Ecological Research


    Vol. 36 (2021)
    No. submitted articles: 267
    No. accepted articles: 92


    Statistics in the 6 months (2022.01-06)
    Days to First Decision (All Manuscripts): 38.96 (days)
    Days to First Decision (Mss. with Final Decisions Only): 41.76 (days)

    Current issue
    (vol. 37, issue 6)
    Days for acceptance:
    136.0 (92–267)
    Days for Early View:
    180.7 (140–376)
    Days for publication:
    281.78 (225–417)

Award Articles (List after Vol.32)


  • Ecological impacts of fungal wood decay types: A review of current knowledge and future research directions

    Yu Fukasawa

    Ecological Research Vol. 36, Issue 6, pp 910–931

    Keywords: Carbon cycling; Deadwood; Ecological networks; Forest biodiversity; Wood decay fungi

    Abstract: I summarize current knowledge about the ecosystem functions of wood decomposition in forests with a particular focus on the effects of fungal wood decay types (traditionally categorized into white-, brown-, and soft-rot) on the community composition of saproxylic organisms, forest tree regeneration, and carbon sequestration. Deadwoods of different decay types show markedly different physicochemical and biological properties. High carbohydrate availability in white-rotted wood promotes the activities of nitrogen-fixing bacteria; thus white-rotted wood is a good dietary source for many wood-eating invertebrates. In contrast, brown-rotted wood is unattractive to saproxylic communities due to the high recalcitrance of accumulated lignin, low nutrient content, and low pH. Nevertheless, some species have adapted to these conditions and form distinctive communities on brown-rotted wood. Tree seedlings that are associated with brown-rotted wood are symbiotic with arbuscular and ericoid mycorrhizal fungal species, but not ectomycorrhizal species. Thus, the diversity of fungal communities associated with a variety of wood decay types produces habitat diversity for saproxylic communities and promotes biodiversity in forest ecosystems. Wood decay type also affects carbon sequestration in forests as brown-rotted wood might be more instrumental in soil organic matter accumulation than white-rotted wood. An important aspect of wood decay type is that the wood decay activities of fungi can have indirect long-lasting cascading impacts on forest biodiversity by altering the physicochemical properties of deadwood. Including the effects of wood decay type in ecological models is thus important for predicting the long-term dynamics of biodiversity, vegetation, and carbon cycling in forest ecosystems.

    Yu Fukasawa is the recipient of the 23rd Denzaburo Miyadi Award!!

  • Animal linguistics: Exploring referentiality and compositionality in bird calls

    Toshitaka N. Suzuki

    Ecological Research Vol. 36, Issue 2, pp 221–231

    Keywords: Bird; Communication; Compositionality; Language evolution; Referentiality

    Abstract: Establishing the theory of language evolution is an ongoing challenge in science. One profitable approach in this regard is to seek the origins of linguistic capabilities by comparing language with the vocal communication systems of closely related relatives (i.e., the great apes). However, several key capabilities of language appear to be absent in non-human primates, which limits the range of studies, such as direct phylogenetic comparison. A further informative approach lies in identifying convergent features in phylogenetically distant animals and conducting comparative studies. This approach is particularly useful with respect to establishing general rules for the evolution of linguistic capabilities. In this article, I review recent findings on linguistic capabilities in a passerine bird species, the Japanese tit (Parus minor). Field experiments have revealed that Japanese tits produce unique alarm calls when encountering predatory snakes, which serve to enhance the visual attention of call receivers with respect to snake-like objects. Moreover, tits often combine discrete types of meaningful calls into fixed-ordered sequences according to an ordering rule, conveying a compositional message to receivers. These findings indicate that two core capabilities of language, namely, referentiality and compositionality, have independently evolved in the avian lineage. I describe how these linguistic capabilities can be examined under field conditions and discuss how such research may contribute to exploring the origins and evolution of language.

    Toshitaka N. Suzuki is the recipient of the 22nd Denzaburo Miyadi Award!!

  • Modeling dispersal using capture–recapture data: A comparison of dispersal models

    Akira Terui

    Ecological Research Vol. 35, Issue 5, pp 686–699

    Keywords: Markov chain Monte Carlo; Movement; Simulation; Spatial ecology; Statistical inference

    Abstract: Capture–recapture methods have been a cornerstone of field‐based dispersal ecology. However, obtaining unbiased estimates of dispersal parameters from capture–recapture data is challenging because it is impossible to survey all possible range of dispersal in the field. There are several approaches to address this critical issue of capture–recapture methods. Still, a lack of formal comparisons among these modeling approaches has confused about which is the best practice given the available dataset. Here, I compared the performance of three dispersal models using test datasets simulated under various sampling designs. In the first approach, a probability distribution (a dispersal kernel) was simply fitted to the capture–recapture data (the “simple dispersal model”). In the second approach, a truncated probability distribution was used to account for the finite range of observations (the “truncated dispersal model”). Finally, the dispersal and observation processes were coupled to consider the spatial organization of sampling designs (the “dispersal–observation model”). The simulation study provided three important insights. First, the dispersal–observation model provided reliable estimates of dispersal parameters, even under sampling designs with a few recaptures. Second, the truncated dispersal model was also effective, but only when the number of recaptures was large. Finally, the use of the simple dispersal model caused a substantial underestimation of dispersal parameters regardless of sampling designs; this modeling approach should be avoided where possible. The results of this simulation study should help choose a suitable modeling approach.

    Akira Terui is the recipient of the 23rd Denzaburo Miyadi Award!!

