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The classical “low latitude–high defense” hypothesis is seldom supported by empirical evidence. In this context, we tested latitudinal patterns in the leaf defense traits of deciduous broadleaved (DB) and evergreen broadleaved (EGB) tree species, which are expected to affect herbivore diversity. We examined the co-occurrence of leaf defense traits (tannin and phenol content, leaf mechanical strength, leaf dry matter content, leaf mass per area, and leaf thickness) in 741 broadleaved tree species and their correlations with species geographical range in East Asian island flora. We discovered contrasting latitudinal defense strategy gradients in DB and EGB tree species. DB species employed chemical defenses (increasing tannin and phenol content) at higher latitudes and physical defenses (softer and thinner leaves) at lower latitudes, whereas EGB tree species exhibited opposite latitudinal defense patterns. The “low latitude high defense” hypothesis included a paradoxical aspect in chemical and physical defense traits across broadleaved tree species. To reconcile paradoxical defense strategies along the latitudinal gradient, we conclude that interactive correlations among leaf traits are controlled by leaf longevity, which differs between DB and EGB tree species.

Aim To examine the roles of geohistorical and ecological factors in the development of butterfly assemblages on continental islands with multiple source pools. Location The Ryukyu Islands, Japan. This arc of continental islands is located between two source islands, Kyushu and Taiwan, and contains two major straits, the Tokara and Kerama gaps. Methods A total of 489 butterfly species were identified on 59 islands, including the two source islands. The influences on species richness and rarity of latitude, area, elevation, and distances from the nearest source and from the nearest larger island were analysed using generalized linear models. The relationships between differences in area, elevation, and distance and dissimilarity between island butterfly faunas were evaluated by multiple regressions on distance matrices. The relationships between area, elevation, and distance from the source and dissimilarity to the source fauna were examined using linear models. The dissimilarity was based on the Sorensen index and its nestedness and turnover components. Results Latitude, area and isolation determined species richness and rarity, whereas differences in elevation and distance regulated species turnover between islands. The gaps between islands were associated with nestedness between island faunas. Area consistently had a negative relationship with the total dissimilarity to source fauna. The overall dissimilarity to Kyushu decreased with the distance from Kyushu, whereas dissimilarity to Taiwan increased with distance from Taiwan. Main conclusions Both environmental filtering and dispersal limitation determine the geographical patterns of butterfly assemblages in the Ryukyus. The present study focuses on the unique pattern wherein migration from Kyushu is facilitated on islands farther from Kyushu, while migration from Taiwan is inhibited on islands farther from Taiwan. The two source islands have contrasting roles that affect butterfly distributions unidirectionally. This study highlights the importance of resolving dissimilarity into nestedness and turnover components to elucidate the formation of island biota.

Aim We addressed the roles of geohistorical and ecological factors on beta diversity patterns of woody plants in the Japanese archipelago. We scrutinized the contribution of recent diversification in shaping the woody plant diversity of insular areas in East Asia. Location The Japanese archipelago. Methods The distribution data of 1030 woody plant species were compiled for 65 localities in the archipelago. First, the relationships between geohistorical (straits, distance and area) and ecological (topographical heterogeneity, minimum temperature and annual precipitation) variables and taxonomic and phylogenetic beta diversity were tested using regression models. Second, geographical patterns of phylogenetic beta diversity were compared with those of taxonomic beta diversity using ordination and randomization tests. These analyses were applied to the woody plants overall and their functional groups defined by life-form (coniferous, deciduous broad-leaved and evergreen broad-leaved groups). Results Distance and minimum temperature showed significant positive relationships with both measures of beta diversity across the woody plants overall and the functional groups. The contributions of geographical barriers, topographical heterogeneity and annual precipitation varied among groups. Ordinations by phylogenetic beta diversity produced patterns that were consistent with those generated by taxonomic beta diversity, showing three clusters of localities in relation to geographical barriers, except in the coniferous group. The regression slopes of phylogenetic beta diversity versus distance were significantly smaller than those of taxonomic beta diversity versus distance across all groups. Main conclusions In the Japanese archipelago, the combination of geographical isolation and environmental filtering in response to geohistorical perturbations and environmental gradients has configured the beta diversity patterns of woody plants. The recent diversification of phylogenetically close relatives probably caused the spatial variations that exist in woody plant diversity. The archipelago functions as a refugium for relict taxa and as a hotspot for neoendemics, contributing to the broad-scale diversity bias favouring East Asia.

