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In this paper, we analyze the interaction of localized patterns such as traveling wave solutions for reaction-diffusion systems with nonlocal effect in one space dimension. We consider the case that a nonlocal effect is given by the convolution with a suitable integral kernel. At first, we deduce the equation describing the movement of interacting localized patterns in a mathematically rigorous way, assuming that there exists a linearly stable localized solution for general reaction-diffusion systems with nonlocal effect. When the distances between localized patterns are sufficiently large, the motion of localized patterns can be reduced to the equation for the distances between them. Finally, using this equation, we analyze the interaction of front solutions to some nonlocal scalar equation. Under some assumptions, we can show that the front solutions are interacting attractively for a large class of integral kernels.

In this paper, we introduce a continuation method for the spatially discretized models, while conserving the size and shape of the cells and lattices. This proposed method is realized using the shift operators and nonlocal operators of convolution types. Through this method and using the shift operator, the nonlinear spatially discretized model on the uniform and nonuniform lattices can be systematically converted into a spatially continuous model; this renders both models point-wisely equivalent. Moreover, by the convolution with suitable kernels, we mollify the shift operator and approximate the spatially discretized models using the nonlocal evolution equations, rendering suitable for the application in both experimental and mathematical analyses. We also demonstrate that this approximation is supported by the singular limit analysis, and that the information of the lattice and cells is expressed in the shift and nonlocal operators. The continuous models designed using our method can successfully replicate the patterns corresponding to those of the original spatially discretized models obtained from the numerical simulations. Furthermore, from the observations of the isotropy of the Delta–Notch signaling system in a developing real fly brain, we propose a radially symmetric kernel for averaging the cell shape using our continuation method. We also apply our method for cell division and proliferation to spatially discretized models of the differentiation wave and describe the discrete models on the sphere surface. Finally, we demonstrate an application of our method in the linear stability analysis of the planar cell polarity model.

Sutures, the thin, soft tissue between skull bones, serve as the major craniofacial growth centers during postnatal development. In a newborn skull, the sutures are straight; however, as the skull develops, the sutures wind dynamically to form an interdigitation pattern. Moreover, the final winding pattern had been shown to have fractal characteristics. Although various molecules involved in suture development have been identified, the mechanism underlying the pattern formation remains unknown. In a previous study, we reproduced the formation of the interdigitation pattern in a mathematical model combining an interface equation and a convolution kernel. However, the generated pattern had a specific characteristic length, and the model was unable to produce a fractal structure with the model.In the present study, we focused on the anterior part of the sagittal suture and formulated a new mathematical model with time–space-dependent noise that was able to generate the fractal structure. We reduced our previous model to represent the linear dynamics of the centerline of the suture tissue and included a time–space-dependent noise term. We showed theoretically that the final pattern from the model follows a scaling law due to the scaling of the dispersion relation in the full model, which we confirmed numerically. Furthermore, we observed experimentally that stochastic fluctuation of the osteogenic signal exists in the developing skull, and found that actual suture patterns followed a scaling law similar to that of the theoretical prediction.Author summarySkull sutures (thin, undifferentiated tissue between bones) act as the growth centers for the skull. Sutures are straight at birth but later develop an interdigitated pattern that ultimately becomes a fractal structure. While our previous mathematical model of sutures generated a periodic pattern, the mechanism underlying the fractal structure formation remained to be elucidated. Here, we focused only on the anterior part of the sagittal suture and formulated a reduced model representing the initial linear phase of pattern formation with the addition of a time–space-dependent noise term. We showed analytically that the model generates patterns with a scaling law. This result was confirmed numerically and experimentally.

A new method to derive an essential integral kernel from any given reaction-diffusion network is proposed. Any network describing metabolites or signals with arbitrary many factors can be reduced to a single or a simpler system of integro-differential equations called "effective equation" including the reduced integral kernel (called "effective kernel") in the convolution type. As one typical example, the Mexican hat shaped kernel is theoretically derived from two component activator-inhibitor systems. It is also shown that a three component system with quite different appearance from activator-inhibitor systems is reduced to an effective equation with the Mexican hat shaped kernel. It means that the two different systems have essentially the same effective equations and that they exhibit essentially the same spatial and temporal patterns. Thus, we can identify two different systems with the understanding in unified concept through the reduced effective kernels. Other two applications of this method are also given: Applications to pigment patterns on skins (two factors network with long range interaction) and waves of differentiation (called proneural waves) in visual systems on brains (four factors network with long range interaction). In the applications, we observe the reproduction of the same spatial and temporal patterns as those appearing in pre-existing models through the numerical simulations of the effective equations. (C) 2020 The Authors. Published by Elsevier Ltd.