  • Dynamic and synergistic influences of air temperature and rainfall on general flowering in a Bornean lowland tropical forest

    Masayuki Ushio, Yutaka Osada, Tomo'omi Kumagai, Tomonori Kume, Runi anak Sylvester Pungga, Tohru Nakashizuka, Takao Itioka, Shoko Sakai

    Ecological Research Vol. 35, Issue 1, pp 17–29

    Keywords: Borneo; Empirical dynamic modeling; General flowering; Lambir Hill national park; Time series; Tropical forest

    Abstract: Supra‐annually synchronized flowering events occurring in tropical forests in Southeast Asia, known as general flowering (GF), are “spectacular and mysterious” forest events. Recently, studies that combined novel molecular techniques and model‐based theoretical approaches suggested that cool temperature and drought synergistically drove GF. Although these advanced our understanding of GF, it is still difficult to know whether the individual‐based molecular measurements and model‐based mathematical representations reasonably well capture the complex and dynamic GF processes at the community level. In the present study, we collected a 17‐year set of community‐wide phenology data from Lambir Hills National Park in Borneo, Malaysia, and analyzed it using a model‐free approach, empirical dynamic modeling (EDM), which does not rely on specific assumptions about the underlying mechanisms, to overcome and complement the previous limitations. We found that GF in the region is driven synergistically, not independently, by cool air temperature and drought, which is consistent with the previous studies. More importantly, our model‐free approach showed for the first time that effects of cumulative meteorological variables on GF changed over time. The time‐varying influences of meteorological variables on GF imply that the relationship between GF and meteorological variables might be influenced by other factors such as plant/soil nutrient resource dynamics. Our study provides a novel insight about the mechanism underlying the spectacular tropical forest event GF, and future studies integrating advanced mathematical/statistical frameworks, long‐term and large spatial scale ecosystem monitoring and molecular phenology data are promising for achieving better understanding and forecasting of GF events in Southeast Asia.

    Masayuki Ushio is the recipient of the 22nd Denzaburo Miyadi Award!!

  • Charcoal ecology: Its function as a hub for plant succession and soil nutrient cycling in boreal forests

    Kobayashi Makoto, Takayoshi Koike

    First published: 08 October 2020

    Keywords: Above‐ and belowground linkages; Black carbon; Climate change; Forest fire; Succession

    Abstract: We summarize current knowledge about the ecosystem functions of fire‐produced charcoal in boreal forests with a special focus on its effects on soil carbon, nitrogen and phosphorous dynamics as well as on plant succession. Charcoal is a carbon‐enriched material with a highly aromatic and porous structure. Charcoal is highly resistant to microbial decomposition and thus remains in soil for thousands of years, providing recalcitrant carbon to boreal forest soils. The abundant pores in and on charcoal surfaces have powerful adsorption abilities that can influence biogeochemical cycles and plant succession after fire. Our review details the influence of charcoal on plant and soil systems and explains the complex direct and indirect pathways of these influences that occur during succession after fires in boreal ecosystems. Among these pathways, the most important pathway through which charcoal influences plant and soil systems relates to the element composition and nutrient availability in soils and to the abundance of phenolics released from Ericaceae plants in the understory of boreal forests. We found a strong bias in the studied processes towards nutrient mineralization rather than immobilization, which suggests that it is risky to draw general conclusions about the influence of charcoal on soil nutrient dynamics. Last, the latest studies shed light on the enhancement of litter and humus decomposition by charcoal, given the possibility that charcoal accelerates CO2 release in a postfire forest. This review suggests comparative studies that are necessary to test the context‐dependency of charcoal functions across a variety of boreal forest ecosystems.

    Kobayashi Makoto is the recipient of the 22nd Denzaburo Miyadi Award!!

  • Perspectives on biodiversity informatics for ecology

    Takeshi Osawa

    Ecological Research Vol. 34, Issue 4, pp 446–456

    Keywords: Data management; Data reuse; Data sharing; Natural history; Open data

    Abstract: Biodiversity informatics is the application of informatics techniques to ecology and biodiversity sciences. The premise is utilizing natural history collections/data, such as specimens and biodiversity observations, with information and communication technology. During the past two decades, biodiversity informatics has improved dramatically and has been applied increasingly in ecology science. In this paper, I review biodiversity informatics for ecology with a particular focus on the treatment of data. First, I discuss the traditional perspective of data collection and its usage in the ecological community. Then, I provide an overview of the trajectory of changing perspectives of data treatment relative to developing biodiversity informatics (i.e., the infiltration of the data reuse and sharing concepts). Specifically, I discuss the significance of data reuse, which offers numerous benefits for research, and data sharing with their supporting mechanisms and case studies. Finally, I discuss potential future developments in biodiversity informatics relative to the field of ecology.

    Takeshi Osawa is the recipient of the 21st Denzaburo Miyadi Award!!

  • Use of compound-specific nitrogen isotope analysis of amino acids in trophic ecology: assumptions, applications, and implications

    Naoto F. Ishikawa

    Ecological Research Vol. 33, Issue 5, pp 825–837

    Keywords: Diet source; Mixing model; Trophic discrimination factor; Trophic position; Trophic transfer efficiency

    Abstract: Knowledge of the diet source and trophic position of organisms is fundamental in food web science. Since the 1980s, stable isotopes of light elements such as 13C and 15N have provided unique information on the food web structure in a variety of ecosystems. More recently, novel isotope tools such as stable isotopes of heavy elements, radioisotopes, and compound-specific isotope analysis, have been examined by researchers. Here I reviewed the use of compound-specific nitrogen isotope analysis of amino acids (CSIA-AA) as a useful dietary tracer in food web ecology. Its three key features—(1) offsetting against isotopic variation; (2) universality of the trophic discrimination factor; and (3) sensitivity to source mixing—were compared with conventional isotope analysis for the bulk tissue of organisms. These three advantages of CSIA-AA will allow future researchers to (1) estimate the integrated trophic position (iTP) of animal communities; (2) infer trophic transfer efficiency (TTE) in food webs; and (3) quantify contributions from different resources to animals, all of which are crucial for understanding the relationship between biodiversity and multi-trophic ecosystem functioning. Further development of trophic ecology will be facilitated by both methodological refinement of CSIA-AA and its application to a wider range of organisms, food webs, and ecosystems.

    Naoto F. Ishikawa is the recipient of the 21st Denzaburo Miyadi Award!!