Understandings of the effect of host plant phylogeny on the structure of herbivore assemblage is useful for estimating global species richness of herbivores. Here we test the relationship between host plant phylogeny and two assemblages including ambrosia beetle assemblage that have been considered to be the lowest host specificity among plant-dependent guilds. These results of local scale were used for estimating regional species richness by extrapolating to the number of plant order and species in Japan. The estimated numbers were compared with the numbers of described species in Japan. Tree trunks of 17 plant species representing 17 orders of all major lineages of Japanese tree flora were exposed for collecting wood boring beetle species. A total of 12 ambrosia and four bark beetle species were collected. Similarity of both ambrosia and bark beetle assemblages showed a significant negative trend with phylogenetic distance between focal host plant species. The regression model for this relationship was well fit by a linear model whereas previous studies used a semi-log model, which suggests a difference in mechanism of host utilization with host taxonomic levels. Our results showed a broader host range of ambrosia beetle assemblage in temperate forest than to a comparable study in tropical rainforests. Species richness estimated is lower than the described species in Japan, suggesting the need for more samples along the altitudinal gradients for accurate estimation for the Japanese fauna.

Species abundance distributions of moth and beetle assemblages, in addition to beetle feeding guilds, were examined using data collected by light traps in a cool-temperate deciduous forest at Hokkaido, Japan. Four types of species abundance distributions with a continuous shift in shape (broken stick, log-normal, power function, and dispersal-limited multinomial) were fitted and compared, and then the deviation of observed data from that expected for the neutral model (dispersal-limited multinomial distribution) was tested using species evenness and richness. Significantly better fits were obtained for the neutral model than for the other models for all assemblages and all beetle guilds. This result implies that the better fits of the neutral model might be characteristic of transient assemblages having an excess of rare species. The evenness of species abundance distributions for assemblages and guilds, except for moths associated with the understorey and predatory beetles, significantly deviated from that expected by the neutral model. The departure of beetle guilds (detritivores, herbivores, and xylophages) from the neutral model suggests their microhabitat dependence. The neutral model may prove to be a viable null hypothesis for examining the species abundance distributions of insect assemblages. In this study, we found that although stochastic dynamics appeared to have an increasing influence on insect community assembly, there are also complex biological processes still likely to be present. The fits of the neutral model suggest that habitat connectivity and microhabitat diversity are potentially important for conserving moth and beetle diversity in a temperate forest.

Aim Anolis lizard invasions are a serious threat world-wide, and information about how this invasive predator affects the diversity of prey assemblages is important for many strategic conservation goals. It is hypothesized that these predators reduce the slope of species–area relationships (SARs) of their prey assemblages. The effects of island area and predation by anolis lizards on the species richness of insular insect assemblages were investigated. Location Twenty-four isles around Staniel Cay, Exuma Cays, Bahamas. Methods Flying insects were sampled using half-sized Malaise traps for three consecutive days on each island in May 2007. First, the effect of island area on the probability of lizard presence was evaluated. Then, the effects of the presence–absence of predatory lizards on SARs were analysed for the overall insect assemblage and for the assemblages of five dominant insect orders. Results Our results indicated that anolis lizards occurred primarily on larger islands. The species richness of the overall insect assemblage and five dominant insect orders significantly increased with island area. The interaction between island area and predator presence–absence significantly affected the overall insect assemblage and Diptera and Hymenoptera assemblages (but not Coleoptera, Hemiptera and Lepidoptera assemblages). The presence of predators caused decreases in the slope of the SARs. Main conclusions The presence of predatory lizards strongly affects species richness of insular insect assemblages with the island area being a crucial determinant of the species richness. Therefore, the slope of the SAR can serve as a measure of the consequence of invasive predatory species on native insect assemblages.

The article “A paradox of latitudinal leaf defense strategies in deciduous and evergreen broadleaved trees”, written by Saihanna Saihanna, Tomoe Tanaka, Yu Okamura, Buntarou Kusumoto, Takayuki Shiono, Toshihide Hirao, Yasuhiro Kubota, and Masashi Murakami, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 01 June 2018 without open access.

