±Genetic structure of the oak wilt vector beetle Platypus quercivorus: inferences toward the process of damaged area expansion

<p>Abstract</p> <p>Background</p> <p>The ambrosia beetle, <it>Platypus quercivorus</it>, is the vector of oak wilt, one of the most serious forest diseases in Japan. Population genetics approaches have made great progress toward studying the population dynamics of pests, especially for estimating dispersal. Knowledge of the genetic structuring of the beetle populations should reveal their population history. Using five highly polymorphic microsatellite loci, 605 individuals from 14 sampling sites were assessed to infer the ongoing gene flow among populations as well as the processes of expansion of damaged areas.</p> <p>Results</p> <p>Population differentiation (<it>F</it>_ST= 0.047, <it>G'</it>_ST= 0.167) was moderate and two major clusters were detected by several methods, dividing the samples into north-eastern and south-western populations, a similar genetic divergence was reported in host oak trees. Within the north-eastern populations, the subgroups mostly corresponded to differences in the collection period. The genetic characteristics of the population might have changed after 2 years due to the mixing of individuals between populations with enhanced migration related to population outbreaks. Because isolation by distance was detected for whole populations and also within the north-eastern populations, migration was considered to be limited between neighbouring populations, and most populations were suggested to be in genetic equilibrium of genetic drift and gene flow. Recent bottlenecks were found in some populations with no geographical bias; however, they were all from newly emerged oak wilt forests. The emergence of oak wilt should have induced intense fluctuations in the beetle population size.</p> <p>Conclusions</p> <p>Because the genetic boundaries coincide, we suggest that the geographical structuring of the beetle was formed by co-evolution with the host species. Our findings indicate the oak wilt expansion process.</p

Comparison of the Ecological Traits and Boring Densities of <i>Aromia bungii</i> (Faldermann, 1835) (Coleoptera: Cerambycidae) in Two Host Tree Species

We investigated the ecological traits of emerging adults and the boring density in Aromia bungii-infested flowering cherry (Cerasus × yedoensis ‘Somei-yoshino’) and peach (Prunus persica) trees to evaluate their suitability as food resources for A. bungii, and their vulnerability to infestation. The number of adults per m3 that emerged from P. persica was 10-times larger than from C. × yedoensis, and the numbers of emergence holes, entrance holes, and pupal chambers were also larger in P. persica logs. The lifetime fecundity of adults that emerged from P. persica was also higher. Elytral length, sex ratios, and adult lifespans did not differ between the two host trees. Our results indicate that peach trees provide more suitable conditions than do flowering cherry trees for A. bungii larvae. Although flowering cherry trees, primarily C. × yedoensis, which are currently grown as street or ornamental trees in Japan, have been more severely affected by A. bungii to date, the greater risk in the long term is to P. persica, an agricultural species in the main producing areas surrounding the Kanto region

Pine wilt disease and vector beetle records in northern Japan

This is the Microsoft excel file containing the information of the incidences of pine wilt disease, of the abundance of sawyers and of the location. All the data of PWD incidences and sawyer densities were extracted from FFPRI repository (https://www.ffpri.affrc.go.jp/pubs/bulletin/433/documents/433-9.pdf) (Forest Conservation Departmental Meeting of Tohoku Forestry Research Institute Liaison Council, 2008, 2014). The "pwd" sheet has the abundance of newly infected trees, 0 (0 infected trees / municipality), 1 (1-10 trees / municipality), 2 (11-100 trees / municipality) and 3 (>100 trees / municipality) in each year (column) at each municipality (row). The "beetle" sheet has the abundance of sawyers, 0 (0 sawyer), 1 (low abundance) and 2 (high abundance) in each year (column) at each municipality (row). The "info" sheet has the information of the municipalities. Citycode is the municipality codes used in the other sheets. The Lon and Lat are the longitude and the latitude of the centroids of the municipalities in JGD2011 (The Japanese Geodetic Datum 2011), respectively. Municipality is the names of municipalities in each District of each Prefecture. Villages and towns are classified in Districts but cities are directly belonging to Prefectures

Efficacy of Two Neonicotinoid Insecticides against Invasive Wood Borer Aromia bungii Larvae in Dietary Toxicity Test

In recent years, insecticide trunk injection was put into practical use for controlling wood boring pests. However, few studies have investigated the dose–response relationships between insecticides and wood–boring pests in detail. This study used two commercial formulations of the neonicotinoid insecticides thiamethoxam and dinotefuran and investigated their dose–response relationships with invasive wood borer Aromia bungii (Coleoptera: Cerambycidae) larvae. Neonates and late instar larvae were reared with an artificial diet containing different insecticide concentrations (0.01–100 ppm) in the laboratory, and their diet excavation activity, survival rate, and weight change were recorded. Diet excavation immediately dropped in larvae exposed to high concentrations of thiamethoxam or dinotefuran (≥1 ppm in neonates and ≥10 ppm in late instar larvae). The weight and survival rate gradually declined over 12 weeks in late instar larvae. These results suggest that the two neonicotinoids intoxicate and debilitate A. bungii larvae gradually to death. In practical use, rapid suppression of A. bungii wood boring damage can be expected by trunk injection of neonicotinoid insecticides. However, a relatively long-term retention of the insecticides may be required to kill large larvae. Neonates may be controlled with lower insecticide dosage and shorter exposure than larger larvae

Data from: Evolution of a key trait greatly affects underground community assembly process through habitat adaptation in earthworms

Underground community assemblies have not been studied well compared with aboveground communities, despite their importance for our understanding of whole ecosystems. To investigate underground community assembly over evolutionary time scales, we examined terrestrial earthworm communities (Oligochaeta: Haplotaxida) in conserved mountainous primary forests in Japan as a model system. We collected 553 earthworms mostly from two dominant families, the Megascolecidae and the Lumbricidae, from 12 sites. We constructed a molecular taxonomic unit tree based on the analysis of three genes to examine the effects of a biogeographic factor (dispersal ability) and an evolutionary factor (habitat adaptation) on the earthworm community assembly process. The phylogenetic distance of the earthworm communities among sites was positively correlated with geographic distance when intraspecific variation was included, indicating that the divergence within species was affected by biogeographic factors. The community assembly process in the Megascolecidae has also been affected by environmental conditions in relation to an evolutionary relationship between habitat environment and intestinal caecum type, a trait closely related to habitat depth and diet, whereas that in the Lumbricidae has not been affected as such. Intestinal caecum type showed a pattern of niche conservatism in the Megascolecidae lineage. Our results suggest that investigating the evolution of a key trait related to life history can lead to the clear description of community assembly process over a long time scale and that the community assembly process can differ greatly among related lineages even though they live sympatrically