  • Individual interaction data are required in community ecology: a conceptual review of the predator–prey mass ratio and more

    Takefumi Nakazawa

    Ecological Research Vol. 32, Issue 1, pp 5–12

    Keywords: Allometry; Individual interaction; Life‐history stage; Ontogenetic niche shift; Size structure

    Abstract: Community ecology is traditionally species‐based and assumes that species comprise identical individuals. However, intraspecific variation is ubiquitous in nature because of ontogenetic growth and critical in food‐we dynamics. To understand individual interaction‐mediated food webs, researchers have recently focused on body size as the most fundamental biological aspect and assessed a parameter called the predator–prey mass ratio (PPMR). Herein, I review the conceptual development of the PPMR and suggest four major concerns regarding its measurement: (1) PPMR should be measured at the individual level because species‐averaged values distort actual feeding relationships, (2) individual‐level PPMR data on gape‐unconstrained predators (e.g., terrestrial carnivores) are limited because previous studies have targeted gape‐limited fish predators, (3) predators’ prey size selectivity (preferred PPRM) is conceptually different from dietary prey size (realized PPMR) and should be distinguished by incorporating environmental prey abundance information, and (4) determinants of preferred PPMR, rather than those of realized PPMR, should be identified to describe size‐dependent predation. Future studies are encouraged to explore not only predation but also other interaction types (e.g., competition, mutualism, and herbivory) at the individual level. However, this is not likely to occur while ecological communities are still considered to be interspecific interaction networks. To resolve this situation and more comprehensively understand biodiversity and ecosystem functioning, I suggest that community ecology requires a paradigm shift in the unit of interaction from species to individuals, similar to evolutionary biology, which revolutionized the unit of selection, because interactions occur between individuals.

    Takefumi Nakazawa is the recipient of the 20th Denzaburo Miyadi Award!!

  • Characteristics of fruits consumed by mammalian frugivores in Japanese temperate forest

    Shinsuke Koike, Takashi Masaki

    Ecological Research Vol. 34, Issue 2, pp 246–254

    Keywords: Frugivory; Macaca fuscata; Martes melampus; Nyctereutes procyonoides; Ursus thibetanus

    Abstract: Understanding the interactions among fruits and frugivore assemblages provides fundamental information for the management of ecosystems. Asian temperate forests are inhabited by distinct frugivores, namely, large tree‐climbing mammals such as bears and macaques, suggesting that fruits and frugivore assemblages may vary from those of other temperate forests. Our aim here was to systematically analyze the characteristics of fruits consumed by four dominant frugivorous mammals in Japanese temperate forests and to clarify the fruit palatability or preference of each species by comparing the fruit consumption patterns of the frugivores. We collected fruit feeding records of Asian black bear, Japanese marten, raccoon dog and Japanese macaque, as well as detailed information on the characteristics of the fruits consumed. Among the 299 fruit species recorded, the size, color and type of fruits consumed by bears and macaques were similar, and the fruiting season and life form of plants bearing fruits consumed by bears, macaques and raccoon dogs were similar. However, the characteristics of fruits consumed by martens were different. The ability to climb trees, body weight and manual dexterity may influence these differences.

    Shinsuke Koike is the recipient of the 19th Denzaburo Miyadi Award!!

  • Genome‐wide population genetic analysis identifies evolutionary forces establishing continuous population divergence

    Yuma Takahashi

    Ecological Research Vol. 32, Issue 4, pp 461–468

    Keywords: Balancing selection; Cline; Damselfly; Divergent selection; Stochastic factor

    Abstract: Elucidating the mechanism shaping the spatial variations of traits has long been a central concern of evolutionary biologists. Geographic clines of allele/morph frequencies along environmental gradients are suggested to be established and maintained by the balancing of two opposing evolutionary forces, namely selection that generates spatial differentiation in morph frequencies, and selection and/or stochastic factors that lead to the coexistence of multiple morphs within a population. Thus, testing for both selection and stochastic factors is necessary for a comprehensive understanding of the mechanism underlying clinal variation in morph/allele frequency in natural populations. Here, I identified the evolutionary forces responsible for clinal variation of color morph frequency in Ischnura senegalensis by comparing the population divergence of putatively neutral loci generated by high‐throughput next‐generation sequencing (FSTn) with that of the putative color locus (FSTc). No strong correlation was observed between FSTn and FSTc, suggesting that stochastic factors contribute less to color‐locus population divergence. FSTc was less than FSTn between populations exposed to similar environmental conditions, but greater than FSTn between populations exposed to different environmental conditions, suggesting that both balancing selection and divergent selection act on the color locus. Therefore, two antagonistic selection factors rather than stochastic and historical factors contribute to establishing the clinal variation of morph frequency in I. senegalensis.

    Yuma Takahashi is the recipient of the 19th Denzaburo Miyadi Award!!


  • Red foxes in Japan show adaptability in prey resource according to geography and season: A meta-analysis

    Masumi Hisano, Maldwyn J. Evans, Masashi Soga, Hiroshi Tsunoda

    Ecological Research Vol. 37, Issue 2, pp 197–214

    Keywords: Biogeography; Dietary switching; Mesocarnivore; Optimal foraging; Vulpes vulpes

    Abstract: The red fox (Vulpes vulpes) is the world's most widespread member of the order Carnivora, occurring across a large range of latitudes and inhabiting multiple habitat types. There is no comprehensive study of how the diets of this flexible generalist vary across the whole Asian continent. We conducted a meta-analysis of red fox diets in Japan, examining the patterns in food type selection and their associations with seasonality, regional climate, vegetation productivity, and human influences at the national scale. Using linear mixed models, we revealed significant seasonal effects on the frequency of occurrence of mammals in general, ungulate carcasses, birds, and invertebrates in the diets of red foxes. Furthermore, the frequency of occurrence of mammals significantly decreased with mean annual temperature and increased with vegetation productivity. The frequency of invertebrate occurrences increased with temperature, and that of anthropogenic foods increased with human population density. Trophic diversity and dietary niche breadth increased with annual temperature but decreased with vegetation productivity and population density. These results suggest that the red fox is a flexible predator in Japan that adapts its foraging patterns according to variations in resource availability and abiotic conditions, while persistently consuming a certain ratio of animal prey to meet its metabolic requirements. Modifications of predators' trophic niches can influence structures of prey communities and interactions with sympatric competitors. Our findings are important for informing ecosystem management practices under ongoing environmental and social changes in Japan.

    Masumi Hisano is the recipient of the 8th Nobuhiko Suzuki Award!!