The vertical stratification of lepidopteran and coleopteran communities in a cool-temperate deciduous forest in Japan was examined to evaluate the hypothesis of an expected uniform distribution of mobile flying insects between the canopy and understory of temperate forests. Lepidopteran and coleopteran insects were trapped using light traps at three sites in each of the canopy and understory for three consecutive nights each month from April to October 2001. For Lepidoptera, species richness, abundance, and family richness were significantly higher in the understory than in the canopy. For Coleoptera, only abundance was larger in the canopy relative to the understory; species and family richness did not differ between the strata. The beta diversity of the lepidopteran community was larger between the strata than among sites, but the coleopteran community showed an inverse pattern. These results imply the presence of vertical stratification within the lepidopteran community, but not within the coleopteran community, in the temperate forest. The understory contributes more than the canopy to lepidopteran diversity in the temperate forest, although this stratification may be relatively weak because, in contrast to the situation in tropical forests, the canopy and understory assemblages share many species.

The dispersal of organisms among patches affects community structure in spatially heterogeneous habitats. The enhancement of dispersal frequency among patches can be expected to increase potential interaction between organisms in food webs. However, it has been difficult to fairly evaluate the effects of dispersal on the food web structure because the quantification of actual dispersal is difficult. In this study, in order to manipulate the dispersal frequency, two oak plantations (each with 100 oak trees) were established as high-patch connectivity (1-m interval) and low-patch connectivity (3-m interval) plots. Quantitative food webs of herbivores and their parasitoids were constructed for the high- and low-connectivity plots, and quantitative measures of food web metrics as indices of structure were calculated for both webs to examine dispersal effects on food web complexity. In the entire web, 86 herbivore species (Lepidoptera and Coleoptera) were attacked by 50 parasitoid species (Hymenoptera and Diptera). As a result, although we found no significant difference in herbivore abundance between high- and low-connectivity plots, a higher parasitism rate and greater complexity in web structure were observed in many food web metrics for the high-connectivity plot. Furthermore, the parasitoid overlap diagram showed a higher potential for indirect interactions among herbivore species in the high-connectivity plot. These results imply that the increase in dispersal frequency among habitat patches facilitates food web complexity, and the role of dispersal as a determinant of food web structure should be considered in food web ecology.

1 Light traps have been widely used for surveying insect community structure, but some biases are known to occur under certain meteorological conditions. 2 In addition to weather factors, we raise the novel hypothesis that if the daily movement distance of focal insects is shorter than the effective range of the light trap, then the species richness and abundance of the daily captures will increase during the course of the night. 3 This study examined the daily attraction patterns of Lepidoptera and Coleoptera to light traps and the factors affecting the attraction of these communities. Light traps were run for three consecutive nights in each month from April to October 2001 in a cool-temperate forest in Japan. 4 The species richness and abundance of Coleoptera increased during trap nights, whereas lepidopteran captures remained constant. Meteorological factors influenced the capture of both communities throughout the sampling season, but the daily increment in Coleoptera was not explained by the daily trends in weather conditions. 5 We argue that the daily augmentation of Coleoptera capture rate results from the daily movement distance of Coleoptera being generally shorter than the effective and perceivable range of the light traps. These results suggest that consideration of the typical daily movement of a focal taxon is required when conducting biological monitoring using light trap sampling.

1. Forest entomofauna retain high diversity, and examining beta diversity, or species turnover, among assemblages in a forest community is vital to elucidate the source of this diversity. 2. Under the DIVERSITAS in Western Pacific and Asia–International Biodiversity Observation Year (DIWPA–IBOY) project for simultaneously documenting biodiversity throughout the Western Pacific and Asian Region, 892 lepidopteran species (51 742 specimens) and 355 coleopteran species (11 633 specimens) were collected in 2001 by light traps in a cool–temperate forest in northern Japan. 3. This study evaluated the beta diversity of lepidopteran and coleopteran communities by ecological categories (i.e. trap location, forest strata, sampling days, and months), and assessed the habitat preferences of lepidopteran and coleopteran species. 4. anova-like additive apportioning models were used to quantify the beta diversity among the categories. The models simultaneously provide assessments of whether species distributions are biased in favour of particular habitats. 5. Significantly high beta diversity was observed among months for both Lepidoptera and Coleoptera. The category of months corresponded fairly well to the number of specialist species detected in the category, although a remarkably large number of significant specialists in Coleoptera were observed on strata. 6. The high beta diversity and number of specialist species among strata in both communities indicate that stratification between canopy and ground, and seasonal variation, played major roles in species composition and the rich entomofauna in the forest. Highly mobile adults were influenced by the vertical spatial scale, as previously suggested for larvae.

