Using hierarchical levels for urban ecology.

alkaline waste spoils [4]). Some argue that the increase in hard surfaces in cities represents a replication of many of the key features of natural habitat templates [7] found in unproductive rocky areas [5,8,9]. Urban habitats probably provide a continuum of selective novelty, from remnant natural habitats or anthropogenic analogs of other habitats to wholly novel environments. Such research can be married with the mechanistic approach described byShochat et al. [1] by examining urban habitat templates across the continuum of ecological novelty. How much population differentiation occurs when a species successfully colonizes an urban environment? What specific habitat templates does urban form create and how similar are these to natural ecosystems? A mechanistic approach to answering these questions should examine the causes of patterns at a variety of spatial and temporal scales, with particular reference to built, managed and unmanaged habitats across a range of motile and sessile taxa.