Neutral theory in ecology is based on the symmetry assumption that ecologically similar species in a community can be treated as demographically equivalent on a per capita basis—equivalent in birth and death rates, in rates of dispersal, and even in the probability of speciating. Although only a first approximation, the symmetry assumption allows the development of a quantitative neutral theory of relative species abundance and dynamic null hypotheses for the assembly of communities in ecological time and for phylogeny and phylogeography in evolutionary time. Although Steve Gould was not a neutralist, he made use of ideas of symmetry and of null models in his science, both of which are fundamental to neutral theory in ecology. Here I give a brief overview of the current status of neural theory in ecology and phylogeny and, where relevant, connect these newer ideas to Gould's work. In particular, I focus on modes of speciation under neutrality, particularly peripheral isolate speciation, and their implications for relative species abundance and species life spans. Gould was one of the pioneers in the study of neutral models of phylogeny, but the modern theory suggests that at least some of the conclusions from these early neutral models were premature. Modern neutral theory is a remarkably rich source of new ideas to test in ecology and paleobiology, the potential of which has only begun to be realized.

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