Ryûtarô Iwata

Effective Dispersal of Brown Bears (Ursus arctos) in Eastern Hokkaido, Inferred from Analyses of Mitochondrial DNA and Microsatellites

Abstract. Male brown bears (Ursus arctos) generally disperse over longer distances than females, which have conservative habitats around their natal areas. Our previous study indicated that the distributions of mitochondrial DNA (mtDNA) subhaplotypes in females were allopatric in the southern Akan—Shiranuka region of eastern Hokkaido. Dispersal of males from their natal area to another natal area is easily detected from the allopatric distributions of two of the mtDNA subhaplotypes of female bears (HB02a and HB13b). Here, to investigate the effectiveness of gene flow and dispersal of male bears between two natal areas, we assessed the genetic diversity and kinship of 132 brown bears from 1996 and 2008 in this area by analyzing the polymorphisms of mtDNA and microsatellite DNA. Parentage testing revealed that there were 48 potential father—offspring pairs, nine potential mother—offspring pairs, and four potential parent—offspring trios. Among 33 of the 48 father—offspring pairs, the mtDNA subhaplotypes differed between father and offspring, suggesting that these potential fathers moved from one natal area to the other and had reproductive success. The results show that effective dispersal of male bears has maintained the genetic diversity and gene flow between the two natal areas.

Performances of four chemicals with floral scents as attractants for longicorn beetles (Coleoptera: Cerambycidae) in a broadleaved forest

White plastic insect traps (manufactured by Sankei Chemical Co., Ltd.) equipped with four chemicals with floral scents, namely, benzyl acetate, methyl benzoate, methyl phenylacetate and linalool, were set from June 28 to August 9, 1996. The traps were placed in a Japanese beech (Fagus creata) forest, Minakami, Gunma Prefecture, Central Japan, and trapped longicorn beetles were collected weekly. The greatest number of species and individuals belonged to the subfamily Lepturinae dominated by the genusPidonia. No significant differences were observed in the performances of the above four chemicals in either the total number of species or of individuals. However, more Lamiinae species were captured in the traps with methyl phenylacetate, than in those with methyl benzoate.

Super-Protective Child-Rearing by Japanese Bess Beetles, Cylindrocaulus patalis: Adults Provide Their Larvae with Chewed and Predigested Wood

Beetles of the family Passalidae (Coleoptera: Scarabaeoidea) are termed subsocial. The insects inhabit rotten wood as family groups consisting of the parents and their offspring. The Japanese species Cylindrocaulus patalis has the lowest fecundity among passalids because siblicide occurs among the first-instar larvae; accordingly, parental care toward the survived larva is the highest among Passalidae. To clarify the nutritional relationships between the parents and their offspring, we investigated their ability to digest three types of polysaccharides that are components of wood (cellulose and β-1,4-xylan) and fungal cell walls (β-1,3-glucan). Although carboxymethyl-cellulase activity was barely detectable, β-xylosidase, β-glucosidase, β-1,4-xylanase and β-1,3-glucanase activities were clearly detected in both adults and larvae. Because the activities of enzymes that digest β-1,3-glucan were much higher than those for degrading β-1,4-xylan, in both adults and larvae, it is concluded that they are mainly fungivorous. Furthermore, these digestive enzymatic activities in second- and third-instar larvae were much lower than they were in adults. Although all larval instars grew rapidly when fed chewed wood by their parents, larvae ceased growing and died when fed only artificially ground wood meals. We conclude that the larvae are assumed to be provided with chewed predigested wood in which β-1,3-glucan is degraded by parental enzymes.

