Yuichi Yamaura

Relative Importance of the Area and Shape of Patches to the Diversity of Multiple Taxa

Although enhancing reserve shape has been suggested as an alternative to enlarging nature reserves, the importance of reserve shape relative to reserve area remains unclear. Here we examined the relative importance of area and shape of forest patches to species richness, species composition, and species abundance (abundance of each species) for 3 taxa (33 birds, 41 butterflies, and 91 forest-floor plants) in a fragmented landscape in central Hokkaido, northern Japan. We grouped the species according to their potential edge responses (interior-, neutral-, and edge-species groups for birds and forest-floor plants, woodland- and open-land-species groups for butterflies) and analyzed them separately. We used a shape index that was independent of area as an index of shape circularization. Hierarchical partitioning and variation partitioning revealed that patch area was generally more important than patch shape for species richness and species composition of birds and butterflies. For forest-floor plants, effects of patch area and shape were small, whereas effects of local forest structure were large. Patch area and circularization generally increased abundances of interior species of birds and forest-floor plants and woodland species of butterflies. Nevertheless, only patch circularization increased abundances of 1 woodland species of butterfly and 2 and 6 interior species of birds and forest-floor plants, respectively. We did not find any significant interaction effects between patch area and shape. Our results suggest that although reserves generally should be large and circular, there is a trade-off between patch area and shape, which should be taken into consideration when managing reserves.

Land sharing vs. land sparing: does the compact city reconcile urban development and biodiversity conservation?

Summary As cities around the world rapidly expand, there is an urgent need to implement the best development form to minimize the negative impacts of urbanization on native biodiversity. Two divergent forms for the expansion of cities are land-sharing and land-sparing developments. To date, their relative benefits for biodiversity conservation are poorly understood. We quantified the relative conservation benefits of land-sharing and land-sparing developments for butterflies and ground beetles in Tokyo, Japan. For each insect species, we determined which approach resulted in a larger total population size. At a higher level of urbanization (higher number of buildings in a landscape), land sparing rather than land sharing resulted in a higher total population size for the majority species of both taxa. However, at a lower level of urbanization, butterflies and ground beetles showed different responses to city development forms. Ground beetles had their highest total population sizes under land sparing, whereas for butterflies, especially open-land and matrix-dwelling species, larger populations were achieved under land sharing. The negative impacts of urbanization on biodiversity differ greatly between land-sharing and land-sparing development forms. We also revealed that the relative conservation benefits of land sharing and land sparing depend on the level of urbanization. Synthesis and applications. In areas that will be heavily urbanized in the future, city planners and policymakers should adopt approaches that follow a land-sparing strategy and that keep large blocks of greenspace free from development. At lower levels of urbanization, on the other hand, as land sharing was suggested to be the better strategy for many butterfly species, a hybrid development form could be adopted that integrates areas of land sharing and land sparing, which might have the additional benefit of enhancing the delivery of some ecosystem services by bringing nature and people closer together in some areas.

Plantation vs. natural forest: matrix quality determines pollinator abundance in crop fields.

In terrestrial ecosystems, ecological processes and patterns within focal patches frequently depend on their matrix. Crop fields (focal patches) are often surrounded by a mosaic of other land-use types (matrix), which may act as habitats for organisms and differ in terms of the immigration activities of organisms to the fields. We examined whether matrix quality affects wild pollinator abundance in crop fields, given that the species (Apis cerana) generally nest in the cavities of natural trees. We examined fields of a pollination-dependent crop surrounded by plantations and natural forests, which comprised the matrix. Our analysis revealed a clear positive effect of the natural forest on the pollinator abundance, but the plantation forest had little effects. These indicate that agricultural patches are influenced by their matrix quality and the resulting crop pollinator abundance, suggesting the importance of matrix management initiatives such as forest restoration surrounding agricultural fields to improve crop production.

Effects of stand, landscape, and spatial variables on bird communities in larch plantations and deciduous forests in central Japan

We examined the effects of stand, landscape, and spatial variables on bird communities in deciduous forests and Japanese larch (Larix leptolepis (Sieb & Zucc.) Gord.) plantations in a montane region of Nagano Prefecture, central Japan. We used plot-transect methods at 97 sites: 33 in winter 2003 and 18 sites were added in the 2004 breeding season in deciduous forests, and 32 in winter 2004 and 14 sites were added in the 2005 breeding season in larch plantations. Bird–environment relationships were explored using partial redundancy analysis and partial regression analysis. We used spatial variables derived from principal coordinates of neighbor matrices as explanatory variables to detect nonrandom spatial structure of bird communities. Variation in bird communities was mainly explained by stand and spatial variables for both forest types, whereas the effects of landscape variables were small. In plantations, important stand variables for both seasons included stand height, elevation, and the basal area of ...

