The next most significant factor is the feeding type, which is determined by body size and the ratio between beak length and head length. The population size is influenced much less by all other factors related to patterns of feeding and nesting. The absence of a significant effect of these characteristics on the population size and range of geese and brants may be interpreted as the result of anthropogenic impact, which does not yet seem to be able to be estimated quantitatively. The disappearance of geese and brants within considerable areas in the Arctic Region may cause serious ecological consequences.