Few studies have addressed the movements of animals as a source of various kinds of encounters, a proportion of which lead to interaction of individuals. The author proposed the trail density of an animal group as density × mean speed. Compared to density, the trail density is a more direct parameter of, for example, activity, density effect and encounter frequency. The frequency of encountering each resource consists of a proper denominator to estimate the selectivity of resource use by animals. A simple method for estimating trail density is to count the number of animals visiting an area or a trap. The distribution range of the trail of an individual is a unit area of encounter and interaction. An animal group consisting of widely moving individuals tends to have a less concentrated trail density and can enjoy high selectivity of many kinds of resources. The distribution pattern of trail density, decided by the mode of animal movement, creates several structures within a community.
This report presents a general model that shows the processes of warming effects on snow patch vegetation. Snowmelt and soil temperature modeling are mainly discussed. Influences of climatic change on snow patch vegetation will be reported later. We made a micrometeorological model to calculate snowmelt and subsequent soil temperature evolution. The model was used to calculate the spatial difference of snowmelt and the rise in soil temperature after release from snow cover. The energy budget was observed on Mt. Zarumori (Akita Prefecture, Japan) above the snow and vegetation surfaces to determine bulk transfer coefficients and other factors involved in heat transfer. The input data required by the model were also obtained by observations at the site. The results of the calculations were verified by the data measured at the same site. The model was able to estimate the movement of snow boundary according to snowmelt with a temporal error of about three days and a spatial error of 5 m. Using the soil temperature evolution model, we calculated the accumulated soil temperature as an index of climatic resource for snow patch vegetation. Then we tried to clarify the relationships between the temperature field and the phenology of snow patch vegetation.
Winter buds of Cornus controversa are known to develop to first-order shoots, whose axillary buds sometimes elongate one or two second-order shoots. Such a twig growth pattern can form fifth-order shoots. In a man-made Cryptomeria japonica stand, current-year twigs of C. controversa had a larger total leaf area and shorter mean leaf longevity when under higher relative light intensity. This shorter mean leaf longevity resulted from a much shorter longevity of leaves on higher-order shoots, which were often produced by twigs under higher relative light intensity. Nitrogen content per unit area or unit dry weight of leaf was larger in higher-order shoots, suggesting a higher photosynthetic ability of such leaves. The size of winter buds per total leaf area per shoot on the higher-order shoots exceeded than that on first-order shoots. Mean number of leaves in winter buds of S3 twigs (first to third shoots) was largest on the first-order shoots. However that of S5 twigs (first to fifth shoots) was not different between first- and fourth- or fifth-order shoots. These facts suggest that the leaves of higher-order shoots have higher photosynthetic ability and make winter buds more efficiently than first-order shoots.
Recently, lattice models of population dynamics have been developed, in which sites are arranged regularly and each site may be occupied by an individual or a local population. Lattice models show that self-organizing heterogeneous spatial patterns often cause dynamics different from traditional population dynamics models without spatial structure. However, due to difficulty with mathematical analysis, most lattice models have been analysed only by computer simulations. Pair approximation is a useful technique for analysis of lattice models because it can predict the population dynamics fairly accurately even when mean-field approximation (which neglects spatial structure) gives qualitatively poor results.
This paper reviews studies on the community structure and adaptive radiation of Madagascar birds. Fission from Gondwana and formation of the Mozambique Channel before the evolutionary expansion of birds have caused a paucity of species number, a high level endemism and ecological release in Madagascar birds. Most forest bird species behave as mixed-species flocks. The guild structure of the community of Madagascar birds shows a unique configuration, with high proportions of 1) forest living species, 2) foliage gleaning species and frugivorous species, and 3) ground foraging species. Adaptive radiation is remarkable in the Couinae and Vangidae. In Couinae there are no large variations in morphology, and sympatric species have segregated micro-habitats. There are great variations in body size, bill shape and size, and foraging ecology (i. e. foraging location and technique) among the Vangidae. Species with similar bill morphology do not belong to the same foraging guild, with one exception. Members of the Vangidae forage primarily on boughs and trunks, filling the niche of woodpeckers. In the non-breeding season, the degree of aggregation varies from solitary pairs to large flocks, while territorial spacing out prevails in all Vangidae species in the breeding season. All of them are socially monogamous. Helping behaviour has been found in two species, Leptopterus chabert and Schetba rufa. Narrow ranges of variations in diet and habitat selection may have caused a lower level of variation in the mating system.
Recent developments in methods of comparative analysis were reviewed. The difference in correlation between traits of extant (tip) species and that between changes in traits along branches of a phylogenetic tree was critical. Techniques of comparative methods for considering the effects of phylogeny were reviewed. They included comparison of higher taxon means, comparison within higher taxa, division of variation using a matrix of phylogenetic similarity, independent comparison method and cladistic methods. The nature of statistical inference in comparative methods, and the connection between comparative ecology and phylogenetics were discussed.