Evolutionary Potential of Invasive Populations

在大量被引入新栖息地的物种中，很少有作为入侵者成功的。允许一些物种入侵而另一些物种不入侵的进化过程，人们知之甚少。种群的进化潜力（可进化性）可能影响入侵新栖息地的能力。可进化性取决于种群中存在的遗传变异，自然选择可以对其起作用。本研究将比较甲壳类物种中入侵种群和非入侵种群的进化差异。这种小的甲壳类动物，也就是affinis，多次从咸水栖息地入侵淡水栖息地。这些入侵伴随着渗透耐受性的进化转变。源种群需要有足够的遗传变异来适应渗透，才能在向淡水的过渡中存活下来。本研究检验了产生和维持遗传变异的两种主要力量的重要性：性状因新突变而变化的趋势，以及波动选择对遗传变异维持的影响（如盐度的季节性波动）。这项研究还研究了海水和淡水耐受性的遗传优势模式，以及不同栖息地的优势如何变化。入侵物种对生态系统完整性和公众健康构成重大威胁。通过更好地了解允许物种入侵的机制，我们可以提高控制这种入侵的能力。

Of the large number of species that are introduced into new habitats, few are successful as invaders. The evolutionary processes that allow some species to invade while others do not are poorly understood. The evolutionary potential (evolvability) of populations might affect the ability to invade novel habitats. Evolvability depends on existing genetic variation in a population on which natural selection could act. This study will compare differences in evolvability between invasive and noninvasive populations within a crustacean species. The small crustacean, Eurytemora affinis, repeatedly has invaded fresh water habitats from saltwater habitats. These invasions were accompanied by evolutionary shifts in osmotic tolerance. The source populations would have required sufficient genetic variance for osmotic tolerance to survive the transition into fresh water. This study tests the importance of two main forces that could generate and maintain genetic variance: the tendency of traits to vary due to new mutations, and the effect of fluctuating selection on the maintenance of genetic variation (such as seasonal fluctuations in salinity). This study also examines patterns of genetic dominance for saltwater and freshwater tolerance, and how dominance varies across habitats. Invasive species pose major threats to ecosystem integrity and public health. By better understanding the mechanisms that allow a species to invade, we can improve our ability to control such invasions.