In terrestrial ecosystems, plant species and diverse root-associated fungi form complex networks of host-symbiont associations. Recent studies have revealed that structures of those below-ground plant-fungus networks differ between arbuscular mycorrhizal and ectomycorrhizal symbioses. Nonetheless, we still remain ignorant of how ericaceous plant species, which dominate arctic and alpine tundra, constitute networks with their root-associated fungi. Based on a high-throughput DNA sequencing data set, we characterized the statistical properties of a network involving 16 ericaceous plant species and more than 500 fungal taxa in the alpine-subalpine region of Mt. Tateyama, central Japan. While all the 16 ericaceous species were associated mainly with fungi in the order Helotiales, they varied remarkably in association with fungi in other orders such as Sebacinales, Atheliales, Agaricales, Russulales and Thelephorales. The ericaceous plant-fungus network was characterized by high symbiont/host preferences. Moreover, the network had a characteristic structure called 'anti-nestedness', which has been previously reported in ectomycorrhizal plant-fungus networks. The results lead to the hypothesis that ericaceous plants in harsh environments can host unexpectedly diverse root-associated fungal taxa, constituting networks whose structures are similar to those of previously reported ectomycorrhizal networks but not to those of arbuscular mycorrhizal ones.

Flower visitors often fly among plants of the same species more often than is expected from plant frequency and distribution, a behavior known as flower constancy. Because of its implications for the evolution of floral traits, whether flower constancy is associated with perceptual stimuli, reward value, and/or flower handling skills has been debated by many authors. However, it remains unknown whether flower handling skill has a substantial influence on flower constancy because flowers that require different handling skills generally also differ in their appearance (i.e., shape). We investigated the foraging type constancy of Bombus terrestris workers that foraged flower patches consisting of two (Trifolium pratense and Trifolium repens) or three (T. pratense, T. repens, and Lotus corniculatus) plant species. In these flower patches, individual bees foraged T. pratense flowers by either one of the two foraging modes that require different foraging techniques (legitimate foraging versus nectar robbing). Behavioral and pollen load analysis indicated that bees sometimes switched their foraging types between legitimate visits to T. pratense and visits to T. repens and between nectar robbing on T. pratense and visits to L. corniculatus, though they rarely switched between other combinations of foraging types. These results indicate that factors other than perceptual stimuli and spatial distribution of plants affected foraging type constancy. After considering other factors, such as the rewards and the sizes of individual foragers, we argue that handling skills required to forage flowers affected flower constancy observed in this study.

In this paper, we study the existence of traveling wave solutions connecting two constant states to a nonlocal scalar equation with sign-changing kernel. A typical example of such kernel in the neural fields is the Mexican hat type function. We first introduce a new notion of upper-lower-solution for the equation of wave profile for a given wave speed. Then, with the help of Schauder's fixed point theorem, we construct two different pairs of upper-lower-solutions to obtain traveling waves for a continuum of wave speeds under two different assumptions. Due to the sign-changing nature of the kernel, the wave profiles may take both positive and negative values. Finally, we analyze the limit of the right-hand tail of wave profiles. Under some further condition on the wave speeds, we prove that the right-hand tail limit of the wave profile does exist. In particular, we obtain the existence of nonnegative traveling waves connecting the unstable state 0 and the stable state 1 for wave speeds large enough.

Sphaerularia bombi Dufour is a major parasite of bumble bee queens that manipulates its host's behavior: parasitized queens do not breed and found nests but continue to fly into the early summer months. We examined the indirect consequences of this host manipulation on non-host workers in central Hokkaido Island, Japan. In this area, parasitism of Bombus terrestris by S. bombi is common but does not affect every queen; therefore, as summer begins, B. terrestris queens continue to dominate some flower patches and disappear from others. At sites dominated by parasitized queens, we found that the nectar standing crop of red clover was smaller, B. terrestris workers carried out fewer legitimate visits to red clover and more nectar robberies, and the workers were smaller than at other sites. Removing queens from a site increased the nectar standing crop of red clover, the frequency of worker visits to red clover, and the size of the workers. These results suggest that host manipulation by S. bombi increased competition for flower resources among host queens and non-host workers and altered the interaction between plants and non-host flower visitors.

The associative learning of spatial and reward information is generally considered an adaptive behavior of foraging animals that collect food from renewable resources. However, learning may not always maximize foraging efficiency if choosing a high-reward location accurately based on learned information imposes a time cost on the forager (speed-accuracy trade-off). To examine the effect of speed-accuracy trade-offs on associative learning, we observed bumble bees, Bombus ignitus (Smith), foraging in mixed arrays of high- and low-rewarding artificial flowers under two conditions, i.e., arrays of small flowers where bees could not easily detect the next nearest flowers on leaving a flower and arrays of large flowers where bees could easily recognize the next nearest flower. When flowers were small, bees created foraging routes by selectively incorporating the locations of high-rewarding flowers with their experience. When flowers were large, bees flew between flowers more quickly than when flowers were small, creating foraging routes without accounting for the locations of high-rewarding flowers. Estimated foraging efficiency was higher when flowers were large than when they were small, at least until flower visitation number reached 3000, suggesting that rapid foraging might be a better choice than accurate foraging when individuals are able to locate flowers easily. These results suggest that associative learning of spatial and reward information might be a choice that foragers can apply according to the cost-benefit balance of learning. Previous studies focusing on spatial-reward associative learning in foraging animals assumed that foraging efficiency increased as the forager learned the locations of greater rewards. However, this study suggests that bumble bees learn the location of high-rewarding flowers depending on the cost–benefit balance of learning, irrespective of the opportunity or their aptitude for learning. Thus, learning might be a choice that foragers can apply according to the circumstances.

