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Yamaguchi Y.,Niigata University | Yazawa H.,Niigata University | Iwanishi S.,Echigo Matsunoyama Museum of Natural Science | Kudo K.,Niigata University
Entomological Science | Year: 2016

In several poneroid ant species, mated workers alone undertake reproduction. The reproductive systems of such species have been examined extensively. However, few studies have investigated species with alate queens, which reproduce after shedding their wings. We compared body sizes and the numbers of ovarioles between queens and workers in the ant Cryptopone sauteri with alate queens. We also compared ovariole development between the castes to evaluate their reproductive systems. Approximately 60% of the nests collected were queenless. We often detected unmated queens in the nests throughout the year, but did not obtain strong evidence for their reproduction. Although significant differences were observed in the number of ovarioles and body characteristics between the queens and workers, the differences were not as prominent as those observed in Formicinae and Myrmicinae. We propose two alternative hypotheses, failure of nuptial flight or postponement of reproduction, to explain the presence of unmated queens in the nests. © 2016 The Entomological Society of Japan. Source


Ohwaki A.,Echigo Matsunoyama Museum of Natural Science
Journal of Asia-Pacific Entomology | Year: 2015

The ground arthropod communities in paddy fields during the dry period and the effects of different farming methods adopted during the cropping season on these communities were evaluated. Pitfall traps were used in six conventional, two herbicide-only, and four organic paddy fields in early November and early May at two sites in Niigata Prefecture, Japan. A total of 202 ground arthropods belonging to 18 taxa were collected, with eight taxa identified at the species level. The most abundant taxa were two predator groups, spiders and carabid beetles. Farming methods did not affect taxon richness, total abundance, abundance of individual taxa, or species composition, but the site marginally affected the abundance of some taxa. These results suggest that during the dry period paddy fields contained abundant predatory arthropods, and that the communities were not affected by the use of pesticides during the cultivation period. Because these predators are important natural enemies of rice pests, management strategies should be focused on both the cultivation period and the uncropped, dry period to enhance predator populations. © 2015 Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society. Source


Kitamura K.,Japan Forestry and Forest Products Research Institute | Matsui T.,Japan Forestry and Forest Products Research Institute | Kobayashi M.,Echigo Matsunoyama Museum of Natural Science | Saitou H.,Kuromatsunai Beech Tree Museum | And 2 more authors.
Tree Genetics and Genomes | Year: 2015

The species distribution of Fagus crenata, or Japanese beech, in the Japanese archipelago shifted northward during phytogeographical changes that occurred during the Pleistocene and Holocene epochs. Presently, the continuous natural distribution of beech reaches north to the Kuromatsunai Depression of Hokkaido Island, Japan. In addition, dozens of marginal patches and isolated individuals north of the continuous distribution have been observed. F. crenata grows remarkably well among these small-scattered northern marginal populations, which must have originated from seeds dispersed beyond the northern limit of the continuous beech forest. It is conceivable that the distribution of F. crenata is still in the process of expanding northward. We investigated the genetic structure of 33 beech populations to evaluate the population gene diversity at the leading northern edge of the range expansion. We analyzed 12 nuclear microsatellite loci in each of the 1,693 individuals. Genetic diversity parameters such as expected heterozygosity and allelic richness were clearly lower in the northernmost populations. We found genetic differentiation in the northernmost distribution range (FST = 0.045, G′ST = 0.242). STRUCTURE analysis revealed that the southwestern continuous populations consisted of homogeneous ancestral clusters. However, northeastern marginal populations consisted of mixtures of highly differentiated clusters with higher levels of genetic drift than found in the continuous populations. © 2015, Springer-Verlag Berlin Heidelberg. Source


Kobayashi M.,Echigo Matsunoyama Museum of Natural Science | Kobayashi M.,Hokkaido University | Kitamura K.,Echigo Matsunoyama Museum of Natural Science | Kitamura K.,Japan Forestry and Forest Products Research Institute | And 4 more authors.
Silvae Genetica | Year: 2013

To understand the population dynamics of tree populations at the range limit of a species' range, it is important to determine which population size and disturbance regime are critical to genetic diversity. Siebold's beech (Fagus crenata Blume) is a major canopy tree species of cool-temperate forests in Japan, with the northernmost distribution reaching the Kuromatsunai Depression in southwestern Hokkaido, Japan. We examined the genetic variation and dynamics of three beech forests, with different disturbance history and population attributions in the northernmost population. The Tsubamenosawa (TSU) and Sannosuke (SAN), both natural forest, have historically experienced little artificial disturbance, whereas the Soibetsu (SOI), a secondary forest, was intensively logged, and thus strongly disturbed in the past. In total, 35 alleles were detected among 12 loci, encoding 9 enzyme systems. At TSU, He and RS were 0.141 and 2.280, respectively. At SAN, He and RS were 0.142 and 2.604, respectively. At SOI were 0.182 and 2.628, respectively. Parameters of genetic diversity changed with population size, small isolated population indicated low values. Gene flow distance for low density mature trees in the natural forests was greater than that for high-density secondary forest. However, effective population sizes (Ne) were 34.7, 64.3 and 60.3 in TSU, SAN and SOI, respectively, reflecting differences in the density of mature individuals. The results suggested that the population with the low density of mature trees kept genetic diversity through long distance gene flow. The mature tree density affected the effective population size in the northernmost beech populations. Source


Sugiura S.,Japan Forestry and Forest Products Research Institute | Tsuru T.,Echigo Matsunoyama Museum of Natural Science | Yamaura Y.,Hokkaido University
Biological Invasions | Year: 2013

Native vegetation is frequently replaced by alien plants on isolated oceanic islands. The effects of such replacements by invasive plants on the diversity and temporal dynamics of island-endemic insects remain unclear. We examined flying insect communities using Malaise traps on the small island of Nishi-jima in the oceanic Ogasawara Archipelago in the northwestern Pacific. On the island, an alien tree, Casuarinaequisetifolia, has become dominant, occupying 57. 3 % of the vegetation area. The species richness, composition, and abundance of pollinators (bees), predators (wasps), and wood-boring beetles (cerambycids, mordellids, and elaterids) were compared in each summer season of 4 years among three vegetation types: C. equisetifolia forest, natural forest, and grassland. In the traps, 82. 3 % of species captured were endemic to the archipelago. The grassland harbored the highest species richness of native bees and wasps, whereas the natural forest had the highest species richness of native wood-boring beetles. The C. equisetifolia forest had the poorest species richness for most insect groups. Principal response curves indicated that differences in species composition among the three vegetation types were consistent through time for all insect groups. Most insect species were more abundant in natural forest or grassland than in C. equisetifolia forest. Standard deviations in both the numbers of individuals and species estimated under a Bayesian framework suggested that annual fluctuations of abundance and species density were similar among vegetation types (except for elaterid abundance). Therefore, replacement by C. equisetifolia has likely altered insect species composition but has not necessarily dramatically affected the temporal dynamics of insect assemblages on the island. © 2012 Springer Science+Business Media B.V. Source

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