Testing a invasive species hypothesis on Platypus quercivorus, a vector insect of the Japanese oak wilt by DNA analysis among regional populations

在开始这个项目之前，鸭嘴兽quercivorus记录来自日本，印度，印度尼西亚，新几内亚和台湾。在泰国和越南采集到该种，为该种分布的新记录。我们发现在日本分布有两个类型，它们被认为是两个独立的种（“日本海型”和“太平洋型”）。这两种类型在形态和遗传上彼此不同。这些形态学和遗传学上的差异是一致的。关于“日本海型”，通过DNA分析确定了两个种群：大陆种群和琉球中部种群。DNA分析表明，泰国和印度尼西亚四个地区群体中，两个群体之间的遗传距离最远。大陆人口与泰国人口最接近，琉球中部人口与印尼人口最接近。这一结果很难用自然规律来解释。大陆种群可能是在最后一次冰川时代后由泰国引入的。相反，致病真菌Raffaelea quercivora的变异没有P quercivorus那么大：R.台湾和日本的栎属（P. quercivorus），分属同一行业。我们假设日本栎枯萎病的起源如下：日本-海洋型P quercivorus，从泰国引进后，冰川时代被劫持的R。在九州南部，这两种类型共存的太平洋-海洋类型携带的quercivora。由于皱皮栎是一种高度感病的植物。同时，由于栎瘿螨在死栎体内繁殖率高，随着日本栎枯萎病的迅速蔓延，“日本海型”栎冠实蝇泰国种群的分布范围迅速扩大

Before starting this project, Platypus quercivorus was recorded from Japan, India, Indonesia, New Guinea, and Taiwan. We collected the species from Thailand and Vietnam, which is the new record of the distribution of this species. We found that two types were distributed in Japan, which were thought to be two independent species ("Japan-Sea type" and "Pacific -Ocean type" in this MS). These two types differed from each other morphologically and genetically. These morphological and genetic differences coincided. Regarding the "Japanese-Sea type" two populations were recognized by DNA analysis: mainland population and central Ryukyu population. Genetic distance between the two populations was farthest among four regional populations by DNA analysis including Thai and Indonesian populations. The mainland population was most close to Thai population, and the central Ryukyu population was to the Indonesian. It was difficult to explain this result by natural pattern. The mainland population was introduced from Thailand after the last glacier age probably by human activity. On contrary, the pathogenic fungus, Raffaelea quercivora did not varied so much as P quercivorus did: R. quercivora that was collected from P quercivorus in Taiwan and Japan were classified into one trade. We hypothesized an origin of the Japanese oak wilt disease as follows: Japan-Sea-type P quercivorus that were introduced from Thailand after glacier age were hijacked by R. quercivora carried by the Pacific-Ocean type at southern Kyushu, in which these two types coexist. Because Quercus crispula is highly susceptible to R. quercivora and because reproduction rate of P quercivorus is high in dead Q. crispula, epidemics of the Japanese oak wilt spread rapidly and the distribution range of the Thai population of the "Japan-Sea-type" P. quericovrus expanded fast