Metapopulation structure of stream-dwelling Dolly Varden charr inferred from patterns of occurrence in the Sorachi River basin, Hokkaido, Japan

1. We investigated the occurrence (presence or absence) of stream‐dwelling Dolly Varden (Salmonidae: Salvelinus malma) in the 78 tributaries of the Sorachi River system, Hokkaido, Japan to examine evidence for metapopulation structure. 2. We hypothesised (i) that the occurrence of Dolly Varden would be less likely in small tributaries because of the higher extinction risk and (ii) that occurrence would be less likely in isolated tributaries because of reduced rates of dispersal and colonisation. In addition to these two general predictions, we hypothesised (iii) that the occurrence would be more likely in spring‐fed tributaries, because Dolly Varden prefer cold water as present in these systems. 3. When all the tributaries were included in a multiple logistic regression analysis, habitat size and habitat type (spring‐fed versus non‐spring‐fed tributaries) were selected for the best model, whereas isolation was not important. However, when tributaries in the lower Sorachi basin (an area likely influenced by human activities) were excluded from the analysis, the effect of isolation became significant. 4. Our results indicate there is a potential metapopulation structure of the Dolly Varden in the Sorachi River basin. Furthermore, it is possible that metapopulation dynamics follow a clinal pattern. In the upper and middle reaches of the Sorachi River basin, an equilibrium between extinction and colonisation of Dolly Varden populations is a possibility. In the lower portion of the basin, isolation appeared to be less important, and extinction rate may be driving patterns of occurrence toward systematic extinction of local populations. 5. Our results illustrate the possibility of spatial variation in the processes influencing occurrence of Dolly Varden within a single river basin, and the potential influences of habitat alteration on extinction and colonisation processes.     

Variation in migratory history of Dolly Varden in a stream with an artificial dam in the Shiretoko Peninsula,Hokkaido, Japan

The variation of migration patterns in Dolly Varden Salvelinus malma in a stream with an artificial dam (erosion-control-dam) in the Shiretoko Peninsula, Hokkaido Island, Japan, at the southernmost part of its distribution, was examined by otolith Sr:Ca ratio analysis. All specimens from the above-dam area showed consistently low Sr:Ca ratios (<5.0 × 10⁻³) throughout the otolith. In contrast, many specimens from the below-dam area had higher ratios (>5.0 × 10⁻³) throughout the otolith or only at the outer part than do those from the above-dam area. This higher ratio is probably due to salinity effects. Specimen from the below-dam area could be divided into three types: (1) Consistently low Sr:Ca ratios throughout the otolith, being freshwater residents. (2) Low Sr:Ca ratios around the inner part of the otolith, and thereafter higher ratios toward the outer part, being typically anadromous. (3) Relatively higher Sr:Ca ratios throughout many or in some parts of the otolith, indicating that these have migrated from the freshwater to brackish water or seawater from the early life stage. These findings suggest that Dolly Varden has a high degree of plasticity in its migratory behavior.     

Development trends in taxonomy,with special reference to fungi

Taxonomy is a traditional subject, but it still receives attention and has become a topic of much discussion in recent years. Many of these discussions have raised concerns about the future of taxonomy, especially with regard to the workforce responsible for the discovery of new species in the context of declining biodiversity. Previous discussions were based on the taxonomic data of plants and animals, but the status of fungal taxonomy has not been mentioned. Fungi have one of the highest levels of biodiversity among all living organisms, second only to insects. The discussion of the future of taxonomy without the inclusion of fungal data is incomplete. Here, we present the results of analyses based on all new fungal taxa published since 1753. Fungal taxonomy is an ever‐growing area of study with increasing numbers of new taxa being described and growing numbers of fungal taxonomists. Compared with plants and most animal groups, there has been a much sharper increase in the rate at which new fungal taxa are being described. Furthermore, the number of taxonomists studying fungi has increased at a faster speed than those studying plants or animals. This indicates that fungal taxonomy is a prosperous subject and a dynamic area for scientific studies, and that it deserves much more attention and support. The study of fungal taxonomy will deepen our understanding of the biodiversity of our planet.     

Widespread rapid reductions in body size of adult salamanders in response to climate change

Reduction in body size is a major response to climate change, yet evidence in globally imperiled amphibians is lacking. Shifts in average population body size could indicate either plasticity in the growth response to changing climates through changes in allocation and energetics, or through selection for decreased size where energy is limiting. We compared historic and contemporary size measurements in 15 Plethodon species from 102 populations (9450 individuals) and found that six species exhibited significant reductions in body size over 55 years. Biophysical models, accounting for actual changes in moisture and air temperature over that period, showed a 7.1–7.9% increase in metabolic expenditure at three latitudes but showed no change in annual duration of activity. Reduced size was greatest at southern latitudes in regions experiencing the greatest drying and warming. Our results are consistent with a plastic response of body size to climate change through reductions in body size as mediated through increased metabolism. These rapid reductions in body size over the past few decades have significance for the susceptibility of amphibians to environmental change, and relevance for whether adaptation can keep pace with climate change in the future.     

