Neutral theory is here to stay, and it is likely to have an important role to play in theoretical ecology henceforth. With the development of a full sampling theory, the UNT has become one of the important quantitative tools for ecologists to use in understanding the assembly of ecological communities. Few current theories in ecology besides neutral theory provide a formal sampling theory for testing and potentially rejecting themselves. Neutral theory sometimes fits empirical patterns well, but in many cases, it can be rejected. Frequent rejection is to be expected because the assumption of ecological equivalence will often be violated in real ecological communities. The fits of neutral theory to data from some communities, however, are quite good (e.g., Figure 2). Such cases lead ecologists to ask deeper questions about when the UNT assumption of ecological equivalence (all species are symmetric and obey the mean) is a good approximation and when it is not. Frequent rejection of neutral theory may also be due in part to the simple fact that having a sampling theory makes it an easier theory to reject than other ecological theories that do not yet have a sampling theory.
The UNT has stimulated much discussion in ecology about what it means to test theory in ecology, and it has raised further questions such as: To what qualitative and quantitative standards of accuracy and precision do ecol-ogists hold their theories.? How many predictions per free parameter do we expect from simple, idealized theory versus complex theory. When there is good agreement of the UNT with data, does this imply that the underlying mechanisms are neutral? Most of the empirical tests of the UNT have thus far evaluated fits to patterns of relative species abundance, but there are many other predicted patterns that come out of the UNT that remain to be tested, including many patterns not previously anticipated before the arrival of neutral theory. For example, Latimer, Silander, and Couwling found that neutral theory revealed very rapid speciation rates and isolation in the Cape Floristic region of South Africa. Because the study of neutral theory in ecology is recent, we can expect many new theoretical and empirical developments in this area of inquiry in the future. There are many parallels between neutral theory in ecology and population genetics, which is more than 40 years older and a much more mature field. We can anticipate that many of the tools in population genetics will be adapted for use in neutral theory in ecology.
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