Pollinators often sequentially visit 1 flower type while bypassing other equally rewarding flower types, behavior known as flower constancy. One explanation for flower constancy is that pollinators use the search image of a specific flower type to efficiently find flowers because they are often cryptic. The so-called search image hypothesis predicts that temporal specialization to 1 flower type by an individual pollinator declines as flower conspicuousness increases because if flowers are conspicuous, pollinators can divide their attention among different flower types. To test this prediction, we investigated visitation sequences of individual bumble bees (Bombus ignitus) to a patch of blue and yellow artificial flowers. We used different flower sizes and interflower distances as independent determinants of flower visual size and noisiness of the background and, thus, of flower crypsis. Flower color selectivity and flower search time decreased and subsequently increased with visual size of the nearest flowers, with a minimum of approximately 15° of the visual angle. Within-bout constancy, measured as the tendency of flying to the same flower types in succession compared with the expectation of a given flower selectivity within a bout, increased with visual size of the nearest flowers. Flower selectivity and within-bout constancy did not differ among arrays that shared the same floral visual angle, indicating that visual size, rather than flight distance or flower size itself, had a substantial effect on flower choices. Our results suggest that flower visual size and background noisiness affect flower crypsis and constancy, providing support for the search image hypothesis.

Despite the ubiquity and the importance of interspecific interactions among flower visitors, few studies have examined their effects on the realized feeding niches of visitor species in a community context. To evaluate the community-wide effects of interactions among flower visitors, I have examined changes in the flower utilization patterns of each visitor species at several sites where the component of the visitor’s community differed. Specifically, I compared the flower preferences and foraging habits (legitimate foraging vs. primary nectar robbing vs. secondary nectar robbing) of five bumble bee species in flower patches consisting of Trifolium pratense L. (red clover) and T. repens L. (white clover) on Hokkaido Island, Japan. I also examined the nectar production and standing crops of each flower species to evaluate the exploitation competition based on nectar. The bumble bee species exhibited different flower utilization patterns among sites. At sites where the long-tongued Bombus diversus tersatus was common and the exotic short-tongued B. terrestris was rare, B. diversus tersatus visited red clover (long-tubed flowers) exclusively, whereas medium-tongued B. pseudobaicalensis and short-tongued B. hypocrita sapporoensis and B. hypnorum koropokkrus preferentially visited white clover (short-tubed flowers). Conversely, at sites where the long-tongued bee was rare, four other species frequently visited red clover in different modes: B. pseudobaicalensis visited legitimately, B. hypocrita sapporoensis and B. terrestris visited as primary nectar robbers, and B. hypnorum koropokkrus visited as a secondary nectar robber. The presence or absence of resource exploitation by the long-tongued species and the interaction between primary and secondary nectar robbers via robbing holes was the major ecological sources of these differences. Diverse effects of interactions among flower visitors played important roles in shaping pattern of plant and flower visitor interactions.

Summary 1. Flowering-time differences within and among protandrous, hermaphroditic plants shift the floral sex ratio from male- to female-dominated during a population’s flowering season. This dynamic should induce negative frequency-dependent selection favouring relatively greater investment of resources and time in female function by early flowers and early-flowering plants than by late flowers and late-flowering individuals. In contrast, selection for floral integration to facilitate pollen export and import should limit floral variation. 2. We assessed these contrasting expectations for the protandrous Delphinium glaucum by considering the relation of variation and covariation in the lengths of perianth segments, anther and ovule number, and male- and female-phase duration for flowers at three positions within inflorescences to the first flowering date, mean gender and size of 34 plants. 3. Reproductive phenotypes varied among and within plants in association with a shift in population floral sex ratio from male- to female-biased, but not with plant size. Early-flowering plants had female-biased phenotypic gender and smaller flowers with fewer anthers per ovule and shorter male phases than late-flowering plants. Within individuals, earlier (lower) flowers were larger with higher female effort, in terms of both the relative production of ovules and anthers and the relative durations of female and male phases, than later (upper) flowers. Overall, these results are more consistent with the expectations of negative frequency-dependent selection than with proximate resource allocation. 4. Correlations among floral traits indicated significant floral integration. However, these correlations weakened from lower to upper flowers, suggesting that the patterns of intra-individual variation limit the extent of integration. 5. Synthesis. Reproductive phenotypes that incorporate systematic among-flower variation and vary consistently among individuals with flowering time, such as those exhibited by D. glaucum, may be typical of dichogamous species with multi-flowered inflorescences. Such diversity within and among plants should result from a combination of density-dependent selection against simultaneous flowering of individuals and frequency-dependent selection favouring emphasis on the least common sex role during specific stages of the flowering season, both facilitated by the positive assortative mating that accompanies asynchronous flowering among individuals.