Environmental rugosity, body size and access to food: a test of the size-grain hypothesis in tropical litter ants

In terrestrial walking organisms, long legs help to decrease the cost of running, allowing animals to step over environmental interstices rather than walking through them. However, long legs can complicate the infiltration of these interstices, which may contain food sources and refugia. Since the number of environmental interstices perceived by an organism (rugosity) increases as it body size decreases (size-grain hypothesis, SGH), natural selection should favor proportionally smaller legs with decreasing body size. Recent work demonstrated that ants fit this hypothesis. We experimentally tested the assumption of the SGH that small ants, which have proportionally smaller legs than larger ants, are more successful in exploring environmental interstices because they can easily penetrate them. We examined the ability of tropical litter ant species with different body sizes to access food baits in 'landscapes' (=plots) with different levels of rugosity and food exposure. In the first experiment, three levels of landscape rugosity were defined by manipulating the density of leaf litter placed on the ground plots: a) plain landscape: no litter fall, b) intermediate rugosity (∼0.5 kg of litter fall) and c) high rugosity (∼1 kg). In a second experiment, food baits were in plain landscapes, exposed or covered by leaf litter. The body lengths of ants that first accessed food baits ranged from 1.5 to 12 mm. Ants that first reached food baits in the most rugose landscapes were ∼40% smaller than ants that first found baits in plain landscapes. Smaller ants were also the first to access covered food. The application of a phylogenetic comparative method suggested the same patterns. We conclude that these results support the size grain hypothesis. Environmental rugosity might have operated as a selective force to shape the morphological characteristics of litter ant species.     

Seasonal trends in body size of adult male mosquitofish,Gambusia affinis,with evidence for their social control

Synopsis Collections from a natural population of mosquitofish,Gambusia affinis, in southern Indiana showed that males born early in the breeding season mature rapidly at a small body size, while males born later in the breeding season delay maturation and achieve larger body sizes. A field experiment, involving removal of males from pond populations, was conducted to test the hypothesis that delayed maturation by late summer males is, at least in part, under social control. Mean total length (TL) of adult and maturing males in late summer in ponds from which large numbers of males had previously been removed was significantly lower than mean TL of males in control ponds. These data support the hypothesis of social control and support Sohn's competition-predation hypothesis for control of adult male body size inGambusia.     

A morphological classification of plants,with special reference to the New Zealand alpine flora

Abstract. A plant is a complex of integrated systems (leaves, leaf groups, stems, roots, inflorescences), coexisting side by side or superimposed on each other to produce the life form (orphysiognomy) of the individual. The classic Raunkiaer classification based fundamentally on one character (apex position) is insufficient for the purpose of a functional classification. Five keys are given to determine the categories of:

• 1) the plant silhouette or general shape resulting from a combination of other systems, with 11 categories proposed;
• 2) the leaf group, with 14 categories;
• 3) the stem, with 27 categories;
• 4) the root, with 5 categories; and
• 5) the inflorescence, with 3 categories.

Each plant can be named according to the category or model of each of the five different systems that they most resemble, or by using only the name(s) of systems which are more conspicuous than others. Characters are selected primarily for their influence on form and secondarily on size. This scheme allows for detailed studies of a flora in terms of morphological characteristics (alone or in systems), expressed as frequency of occurrence of each character in the flora. Characters can be analysed separately (e.g. entire margined leaves), as a combination of characters (e.g. leaf groups) or as a combination of systems (e.g. rosettes without stems). Thus correlations between environmental variables and plants canbe made with more precision than in previous classification schemes. The classification also serves as the framework for including additional morphological data and incorporating new models. The New Zealand alpine flora is used as a test case and to exemplify the classification.     

Stream-dwelling Dolly Varden (<Emphasis Type="Italic">Salvelinus malma</Emphasis>) density and habitat characteristics in stream sections installed with low-head dams in the Shiretoko Peninsula,Hokkaido, Japan

Numerous low-head dams have been constructed for erosion control and installed in almost all mountainous streams in Japan. Shiretoko Peninsula, Hokkaido, is considered as one of the most intact areas in Japan, however, more than 331 low-head dams have been installed in 39 streams of the peninsula since the 1960s. In this study, the density of stream-dwelling Dolly Varden (Salvelinus malma) and the habitat characteristics in dam-installed sections were investigated in Shiretoko streams and compared with unaltered sections in which no dams have been installed as a reference. Fish density in dam-installed sections was significantly lower than reference sections. Canopy cover, maximum temperature, wetted width, frequencies of pebble, bedrock and boulder, and areas of rapid, glide and riffle was significantly differed between dam-installed and reference sections. High stream temperature, occurrence of glides, and loss of boulder in dam-installed sections may reduce the suitability of habitats for fish and minimize the population size. We suggest that negative effects of dam installations on Dolly Varden populations have occurred in Shiretoko streams.     

