杂草是一种植物,* * *你* * *不希望它。完全的上下文。蒲公英是外乡人,介绍了几个世纪前。我猜你的意思是植物的入侵物种已经被人类传播,破坏生态系统在世界上大多数直到最近,这些植物我们考虑杂草的范围是有限的家庭环境只需周围地理障碍和不友好的环境。和自然的消费者,寄生虫和竞争对手在家庭环境已经适应了这些植物,并把它们保存在检查。当非植物被人引入一个新环境,他们中的大多数不繁荣,但偶尔植物是非常成功的。最终潜在消费者、寄生虫和竞争对手的新环境将通过进化调整。但悲剧的是,许多或者大多数的原始物种将被摧毁之前恢复新的平衡,更简化的形式。景观本身可能完全改变了。删除一个关键原始物种也可以造成巨大的变化:[狼如何改变河流][1]。 Not only will many ecologies be reduced to much simpler versions, even if they eventually conquer the invasive plant, those simplified ecologies will closely resemble each other, if their geography is similar, even if on the other side of the world. If humans were to totally stop transplanting invasive species (collapse of civilization?), diversity would return after millions of years. We know this from [Extinction Events][2]. So to answer you question, weeds before human intervention generally did not take over because in their home environments because the potential weeds and their natural consumers, parasites and competitors all evolved together in a quasi-equilibrium. Now however most ecologies throughout the world are out of equilibrium because of environmental change and/or invasive species. This will inevitably lead to simplified, usually less robust, weedy ecologies throughout the world. This might as well be considered a permanent situation compared to the timescale of civilization. [1]: http://voices.nationalgeographic.com/2014/02/16/this-will-shatter-your-view-of-apex-predators-how-wolves-change-rivers/ [2]: http://en.wikipedia.org/wiki/Extinction_event#Effects_and_recovery