Morphological dispersion of Rhytidoponera assemblages: The importance of spatial scale and null model

A series of spatially nested assemblages of Rhytidoponera operational taxonomic units (OTUs) (Formicidae: Hymenoptera) from Sturt National Park, New South Wales, Australia, were examined for patterns of dispersion in multivariate morphological space. Morphological overdispersion within an assemblage, relative to a null model, is hypothesized to be a result of the structuring influence of interspecific competition. We compared up to 45 observed assemblages, from across multiple spatial scales, to two null models. Meta-analysis of the null model analyses indicated a general trend to morphological overdispersion, particularly so at restricted scales. Larger scale assemblages were overdispersed relative to only one of the two null models, which we tentatively interpret as being indicative of different competition-driven mechanisms operating at different spatial scales. We also demonstrate that the observed assemblages represent a larger number of species groups than expected by chance, and that this pattern of phylogenetic overdispersion is closely related to the observed morphological patterns.