  • Seed beetles as a modern model system of interspecific competition

    Daisuke Kyogoku

    Ecological Research Vol. 36, Issue 4, pp 580–589

    Keywords: Callosobruchusn; Coexistence; Competition; Extinction; Reproductive interference

    Abstract: When and how multiple species can or cannot coexist is a fundamental question in ecology. Recent theory suggests that mechanisms other than trophic tradeoff could enhance the coexistence of ecologically similar species, with a strong emphasis on reproductive processes. Therefore, how resource competition and reproductive interactions jointly drive competitive dynamics is an empirical question of interest. In this context, interspecific competition between two congeneric seed beetles, Callosobruchus maculatus and C. chinensis, is a particularly interesting system; they are ecologically similar, their reproductive biology is well understood, and the two species interact with each other reproductively (through reproductive interference). Here, I review the literature for those who are interested in studying the interspecific interactions within this system, with a special emphasis on their reproductive biology and reproductive interference. I also reanalyze the results of a previous study to provide additional insight. At the end of the paper, I suggest several future directions to encourage future work that could provide further general ecological and evolutionary insights.

    Daisuke Kyogoku is the recipient of the 7th Nobuhiko Suzuki Award!!

  • Museum specimens: An overlooked and valuable material for conservation genetics

    Naoyuki Nakahama

    Ecological Research Vol. 36, Issue 1, pp 13–23

    Keywords: Conservation genetics; Genetic diversity; Museum; Next-generation sequencing; Specimen DNA

    Abstract: Museum specimens include genetic information from when they were collected. This historical information, which is very difficult to ascertain from samples collected currently, could be a valuable material for use in conservation genetics. However, the genetic analysis of museum specimens is technically difficult because of DNA fragmentation and the deamination of cytosine to uracil. In recent years, various methods have been developed for the genetic analysis of museum specimens, such as data analysis techniques including next-generation sequencing. The development of approaches that extract historical genetic information from museum specimens is expected to provide a new perspective on conservation genetics. This review focuses on the availability of museum specimens as genetic resources for conservation genetics. Some case studies are introduced, and perspectives on the future utility of conservation genetic studies using museum specimens are discussed. Moreover, recommended genetic analysis methods and important points for the usage of museum specimens are presented. This review provides a strong case for increasing the usage of museum specimens in conservation genetics studies in the future.

    Naoyuki Nakahama is the recipient of the 7th Nobuhiko Suzuki Award!!

  • The inequalities of the extinction of experience: The role of personal characteristics and species traits in the distribution of people–plant interactions in Japan

    Masashi Soga, Kazuaki Tsuchiya, Maldwyn J. Evans, Soki Ishibashi

    Ecological Research Vol. 34, Issue 3, pp 350–359

    Keywords: Biodiversity conservation; Connection to nature; Cultural ecosystem services; Human well‐being; Human–nature interactions; Nature relatedness; Personalised ecology; Urban ecology; Urban greenspace

    Abstract: There is concern about the increasing loss of people's direct interactions with fauna and flora. This extinction of experience has many potential far‐reaching implications for both biodiversity and humans, including the decrease of public support for conservation issues and a reduction in the health benefits that humans experience when interacting with nature. However, knowledge of how experiences with biodiversity are distributed among different sectors of society and the key drivers of this distribution remains poor. Here, we report on the results of a nation‐wide online survey in Japan in which we explored the extent, distribution, and drivers of participant's direct experiences with wild flowering plants. Participants were asked to provide information on their sociodemographics, orientation toward nature, childhood residential environment, and whether they had experienced each of 21 wild flowering plant species. The reported number of wild flowering plant species that participants had experienced varied greatly. Older and female participants and those with childhoods in rural areas and with a greater orientation toward nature experienced a significantly higher number of interactions with flowering plant species. Plant species that prefer roadside environments (compared to grassland/farmland and forest‐dependent species) and are not on the Red List were likely to be experienced by participants. This novel study provides unique information about the interactions of people and the wildlife around them. Such information is crucial for the development of policies and strategies targeted to reduce the ongoing extinction of experience and its negative consequences.

    Masashi Soga is the recipient of the 6th Nobuhiko Suzuki Award!!

  • Genetic and ecological conservation issues for oceanic island birds, revealed by a combination of the latest molecular techniques and conventional field work

    Haruko Ando

    Ecological Research Vol. 34, Issue 2, pp 255–264

    Keywords: Food selection; Genetic structure; Inter‐island movement; Introduced species; Molecular markers

    Abstract: Oceanic island ecosystems are vulnerable to artificial disturbances, and many island endemics are at risk of extinction. Conservation of island endemics is a high priority for reducing biodiversity loss, but fundamental studies on many species remain lacking due to the small population size and limited accessibility to island habitats. In this review, I explored conservation issues of endangered bird species in oceanic island habitat, which have been revealed by the latest molecular techniques with a combination of conventional field work. Recent genetic studies revealed low genetic diversity of endangered island endemics. Analyses of genetic structure have revealed the gene flow of endemic birds among islands according to their flying abilities. Seasonal inter‐island movement of Columbiformes and some finches have been observed, which might be related to fluctuating food resource availability among island habitats. Dietary analyses based on DNA metabarcoding for Columba janthina nitens revealed frequent consumption of introduced plants by this bird. This review may provide a new perspective for conservation biology in oceanic island ecosystems. That is, (a) appropriate management of genetic diversity within and outside of habitat before serious population declines occur, (b) detection of meaningful evolutionarily significant units (ESUs) considering flying ability of birds among islands and management of total habitat range within each ESU and (c) introduced species eradication designed to not to cause a negative impact on endangered species that may depend on introduced species for their food.

    Haruko Ando is the recipient of the 5th Nobuhiko Suzuki Award!!

