Thrips and Erigeron glaucus: Local Adaptation to IndividualPlant Clones and the Role of Sexuality

食叶食草动物的局部适应是否发生在单个植物基因类型的小范围内，以及有性繁殖中的重组和引入新的等位基因如何影响植物和昆虫的局部适应的问题将被研究。寄主植物灯盏花是一种长寿的垫状植物，既能产生无融合生殖种子，也能产生异交种子。这种食草动物是一种片角蓟马，每年经历许多世代，产生无性或有性繁殖的后代。植物和食草动物的繁殖模式(有性和无性)都可以通过实验来操纵。前人的研究表明，寄主植物变异对蓟马种群增长有很大影响。相反，初步证据表明，蓟马会减少寄主的种子产量。为了确定蓟马是否表现出对单个宿主的局部适应，将比较来自蓟马的遗传系在五个不同宿主克隆上的种群增长。如果已经发生了对单个克隆的适应，那么每个克隆的蓟马可能会在它们的祖先所在的克隆上表现得最好。这项实验的初步运行表明，蓟马已经适应了个别植物。如果蓟马已经适应了宿主的遗传线，宿主能否通过有性繁殖来逃脱寄生虫？这个问题将通过比较无融合生殖产生的植株和异交产生的植株上蓟马的种群增长来回答。同样，将研究繁殖模式在寄主植物品系上利用孤雌生殖或有性繁殖的蓟马后代成功繁殖的作用。

The question of whether local adaptation by leaf feeding herbivores occurs at the small scale of individual plant genotypes and how recombination and the introduction of new alleles through sexual reproduction affect local adaptation by both plant and insect will be examined. The host plant, Erigeron glaucus, is a long-lived, mat forming plant that produces both apomictic seeds and outcrossed seeds. The herbivore, a thrips Apterothrips secticornis, goes through many generations each year and produces offspring either asexually or sexually. The mode of reproduction (sexual vs. asexual) of both the plant and the herbivore can be experimentally manipulated. Previous work showed that population growth of thrips was very strongly affected by host plant variation. Conversely, preliminary evidence indicates that thrips can reduce seed production of their hosts. To determine if thrips show local adaptation to individual hosts, the population growth of genetic lines derived from thrips on five different host clones will be compared. If adaptation to individual clones has taken place, then thrips from each clone may be expected to perform best on the clone from which their ancestors were taken. A preliminary run of this experiment suggested that thrips have adapted to individual plants. If thrips have adapted to host genetic lines, can hosts escape their parasites by reproducing sexually? This question will be answered by comparing the population growth of thrips on plants that were produced apomictically versus those that were produced by outcrossing. Similarly, the role of mode of reproduction, in the success of thrips on host plant lines by using parthenogenetically-produced or sexually-produced thrips progeny will be examined.