RUI: Experimental Investigation of Ecological and Genetic Correlates of Parthenogenetic and Reproduction in a Fresh Water Snail

9629287约翰逊当今生物学中的一个突出问题是，与孤雌生殖(个体从未受精卵发育而来)等替代方法相比，有性繁殖似乎有相当大的成本，为什么有性繁殖在许多生物体中如此普遍。在许多假说中，寄生虫理论似乎是最可信和最可验证的，这些假说解释了许多生物体中普遍存在的有性繁殖。根据寄生虫理论，在寄生风险较高的宿主中，有性繁殖比孤雌生殖更受青睐，因为有性后代可能不太容易受到寄生虫的感染。当寄生风险最小时，应支持孤雌生殖。然而，如果寄生虫以有限的遗传变异重新克隆孤雌生殖种群，孤雌生殖可能遭受高水平的寄生。将进行现场和实验室实验，以区分北美淡水蜗牛孤雌生殖种群中寄生扁虫水平较高的原因。孤雌生殖可能是由于吸虫引起的精子限制，或者，在冰川消退后，孤雌原虫在湖泊和河流定居可能具有优势。高寄生率是由于无性种群缺乏遗传变异所致。现场和实验室实验将检验寄生虫理论的预测，即与孤雌生殖个体相比，有性个体应该经历较低的感染水平和较大的感染差异。上面概述的研究应该为流行病如何在遗传变异有限的生物体中传播提供重要的见解。两个可能具有有限遗传变异的重要生物群体是农作物近交系和濒危动植物的小种群。

9629287 Johnson One of the outstanding problems in biology today is why sexual reproduction is so common in many organisms when there appear to be considerable costs to sexual reproduction relative to alternatives like parthenogenetic reproduction (individuals develop from unfertilized eggs). Of the many hypotheses developed to explain the widespread maintenance of sexual reproduction in many organisms, the parasite theory appears to be the most plausible and testable. According to the parasite theory, sexual reproduction is favored over parthenogenetic reproduction in hosts under high risk of parasitism because sexual offspring may be less susceptible to infection by parasites. Parthenogenesis should be favored when there is minimal risk of parasitism. Parthenogens may, however, suffer high levels of parasitism if parasites recolonize parthenogenetic populations with limited genetic variation. Field and laboratory experiments will be undertaken to distinguish among the causes of higher levels of parasitic flatworms in parthenogenetic population of the North American freshwater snail, Campeloma decisum. Parthenogenesis may be favored due to sperm limitation caused by a trematode worm or, alternatively, parthenogens may have had an advantage colonizing lakes and rivers after glaciers receded. High parasitism results from lack of genetic variation in asexual populations. Field and laboratory experiments will test the prediction from the parasite theory that sexual individuals should experience lower levels of infection and greater variation in infection relative to parthenogenetic individuals. The research outlined above should provide important insights into how epidemic diseases spread in organisms with limited amounts of genetic variation. Two important groups of organisms that may have limited genetic variation are inbred lines of agricultural crops and small populations of endangered plants and animals.