• Despite the wide inflorescence diversity among angiosperms, the effects of inflorescence architecture (three-dimensional flower arrangement) on pollinator behaviour and mating success have not been sufficiently studied in natural plant populations. • Here, we investigated how inflorescence architecture affected inter- and intra-plant pollinator movements and consequent mating success in a field population of Spiranthes sinensis var. amoena (S. sinensis). In this species, the flowers are helically arranged around the stem, and the degree of twisting varies greatly among individuals. The large variation in inflorescence architecture in S. sinensis results from variation in a single structural parameter, the helical angle (the angular distance between neighbour-flower directions). • The numbers of visits per inflorescence and successive probes per visit by leaf-cutting bees decreased with helical angle, indicating that individual flowers of tightly twisted inflorescences received less visitations. As expected from pollinator behaviour, pollinia removal and fruit set of individual flowers decreased with helical angle. Meanwhile, geitonogamy decreased in tightly twisted inflorescences. • Our novel findings demonstrate that natural variation in inflorescence architecture significantly affects pollinator behaviour and reproductive success, suggesting that inflorescence architecture can evolve under pollinator-mediated natural selection in plant populations. We also discuss how diverse inflorescence architectures may have been maintained in S. sinensis populations.

We explored the use of ecological niche-modeling from data compiled in a participatory program of thousands of volunteer observers to quantitatively evaluate the spatial risk of invasion by the alien species Bombus terrestris. B. terrestris has been commercially introduced to Japan for the pollination of greenhouse tomato crops since 1991. Recently, naturalized populations of this species have spread rapidly, particularly in Hokkaido, northern Japan. Two niche-based models were constructed from independent data sets (presence–absence and presence-only data sets) and were used to validate one another. Both models performed well and indicated that the data compiled by participatory programs were useful for generating predictive models of the potential distribution of this invasive species. The models also revealed that the potential distribution of B. terrestris is negatively related to the proportion of woodland area, which corresponds to the known biology of this species. In contrast, the effect of the number of colonies introduced for tomato pollination (represented by tomato production) did not significantly affect the distribution of B. terrestris, indicating that its spread is now entering a phase of dispersal from established feral populations and that primary dispersal from commercial colonies in greenhouses is no longer a limiting factor for the distribution of this invasive species.

Studies of the interspecific relationships between alien and native pollinator species can help forecast the success of alien species as well as assess the extent of disturbance to native plant–pollinator interactions. We examined the habitat and flower resource occupancy by the invasive introduced bumble bee Bombus terrestris and three dominant native bumble bees in central Hokkaido, northern Japan, in relation to a landscape factor (forest cover ratio) and flower morphology with respect to the proboscis length of bees. Three years of monitoring the invasive boundary of B. terrestris indicated that this species, which dominates open agricultural areas, probably will not invade the forests in which the native species dominate. This habitat partitioning likely followed the displacement of the natives by the invader in open agricultural lands. In forested areas, the native species partitioned flower resources on the basis of the relationship between proboscis length and the lengths of the corolla tubes of flowers. However, in open agricultural areas, both the long- and short-tubed flowers were primarily visited by the exotic short-tongued B. terrestris, which foraged illegitimately (by nectar robbing) on long-tubed flowers (Trifolium pratense L.) and legitimately on short-tubed flowers (T. repens L. and Lavandula angustifolia Mill.). The invasion of B. terrestris into open natural vegetation, in addition to open agricultural areas, has recently been reported in Hokkaido. Even though the exotic and dominant native bumble bees partition their habitat according to landscape factors, the invasive bee has the potential to alter the overall interactions within plant–pollinator systems in the regions of open vegetation on Hokkaido Island.

