Biology subjects

Ushimaru, A.

Publications and source records attributed to Ushimaru, A..

13 recordsLinked to original sources

bioRxiv2025

Nectar Sugar Enhancement in Response to Bee Buzzing in Rhododendron x pulchrum: Sound-sensing Organs and Sensitivity Range

Plants can perceive and respond to airborne sounds, but our current understandings of this phenomenon remain limited. Flowers are known to exhibit increased nectar sugar concentration in response to pollinator sounds; however, there has been only a single report from Oenothera drummondii. To test the generality of pollinator-sound-induced nectar enrichment in bee-pollinated plants, we examined nectar responses to airborne sounds, particularly those produced by bee buzzing, in Rhododendron x pulchrum and Lamium amplexicaule. We exposed the flowers to playback sounds of bee buzzing, a similar synthetic sounds signal (200 Hz) and those with higher frequency (5000 Hz) and compared nectar sugar concentrations among these sound-treated and silent control flowers. We found an approximately 10% increase in nectar sugar concentration in response to playback sounds of bee buzzing and synthetic sounds signals at bee-like frequency (200 Hz), while no such response was observed under higher-frequency stimuli or silent condition in R. x pulchrum. A similar response to bee sounds was also observed in L. amplexicaule. Furthermore, these responses were observed at a sound pressure level of 65 or 100 dB, but not at 50 dB in R. x pulchrum, indicating a sound sensitivity threshold. We experimentally removed petals, stamens, or pistils (alone or in combination) from flowers and exposed them to 200 Hz sounds and silent treatments and found that both petals and stamens were necessary for such sound responses, suggesting that these floral organs are involved in acoustic sensing. Our findings provide new insights into floral sound sensing and suggest that acoustic responses to pollinator visitations may be more widespread among bee-pollinated flowering plants.

plant biology↗

bioRxiv2025

Feasibility of an eDNA-based educational program for high school students

O_LIEnvironmental education plays a crucial role in raising public awareness of ecosystem conservation. Environmental DNA (eDNA) analysis is a promising environmental education tool because it enables easy and comprehensive biodiversity assessment through simple water sampling. Despite several citizen-based surveys using eDNA analysis, minimal attention has been paid to its educational effectiveness. C_LIO_LIIn this study, we examined the educational feasibility of eDNA analysis by conducting an environmental education program that incorporated eDNA-based local fish surveys in three high schools in Japan. Through detailed questionnaire surveys conducted before and after the program, we verified whether our program increased student interest in biodiversity and ecosystem services. C_LIO_LIIn the program, students proactively identified diverse fish species living in the survey area by simply collecting water. The questionnaire survey results showed that student knowledge of and interest in biodiversity and ecosystem services increased after the program. Students became aware of local fish diversity and expressed their motivation to engage in conservation activities. We confirmed the educational impact of the program not only at the end but also immediately following the water sampling experience. C_LIO_LISynthesis and applications. These results provide the first empirical evidence of the positive effects of eDNA analysis on student environmental awareness and engagement. Our program provides a feasible model for eDNA-based environmental education. Because eDNA analysis can be applied to diverse target taxa that are unique to a given area, similar environmental education programs can be conducted for various citizen groups worldwide. Our research also suggested that eDNA-based environmental education was effective for younger generations with varying levels of interest and experience in nature, showing significant potential for addressing the extinction of natural experiences and motivating citizens to participate in ecosystem conservation activities. C_LI

scientific communication and education↗

bioRxiv2025

Generalist flowers recover rapidly in grassland restoration: The importance of floral traits in community reassembly