Karyomorphology of Davidia involucrata and Camptotheca acuminata, with special reference to their systematic positions

Davidia involucrata Baill. and Camptotheca acuminata Decne were investigated and compared karyomorphologically. Their idiogrammatic formulae are, respectively, 2 n  = 42 = 20m (2SAT) + 16sm + 4st + 2t and 2 n  = 42 = 22m (2SAT) + 14sm + 4st + 2t. The plants are very similar: both belong to the 2B asymmetry karyotype (the karyotypes are reported here for the first time) and in both the prophase chromosomes are of the interstitial type. Davidia is believed to be closely related to Camptotheca . We do not consider it appropriate to remove Davidia from Camptotheca into a different family or subfamily. The cytological data support Davidia and Camptotheca forming a subfamily (Davidioideae) of the broadly circumscribed Cornaceae.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 193-198.     

Trends in body size, diet and food availability in the Cook Islands in the second half of the 20th century

The body size of adult Cook Islanders on Rarotonga for the years 1952, 1966 and 1996 has been increasing. The rate of increase in stature of women aged 20-39 years was 0.5cm per decade across the period 1952-1966, and 0.8cm per decade for the period 1966-1996. The rate of increase of weight in the 20-29 years age group was 0.6kg per decade in period 1, and 7.3kg per decade in period 2. In the age group 30-39 years, the rates were 3.2kg per decade and 5.1kg per decade respectively. Changing food availability for the period 1961-2000 is used to compare estimates of dietary energy availability with estimates of physiological energy requirements. There has been reduced availability of traditional staples, a likely reduction in consumption of fish, increased consumption of meat, and a decline in the availability of dietary fats and oils. Daily per capita energy intakes in 1952 and 1966 greatly exceed an hypothetical physiological maximum value for energy expenditure, suggesting a large positive energy balance in 1952 and an even greater one in 1966, both predisposing to weight gain. Although daily per capita energy availability in 1996 is similar to the hypothetical physiological maximum value for energy expenditure, it exceeds the measured level of energy expenditure at that time. It is speculated that excessive energy intake relative to requirement is more likely to predispose to positive energy balance and weight gain than decline in energy expenditure, although to a lower extent than in 1966 and 1952.     

Steering responses of adult and nymphal crickets to light,with special reference to the head rolling movement

Most tethered adult crickets (Gryllus bimaculatus) assumed flight postures with or without flapping their wings in a windstream. Nymphal crickets (sixth and seventh, i.e. final, instars) also displayed the flight posture in spite of the incompleteness of wing development. These adult nymphal crickets rolled their heads towards the light source in response to unequal illumination of the compound eyes only while maintaining the flight posture. The amphtude of the head rolling movements was proportional to the change of light position up to 120°C, and independent of the light intensity if the duration was longer than 1 sec. The unequal illumination could also induce a transient increase in discharge frequency of the wing muscles on both sides, a decrease in wing beat amplitude of the ipsilateral wing on the illuminated side, and bending movements of the legs and abdomen towards the light. Cutting either of the nerve connectives at any level between the subosophageal and metathoracic ganglia did not affect the response of either the head or the abdomen to illumination. These results are discussed in relation to the steering mechanism associated with the dorsal light reaction.     

Postembryonal growth and its variability of the three marine fishes with special reference to the mechanism of growth variation in fishes

1. To study the relation of growth variation to the behaviour pattern, newly hatched Hemiramphus sajori, Chrysophrys major and Zebrias zebra were reared in 30 litter aquaria during one month, and body length was measured four times.
2. In Hemiramphus sajori coefficient of variation of body length (CV) first increased but showed a tendency to decrease with development of schooling behaviour.
3. In Chrysophrys major CV markedly increased and mode of the distribution curve of body length inclined towards the left side, associated with appearance of aggression and cannibalism.
4. In Zebrias zebra, when behaviour pattern changed from planktonic to demersal some of the small individuals nearly ceased growing. At that time CV of body length remarkably increased and the mode of the distribution curve of body length shifted towards the right side.
5. In all the species a positive correlation was seem between specific growth rate and initial body length soon after intensive feeding began. An negative correlation was observed in most of individuals of Hemiramphus sajori after the appearance of schooling behaviour. When a conspicuous increase in CV and skewness in distribution curve took place, a separate type of correlation was seen in large and small group in the population.
6. Based on above mentioned and other materials a general mechanism of growth variation in fishes was discussed.

     

The growth form of populations in some aphids,with special reference to the relation between population density and the movements

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National Institute of Agricultural Sciences