In order to make geophysical and geological investigations of the Nojima Fault on Awaji Island, Japan, three boreholes measuring 1800 m, 800 m and 500 m deep were drilled into the fault zone. The fault is one of the seismic source faults of the 1995 Hyogo-ken Nanbu earthquake of M7.2. A new multicomponent borehole instrument was installed at the bottom of the 800 m borehole and continuous observations of crustal strain and tilt have been made using this instrument since May 1996. A high-pressure water injection experiment within the 1800 m borehole was done in February and March 1997 to study the geophysical response, behavior, permeability, and other aspects of the fault zone. The injection site was located approximately 140 m horizontally and 800 m vertically from the instrument. Associated with the water injection, contraction of approximately 0.7 × 10−7 str (almost parallel to the fault) and tilt of approximately 1 × 10-7 rad in the sense of upheaval toward the injection site were observed. In addition to these controlled experiments, the strainmeter and tiltmeter also recorded daily variations. We interpret strain and tilt changes to be related to groundwater discharge and increased ultra-micro seismicity induced by the injected water.

An 800 m borehole was drilled near the Nojima Fault, on which a strike–slip larger then 1 m occurred during the 1995 Hyogo-ken Nanbu earthquake (M = 7.2). Crustal activity near the fault has been observed since May 1996 using a multicomponent instrument installed at the bottom of the borehole. Data of three components of strain, two components of tilt and temperature observed from May 1996 to December 1998 were analyzed. Long-term changes of strain and tilt show a north-east–south-west extension and southwards subsidence. As for the Earth tides and atmospheric effect, orientation of the principal axis of strain was mainly east-west and orientation of the maximum subsidence was mainly north-south. The observational data of strain had variations corresponding to a change in temperature at a depth of 800 m. The thermal expansion coefficient of the crust was calculated to be approximately 2.0 × 10−6/°K.

Pollen dispersal by pollinators is governed by the extent to which diverse effects on pollinator behaviour act independently or augment or moderate each other. Using artificial inflorescences, we assessed the behavioural responses of bumble bees to inflorescence architecture (raceme, panicle, and umbel), inflorescence size (7 or 13 flowers), inter-inflorescence distance and the proportion of empty flowers per inflorescence. The advantage of large inflorescences in terms of attractiveness was larger for racemes and umbels than for panicles, whereas the effect of inter-inflorescence distance on the number of successive probes was smaller for racemes than for panicles and umbels. The number of flowers probed per visit increased almost proportionally with display size when fewer flowers were empty, whereas the number increased less when many flowers were empty. Our results suggest that display size and the spatial arrangement of flowers and nectar within inflorescences can contribute to efficient pollination by affecting pollinator behaviour interactively.

Floral color change has been recognized as a pollination strategy, but its relative effectiveness has been evaluated insufficiently with respect to other floral traits. In this study, effects of floral color change on the visitation pattern of bumblebees were empirically assessed using artificial flowers. Four inflorescence types were postulated as strategies of flowering behavior: type 1 has no retention of old flowers, resulting in a small display size; type 2 retains old flowers without nectar production; type 3 retains old flowers with nectar; and type 4 retains color-changed old flowers without nectar. Effects of these treatments varied depending on both the total display size (single versus multiple inflorescences) and the pattern of flower-opening. In the single inflorescence experiment, a large floral display due to the retention of old flowers (types 2-4) enhanced pollinator attraction, and the number of flower visits per stay decreased with color change (type 4), suggesting a decrease in geitonogamous pollination. Type-4 plants also reduced the foraging time of bees in comparison with type-2 plants. In the multiple inflorescence experiment, the retention of old flowers did not contribute to pollinator attraction. When flowering occurred sequentially within inflorescences, type-4 plants successfully decreased the number of visits and the foraging time in comparison with type-2 plants. In contrast, floral color change did not influence the number of visits, and it extended the foraging time when flowering occurred simultaneously within inflorescences but the opening of inflorescences progressed sequentially within a plant. Therefore, the effectiveness of floral color change is highly susceptible to the display size and flowering pattern within plants, and this may limit the versatility of the color change strategy in nature.

Summary 1 Animal-pollinated plants influence their mating success through characteristics of their individual flowers and the arrangement of flowers into inflorescences. Previous studies of inflorescence function have focused on flower number, so the influences of traits of individual flowers on pollinator attraction and self-pollination between flowers remain unknown. 2 To investigate the effects of flower size and number on pollinator attraction and behaviour on inflorescences, we reduced the perianth size of flowers of Delphinium bicolor Nuttall and Delphinium glaucum S. Watson. 3 Reduction in flower size decreased the number of visits per inflorescence by bumble bees (Bombus spp.), but increased the number of probes per visit. In contrast, both attraction and probes per visit increased in a decelerating manner with number of open flowers. The average number of probes per flower, which combines the effects of pollinator attraction and behaviour on inflorescences, did not differ significantly between small- and large-flowered plants, or with flower number. 4 The absence of significant variation among plants with different floral and inflorescence characteristics in visits per flower and nectar standing crop per flower indicate that bees achieved an ideal free distribution. 5 Our results suggest that large flowers reduce the incidence of geitonogamous pollination without reducing the frequency of probes per flower.

