Ecological Research

  • STATISTICS

    Vol. 31 (2016)
    Submitted: 469
    Accepted: 98

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AWARD ARTICLES

  • SUZUKI AWARD

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

    Masaru Hasegawa

    Ecological Research Vol. 31, Issue 3, pp 307–319

    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 Suzuki Award!!

  • OSHIMA AWARD

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

    Han Q, Kabeya D

    Ecological Research Online

    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 Oshima Award!!

  • BIWAKO AWARD

  • Empirical dynamic modeling for beginners

    Chang C-W, Ushio M, Hsieh C-h

    Ecological Research Online

    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.

    Hsieh C-h is the recipient of the 18th Biwako Prize for Ecology!!

  • 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 31, issue 3, pp. 289–305

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

    Abstract nakazawa_2016Community 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!!

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

    Yuma Takahashi

    Ecological Research

    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 (F[STn]) with that of the putative color locus (F[STc]). No strong correlation was observed between F[STn] and F[STc], suggesting that stochastic factors contribute less to color-locus population divergence. F[STc] was less than FSTn between populations exposed to similar environmental conditions, but greater than F[STn] 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!!

  • ECOLOGICAL SOCIETY OF JAPAN AWARD

  • Possible ideas on carbon and nitrogen trophic fractionation of food chains: a new aspect of food-chain stable isotope analysis in Lake Biwa, Lake Baikal, and the Mongolian grasslands

    Eitaro Wada, Reiichiro Ishii, Maki Noguchi Aita, Nanako O. Ogawa, Ayato Kohzu, Fujio Hyodo & Yoshihiro Yamada

    Ecological Research vol.28, issue 2, pp.173–181

    Keywords: Δ15N–δ13C relationship; Food chain; Lake Biwa; Lake Baikal;Mongolian grassland

    Abstract Trophic fractionation of carbon and nitrogen isotopes (Δδ13C, Δδ15N) was examined using previously complied databases for food chains in Lake Biwa, Lake Baikal, and Mongolian grassland. The following two features were clarified: (1) For each ecosystem, the ratios of trophic fractionation of carbon and nitrogen isotopes (Δδ15N/Δδ13C) throughout food chain could be obtained as the slope of linear regression line on the δ15N–δ13C plot. (2) Further, analysis of covariance (ANCOVA) revealed the slopes on 15N–δ13C were not significantly different among these various ecosystems and allowed us to have the regression by setting δ15N as the response variable: δ15N = 1.61 δ13C + [ecosystem specific constant] with standard errors of [±0.41] and [±9.7] for the slope and the intercept, respectively. It was suggested that the slope of the regression (or the ratio Δδ15N/Δδ13C) could be applicable to more complicated food webs in case nitrogen and carbon isotope ratios of primary producers can be assumed constant in space and time within the ecosystems. The results from simple linear regression analyses coincided well with the ANCOVA results for these ecosystems, although there was some discrepancy between the results of the two statistical analyses. Possible factors that govern the linear relationship between δ15N and δ13C along a food chain are discussed together with a new scope for the stable isotope food chain analyses.

    Eitaro Wada is the recipient of the 7th Ecological Society of Japan Award!!

  • The 16th ECOLOGICAL RESEARCH AWARD

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  • Biogeochemical nitrogen properties of forest soils in the Japanese archipelago

    Rieko Urakawa, Nobuhito Ohte, Hideaki Shibata, Ryunosuke Tateno, Takuo Hishi, Keitaro Fukushima, Yoshiyuki Inagaki, Keizo Hirai, Tomoki Oda, Nobuhiro Oyanagi, Makoto Nakata, Hiroto Toda, Tanaka Kenta, Karibu Fukuzawa, Tsunehiro Watanabe, Naoko Tokuchi, Tatsuro Nakaji, Nobuko Saigusa, Yukio Yamao, Asami Nakanishi, Tsutomu Enoki, Shin Ugawa, Atsushi Hayakawa, Ayumi Kotani, Megumi Kuroiwa, Kazuo Isobe

    Ecological Research vol.30, No. 1 pp. 1–2

    Keywords: Gross nitrogen transformation rate; Litter layer stock; Net nitrogen transformation rate; Nitrification; Nitrogen cycle; Nitrogen mineralization; The Japanese archipelago; Total carbon and nitrogen concentrations; Water-soluble ions; Water-soluble organic carbon