Biological invasion into the nested assemblage of tree–beetle associations on the oceanic Ogasawara Islands

Invasion by alien organisms is a common worldwide phenomenon, and many alien species invade native communities. Invasion by alien species is especially likely to occur on oceanic islands. To determine how alien species become integrated into island plant–insect associations, we analyzed the structure of tree–beetle associations using host plant records for larval feeding by wood-feeding beetles (Coleoptera: Cerambycidae) on the oceanic Ogasawara Islands in the northwestern Pacific Ocean. The host plant records comprised 109 associations among 28 tree (including 8 alien) and 26 cerambycid (including 5 alien) species. Of these associations, 41.3% involved at least one alien species. Most native cerambycid species feed on host trees that have recently died. Alien trees were used by as many native cerambycid species (but by significantly more alien cerambycid species) as were native trees. Native cerambycid species used as many alien tree species (but significantly more native tree species) as did alien cerambycids. Thus, we observed many types of interactions among native and alien species. A network analysis revealed a significant nested structure in tree–cerambycid associations regardless of whether alien species were excluded from the analysis. The original nested associations on the Ogasawara Islands may thus have accepted alien species.

Beetle responses to artificial gaps in an oceanic island forest: implications for invasive tree management to conserve endemic species diversity

Natural forests are often replaced by invasive alien trees on isolated oceanic islands. Adequate eradication of invasive trees should be conducted with the goal of biodiversity conservation, because islands support many endemic organisms that depend on native forests. An invasive alien tree, Bischofia javanica Blume (Euphorbiaceae), has invaded and replaced natural forests on the oceanic Ogasawara (Bonin) Islands, Japan, in the northwestern Pacific Ocean. To determine how the removal of B. javanica trees affects insect diversity, we examined flying beetles captured using Malaise traps in B. javanica forests on Hahajima. The abundance, species density, and species composition of wood-boring beetles (Coleoptera: Cerambycidae, Elateridae, Mordellidae, and Scolytidae) were compared between closed-canopy sites and gaps created by girdling B. javanica trees in alien forests during two seasons (June–July and October–November 2005). Of the collected beetles, 75.8, 87.5, 90.0, and 0.0% of cerambycid, elaterid, mordellid, and scolytid beetle species, respectively, were endemic to the Ogasawara Islands. More cerambycid, elaterid, and mordellid individuals were captured in June–July than in October–November; the number of scolytid individuals did not differ between seasons. More cerambycid, elaterid, and scolytid individuals were captured in artificial gaps than on the closed-canopy forest floor. Although fewer mordellid individuals were captured in gaps, more endemic mordellids were captured in gaps. More cerambycid and scolytid species were captured in artificial gaps than in closed-canopy areas. The positive responses of beetles to artificial gaps suggest that the removal of B. javanica increases beetle diversity and the abundance of endemic beetles.

Confronting Imperfect Detection: Behavior of Binomial Mixture Models under Varying Circumstances of Visits, Sampling Sites, Detectability, and Abundance, in Small-Sample Situations

Abstract Binomial mixture models (BMMs) have been increasingly applied to account for imperfect detection and to estimate abundance from count data, but their performance has not been thoroughly evaluated. Here, I conducted simulation experiments to examine parameter estimates in BMMs under various situations. I generated data by assuming that abundance followed a Poisson distribution with an expected value &lgr; and that the number of detected individuals followed a binomial distribution with an individual detection probability p. In simple simulations without covariates for &lgr; and p, when the number of sampling sites (n) was between 20 and 160, BMMs could recover &lgr; and p under the following conditions: 0.1≤&lgr;≤160 and p≥0.1. However, within these ranges of &lgr; and p, the estimates were variable under lower values of &lgr; and p, although the situation improved as n increased. When &lgr; and p are expected to exceed these ranges and the sample size is small, the results suggest that sampling and/or modeling designs should be reconsidered. I then conducted simulation experiments with covariates. I assumed that &lgr; increased with a covariate (x) across 20 sampling sites. I varied p, number of visits (v), and their dependency on a covariate. To compare BMMs with analyses that did not accommodate imperfect detection, I fitted ordinary Poisson generalized linear models to mean and maximum counts (GLMmean and GLMmax). The results showed that GLMmax was superior to GLMmean because GLMmean underestimated &lgr; when p was small. GLMmax underestimated a coefficient of the covariate (slope) when v was negatively correlated with x. BMMs successfully recovered true values of the intercepts, slopes, and &lgr; in most cases. However, when p and v were small, and when p and &lgr; were highly negatively correlated due to their inverse dependency on x, estimates from BMMs were more variable.