Because pollinator behaviour within plants affects the mating outcomes of animal-pollinated plants, plants may regulate the pollinator behaviour by controlling floral design and display to maximize pollination efficiency. We assessed how extent of the display size, inflorescence architecture, and nectar distribution within inflorescences alter bumblebee behaviour (number of flowers visited, time of stay, and nectar intake efficiency) under controlled conditions using artificial inflorescences. The effect of display size on bumblebee attraction was also measured. Eighteen types of artificial inflorescences, two display sizes (large and small) × three architectures (panicle, umbel, and raceme) × three nectar distributions (constant nectar content in every flower, gradual changes in nectar content, and random distribution of empty and rewarded flowers) were visited by bumblebees. The mean nectar amount per flower was set as 3 μL in 2003 and 1 μL in 2004. Although the inflorescence architecture had little effect on bumblebee behaviour, the random nectar distribution decreased the number of successive flower visits (both 3 μL and 1 μL) and staying time (only 3 μL) during a single visit and increased the foraging efficiency (both 3 μL and 1 μL). These features may contribute to decreases in the geitonogamous pollination and pollen loss during pollinator movements. Display size did not influence the attraction of bumblebees in this study. Our results suggest that nectar distribution within inflorescences can be a strategy for efficient pollination by manipulating pollinator behaviour.

Although the sizes of individual flowers within one plant vary, few studies to date have investigated correlations among floral traits at the intra-plant level. Variations of the pleiotropic genes or linkage disequilibrium of genes, those have been said to create larger correlations between some combinations of traits than others at the inter-plant level, cannot predict intra-plant level correlations. In this study, correlations between several combinations of floral traits, including the number and volume of pollen grains and ovules, were investigated at both intra- and inter-plant levels in Iris gracilipes. The pattern of intra-plant level correlations was similar to that of inter-plant level correlations with some exceptions; correlations between functionally related traits tended to be larger than others at both levels. For example, correlations between sepal and petal size, and between petaloid style and filament length were large at both levels. This may be explained by the genetic and the developmental relationships between some combinations of traits, rather than by (co)variations of the peculiar properties of the individual plants such as genetic variations.

Pollinators whose foraging habitats consist of several plant types (species or morph) may continue to choose the plant type last visited because information about the type of plant last visited dominates over all other memory contents, in particular of short-term memory. In this study, I extracted this overstrike effect on the plant choices of pollinators by analyzing patterns of visitation sequences within a single round-trip between the hive and foraging patch (bout). First, I simulated the visitation sequences within single bouts with a model to show how factors, including the bees’ plant-type preferences, the arrangement of plants and the effect of overstrike on short-term memory, affect visitation sequences. Here, bees are assumed to forage in a patch consisting of two plant types (H and L). The model predicts that only the effect of overstrike on short-term memory causes assorted visitation sequences according to plant type (within-bout flower constancy). That is, if the overstrike-effect on short-term memory is the primary determinant of plant choice, then bees will fly to a type-L plant after visiting a type-L plant even if they predominantly visit type-H plants and vice versa. Next, I investigated individual bumblebees’ visitation sequences at a patch of artificial inflorescences with a set-up similar to that assumed in the model. Two types of inflorescences were arranged on a Cartesian grid. Assorted visitation sequences according to inflorescence type were observed, depending on the distances among inflorescences. This result supports the hypotheses that bees fly to the same plant type as that last visited because short-term memory is displaced (overstruck) with information about the most recently visited plant type.

Summary 1In animal-pollinated plants, female function is expected to increase with size because increased pollen production leads to more competition for ovules by pollen grains from the same parent, and a large flower number results in increased geitonogamy and, in turn, increased pollen discounting. To date, many studies have supported this prediction. 2In Narthecium asiaticum (Maxim), an animal-pollinated plant, however, male reproductive components in flowers increased with raceme size whereas female reproductive components did not. This was mostly because of the similar trend for middle to upper flowers within racemes. 3Height above ground for middle to upper flowers was associated with raceme size, and higher flowers attracted more pollinators. Accordingly, more pollen grains were removed from upper flowers in larger racemes. Furthermore, an increased number of flowers may not increase local mate competition and geitonogamy in this species because only a few flowers function as males at any one time, irrespective of raceme size. 4This may be the reason why male reproductive components of upper flowers increased with size, even though N. asiaticum is an animal-pollinated plant. Male reproductive components of lower flowers did not increase, probably because the height of lower flowers was not associated with raceme size.

The sizes of various floral organs of andromonoecious Commelina communis were measured to test the hypothesis that size correlations among floral organs are regulated by natural selection. Size correlations among six floral organs in both perfect flowers and staminate flowers with sterile pistils were compared. The stigma-long stamen anther (Lanther) correlation for perfect flowers was the strongest of all C. communis floral correlations, whereas this correlation was weak in staminate flowers. This suggests that the position of fertile stigmas may have evolved to maximize receipt from pollinators of pollen grains from L-anthers of the same height in perfect flowers.