    Abstract This data paper provides some biogeochemical nitrogen (N) properties and related chemical properties of forest soils from 39 sites throughout the Japanese archipelago. The data set was collected and analyzed under the GRENE (Green Network of Excellence) environmental information project and the ReSIN (Regional and comparative Soil Incubation study on Nitrogen dynamics in forest ecosystems) project. The sites cover 44°20”N to 26°50’N and the climate ranges from cool-temperate zone to subtropical zone. At each site, litter on forest floor and soil samples (three or four layers to 50 cm depth) were collected between August and November in 2010–2013 from five soil profiles. From the litter layer samples, the stocks and concentrations of total carbon (C) and N were measured. From the mineral soil samples, bulk density, pH (H2O), total C and N concentrations, net and gross rates of N mineralization, nitrification and concentrations of water-soluble substances were measured. The measurements are relevant for other biogeochemical N studies in forest ecosystems and the data set provides basic information on the N pool and fluxes with related chemical properties of forest soils across the Japanese archipelago. The average rates of net and gross N transformation at 20 °C across the sites were 0.26 ± 0.47 mgN kg-1 soil d-1 for net N mineralization, 0.25 ± 0.45 mgN kg-1 soil d-1 for net nitrification, 4.06 ± 0.47 mgN kg-1 soil d-1 for gross N mineralization, and 1.03 ± 1.29 mgN kg-1 soil d-1 for gross nitrification (average ± SD).

  • Antifungal activity of a termite queen pheromone against egg-mimicking termite ball fungi

    Kenji Matsuura, Takeshi Matsunaga

    Ecological Research vol.30, No. 1 pp. 93–100

    Keywords: Queen pheromone; Termite ball; Semiochemical parsimony; Insect-fungal interaction; Antimicrobial compounds

    Abstract The sophisticated colony organization of eusocial insects is attributed to their elaborate chemical communication systems. Pheromones mediate most behaviors involved in colony organization including foraging, defense, brood care, and caste regulation. The number of candidate compounds available to regulate multiple systems may be biosynthetically finite and the production of several compounds instead of a single one may be more costly. Therefore, strong selection pressures encourage the use of single natural products for many purposes. Such versatility of signal substances is especially characteristic of queen pheromones in eusocial Hymenoptera. However, little is known about the multifunctionality of the recently identified termite queen pheromone. Here, we demonstrate that volatile compounds in the queen pheromone of a termite, Reticulitermes speratus (Kolbe), have fungistatic properties. Application of the pheromone compounds n-butyl-n-butyrate and 2-methyl-1-butanol significantly reduced the germination rates of the egg-mimicking parasitic termite ball fungus. These pheromone compounds also suppressed mycelial growth of the termite ball fungus and some entomopathogenic fungi. However, the inhibitory activity of each substance differed among fungal strains. Termites likely employ these antimicrobial volatiles to protect eggs and queens, and secondarily as communication agents informing queen fertility. This study supports the notion of evolutionary parsimony, wherein pheromones are originally used as defensive compounds and their communicative function develops secondarily, which is well-documented in social Hymenoptera.

  • Relationships among plant genetics, phytochemistry and herbivory patterns in Quercus castanea across a fragmented landscape

    Yurixhi Maldonado-Lopez, Pablo Cuevas-Reyes, Antonio Gonzalez-Rodriguez , Griselda Perez-Lopez, Carlos Acosta-Gomez, Ken Oyama