Community assembly process, through biotic and abiotic filtering of species traits, is crucial for understanding the recovery of biodiversity and ecosystem function in restored ecosystems. While previous studies have highlighted very slow recovery of pollination networks in ecological restoration, the reassembly process of plant communities focusing on floral traits that influence pollination networks remains underexplored. We hypothesised that plant species with flowers that allow visits by various pollinators (generalist flowers) would recover more easily than those with flowers which limit pollinators (specialist flowers) during grassland restoration. We investigated floral trait assemblages, interaction patterns with pollinators, and pollination success for each floral trait (floral tube and colour) across 28 pollination networks. We examined their temporal change patterns within restored grasslands (2-75 years old) and compared them with reference old grasslands (>165 years old). Our results revealed that generalist (open/shallow and white/yellow) flowers have recovered rapidly, interacting with many pollinator species with similar traits in the early stages of restoration. In contrast, specialist (long-tubed and blue/purple) flowers exhibited more delayed recovery due to low pollination success, taking approximately 75 years for the recovery to the levels of reference old grasslands. Importantly, we found that functional specialisation was crucial for the recovery of these specialist flowers. Corresponding to temporal changes in floral trait assemblages, pollinator composition has shifted from dipteran dominance to a greater abundance of long-tongued bees, with interaction patterns of each trait group approaching those of old grasslands. Our findings underscore the pivotal role of floral trait reassembly in influencing temporal changes in pollinator community, network structure, and pollination function during grassland restoration. By integrating trait-based framework, this study provides novel insights into the co-reassembly process of plants and pollinators in restored ecosystems.

ecology↗

bioRxiv2024

Temporal continuity of habitat strengthens covariation between plant and arbuscular mycorrhizal fungal communities

Old grassland is considered one of the most biodiverse terrestrial ecosystems. The habitat temporal continuity may promote the accumulation of host species and symbiont arbuscular mycorrhizal fungi (AMF) diversity and strengthen symbiont interactions. We tested the hypothesis that covariation between AMF and plant communities is stronger in old grasslands. We compared the relationship between AMF and plant communities in forests and in new and old semi-natural grasslands in Japan. DNA was extracted from bulk roots collected at each site and from roots of Miscanthus sinensis at each grassland site. AMF operational taxonomic unit was characterized on the basis of small subunit rRNA gene sequences. Old grasslands harboured the highest diversity of AMF among vegetation types. The AMF compositions were significantly related to those of plant species. The covariation of plant-AMF communities was stronger in old grasslands than in new grasslands. Individuals of M. sinensis were found to share AMF with bulk roots comprising different species. This suggests that AMF form a common mycorrhizal network among several coexisting plants of different species. Increasing AMF diversity in the shared rhizosphere has been proposed to lead to more efficient utilization of soil nutrients and to increase overall benefits of plant-AMF facilitation.

ecology↗

bioRxiv2024

Long-lasting negative effects of past forestation on grassland pollination networks and their function

O_LIGrasslands are facing a rapid decline worldwide. Among the primary threats to these ecosystems are changes in land use, such as land abandonment and forestation, which promote forest vegetation in detriment of grassland plant diversity. To support the conservation and restoration of grasslands, it is key to understand what ecological processes limit the recovery of their biodiversity and functions after perturbations. However, we still know little about the legacy effects of forestation on the ecological mechanisms involved in the recovery of grasslands, especially concerning long-lasting impacts on plant-pollinator interaction networks and plant reproduction. C_LIO_LIHere, we aim to fill this gap of knowledge by comparing the plant and pollinator diversity, the degree of network generalization, the pollination success and pollen limitation of native plant species in 30 plant-pollinator networks of old-growth and restored grasslands of different ages since recovery (from 2 to 84 years). We hypothesized that past forestation would exert long-lasting legacy negative effects on plant richness and plant-pollinator networks, increasing pollen limitation for native plants, thereby delaying community recovery in restored grasslands. C_LIO_LIResults showed that restored grasslands exhibited significantly lower plant richness, less specialized (more generalized) interaction networks, lower pollination success and pollen-limited seed reproduction of native plants compared to old-growth grasslands. Meanwhile, the degree of network specialization and pollination success gradually increased with time after grassland restoration initiated. Overall, network generalization, which was caused by low plant richness, reduced pollination and reproduction success in native grassland plants, and degraded pollination networks and functions could recover in restored grasslands with continuous management. These findings imply that plant diversity restoration was slow because of the negative feedbacks associated with low plant richness and consequently, generalized plant-pollinator interaction networks, which diminished native plant reproduction in restored grasslands. C_LIO_LISynthesis and applications Our findings suggest that the recovery of specialized plant-pollinator networks by enhancing plant diversity is essential for restoring pollination function. For quicker grassland restoration, it may be effective to facilitate the establishment of highly specialized pollination networks by seeding or planting diverse native plants collected from neighbouring areas while avoiding genetic contamination. C_LI

ecology↗

bioRxiv2024

Allopolyploidy enhances survival advantages for urban environments in the native plant genus Commelina