  • Risk sensitivity of a forager with limited energy reserves in stochastic environments

    Hiromu Ito

    Ecological Research Vol. 34, Issue 1, pp 9–17

    Keywords: Adaptive behavior; Foraging theory; Geometric mean fitness; Mathematical modeling; Optimal behavior

    Abstract: Long‐term environmental stochasticity is known to affect the adaptive evolution of life history traits. In stochastic environments, there are two different levels of behavioral optimization, as follows: Level 1, the optimal strategy under an intrageneration stochastic environment and Level 2, the optimal strategy under an intergeneration stochastic environment. This article presents a simple optimal foraging model under predation risks and verified the effect of behavioral optimization on the foraging time ratio. In this model, foragers are exposed to predation risks during foraging but are safe if they stay in their nests without any food. The foraging time allocation strategies that optimize the geometric mean fitness (Level 2) were compared with the arithmetic mean fitness (Level 1) to verify the effects of intergenerational stochasticity, whereby there is an alternation in good/bad environments across generations. As in previous studies, risk‐averse strategies (a shorter foraging time is adopted for Level 2 than for Level 1) were commonly observed using this model. Unexpectedly, the model showed a tendency toward a preference for risk‐prone strategies. This qualitative difference became prominent when food was abundant and the maximum energy reserves were small. Theoretical studies have shown that risk‐averse strategies are commonly adopted during food shortages and result in starvation. However, the current results indicate that risk‐prone strategies may become optimal under a limited reserve capacity. Thus, the optimal strategy depends not only on the individual status and environmental conditions, but also on the detailed selection regimes.

    Hiromu Ito is the recipient of the 5th Nobuhiko Suzuki Award!!

  • Beauty alone is insufficient: female mate choice in the barn swallow

    Masaru Hasegawa

    Ecological Research Vol. 33, Issue 1, pp 3–16

    Keywords: Female mate preference; Hirundo rustica; Nestling-like traits; Secondary sexual characteristics; Territory quality

    Abstract: The barn swallow, Hirundo rustica, is a model species for studying sexual selection, particularly female mate choice. Although there have already been several reviews of female mate choice and its geographic variation in this species, all of them have focused on secondary sexual characteristics. Here, for better understanding of the general pattern of female mate choice and their influence on male phenotype, I review all of the female mate choice criteria ever reported in the barn swallow, emphasizing the importance of relatively inconspicuous male traits. These include resources defended or provided by males, such as territory and paternal investment. In addition, females prefer a nestling-like vocalization, enticement call, which is particularly noteworthy because females prefer immature calls. This pattern contrasts with female choice based on secondary sexual characteristics, in which more mature, elaborate male traits are almost always favored. Nestling-like male traits are widespread, and thus female avoidance of, rather than preference for, mature forms might be common. In addition to selection on the target trait itself, these resources and nestling-like male traits would also matter in understanding the evolution of the overall male phenotype and its geographic variation, due to the interrelationships among male target traits and those among female mate preferences. Female preferences for inconspicuous traits are highly dependent on ecological factors such as nest predation pressure, and thus overall male phenotype including secondary sexual characteristics might be more predictable than previously thought. Future studies should focus on not only conspicuous secondary sexual characteristics but inconspicuous male traits.

    Masaru Hasegawa is the recipient of the 4th Nobuhiko Suzuki Award!!

  • Toxic males: Density‐dependent male mating harassment can explain geographic parthenogenesis

    Masato Yamamichi, Ichiro Koizumi

    Ecological Research Vol. 35, Issue 2, pp 281–288

    Keywords: Lotka‐Volterra model; Maintenance of sex; Positive frequency‐dependence; Reproductive interference; Sexual conflict

    Abstract: Understanding evolutionary forces that maintain sexual reproduction has been a central question in evolutionary biology, because the well‐known “two‐fold” cost of sex demands an explanation, especially since asexual reproduction (vegetative reproduction and parthenogenesis) often arises by mutation and hybridization. Geographic parthenogenesis, where asexual reproduction by close relatives of sexual lineages tends to be found in “marginal” habitats, has been considered a key pattern for studying the maintenance of sex. Recent studies of sexually reproducing populations have revealed that mating attempts by males can be harmful to females due to sexual conflict. Where that occurs and where there is a mixture of both sexual and asexual females, if male mating harassment is more harmful to asexual females than to sexual females, this may prevent the invasion of rare asexuals. Here, we use a simple ecological model with density‐dependent male mating harassment to show how asexual reproduction can become prevalent in habitats when environmental conditions are poor (i.e., low carrying capacities). The maintenance of sex is possible in a bistable system where abundant males are so harmful that they prevent the invasion of rare asexuals. However, male density is not large enough to suppress asexuals and sex is lost when carrying capacities are low or when sex ratio is highly male‐biased. While previous theoretical studies employed a frequency‐dependent model to study male mating harassment, we demonstrate that density‐dependence may be important to explain the dynamics in low population densities where there is geographical parthenogenesis.

    Masato Yamamichi is the recipient of the 3rd Nobuhiko Suzuki Award!!

  • Towards linking species traits to demography and assembly in diverse tree communities: Revisiting the importance of size and allocation

    Yoshiko Iida, Nathan G. Swenson

    Ecological Research Vol. 35, Issue 6, pp 947–966

    Keywords: Allometry; Biomass allocation; Functional trait; Ontogeny; Size‐dependency

    Abstract: One of the important goals in plant ecology is to form a mechanistic link between the underlying processes driving the dynamics and structure of communities and the observed demography (i.e., growth, survival, and recruitment) and assembly (i.e., distribution of species) in a community via traits. Although the importance of traits to performance is evident, their direct links to demography and the resulting assembly in tree communities are often found to be fairly weak probably because a single “mean” trait value for a species is not enough to capture complex life histories. In this paper, we review how traits at the organ‐level and at the whole plant level, demography, and assembly change with size in diverse tropical forests and summarize what know so far. We argue the importance of trait‐based life‐history strategies revealing trait‐environment‐demography linkages across ontogenetic stages to achieve the ultimate goal of forming a mechanistic link between the underlying processes driving the dynamics and structure of communities and the observed demography and assembly.

    Masaru Hasegawa is the recipient of the 2nd Nobuhiko Suzuki Award!!


