Genetic connectivity of the coral‐eating sea star Acanthaster planci during the severe outbreak of 2006–2009 in the Society Islands,French Polynesia          下载免费PDF全文

Nina Yasuda  Coralie Taquet  Satoshi Nagai  Terutoyo Yoshida  Mehdi Adjeroud 《Marine Ecology》2015,36(3):668-678

Occasional population outbreaks of the crown‐of‐thorns sea star, Acanthaster planci, are a major threat to coral reefs across the Indo‐Pacific. The presumed association between the serial nature of these outbreaks and the long larval dispersal phase makes it important to estimate larval dispersal; many studies have examined the population genetic structure of A. planci for this purpose using different genetic markers. However, only a few have focused on reef‐scale as well as archipelago‐scale genetic structure and none has used a combination of different genetic markers with different effective population sizes. In our study, we used both mtDNA and microsatellite loci to examine A. planci population genetic structure at multiple spatial scales (from <2 km to almost 300 km) within and among four islands of the Society Archipelago, French Polynesia. Our analysis detected no significant genetic structure based on mtDNA (global F_ST = ?0.007, P = 0.997) and low levels of genetic structure using microsatellite loci (global F_ST = 0.006, P = 0.005). We found no significant isolation by distance patterns within the study area for either genetic marker. The overall genetically homogenized pattern found in both the mitochondrial and nuclear loci of A. planci in the Society Archipelago underscores the significant role of larval dispersal that may cause secondary outbreaks, as well as possible recent colonization in this area.  相似文献   

Runoff and water budget of the Liudaogou Catchment at the wind–water erosion crisscross region on the Loess Plateau of China     

Huang Jinbai  Wen Jiawei  Hinokidani Osamu  Yasuda Hiroshi 《Environmental Earth Sciences》2014,72(9):3623-3633

The objectives of this study were to examine the runoff characteristics and to estimate water budget at the wind–water erosion crisscross region on the Loess Plateau of China. A small catchment known as Liudaogou that has representative meteorological and hydrological conditions of the wind–water erosion crisscross region was chosen as the study location. A numerical model for rainfall-runoff was developed and verified; rainfall-runoff calculation for 5 years (2005–2009) was performed. The observed data and numerical result of the surface runoff were used for evaluating runoff characteristics and estimating the annual water budget. Runoff rate was proportional to average intensity of rain. Even though rainfall duration was for few minutes, surface runoff was generated by intensity of more than 2.6 mm × 5 min^?1, when rainfall duration exceeded 10 h; surface runoff was generated by an intensity of 0.6 mm × 5 min^?1, while annual runoff rate was 10–15 %. The unit area of 1 km² was adopted as the index area for estimating annual water budget. Runoff, evapotranspiration, variation of water storage, and habitant water consumption accounted for 20.4, 75.6, 0, and 4 % of the total annual precipitation, respectively. Results of this study provide the basis for further research on hydrology, water resources, and sustainable water development and utilization at the wind–water erosion crisscross region on the northern Loess Plateau where annual water resources are relatively deficient.  相似文献   

Two-dimensional asymmetric vortex merger: merger dynamics and critical merger distance     

Ichiro Yasuda  Glenn R. Flierl 《Dynamics of Atmospheres and Oceans》1997,26(3):159-181

Two-dimensional asymmetric merger of two like-signed vorticity monopoles with different sizes and vorticities is examined by combining simplified analytical models and contour dynamics experiments. The model results can capture the key dynamics and hence allow the prediction of the critical merger distance in a number of the situations. The models ignore deformation of one of the two vortices, replacing it with a point vortex, and employ a corotating frame of reference with a rotation rate estimated by point vortices. Thus, the two vortex problem becomes two separate problems of a single vortex in a background shear flow. Vortex merger is found to happen when the vortex cannot resist the background shear flow. Vortex merger and merging processes depend on the centroid distance d, the circulation ratio, (q_i and r_i are the vorticity and radius, respectively) and initial conditions. In the lowest order, the background flow is approximated by a uniform shear field, and the behavior of an elliptical vortex can be described by the Kida (1981) equation supplemented with one describing the time evolution of the centroid distance. This model reveals that merger takes place because the natural rotation of an elliptical vortex is overcome by the background uniform shear flow; the ellipse inversely rotates and is drawn out by the background straining field. The vortex deformation in a background flow field induces an inward flow at the position of the other vortex; as a result, the centroid distance decreases and two vortices merge. The critical merger distance from this model agrees quite well with the results from contour dynamics experiments for two vortices. Inclusion of higher order non-uniform shear in the background flow extends the critical merger distance, which gives almost perfect estimates for the experiment. In the non-uniform shear flow, partial merger occurs, where the vortex sheds off a filament, but the remaining part of the vortex resumes its natural rotation.  相似文献   

Bayesian tsunami fragility modeling considering input data uncertainty     

Raffaele?De RisiEmail author  Katsuichiro?Goda  Nobuhito?Mori  Tomohiro?Yasuda 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(5):1253-1269

Empirical tsunami fragility curves are developed based on a Bayesian framework by accounting for uncertainty of input tsunami hazard data in a systematic and comprehensive manner. Three fragility modeling approaches, i.e. lognormal method, binomial logistic method, and multinomial logistic method, are considered, and are applied to extensive tsunami damage data for the 2011 Tohoku earthquake. A unique aspect of this study is that uncertainty of tsunami inundation data (i.e. input hazard data in fragility modeling) is quantified by comparing two tsunami inundation/run-up datasets (one by the Ministry of Land, Infrastructure, and Transportation of the Japanese Government and the other by the Tohoku Tsunami Joint Survey group) and is then propagated through Bayesian statistical methods to assess the effects on the tsunami fragility models. The systematic implementation of the data and methods facilitates the quantitative comparison of tsunami fragility models under different assumptions. Such comparison shows that the binomial logistic method with un-binned data is preferred among the considered models; nevertheless, further investigations related to multinomial logistic regression with un-binned data are required. Finally, the developed tsunami fragility functions are integrated with building damage-loss models to investigate the influences of different tsunami fragility curves on tsunami loss estimation. Numerical results indicate that the uncertainty of input tsunami data is not negligible (coefficient of variation of 0.25) and that neglecting the input data uncertainty leads to overestimation of the model uncertainty.  相似文献