Estimating the population structure of brown bears in eastern Hokkaido based on microsatellite analysis

Estimating the genetic structure of a population is important for the conservation and management of wildlife. In the present study, our aim was to estimate the genetic structure of the brown bear (Ursus arctos) population in eastern Hokkaido by performing a Bayesian clustering analysis. To accomplish this goal, we used 15 microsatellites to generate genotypic data from tissue samples collected from 646 bears between 1996 and 2008. Using this genotypic data and the geographic locations where the bears were captured, GENELAND analysis detected six subpopulations. Based on the genotypic data, the STRUCTURE analysis revealed three subpopulations. As inferred from the GENELAND analysis, the core zones of the subpopulations (G-a through G-f) were located in the Shiranuka Hills (G-a), the northern area of the Shiranuka Hills (G-b), the eastern slope of the Daisetsuzan Mountains (G-c), the northern slope of the Akan Mountain Range (G-d), the Shiretoko Peninsula (G-e), and Akkeshi District (G-f). The STRUCTURE analysis indicated that G-b and G-d were influenced by gene flow from other subpopulations. National routes, towns, and farm fields were considered to have formed the distribution boundaries among the subpopulations. A high level of genetic differentiation was not observed among the six subpopulations, with the exception of G-f (Fst = 1.35–0.176, Ds = 0.246–0.349), which showed a geographically discontinuous distribution. We suggest that the loss of forest areas through future regional development and road building should be avoided to facilitate gene flow in brown bears in Hokkaido.

Evaluation of beetle capture in traps as compared with manual capture on flowers in a long-term investigation in a beech forest

Beetle samples captured by traps were compared with those captured manually on flowers in a beech forest in Central Japan. Plastic traps (Sankei Chemical Co., Ltd.) equipped with benzyl acetate were set up from the 2nd of June to the 8th of September 1994, and all beetles captured were collected every week. Beetles were also captured on wild flowers blooming along the forest road. The traps captured 21,650 individuals of 169 species in 37 families. On the other hand, 971 individuals of 77 species in 19 families were captured on the flowers. All of the families and 57 (74%) species of the beetles captured on the flowers were also captured by the traps; all of the species with more than five individuals captured on the flowers were also trapped, except for one species. The present trap system is considered to be useful for faunal monitoring of flower-visiting Coleoptera, because the beetle fauna found on wild flowers was virtually covered by the trap capture.

Glycolytic Activities in the Larval Digestive Tract of Trypoxylus dichotomus (Coleoptera: Scarabaeidae)

The larvae of the Japanese horned beetle, Trypoxylus dichotomus (Coleoptera: Scarabaeidae: Dynastinae), are an example of a saprophage insect. Generally, Scarabaeid larvae, such as T. dichotomus, eat dead plant matter that has been broken down by fungi, such as Basidiomycota. It is thought that β-1,3-glucan, a constituent polysaccharide in microbes, is abundant in decayed plant matter. Studies of the degradation mechanism of β-1,3-glucan under these circumstances are lacking. In the current study, we sought to clarify the relationship between the capacity to degrade polysaccharides and the food habits of the larvae. The total activities and optimum pH levels of several polysaccharide-degrading enzymes from the larvae were investigated. The foregut, midgut and hindgut of final instar larvae were used. Enzymatic activities were detected against five polysaccharides (soluble starch, β-1,4-xylan, β-1,3-glucan, pectin and carboxymethyl cellulose) and four glycosides (p-nitrophenyl (PNP)-β-N-acetylglucosaminide, PNP-β-mannoside, PNP-β-glucoside and PNP-β-xyloside). Our results indicate that the digestive tract of the larvae is equipped with a full enzymatic system for degrading β-1,3-glucan and β-1,4-xylan to monomers. This finding elucidates the role of the polysaccharide-digesting enzymes in the larvae, and it is suggested that the larvae use these enzymes to enact their decomposition ability in the forest environment.