Background and AimsUrbanization-induced environmental changes have profound effects on the geographical distribution limits in natural plant species. Polyploidization, an influential dynamic genome change, may determine survival potentials of plant species in urban environments. This study focused on the native plants, Commelina communis L. (Cc) and closely related subspecies, C. communis f. ciliata (Masam.) Murata (Ccfc) which have different chromosome numbers (e.g. Cc: 2n = 88, Ccfc: 2n = 46). The aim is to investigate polyploidization effects on natural plant distribution in urban environments. MethodsThe geographical distribution across urban-rural gradients was investigated at a total of 218 sites in Japan. Stomata size and density were measured and compared between Cc and Ccfc. Flow cytometry was used to determine genome size and polyploidy. Chromosome karyotyping was performed by using the GISH method. Key resultsUrban areas were exclusively dominated by Cc, while Cc and Ccfc coexisted in rural areas. Cc had larger and fewer stomata and more than twice genome size than Ccfc. GISH results indicated that Cc possesses Ccfc and another unknown genome, suggesting allopolyploidy. ConclusionsThese results show that the ploidy difference affects the geographical distribution, the stomata traits, and genome size between Cc and Ccfc. In addition, GISH results indicate that Cc has Ccfc and another unknown genome, suggesting Cc is an allopolyploid and these two species of the genus Commelina are distinct. Therefore, not only polyploid but also allopolyploid contributes to Cc to enhance survival potentials in urban environments compared to Ccfc. This is the first investigation to clarify the distribution difference related to urban environments, the difference in stomata traits and genome size, and to conduct chromosome composition in Commelina species.

ecology↗

bioRxiv2023

Contrasting urban adaptations of seed dispersal traits in two closely-related plant species

O_LIUrbanisation has largely altered city landscapes, resulting in habitat loss, fragmentation, and environmental degradation. City plants often have adapting traits and ecologies to such urban habitat environments. The existing literature on urban adaptation has often focused on species that shrink the abundances in urban areas compared to rural areas. Meanwhile, the studies on species that expand their range in cities remain limited, although they would exhibit different trait responses to urban environments, particularly in dispersal-related traits. C_LIO_LIIn this study, we compared seed dispersal-related traits between Youngia japonica subsp. japonica (Y.j. japonica), which is expanding its range in urban areas and its closely-relative Y.j. elstonii, which is contracting its range in urban areas along an urban-rural gradient of the Osaka-Kobe megacity area. We also examined relationships between seed traits and terminal velocity which influences seed dispersal ability. C_LIO_LIWe found that achene length increased with the degree of urbanisation only in Y.j. japonica, while pappus length decreased only in Y.j. elstonii. The terminal velocity had a significant relationship only with pappus length in Y. japonica. C_LIO_LISeed traits of two subspecies with different urban distributions showed different responses to urbanisation. Our results suggest that species expanding their distribution in urban areas has increased seed competitiveness while maintaining dispersal ability. In contrast, species that has shrunk in urban areas likely showed a passive response to urban fragmentation, indicating a loss of seed dispersal ability. C_LI

ecology↗

bioRxiv2022

Negative legacy effects of past forest use on plant diversity in semi-natural grasslands on ski slopes