The effect of disturbance on local communities may operate within the context of the spatial landscape. We examined the scale-dependent effects of windthrow disturbance caused by a large typhoon on three arthropod communities in a temperate forest of Japan. Canopy arthropods were collected by beating foliage, forest-floor arthropods were collected by sweeping the vegetation, and flying arthropods were collected in Malaise traps. To assess the “functional spatial scale” at which arthropods responded to tree-fall disturbance, the gap rate was quantified at different spatial scales by sequentially enlarging the radius of a circular landscape sector in 10-m increments from 10 to 500 m. We then analyzed the responses of order richness and abundance to the gap rate for each arthropod community. The spatial scale of the significant best-fitting model, which was selected from the models fitted to the gap rate at stepwise spatial scales, was regarded as the arthropod-specific functional spatial scale. Arthropod order richness was not dependent on the gap rate. In contrast, arthropod order abundance depended significantly on the gap rate in many orders, but varied in the response direction and functional spatial scale. These order-specific, scale-dependent responses to tree-fall gaps could complicate interactions among organisms, leading to complex community organization. An understanding of the spatial processes that link the use of space by organisms with the spatial scale at which ecological processes are experienced is required to elucidate the responses of populations, communities, and biotic interactions to disturbances in a spatial landscape context.

The specialization of herbivores among tree species is poorly understood despite its fundamental importance as a factor regulating diversity. To examine the effect of tree species on larval community structure, the larval communities in 10 temperate deciduous tree species that differed in leaf emergence pattern (flush- vs. intermediate-type) were seasonally surveyed. The newly developed soft, nitrogen-rich leaves of all species became tough and nitrogen-poor as the season progressed. Following the changes in leaf quality, two distinct seasonal lepidopteran larval communities emerged, with a marked turnover in early July. The beta diversity, or dissimilarity, of species composition in the larval communities among tree species was higher in summer than in spring. These results imply that the lepidopteran larval communities as a whole were supported by alpha diversity in spring and by beta diversity in summer, demonstrating that the plant diversity of this forest could support a caterpillar community. We examined the importance of spatio-temporal variations in leaf quality within and among tree species in promoting herbivore diversity, although other factors, such as tree species phylogeny and predators, may also have a large effect on lepidopteran larval communities.

Quantitative food webs were constructed to explore the community structure of leaf-mining moths in the family Gracillariidae and their parasitoid wasps in a deciduous forest in Hokkaido, Japan. A whole food web was constructed from data collected from June to October 2001. In the web, 16 leafminer species on seven tree species were attacked by 58 species of hymenopteran parasitoid; 376 links between leafminers and parasitoids were observed. Leafminers were specialist herbivores, but most parasitoids were generalists. Five webs were constructed for the seasonal prevalence of leafminers over the one-year period to reveal the temporal dynamics in community structure. Among the seasonal webs, the first web in June was distinctive because two tree species, Japanese umbrella tree Magnolia obovata and Japanese magnolia M. kobus, supported the community. Second to fourth webs from July to September were dominated by the leafminer species on Japanese oak Quercus crispula, and the fifth web was marked by that on Carpinus cordata. The extent of potential apparent competition among leafminers was evaluated using quantitative parasitoid overlap diagrams. These diagrams suggested that abundant host species are likely to have large indirect effects on less abundant species. Moreover, the potential for apparent competition between leafminer species inhabiting different host tree species can occur, although leafminers sharing the same tree species are prone to interact via shared parasitoids. In this system, particular leafminer species, acting as potential sources of apparent competition, can affect other species as sinks, and control whole-community dynamics. Directed apparent competition may potentially occur around oak trees.