Ecological traits determine the affinity of birds to a larch plantation matrix, in montane Nagano, central Japan

Although the affinity to the matrix habitat (matrix affinity) determines the fate of species in dynamic landscapes where habitat replacement occurs, only a few studies have examined which ecological traits are associated with matrix affinity. Here, we examined the associations of five ecological traits (i.e., fertility, body weight, migratory behavior, foraging height, and nesting height) with affinity for forest birds to a novel larch plantation matrix habitat. We surveyed the occurrence of birds in larch plantations (matrix habitat) and original deciduous forests (original habitat) in the winter and the breeding season, in a montane region of Nagano prefecture, central Japan. We treated occurrences in the matrix habitat relative to the original habitat as the matrix affinity of each species and examined the associations of ecological traits with matrix affinity, controlling for the relatedness of species. Fertile, resident, and low-nesting species showed high matrix affinity, while an association with body weight was not supported. The associations of foraging groups with matrix affinity were complex. While early successional species showed high matrix affinity, flycatchers had low matrix affinity. The matrix affinity of some foraging groups was greater in the winter than in the breeding season. Based on the results, we predicted that low fertility and migratory, high-nesting species would be sensitive to habitat replacement due to matrix hostility. These predictions may be applicable to other matrix type, region, and taxa.

Health Benefits of Urban Allotment Gardening: Improved Physical and Psychological Well-Being and Social Integration

With an ever-increasing urban population, promoting public health and well-being in towns and cities is a major challenge. Previous research has suggested that participating in allotment gardening delivers a wide range of health benefits. However, evidence from quantitative analyses is still scarce. Here, we quantify the effects, if any, of participating in allotment gardening on physical, psychological and social health. A questionnaire survey of 332 people was performed in Tokyo, Japan. We compared five self-reported health outcomes between allotment gardeners and non-gardener controls: perceived general health, subjective health complaints, body mass index (BMI), mental health and social cohesion. Accounting for socio-demographic and lifestyle variables, regression models revealed that allotment gardeners, compared to non-gardeners, reported better perceived general health, subjective health complaints, mental health and social cohesion. BMI did not differ between gardeners and non-gardeners. Neither frequency nor duration of gardening significantly influenced reported health outcomes. Our results highlight that regular gardening on allotment sites is associated with improved physical, psychological and social health. With the recent escalation in the prevalence of chronic diseases, and associated healthcare costs, this study has a major implication for policy, as it suggests that urban allotments have great potential for preventative healthcare.

Differences in endemic insect assemblages among vegetation types on a small island of the oceanic Ogasawara Islands

Natural vegetation is often replaced by invasive alien plants on isolated oceanic islands. To determine how invasive alien plants affect insect diversity, we compared flying insects captured using Malaise traps among different vegetation types on a small island (Nishijima; 0.49 km2) in the oceanic Ogasawara (Bonin) Islands in the north‐western Pacific. The numbers of individuals and species, and the species composition of pollinators (bees), predators (wasps) and wood borers (cerambycid, mordellid and elaterid beetles) were compared among three vegetation types: Casuarina equisetifolia (an invasive alien tree) forest, natural forest and natural grassland (forest edge), during two seasons (June and October–November 2005). In traps, 80.0, 66.7, 87.5, 85.7 and 100.0% of bee, wasp, cerambycid, mordellid and elaterid beetle species, respectively, were endemic to the Ogasawara Islands. Grassland had the highest wasp and bee species richness, whereas natural forest had the highest species richness of wood‐boring beetles. The C. equisetifolia forest had the poorest species richness for most insect groups (except mordellid beetles). More individuals of most insect groups (except bees) were captured in June than in October–November. More individual bees and wasps were captured in grassland than in forests, whereas more individual mordellid and elaterid beetles were captured in forests than in grassland. The number of cerambycid individuals did not differ among vegetation types. Redundancy analysis suggested that most insect species preferred natural forest or grassland to alien forest. Therefore, further invasion of natural grassland and forest by the alien tree C. equisetifolia may negatively affect the endemic insect fauna of Nishijima.