Ecological guilds can generate repeatable indicator values and realistic patterns of habitat partitioning: Insights from metacommunity simulations

The working assumption within most community ecology and biodiversity research is that all species common to a given regional species pool respond in unique ways to the environment, and moreover, that the differences among all species’ responses are sufficiently pronounced to matter to the community assembly process.  However, a variety of biogeographical and evolutionary processes could conceivably lead to the co-occurrence of some species that, in practice, would exhibit indistinguishable responses to the environment.  The implications that such a ‘partial equivalence’ scenario might have for community assembly and diversity patterns have only recently begun to be explored, perhaps in part because the notion of ecological equivalence is not easily reconciled with existing biodiversity theory.  Here I use spatially-explicit simulations of competitive metacommunities to show that the concept of ecological guilds – which envisions regional species pools containing sets of co-equal species – is compatible with two ecological patterns that, historically, have been interpreted as evidence in support of the conventional one species-one niche assumption: (i) significantly pronounced habitat partitioning, and (ii) indicator values (i.e. realized optima) that are repeatable from place to place.  These results suggest that conventional perspectives on the nature of fundamental niche differentiation among species may be unnecessarily restrictive.