Phylogeography of the Walnut Twig Beetle, Pityophthorus juglandis, the Vector of Thousand Cankers Disease in North American Walnut Trees
Phylogeography of the Walnut Twig Beetle, Pityophthorus juglandis, the Vector of Thousand Cankers Disease in North American Walnut Trees
复制标题
核桃枝甲虫（Pityophthhorus juglandis）的系统发育地理学，北美核桃树千口溃疡病的传播媒介
作者：
P. Rugman;S. Seybold;A. Graves;R. Stouthamer
核桃(Juglans spp.)结果是核桃小枝甲(WTB)在韧皮部侵略性取食，并在其走廊接种致病真菌Geosmithia morbita。1960年，WTB只在美国四个县(亚利桑那州、加利福尼亚州和新墨西哥州)被发现，但现在(2014年)该物种已经入侵了115多个县，代表了美国西部的大部分地区，以及美国东部至少6个州。东部的扩张使TCD直接靠近价值很高(5000亿美元)的东部黑核桃原生木材林。使用来自近1100个个体的线粒体DNA序列，我们检查了美国WTB种群的77个样本的变异，揭示了高度的多态和两个不同谱系的证据。不同血统的遗传多样性水平最高的分别是邻近的马德里安天空岛和新墨西哥州西部地区。尽管它们距离很近，但几乎没有证据表明这两个地区混合在一起，在179只甲虫中只检测到一只候鸟。事实上，这两个血统的地理重叠只在科罗拉多州和犹他州的部分地区很常见。在最近扩大的范围内，只有两种来自同一血统的单倍型主导了绝大多数。对沃尔巴克氏菌的检测结果为阴性，这表明它在“驱动”特定单倍型的传播，或在维持WTB种内深层差异方面没有作用。核糖体RNA的基因分型证实了线粒体的谱系，但也揭示了它们之间杂交的证据。杂交在共面区特别普遍，在所有侵袭区也很明显，但在每个线粒体谱系中单倍型最丰富的区域缺乏杂交。讨论了关于WTB的特定地位、其最近的扩展以及TCD的潜在进化起源的假说。
Thousand cankers disease (TCD) of walnut trees (Juglans spp.) results from aggressive feeding in the phloem by the walnut twig beetle (WTB), Pityophthorus juglandis, accompanied by inoculation of its galleries with a pathogenic fungus, Geosmithia morbida. In 1960, WTB was only known from four U.S. counties (in Arizona, California, and New Mexico), but the species has now (2014) invaded over 115 counties, representing much of the western USA, and at least six states in the eastern USA. The eastern expansion places TCD in direct proximity to highly valuable (> $500 billion) native timber stands of eastern black walnut, Juglans nigra. Using mitochondrial DNA sequences, from nearly 1100 individuals, we examined variation among 77 samples of WTB populations across its extended range in the USA, revealing high levels of polymorphism and evidence of two divergent lineages. The highest level of genetic diversity for the different lineages was found in the neighboring Madrean Sky Island and Western New Mexico regions, respectively. Despite their proximity, there was little evidence of mixing between these regions, with only a single migrant detected among 179 beetles tested. Indeed, geographic overlap of the two lineages was only common in parts of Colorado and Utah. Just two haplotypes, from the same lineage, predominated over the vast majority of the recently expanded range. Tests for Wolbachia proved negative suggesting it plays no role in "driving" the spread of particular haplotypes, or in maintaining deep levels of intraspecific divergence in WTB. Genotyping of ribosomal RNA corroborated the mitochondrial lineages, but also revealed evidence of hybridization between them. Hybridization was particularly prevalent in the sympatric areas, also apparent in all invaded areas, but absent from the most haplotype-rich area of each mitochondrial lineage. Hypotheses about the specific status of WTB, its recent expansion, and potential evolutionary origins of TCD are discussed.
影响因子：
3.3
作者：
Alan R. Templeton;K. Crandall;C. Sing
通讯作者：
Alan R. Templeton;K. Crandall;C. Sing
影响因子：
3.3
作者：
L. Excoffier;P. Smouse;J. Quattro
通讯作者：
L. Excoffier;P. Smouse;J. Quattro