    Ecological Research vol.30, No. 1 pp. 133–143

    Keywords: Folivores; Leaf miners; Mexico; Microsatellites; Oak

    Abstract Herbivorous insects respond to the chemical variation of their host plants which, in turn, usually has a genetic component. Therefore, it is expected that individual host plants with similar genotypes will have similar secondary chemistries and herbivore communities. However, natural or anthropogenic environmental variation can also influence secondary chemistry and herbivore abundance and composition. Here, we determined the relationships among plant genetics, phytochemistry, and herbivory levels by leaf chewers and miners in the red oak Quercus castanea, across a fragmented landscape. Ten oak individuals were sampled at each of four sites in the Cuitzeo basin, central Mexico. Two sites were small and fragmented forest patches and two were large and continuous patches. Individuals were genotyped with six nuclear microsatellites, and analyzed chemically to determine foliar concentrations of water, total nonstructural carbohydrates, and secondary compounds. Damage by leaf chewers was higher in the small fragments than in the large fragments. Mantel tests indicated significant correlations of the genetic distance among individuals with their chemical similitude, and also of chemical similitude with damage levels by leaf miners, but not with damage by folivores. There was no direct relationship between genetic distance and herbivory levels by any of the two insect guilds. Our results suggest that variation in concentration of secondary metabolites in Q. castanea has a genetic component and that plant chemistry acts as an intermediate link between plant genes and the community of associated herbivores. However, this effect was only apparent for herbivory by leaf miners, probably because these insects interact more intimately with the host, while free-living leaf chewers may be more responsive to environmental variation.

  • Capitulum and rosette leaf avoidance from grazing by large herbivores in Taraxacum

    Noboru Fujita, Ryosuke Koda

    Ecological Research vol.29, No. 4 pp. 529–534

    Keywords: Scape; Livestock; Pasture; Rural habitat; Urban habitat

    Abstract Plants defense against herbivore damage is achieved through resistance and tolerance, of which resistance is composed of avoidance and antibiosis. Plants have developed various adaptations that facilitate escape from herbivory. We hypothesized that post-anthesis prostrate scapes in Taraxacum is an adaptation for avoidance of capitulum grazing by large herbivores. To test this hypothesis, we divided flowering into the following four stages based on the external appearance of the capitulum: green bud, yellow corolla, brown corolla, and white pappus stages. We conducted an experiment in natural pasture in Mongolia to artificially raise capitula and rosette leaves of T. collinum. We measured the natural height of capitula and rosette leaves of the Mongolian pasture and urban species, T. collinum and T. ceratophorum, respectively, and of the Japanese rural and exotic urban species, T. japonicum and T. officinale, respectively. We investigated natural grazing by livestock in the field of the capitula and rosette leaves of the two Mongolian species. In Mongolia, naturally short capitula at the green bud and brown corolla stages and rosette leaves of T. collinum were not grazed. However, artificially raised capitula and rosette leaves of T. collinum and the naturally high capitula and leaves of T. ceratophorum were grazed. Short capitulum and leaf height was shown to be effective for avoidance of livestock grazing in Mongolia. In Japan, T. japonicum and T. officinale showed similar scape behavior to T. collinum and T. ceratophorum, respectively. We discuss the reasons for the capitulum behavior differences in Japan.

  • Variation in microbial function through soil depth profiles in the Kushiro Wetland, northeastern Hokkaido, Japan

    Yukiko Senga, Mikiya Hiroki, Shigeharu Terui, Seiichi Nohara

    Ecological Research vol.30, No. 4 pp. 563–572

    Keywords: Soil microbial function; Decomposition; Phosphate production; Denitrification; Wetland

    Abstract To provide new insights into microbial functions in the Kushiro Wetland, Japan, we measured vertical profiles of fluorescein diacetate hydrolysis (total microbial activity), β-glucosidase and xylosidase (organic matter decomposition), acid phosphatase (phosphate production) and potential denitrifying (denitrification) activities as microbial enzyme activities in soil to depths of approximately 1.5 m from two sites with different vegetation in November 2008 (winter) and August 2009 (summer). Active organic matter decomposition, phosphate production and denitrification were evident in shallow litter and peat layers, and total microbial activity was high. Almost no differences in decomposition and total microbial activity were observed between seasons, whereas phosphate production and denitrification were higher in summer. All activities were low in mid-depth volcanic-ash and clay layers because of low carbon, nitrogen and phosphorus levels. Surprisingly, the total microbial activity and decomposition in deep clay & peat and peat layers were the same as or higher than in shallow layers. However, denitrification was limited, probably because dissolved organic matter containing humic-like substances was unsuitable as a substrate. Moreover, total soil phosphorus levels, acid phosphatase activity and multiple linear regression analysis revealed that the soil in the Kushiro Wetland is likely P limited.

  • The 15th ECOLOGICAL RESEARCH AWARD