  • Ups and downs of non-native and native stream-dwelling salmonids: Lessons from two contrasting rivers

    Kentaro Morita

    Ecological Research Vol. 37, Issue 2, pp 188–196

    Keywords:Habitat fragmentation; Hatchery; Introduced species; Longitudinal distribution; Niche partitioning

    Abstract: Freshwater rivers and lakes are particularly vulnerable to anthropogenic disturbance because of their proximity to human occupation. Anthropogenic impacts in fresh water include those caused by dams, water pollution, channelization, and invasive species. One common action to conserve freshwater biodiversity involves supplementing or reintroducing extirpated species, though the benefits of these efforts are controversial. Installation of fishways to dams and removal of invasive alien species has also resulted in recovery of native species. Herein results of long-term monitoring of salmonids in two rivers in Japan are presented. The first case involves a river above a dam where native white-spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou declined rapidly in number following dam construction, where non-native rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta increased in number, and where stocking of native masu salmon was unsuccessful. The second case involves a river formerly dominated by non-native rainbow trout, in which native Dolly Varden charr Salvelinus curilus and masu salmon increased in numbers following removal of non-native species and fishway installation. Results reveal natural recovery of masu salmon in a river within which they were once completely extirpated, without stocking. Because salmonids are migratory fish and return to natal rivers, when locally extinct, human intervention to stock or reintroduce them has often been deemed necessary. However, restoration of wildlife would not require stocking or reintroduction if factors that impede the self-recovery capability of species are removed.

    Kentaro Morita is the recipient of the 13th Yasuyuki Oshima Award!!

  • Functional diversity of ligninolytic fungi associated with leaf litter decomposition

    Takashi Osono

    Ecological Research Vol. 35, Issue 1, pp 30–43

    Keywords:Acid‐unhydrolyzable residue; Decomposer; Leaves; Selective delignification; Trait

    Abstract: Fungi play central roles in leaf litter decomposition as they are capable of actively decomposing lignin and other recalcitrant components in leaf litter that impact the decomposition in terrestrial ecosystems. Quantitative evaluation is lacking, however, regarding the ability of diverse fungi to decompose leaf litter and the variability of ligninolytic activity among fungal taxa. In this comprehensive synthesis, I summarize the data of 1,232 individual pure culture tests conducted under standardized protocols to examine the functional diversity of fungi associated with leaf litter decomposition, with special emphasis on the ligninolytic activity. Fungal strains tested included 218 species in 69 families of Basidiomycota, Ascomycota, and Mucoromycotina that were derived from tropical and temperate forests to polar tundra. Fungal strains were inoculated adjacent to sterilized leaves and other substrata and incubated in the laboratory in order (a) to examine their functional potentialities in terms of the ability to cause mass loss of leaves and decompose recalcitrant components and (b) to explore the effect of litter quality and various environmental factors. The results of these tests revealed that ligninolytic abilities were specifically detected in fungal strains in such families as Mycenaceae and Marasmiaceae in Basidiomycota, and Rhytismataceae and Xylariaceae in Ascomycota. The ligninolytic activity varied among fungal taxa and with the quality and type of substrata, incubation temperature, and external supply of nutrients. This review provides integrative accounts of the functional diversity of ligninolytic fungi associated with leaf litter decomposition and enhances our understanding of the roles of fungal diversity in decomposition processes.

    Takashi Osono is the recipient of the 11th Yasuyuki Oshima Award!!

  • Recent developments in understanding mast seeding in relation to dynamics of carbon and nitrogen resources in temperate trees

    Qingmin Han, Daisuke Kabeya

    Ecological Research Vol. 32, Issue 6, pp 771–778

    Keywords: Carbohydrate; Masting; Nitrogen; Resource budget model; Resource storage

    Abstract: Mast seeding, the synchronous intermittent production of large seed crops in populations of perennial plants, is a widespread and widely studied phenomenon. Economy of scale has been demonstrated to provide the ultimate selection factor driving the evolution of masting, for example, in terms of the predator-satiation and pollination-efficiency hypotheses; however, its physiological mechanism is still poorly understood. The resource budget (RB) model assumes that an individual plant requires more resources to flower and fruit than it gains in a year, and therefore only flowers when a specific threshold amount of stored resources is surpassed. Although the RB models have been well explored theoretically, including for resource depletion and pollen coupling, empirical data to support these assumptions are still disputed. Here, we explore the extent to which the RB model applies to masting tree species, focusing on the dynamics of carbon and nitrogen resources in natural temperate forests. There is little empirical evidence that plants use carbohydrates stored over several years to produce fruits; however, nitrogen stores in temperate trees are more commonly depleted after masting. We review the internal nitrogen cycle including resorption during leaf senescence, storage and remobilization, discussing the effect of masting on these processes. Overall, carbohydrates and nitrogen are clearly involved in the proximate mechanisms driving mast seeding, but the determinant resource seems to be species specific.

    Qingmin Han is the recipient of the 8th Yasuyuki Oshima Award!!


  • Empirical dynamic modeling for beginners

    Chun-Wei Chang, Masayuki Ushio, Chih-hao Hsieh

    Ecological Research Vol. 32, Issue 6, pp 785–796

    Keywords: Embedding; State space reconstruction; State dependence; Forecast; Interaction

    Abstract: Natural systems are often complex and dynamic (i.e. nonlinear), making them difficult to understand using linear statistical approaches. Linear approaches are fundamentally based on correlation. Thus, they are ill-posed for dynamical systems, where correlation can occur without causation, and causation may also occur in the absence of correlation. "Mirage correlation" (i.e., the sign and magnitude of the correlation change with time) is a hallmark of nonlinear systems that results from state dependency. State dependency means that the relationships among interacting variables change with different states of the system. In recent decades, nonlinear methods that acknowledge state dependence have been developed. These nonlinear statistical methods are rooted in state space reconstruction, i.e. lagged coordinate embedding of time series data. These methods do not assume any set of equations governing the system but recover the dynamics from time series data, thus called empirical dynamic modeling (EDM). EDM bears a variety of utilities to investigating dynamical systems. Here, we provide a step-by-step tutorial for EDM applications with rEDM, a free software package written in the R language. Using model examples, we aim to guide users through several basic applications of EDM, including (1) determining the complexity (dimensionality) of a system, (2) distinguishing nonlinear dynamical systems from linear stochastic systems, and quantifying the nonlinearity (i.e. state dependence), (3) determining causal variables, (4) forecasting, (5) tracking the strength and sign of interaction, and (6) exploring the scenario of external perturbation. These methods and applications can be used to provide a mechanistic understanding of dynamical systems.

    Chih-hao Hsieh is the recipient of the 18th Biwako Prize for Ecology!!