Over the past century, grassland and forest ecosystems globally have been heavily influenced by land use changes driven by diverse socioeconomic activities. Ski resorts are a modern land-use type associated with biodiversity loss in mountain ecosystems worldwide. Below the treeline, by contrast, some ski slopes have been shown to provide suboptimal semi-natural habitats for native grassland plants and animals, depending on specific construction and management practices. We compared environmental factors and grassland vegetation between two types of ski slopes in central Japan with different land-use histories: slopes constructed on old pastures (pasture slopes) and slopes constructed by clearing secondary forests or Larix kaempferi plantations established on abandoned pastures during the 1940s-1990s (forest slopes). We examined the effects of land use history and machine grading as well as other environmental factors on ski slope vegetation, including total species richness and the richness of native, endangered, and exotic plants, using a total of 108 plots of 2 m x 10 m. Compared to pasture slopes, forest slopes exhibited significantly lower richness of total plants and native grassland species, including endangered species. Forest slopes were more graded than pasture slopes, resulting in lower native and higher exotic grassland species richness. A significantly lower duration of direct sunlight on forest slopes than on pasture slopes possibly decreased endangered species diversity. The lower species richness on forest slopes may be partly caused by seed dispersal limitations. Our findings demonstrate that ski slopes have good potential to support numerous native grassland plant species, including endangered species, but this potential is significantly and negatively affected by forest use history and concomitant environmental changes. The conservation of semi-natural conditions on pasture slopes as habitats for native grassland species can be promoted through the maintenance of annual mowing practices, avoidance of machine grading, and wider ski courses. NomenclatureYonekura & Kajita (2003) BG Plants: index of Japanese names and scientific names (YList; http://ylist.info/index.html)

plant biology↗

bioRxiv2022

Habitat preference influences response to changing agricultural landscapes in two long-horned bees.

Agricultural intensification and urban development have drastically influenced pollinators living in semi-natural grasslands. Pollinators are likely to have different responses to these land-use changes; some decline rapidly while others maintain or increase their populations. We predicted differences in interspecific response to land-use changes are partly attributed to differences in habitat preference. We examined the distribution and flower use patterns of two closely related Eucera species with different habitat preferences. Study sites were meadows surrounding traditional, intensified, and urbanised agricultural lands in the Osaka-Kobe metropolitan area, Japan. Forest-associated Eucera nipponensis were significantly fewer in consolidated and urbanised meadows than traditional meadows, whereas open land-associated E. spurcatipes exhibited the opposite. A significant negative relationship between their abundances was also found. Both species foraged on legume flowers most frequently (83.5%), but floral use pattern was significantly different in traditional and consolidated meadows. Bee species preferring stable habitats were vulnerable to land consolidation and urbanisation, while species associated with disturbed habitats maintained or increased population size in meadows with the land-use changes. Thus, recent land uses may have different impacts on species with different habitat preferences.

ecology↗

bioRxiv2021

Prior selfing occur in larger flowers in a mixed mating species with delayed selfing

Theory predicts that prior self-pollination (prior selfing) should not evolve in mixed mating species that enable delayed selfing. In this study, we test the hypotheais that prior selfing has evolved under severe pollinator limitation in the mixed mating species Commelina communis which can reproduce via delayed selfing. The hypothesis predicts that prior selfing occurs more frequently in populations with very low pollinator availability and/or in smaller flowers which receive infrequent visitations. We tested the predictions by comparing the degree of prior selfing among ten populations experiencing various levels of pollinator limitation and by examining a relationship between individual flower size and the occurrence of prior selfing. Populations with higher pollinator availability had higher prior selfing rate. Moreover, prior selfing occurs more frequently in larger flowers. These findings were totally opposite patterns of the predictions and the previous findings. We proposed new hypotheses that prior selfing has been maintained by the presence of reproductive interference from the congener and/or propotency in C. communis to explain our unexpected findings. We should verify potential effects of reproductive interference and propotency in future to elucidate the mystery of prior selfing in this mixed mating species with delayed selfing.

ecology↗

bioRxiv2021

Horizontal orientation facilitates pollinator attraction and rain avoidance in radially symmetrical flowers