An international project, DIWPA-IBOY, took place for simultaneously observing biodiversity throughout the Western-Pacific and Asian regions in 2001–2003, as one of the core projects for International Biodiversity Observation Year, a crosscutting network activity of DIVERSITAS (an international programme of biodiversity science). DIWPA-IBOY provides extensive data on species diversity obtained by the standardized method. Under this project, 51,742 individuals of Lepidoptera and 11,633 of Coleoptera were collected by light traps from the Tomakomai Experimental Forest of Hokkaido University, one of the core DIWPA-IBOY sites, in the cool-temperate region of northern Japan. Based on these data, this study examined the relative abundance distribution (RAD) to evaluate the amount of rare species in the Lepidoptera and Coleoptera communities. The beta diversities between sampling seasons, forest strata, and trap sites were also assessed to evaluate the spatio-temporal variability of species composition in these communities. In the analysis of the RAD, the best-fit model was selected from the log-Normal, Zipf–Mandelbrot, and Zipf models differing in the tail length of the RAD, i.e., the proportion of rare species. To explore the beta diversity between samples, the abundance-based Jaccard index with an unseen species estimator was calculated, and then a hierarchical clustering analysis was conducted. As a result of RAD analysis, the Coleoptera community was regarded as containing a larger proportion of rare species than the Lepidoptera community. The seasonal compartmentalization of the community, deduced from the beta-diversity analysis, was finer in Lepidoptera (seven assemblages recognized) than in Coleoptera (three assemblages). The spatial (vertical and horizontal) compartmentalization was negligible in both communities. The coincidence of the larger proportion of rare species and the lower beta diversity between seasons in the Coleoptera community was explained by the longer life spans of beetles compared to moths, based on the assumption that the length of life span acts as a temporal agent for mass effect on the analogy of the migration rate as a spatial agent for mass effect.

Premise of the study: Microsatellite markers were developed and characterized for the critically endangered birch Betula chichibuensis (Betulaceae) to investigate the genetic structure of this species for conservation purposes. Methods and Results: Sixteen microsatellite markers with di-, tri-, and tetranucleotide repeat motifs were developed and optimized using MiSeq paired-end sequencing. Of these, 14 were polymorphic, with two to five alleles per locus, in 47 individuals from two newly discovered populations of B. chichibuensis in Japan. Observed and unbiased expected heterozygosities per locus ranged from 0.000 to 0.617 and from 0.000 to 0.629, respectively. These markers were tested for cross-species amplification in B. maximowicziana, B. platyphylla var. japonica, and B. schmidtii. Conclusions: This set of microsatellite markers, the first developed for B. chichibuensis, will help elucidate spatial patterns of gene flow and levels of inbreeding in this species to aid its conservation.

Quantifying the roles of historical versus contemporary constraints in determining species diversity is a central issue in island biogeography, and the phylogenetic beta diversity between islands is an essential measure specifying the influence of historical barriers on insular assemblages. In this study, using phylogenetic information for 513 tree species on 26 islands in the subtropical Ryukyu Archipelago, phylogenetic beta diversity between islands was calculated, and effects of historical factors (gaps as surrogate measures of historical barriers) and current ones (distance, area and elevation) on the phylogenetic structure of tree assemblages were examined. The pattern of phylogenetic beta diversity demonstrated that the Tokara Gap and geographical distance were consistently important for characterizing tree assemblages in the Ryukyus relative to other historical and current factors, which suggests that the Tokara Gap and distance-limited dispersal from the two adjacent source islands have left a deep imprint on the phylogenetic structure of the current tree flora of the islands.

1. Ecological assemblages frequently show nestedness patterns of species distribution. Despite the common occurrence, the causality for nestedness patterns remains unclear. The effects of environmental and spatial factors on the patterns of insect species distributions were examined on 28 small islands in central Exuma, Bahamas. 2. Flying insects on each island were surveyed by Malaise traps, island area and vegetation height being used as environmental factors, and the degree of island isolation as a spatial factor. Body and relative wing length, and abundance of insect species were also considered as species traits which, together with environmental and spatial factors, determine insect distributions. 3. Island isolation was determined from distance to the mainland, greatest distance in a stepping-stone pathway, distance to the nearest island, and the island area within 250, 500 and 1000 m of each island’s perimeter. 4. The pattern of island-insect nestedness was examined for the overall insect assemblage and those of five dominant insect orders on the islands. The order of island ranking in the nested matrix was tested relative to area, isolation and vegetation height, the rank order of insect species then being examined relative to body and wing length, and abundance of species. 5. Significant nestedness was found in all assemblages. Significant contributions of environmental factors were found in Diptera and Hemiptera assemblages, whereas relatively large contributions of spatial factors were found in Lepidoptera and Hymenoptera assemblages. These results illustrated the need to include spatial factors in analyses on the assembly of insular insect assemblages.