  • High variation of mitochondrial DNA diversity as compared to nuclear microsatellites in mammalian populations

    Takashi Saitoh

    First published: 15 November 2020

    Keywords:Effective gene number; Haplotype diversity; Heterozygosity; Mutation rate; Population structure

    Abstract: The effective gene number (the number of genes that can be inherited) of mitochondrial DNA (mtDNA) is one‐fourth of that of nuclear DNA (ncDNA) in idealized populations. Therefore, mtDNA haplotype diversity (h) is predicted to be lower than ncDNA heterozygosity (HE) because of the higher effect of genetic drift on mtDNA. This prediction has not yet been systematically tested. To this end, in this study, published data for 739 populations of 108 mammalian species (66 terrestrial and 42 marine species) revealed the following patterns: (a) h was higher than HE in 54.9% of populations, (b) the variance of h (0.097) was significantly higher than that of HE (0.018) and (c) the frequency distribution of h differed between terrestrial and marine species. The terrestrial species exhibited a U‐shaped distribution, whereas the marine species exhibited a right triangle shape. HE showed a unimodal distribution for both groups. (d) The mean of HE was similar between the terrestrial (0.668) and marine (0.672) species, whereas the mean of h was significantly lower for the terrestrial species (0.578) than for the marine species (0.740). Two hypotheses were considered to explain the above‐described patterns, one of which was based on the higher mutation rates of mtDNA, while the other was based on a nested subpopulation structure in which an ncDNA‐based population includes several mtDNA‐based subpopulations. Herein, the plausibility of these two hypotheses was discussed with a focus on the higher intraspecific variation of h.

    Takashi Saitoh is the recipient of the 13th Ecological Society of Japan Award!!


  • Seasonality of leaf litter and leaf area index data for various tree species in a cool-temperate deciduous broad-leaved forest, Japan, 2005–2014

    Shin Nagai, Kenlo Nishida Nasahara, Shinpei Yoshitake, Taku M.Saitoh awd_S_Nagai

    Ecological Research vol.32, No. 3 pp. 297

    Keywords: Deciduous broad-leaved forest; Ground-truth; Leaf litter; Leaf area index (LAI); Leaf mass per area; Leaf seasonality; Japan; Semi-empirical model; Species discrimination; Decadal data set

    Abstract This paper reports seasonal data regarding leaf litter for 14 deciduous broad-leaved species and one evergreen coniferous species as well as leaf area index (LAI) data for the 14 deciduous broad-leaved species in a cool-temperate deciduous broad-leaved forest in Japan. The seasonal leaf biomass of various tree species is important for accurately evaluating ecosystem functions such as photosynthesis and evapotranspiration under climate change. However, there is a lack of freely available, long-term data. We collected litterfall every 1 to 4 weeks from September or October to November or December each year from 2005 to 2014 in Takayama, Japan (36°08′46″N, 137°25′23″E, 1420 m a.s.l.). After sorting the litter into leaves (according to species categories), stems + branches, and “other”, we dried and weighed the litter groups. We also collected seasonal leaf data (number of leaves and leaf length and width) for each broad-leaved species, which we recorded every 1 to 4 weeks from April or May to October or November using multiple target shoots. To estimate the LAI in autumn for each deciduous broad-leaved species, we used a semi-empirical model of the vertical integration of leaf dry mass per unit leaf area. To estimate the LAI in spring and summer, we used the relationship between the LAI in autumn and the seasonal leaf data. Our data provide input, calibration, and validation parameters for determining LAI based on satellite remote-sensing observations or radiative transfer models and for use in ecosystem models.

  • How well are biodiversity drivers reflected in protected areas? A representativeness assessment of the geohistorical gradients that shaped endemic flora in Japan

    Buntarou Kusumoto, Takayuki Shiono, Masashi Konoshima, Atsushi Yoshimoto, Takayuki Tanaka, Yasuhiro Kubota

    Ecological Research vol.32, No. 3 pp. 299–311

    Keywords: Continental island; Evolutionary distinctiveness; Minimum set analysis; Plant species richness; Protected area network

    Abstract Protected areas function as a lifeboat that can preserve the origins and maintenance of biodiversity. We assessed the representativeness of biodiversity in existing protected areas in Japan using a distribution dataset and phylogenetic tree for 5565 Japanese vascular plant species. We first examined the overlap of species distribution with the existing protected areas and identified the minimum set representing all plant species. Second, we evaluated the relative importance of environmental variables in explaining the spatial arrangement of protected areas using a random forest model. Finally, we clarified how potential drivers of plant diversity were sufficiently captured within the protected areas network. Although the protected areas captured the majority of species, nearly half of the minimum set areas were selected from outside the existing protected areas. The locations of existing protected areas are mainly associated with geographical and socio-economic factors rather than key biodiversity features (including evolutionary distinctiveness). Moreover, critical biodiversity drivers, which include current climate, paleoclimatic stability, and geographical isolation, were biasedly emulated within the existing protected areas. These findings demonstrate that current conservation planning fails to represent the ecological and evolutionary processes relevant to species sorting, dispersal limitation, and allopatric speciation. In particular, under-representativeness of historically stable habitats that function as evolutionary hotspots or refugia in response to climate changes may pose a threat to the long-term persistence of Japan’s endemic biota. This study provides a fundamental basis for developing prioritization measures to retain species assembly processes and in situ diversification along current climatic and geohistorical gradients.

  • Tree hollows can affect epiphyte species composition


    Shinichi Tatsumi, Takayuki Ohgue, Wakana Azuma, Veera Tuovinen, Yume Imada, Akira S. Mori, Göran Thor, Åsa Ranlund

    Ecological Research vol.32, No. 4 pp. 503–509

    Keywords: Biodiversity; Cryptogams; Bryophytes; Lichens; Tree cavities

    Abstract Tree hollows often harbor animals and microorganisms, thereby storing nutritive resources derived from their biological activities. The outflows from tree hollows can create unique microenvironments, which may affect communities of epiphytic organisms on trunk surfaces below the hollows. In this study, we tested whether the species richness and composition of epiphytic bryophytes (liverworts and mosses) and lichens differ above and below tree hollows of Aria japonica and Cercidiphyllum japonicum in a Japanese temperate forest. The species richness of epiphytic bryophytes and lichens did not differ above and below hollows; however, the species composition of bryophytes differed significantly above and below hollows. Indicator species analyses showed that the moss species Anomodon tristis and the liverwort species Porella vernicosa were significantly more common below than above hollows, while the liverwort species Radula japonica and four lichen species, including Leptogium cyanescens, occurred more frequently above than below hollows. Our results highlight that tree hollows can produce unique microenvironments on trunk surfaces that potentially contribute to the maintenance of epiphytic diversity on a local scale.