In situ photosynthetic nitrogen-use efficiency (PNUE, photosynthetic capacity per unit leaf nitrogen) was investigated in species that commonly distributed at different altitudes (600–3700 m above sea level) on Mount Kinabalu. Photosynthetic nitrogen-use efficiency was lower in species at higher altitudes, with a mean PNUE at 3700 m being one-third as large as that at 600 m. This difference in PNUE was larger than that explained by the biochemical response to lower air pressures only. Across altitudes a negative correlation between 13C abundance (δ13C) and PNUE was found. Species at higher altitudes tended to have higher δ13C, suggesting that they had a lower conductance for CO2 diffusion from the air to chloroplasts. The lower conductance might be responsible for the lower PNUE in species at higher altitudes. Although leaf nitrogen content per unit area tended to be higher at higher altitudes, it did not seem to contribute to increasing photosynthetic rates. Thus, the idea that a higher nitrogen content at higher altitudes is a compensation for a lower PNUE was not supported. In contrast to the large difference in PNUE among altitudes, PNUE tended to converge within a narrow range among species growing at the same altitude.

Summary 1 We analysed the longevity of individual flowers with respect to the effects of the floral display size of a plant (number of flowers open at one time) and spatial arrangement of flowers in Iris gracilipes (A. Gray). We found that the actual floral longevity of this species (about 2 days) was much shorter than that predicted by the model of Schoen and Ashman (about 7–10 days). 2 A large display size and an overlap of flowering periods within a shoot facilitated successive pollinator probes within a plant, though the frequency of pollinator visits per flower was independent of display size. Consequently, the cost of geitonogamous selfing increased with an increase in display size and an overlap of flowering periods within a shoot. The short floral longevity of this species would be effective in such situations because shorter floral longevity leads to a smaller display size and a smaller overlap of flowering periods within a shoot. 3 A small display size and small overlap of flowering periods within a shoot could also be realized by the strategy that staggers the flowering period of each flower without floral longevity being shortened (extended blooming). However, a mutant plant with an extended blooming schedule would be unlikely to invade the population because of the stabilizing selection pressure on the flowering date. This may be why such a short floral longevity, rather than extended blooming, has evolved in this species.

Summary 1 We analysed the longevity of individual flowers and the effect on pollination success with respect to floral display size of racemes (number of flowers open at one time) for the sequentially blooming plant Narthecium asiaticum (Liliaceae). The longevity of lower- and middle-positioned flowers (about 7 days in 1998 and 6 days in 1999) was much greater than the length of time required for the completion of male (about 3 days) and female (within 3 days) functions. 2 We suggest that such prolonged longevity benefits the plant in terms of pollinator attraction, because prolonged longevity in lower and middle flowers leads to large display sizes of racemes. Increased display size would not have resulted in an increase of geitonogamy in this species, because most pollinators left racemes after probing only one flower. Rather, large displays attracted more pollinators and increased pollen dispersal from individual flowers. 3 The longevity of upper-positioned flowers (about 4 days in 1998 and 3 days in 1999) was less than that of lower- and middle-positioned flowers – almost the same as the length of time required for the completion of male and female functions. This difference is possibly because upper flowers open later within racemes: if there were no subsequent flowers, prolonged floral longevity would not benefit the plants and would only consume resources used to maintain the flower. 4 Floral longevity within inflorescence should be understood in relation to the effects of floral display size and floral positions, in addition to the accrual rates of male and female functions and the maintenance cost of individual flowers.

Crustal stress and strain measurements in a deep borehole are essential for studying plate subduction earthquakes. Especially in the case of the Nankai Trough earthquake, it is expected that crustal movements are detectable even on land, because the focal region caused by the subduction of the Philippine Sea plate is close to land. We have tried to search for a suitable field and a method for observations and investigations based on some hypotheses. Special emphasis is given to better understanding the hinge line as an adequate related field. The hinge line is located on the surface just above the boundary between creep and seismogeniclocked zones on the upper surface of the descending slab. If soft materials such as serpentine exist on the surface of the slab, deformation and flow here will become initiate an earthquake. The basic data of crustal stress and the rock physical properties were acquired by the scientific drilling of a borehole. This borehole was drilled to a depth of 550 m at Shingu city, Wakayama prefecture, on the Kii Peninsula. In-situ experiments such as crustal stress measurements by the hydraulic fracturing method were conducted in the well. Furthermore, we have developed an intelligent strain meter for measuring in-situ rock stress deeper than 500 m using the overcoring method. The final goal of this study is to monitor temporal changes of in-situ stress and strain, and to reveal their storage processes in relation to a great earthquake.

