定义：which agent of biological dispersal moves a dispersal unit, or organism, away from its birth population to another location or population in which the individual will reproduce.
定义：This organism produces this material or substance, either during its life or after death. A produces B if some process that occurs in A has output B.
定义：A group of species that exploit the same food resources, and/or use the same feeding or foraging methods. http://en.wikipedia.org/wiki/Guild_(ecology)