Systematics of rove beetles (Coleoptera: Staphylinidae: Aleocharinae) associated with Hodotermopsis sjostedti (Isoptera: Termopsidae)

Members of the termitophilous subtribe Termitozyrina (Aleocharinae: Lomechusini) associated with Hodotermopsis sjostedti are taxonomically treated. The genera Hodotermophilus Naomi & Terayama and Termophidoholus Naomi & Hirono, and each type species (monotypic) are redescribed. Termophidoholus formosanus, originally described from Taiwan, and its host termite H. sjostedti are newly recorded from Laos. Yakuus iwatai Kanao & Maruyama gen. & sp. nov. and H. gloriosus were collected sympatrically in the same nests in Yaku‐shima, Japan. All of the above species, belonging to the three genera, share the presence of a batch of spurs at the tibial apex of fore and mid legs. Habitus photographs and illustrations of diagnostic features are provided for these species, and their phylogenetic relationships are discussed based on morphological similarities and the extant distribution of the host termite species.

Comparison of Beetle Samples Captured by Traps with Those on Flowers in a Broad-Leaved Forest

Beetle samples were compared between catches by traps and those on flowers in a Japanese beech (Fagus crenata Blume) forest, in Minakami, Gunma Prefecture, Japan. White plastic traps (Sankei Chemical Co., Ltd.) equipped with benzyl acetate were set out for a month from July 23 to August 23, 1993, and all beetles captured were collected every six days. During six days from August 10 to August 16, beetles were captured with traps and on wild flowers (Aruncus sylvester Kostel andAngelica polyclada Franch) at three hour intervals. Over the month, the traps captured 1,677 individuals of 73 species of 20 families, which included 16 (89%) species captured on flowers in the six-day period. Over the six days, the traps captured 327 individuals of 21 species of 12 families, compared with 685 individuals of 18 species of 5 families on the flowers; all of the families and nine (50%) species of beetles taken on the flowers were also captured by the traps; all of the species with more than five individuals captured on the flowers were also trapped. This suggests that capture by traps might sufficiently cover the beetle fauna on flowers. The number of species and individuals, as well as their changing patterns, however, varied more irregularly during the six-day period with the traps than with those on the flowers.

Boring activity on coniferous tree branches byXylotrechus villioni (Villard) larvae (Coleoptera: Cerambycidae)

In anAbies homolepis Sieb. et Zucc. forest at Matsumoto, Nagano Pref., cumulative damage byXylotrechus villioni (Villard) (Coleoptera: Cerambycidae) was observed on tree branches. Of the 14 major branches in one sample tree, six had cumulative damage by boring larvae, of which 3 had been bored by multiple larvae. No adult emergence holes were found on the whole tree, suggesting very low survivorship from boring larva to emerging adult. Galleries made by single larvae were often observed to be terminated by a depression apparently carved by a picid woodpecker, suggesting that they are important predators of the cerambycid. The manner of cicatrix formation with phloem tissue over the larval gallery in anAbies veitchii Lindl. branch at Mt. Fuji, Yamanashi Pref. is presented.

Mating Behavior of Rosalia batesi (Coleoptera: Cerambycidae) Is Mediated by Male-Produced Sex Pheromones

Rosalia batesi Harold (Cerambycidae) is a hardwood boring species endemic to Japan. We investigated the adult mating behavior of this species in the field and laboratory. Most males appeared on mating sites before noon, significantly earlier than females did, in field observations. The female approached and contacted the male; the male responded and started the successive mating sequence, comprising mounting, copulation, and appeasement behavior. Before the encounter, the male raised its fore and mid legs and bent the abdominal tip ventrally. Next, a peculiarly structured bifurcate tip was exposed with opening and closing motion, which can be observed in the entire family Cerambycidae and is thought to be associated with the emission of volatile male sex pheromones. Male and female orientation toward conspecifics was examined using T-shaped olfactometers in four combinations (male–male, female–male, female–female, male–female). Males exclusively attracted females, indicating the existence of male-produced sex pheromones. A laboratory bioassay with three temperature regimes revealed the temperature dependence of this calling behavior. The calling behavior occurred only when the air temperature and male body surface temperature, which are associated with light intensity, were within the range of 26–33 °C and 26–28 °C, respectively.