1. We analysed how male and female success affects the floral longevity in Erythronium japonicum. We found that flower senescence is advanced by deposition of pollen grains on the stigma but that there exists a minimum longevity (13·64 days in 1996 and 12·20 days in 1997) during which the flower never abscises, even if it is pollinated with a sufficient number of pollen grains. 2. We suggest that this floral longevity does not exist to benefit the female function, because the time needed for corolla abscission reacting to ovule fertilization was not so long and the female function was completed within about 3 days. 3. Flowers of E. japonicum do not react to pollen removal, as shown by the fact that anther removal experiments did not affect floral longevity. However, it would be advantageous to have some duration of longevity which benefits male success such that most of pollen grains can be expected to be exported. The duration needed to disperse most pollen grains of a flower was about 12 days, very close to the minimum floral longevity. 4. We conclude that a minimum longevity may exist for male functions and that floral longevity may be influenced differently by the male and the female functions of flowers.

Tilt meters are a widely used tool for monitoring long-term and small-scale deformations. Therefore, they are perfectly suited to test potential subsurface waste repositories. Since November 2005 a high sensitive tilt meter of the ASKANIA-type is recording at a distance of 300 m from Mizunami Underground Research Laboratory, where two vertical shafts are under construction. During the construction of those shafts large pumps were used to reduce the groundwater level, leading to two large- and several small-scale pore pressure induced tilt signals. Due to the fault system nearby, the tilt direction does not coincide with the direction towards the pump as would be expected in homogeneous media. In this study we analyze the main surface tilt direction caused by pore pressure induced deformation. Our results show two main directions which are both nearly perpendicular to the fault. Also, the long-term signals show a high correlation with the short-term pore pressure induced tilt signals.

Terrestrial plants host phylogenetically and functionally diverse groups of below-ground microbes, whose community structure controls plant growth/survival in both natural and agricultural ecosystems. Therefore, understanding the processes by which whole root-associated microbiomes are organized is one of the major challenges in ecology and plant science. We here report that diverse root-associated fungi can form highly compartmentalized networks of coexistence within host roots and that the structure of the fungal symbiont communities can be partitioned into semi-discrete types even within a single host plant population. Illumina sequencing of root-associated fungi in a monodominant south beech forest revealed that the network representing symbiont–symbiont co-occurrence patterns was compartmentalized into clear modules, which consisted of diverse functional groups of mycorrhizal and endophytic fungi. Consequently, terminal roots of the plant were colonized by either of the two largest fungal species sets (represented by Oidiodendron or Cenococcum). Thus, species-rich root microbiomes can have alternative community structures, as recently shown in the relationships between human gut microbiome type (i.e. ‘enterotype’) and host individual health. This study also shows an analytical framework for pinpointing network hubs in symbiont–symbiont networks, leading to the working hypothesis that a small number of microbial species organize the overall root–microbiome dynamics., 植物体内の共生菌社会を動かす中心核 -農業における微生物利用の新たな戦略-. 京都大学プレスリリース. 2016-03-09.

The stresses, strains, and deformations produced by repeated, two-dimensional rolling-sliding contacts are analyzed both in the coated layer of ceramics SiC and in the substrate of two types of steels using a finite element method. Rolling and sliding are simulated by translating an appropriate set of normal and tangential surface tractions across the surface of an elastic-plastic model. A peak-pressure to shear-strength ratio of p0/k = 5 and normal to tangential force ratios of T/P = 0.2 are examined. The effect of thickness of the coated layer on the mechanical behavior of the substrate is discussed.

Friction and wear of contact surfaces during rolling and sliding should be predicted precisely and then controlled well to develop hightechnology in the industry. In order to alalyze the cyclic plastic deformation in the repeated rolling-sliding contact, it is necessary to use the constitutive model for cyclic plasticity. However, there is no analysis in repeated rolling-sliding contact using the constitutive model. Recently, the first author proposed a constitutive model for metallic material subjected to cyclic loading assuming strain hysteresis dependency, using the loading function considered as the motion of the center of the loading surface. In this paper, an attempt is made to analyze the behavior of the inelastic deformation of S20C during rolling and sliding under a contact pressure sufficient to cause yielding, using a finite element method incorporated in the constitutive model. As a result, it is demonstrated that this model is effective for this kind of problem.

Friction and wear of the contact surfaces during rolling and sliding should be predicted precisely and then controlled well to develop high-technology in the industry. It is worth noting that recently, materials are coated with ceramics to decrease the damage sustained in rolling-sliding contact. However, the effect of coating with ceramics on wear has not been examined thoroughly. In this paper, an attempt is made to analyze the behavior of the inelastic deformation of S 20 C and SKD 11 coated with SiC during rolling and sliding under a contact pressure sufficient to cause yielding using a finite element method. The effect of ceramic coating on the deformation and the distribution of stresses and strains in rolling-sliaing contact is demonstrated from the viewpoint of the thickness of the ceramic coating layer and the strain hardening of the substrate material.