What makes outbreaks break out? The ecology and evolution of native and non-native superabundance

当一个物种变得比以前或比其他类似物种更丰富时，它可能对生态系统和人类经济产生严重的有害影响。这种过剩可能是由于新引入生态系统的物种（例如，五大湖的斑马贻贝）或生态系统或非生物环境的重大变化（例如，北美西部的山松甲虫，一种由于暖冬、平均年龄的树木和其他因素的结合而变得过剩的本地物种）造成的。这些本地和非本地的过剩物种在依赖自然资源的经济体中尤其成问题，比如不列颠哥伦比亚省。例如，非本地物种对加拿大农业、渔业和林业的直接影响每年约为1.87亿美元，间接成本为133亿至345亿美元（如自然资源产量下降）。当莱姆病致病菌伯氏疏螺旋体（Borrelia burgdorferi）过剩时——通常是因为宿主物种（如鹿鼠）过剩——它们会导致许多人生病。然而，我们对过度丰富的一般原因的理解非常有限，部分原因是我们缺乏关于物种在时间和空间上的丰富模式的良好信息。

When an individual species becomes much more abundant than it used to be or than other similar species, it can have serious detrimental effects on ecosystems and human economies. Such superabundance can result from a species being newly introduced to an ecosystem (e.g., the zebra mussels in the Great Lakes) or from important changes to an ecosystem or the abiotic environment (e.g., the mountain pine beetle in western North America, a native species that has become superabundant as a result of a combination of warmer winters, even-aged stands of trees, and other factors). These native and non-native superabundant species are especially problematic in economies that depend upon natural resources, like British Columbia. For example, non-native species cost Canada ~$187 million each year in direct impacts on agriculture, fisheries, and forestry, and $13.3 - $34.5 billion in indirect costs (e.g., reduced yield of natural resources). And when pathogens like Lyme disease-causing Borrelia burgdorferi become superabundant-often because of the superabundance of host species, such as deer mice-they can cause many people to become sick. Yet we have a very limited understanding of the general causes of superabundance, in part because we lack good information regarding the patterns of abundance for species across time and space.