PremiseFloral angle, such as upward, horizontal, and downward orientation are known to evolve under both biotic and abiotic agents to enhance pollination success in zoophilious plants. Adaptive significance of horizontal orientation in radially symmetrical (actinomorphic) flowers under biotic and abiotic selection pressures were largely unknown, although those in bilaterally symmetrical flowers have been well studied. MethodsUsing experimentally angle changed flowers, we examined the effects of flower angle on pollinator behaviors, pollination success and rain avoidance in a population of insect-pollinated Platycodon grandiflorus. We further investigated the frequency and amount of precipitation in the flowering season and pollen damage by water in this species. Main results: Horizontally oriented flowers received more visitations and pollen grains on the stigma in male and/or female phases than downward and/or upward oriented flowers and avoided pollen damage by rainfall compared to upward oriented flowers. The pollen germination experiment showed that approximately 30% of pollen grains burst in distilled water, thus pollen damage by rainfall was potentially serious in P. garndiflorus. ConclusionIn this study, our field experiments revealed that upward flowers cannot avoid damage from rainfall during the flowering period whereas both upward and downward flowers suffered from pollinator limitation in female success. Thus, horizontal flower orientation is suggested to be adaptive in this insect-pollinated actinomorphic species which blooms in the rainy season.

ecology↗

bioRxiv2020

The effects of temporal continuities of grasslands on the diversity and species composition of plants

Semi-natural grasslands are ecosystems rich in biodiversity. However, their decline has been reported worldwide, and identification of grasslands with high conservation priority is urgently required. Recently, an increasing number of studies have reported that past vegetation history affects current biological communities. To evaluate whether the temporal continuity of grasslands promotes biodiversity, and thus can be an indicator of conservation priority, we studied vascular plant communities in old (160- 1000s years) and new (52-70 years after deforestation) grasslands, as well as in forests, of Sugadaira Highland in central Japan. The number of plant species was highest in old grasslands, followed by new grasslands and forests. This pattern was much clearer in the number of grassland-dependent native and grassland-dependent endangered species, indicating the role of old grasslands as refugia for those species. The species composition differed between old and new grasslands. New grasslands had species compositions in between those of old grasslands and forests, suggesting that the plant community in new grasslands retains the influence of past forestation for more than 52 years after deforestation. Eleven indicator species were detected in old grasslands, but none in new grasslands, suggesting the uniqueness of the plant community in old grasslands. We conclude that the temporal continuity of grasslands increases plant diversity and can be an indicator of grasslands with high conservation priority.

ecology↗

bioRxiv2020

Eco-evolutionary dynamics of prior selfing rate promotes the coexistence without niche partitioning under reproductive interference

O_LIWhen the two or more plants species share the same pollinators, pollinator-mediated reproductive interference make coexistence difficult. Recent studies suggested prior autonomous selfing mitigate reproductive interference, could enabling coexistence without pollination niche partitioning (pre-emptive selfing hypothesis). However, there are no studies to test whether evolution of prior selfing promote the coexistence, considering eco-evolutionary dynamics of population size, selfing rate and inbreeding depression. C_LIO_LITo examine conditions that the evolution of prior selfing promote coexistence under mutual reproductive interference especially in the point of view for pollinator availability and dynamics of inbreeding depression, we constructed individual-based model in which two plant species compete against each other in the form of mutual reproductive interference and can evolve prior autonomous selfing rate. We expected that purging of deleterious mutations could cause evolutionary rescue because inferior species could rescue population density through the evolution of prior selfing if the strength of inbreeding depression decreases with an increase of populations selfing rate. C_LIO_LIOur simulation demonstrated that the evolution of prior selfing could promote the coexistence while reproductive interference caused competitive exclusion without evolution. We found that lower pollinator availability tended to prefer rapid evolutionary shift to higher prior selfing rate, it neutralizes the negative effect of reproductive interference, and population dynamics exhibit neutral random walk in both species. When the strength of inbreeding depression decreased with an increase in populations selfing rate, moderate pollinator availability resulted in long-term coexistence in which relative-abundance-dependent selection on the prior selfing rate rescue population density of inferior species intermittently. C_LIO_LISynthesis. We showed that the evolution of prior selfing could increase population growth rate of inferior species and consequently enable the long-term coexistence with evolutionary rescue. This is the new mechanisms explaining co-evolutionary coexistence of closely related plant species without niche partitioning and consistent with recent studies reported that closely related mixed-mating species are sympatrically growing even under the mutual reproductive interference. C_LI

ecology↗