Introduction

Assembly is a basic device of nature where a broad range of entities, spanning many levels of scale, interact across time and space to produce oberserved pattern. Entities such as individuals, phenotypes, populations, guilds, and higher levels of organization like hierarchical structures are all subject to the processes of assembly. Because all biological systems are assembled in a dynamical sense, any generality in the process would prove valuable to our understanding of nature. Arguably, such an understanding is essential to fully appreciate the action of mechanisms as they are played out in evolutionary and ecological time.

Community assembly is ultimately driven by the invasion (e.g., speciation, immigration) and extinction of species played out against a complex background of environmental constraint. While the environment acts as a filter, eliminating some species and promoting others, it also provides spatio-temporal complexities which serve as a resource upon which ecological strategies can be built. Assembly processes and rules which operate within one environment may exhibit entirely different outcomes as a function of even minor environmental variation. Despite such obvious descriptions of the course of nature, the essence of the assembly trajectory remains little more than an elusive metaphor. Here, the character of the assembly trajectory is evaluated and a general framework offered which serves to interface the operation of ecological mechanisms and the mechanics of community assembly within the more general realm of complex systems.