A mathematical model is presented to explain the spatial distribution of animal populations which is principally controlled by the environmental conditions. A dynamical equation for the spatial movement of animals in such systems is formulated on an assumption that their movement is under influence of the following fundamental forces : 1) the dispersive force which is associated with random movement of animals in the space ; 2)the attractive force which induces directed movements of animals toward favorable environments;3) population pressure due to interferences between individual animals. By applying this analysis to the population system with discrete spatial changes of the environmental conditions, a distribution function is derived and it is shown that the result becomes equivalent to the Morisita's equation formulated in his theory of "enviornmental density". The analysis is further extended to the population system with continuously changing environmental condition and the stationary density distribution is analytically obtained. By taking advantage of some specific features of the equation, an experimental procedure to estimate the kinetic parameters associated with the postulated fundamental forces is discussed.
This study focuses on the germination of dandelions as the first step in their life cycle and shows the characteristics of the germination pattern in some dandelion species through a field survey and germination experiments. The introduced dandelions T.laerigatum and T.officinale have a synchronous nature in germination. On the other hand, seed populations of T.platycarpum are heterogenous in germination behaviour, and the seed germination in this dandelion is suppressed by the high summer temperature in Tokyo. The germination period in this dandelion is, therefore, divided into two seasons, carly summer and autumn. This two-season germination pattern is discussed from the viewpoint of adaptive strategies for the establishment of this dandelion species.
Small-sized experimental instruments bearing filtered and unfiltered-air growth chambers(named Bryometer), in which gemmae of Marchantia polymorpha were cultivated replicating four times, were located at nine sites around Kashima industrial district. At the same site, rain was collected for six times, then measured on pH and electric conductivity. The degree of phytotoxicity of air was expressed by growth ratio(unfiltered/filtered chamber)in percentage. On four pollutants(SO_2,oxidant, NO, NO_2), mean values of daily maximum concentration and their total values were calculated about experimental periods. The degree of phytotoxicity of air was severe on the leeward of pollution sources(the smallest growth ratio : 78%), where total value was large simultaneously. It was not contradictory to the result measured on precipitation. By employing Bryometer in this way, it is easy to estimate the degree of phytotoxicity of air in practice.
The effect of nitrogen addition on the pattern of nitrogen utilization by buckwheat plants is analyzed by using the concept of nitrogen utility(N.U., ratio of the net dry matter production to the amount of nitrogen uptake). The N.U. changes in inverse relation to the nitrogen availability in the environment. The increase of N.U. with the lowered availability of nitrogen is ascribed mainly to the dilution effects nitrogen limitation on the plant growth ; that is, an efficient nitrogen utilization and a reduced physiological activity resulting from the lowered concentration of nitrogen in the plant.
Field observations of free-ranging Japanese monkeys were made at a feeding ground for three years from the sixth month after the beginning of provisionment(June, 1972 to September, 1974). In a provisioned troop, several social alterations occurred as feeding continued : except for a leader male, adult males gradually began to avoid the feeding ground, the dominance order among adult females changed drastically and then stabilized progressively, and antagonisticinteractions between adult females after their individual childbirths increased in frequency. These effects, probably due to provisioning, indicate that the social organization of non-provisioned troops is not identical with that of provisioned ones, which are the ones described and analyzed by many authors.
A study was made on five species cellular slime mold-Dictyostelium mucoroides BREFELD, D. purpureum OLIVE, D. discoideum RAPER, Polysphondylium pallidum OLIVE and P. violaceum BREFELD-in the forest soil in the Tenryu Valley, Central Japan. D. mucoroides was the species to occur most frequently throughout the year ; next was P. pallidum, to be followed by D. purpreum and P. violaceum ; D. discoideum occurred least frequently of the five. D. mucoroides occurred most frequently in winter, about fifty percent over other seasons. D. purpreum showed the highest frequency in autumn and the lowest in summer, while P.pallidum showed the frequency as high as D. mucoroides in spring and autumn, but lower one in winter and summer. P. violaceum was most frequent in autumn and least in winter. On the average, cellular slime molds of five species showed an increase in autumn and spring, and a decrease in winter and summer.
Tool use of a Japanese ant (Aphaenogaster famelica) was observed. This behavior is innate and consists of two components, putting some tools on the more or less liquid food and carrying tools adhered with food to the nests. As the worker can carry more food by tools than by direct transport at one time, the tool-using behavior gives the species an important survival value. In the present paper the construction, mechanism and function of the tool use were analyzed through both field observation and laboratory experiment.
To examine seasonal change of species diversity, several species diversity indices are calculated, in phototactic coleopterous community on Mt. Iwawaki, Osaka. Average species diversity (H') and relative species diversity (e^H'/S) both in sample, and their expectations in population (E(H'/N) and e^<E (H'/N>/Q) are compared to each other. Average species diversity is divided into two factors, viz, "species richness" measured by S in sample and Q in populations, and "equitability" measured by their relative diversity indices. In connection with the method estimating the total number of species in biological universe (Q), a problem employing "Preston' s lognormal distribution model "on number of species and number of indiviauals in population is discussed. It is suggested that the estimated values of Q lead to noticeable error in some times. It seems to be more practical to use the sample values obtained by standardization of sampling method, comparing with the population values estimated by the model.