  • Web image search revealed large-scale variations in breeding season and nuptial coloration in a mutually ornamented fish, Tribolodon hakonensis

    awd_Atsumiawd_Atsumi Keisuke Atsumi, Itsuro Koizumi

    Ecological Research vol.32, No. 4 pp. 567–578

    Keywords: Citizen science; Global climate change; Google Trends; Sexual selection; Reinforcement

    Abstract Geographic variations in reproductive traits are important for evolutionary biology, but often difficult to investigate because of the need for a large-scale survey and the ephemeral nature of secondary sexual characteristics. Here, using web image searches (Google Images and Twitter), we revealed large-scale geographic variations (>1500 km) in breeding timing and nuptial coloration in the mutually ornamented fish, Japanese dace (Tribolodon hakonensis). As this fish is easily caught and many anglers upload their photographs on the web, we were able to find a total of 401 high-resolution photographs from all over Japan. Breeding periods were determined from dates of photographs with/without nuptial coloration, which matched with previous studies. We also found that breeding periods might have advanced three weeks over the last 80 years in the Chitose River, potentially because of climate change. Additionally, the pattern of latitudinal cline for breeding timing revealed delayed timing in higher latitudes, although regional variations were also high. Finally, we quantified the patterns of nuptial coloration for this mutually ornamented fish, and confirmed that over 80% of individuals showed typical colorations, but others showed rare phenotypes that were never previously described, including an intermediate coloration between T. hakonensis and a potentially hybridizing species, T. brandtii. Our web-based method for estimating breeding phenology could be adopted for organisms with temporal sexual characteristics, such as plants (e.g., flowering time) and some fishes. Web image analyses are still preliminarily with many limitations, but could be promising for investigating variations in visible traits.

  • Impact of climate change on alpine vegetation of mountain summits in Norway

    awd_Vanneste Thomas Vanneste, Ottar Michelsen, Bente Jessen Graae, Magni Olsen Kyrkjeeide, Håkon Holien, Kristian Hassel, Sigrid Lindmo, Rozália Erzsebet Kapás, Pieter De Frenne

    Ecological Research vol.32, No. 4 pp. 579–593

    Keywords: Alpine vegetation; Climate change; Resurvey study; Thermophilization; Cryptogams

    Abstract Climate change is affecting the composition and functioning of ecosystems across the globe. Mountain ecosystems are particularly sensitive to climate warming since their biota is generally limited by low temperatures. Cryptogams such as lichens and bryophytes are important for the biodiversity and functioning of these ecosystems, but have not often been incorporated in vegetation resurvey studies. Hence, we lack a good understanding of how vascular plants, lichens and bryophytes respond interactively to climate warming in alpine communities. Here we quantified long-term changes in species richness, cover, composition and thermophilization (i.e. the increasing dominance of warm-adapted species) of vascular plants, lichens and bryophytes on four summits at Dovrefjell, Norway. These summits are situated along an elevational gradient from the low alpine to high alpine zone and were surveyed for all species in 2001, 2008 and 2015. During the 15-year period, a decline in lichen richness and increase in bryophyte richness was detected, whereas no change in vascular plant richness was found. Dwarf-shrub abundance progressively increased at the expense of lichens, and thermophilization was most pronounced for vascular plants, but occurred only on the lowest summits and northern aspects. Lichens showed less thermophilization and, for the bryophytes, no significant thermophilization was found. Although recent climate change may have primarily caused the observed changes in vegetation, combined effects with non-climatic factors (e.g. grazing and trampling) are likely important as well. At a larger scale, alpine vegetation shifts could have a profound impact on biosphere functioning with feedbacks to the global climate.

  • Integrating isotopic, microbial, and modeling approaches to understand methane dynamics in a frequently disturbed deep reservoir in Taiwan

    awd_Itohawd_ItohMasayuki Itoh, Hisaya Kojima, Pei-Chi Ho, Chun-Wei Chang, Tzong-Yueh Chen, Silver Sung-Yun Hsiao, Yuki Kobayashi, Megumu Fujibayashi, Shuh-Ji Kao, Chih-hao Hsieh, Manabu Fukui, Noboru Okuda, Takeshi Miki, Fuh-Kwo Shiah

    Ecological Research vol.32, No. 6 pp. 861–871

    Keywords: Methane production; Methane oxidizing bacteria; Food web model; Isotope ecology; Environmental microbiology

    Abstract It has been estimated that more than 48% of global methane emissions from lakes and reservoirs occur at low latitudes (<24°). To improve this estimate, knowledge regarding underexplored ecosystems, particularly deep lakes and reservoirs in Asian monsoon regions, is needed because the magnitude of methane emissions is influenced by lake bathymetry and climatic conditions. We conducted long-term studies beginning in 2004 at Feitsui Reservoir (FTR) in Taiwan, a subtropical monomictic system with a maximum depth of 120 m to monitor seasonal and interannual variations of three key characteristics and to understand the mechanisms underlying these variations. Key characteristics investigated were as follows: (1) the balance of primary production and heterotrophic respiration as a determinant of vertical oxygen distribution, (2) methane production at the bottom of the reservoir, oxidation in the water column, and emissions from the lake surface, and (3) the contribution of methane-originated carbon to the pelagic food web through methane-oxidizing bacteria (MOB). This review highlights major achievements from FTR studies integrating isotopic, microbial, and modeling approaches. Based on our findings, we proposed two conceptual models: (1) a model of methane dynamics, which addresses the differences in methane emission mechanisms between deep and shallow lakes, and (2) a spatially explicit model linking benthic methane production to the pelagic food web, which addresses the diversity of MOB metabolisms and their dependence on oxygen availability. Finally, we address why long-term studies of subtropical lakes and reservoirs are important for better understanding the effects of climate on low- to mid-latitude ecosystems.