More widespread species tend to be more locally abundant, both for the population dynamics of a single species across a network of habitat patches (intraspecific) and for many species sampled at a single point in time (interspecific). These abundance-occupancy relationships are fairly well-supported in observational studies, but the underlying factors driving them are less clear. For instance, variation in demographic rates, dispersal, and spatial habitat network structure could all influence resulting abundance-occupancy relationships. We propose a simple simulation model to explore intraspecific and interspecific relationships. We create spatial habitat networks of variable size and dispersal connectivity, and simulate population dynamics across spatial networks by starting from entirely neutral communities, then systematically incorporating complexity in the form of (co)variation in species demographic rates and dispersal processes. We find that intraspecific abundance-occupancy relationships are quite weak and unaffected by the incorporation of demographic or dispersal rate variation or network structure. However, interspecific abundance-occupancy relationships were quite strong and sensitive to the spatial network structure and (co)variation in demographic and dispersal rates. This identifies a clear difference between the two forms of the relationship, as intraspecific abundance-occupancy relationships rely on temporal variation in environmental conditions independent of species trait variation, while interspecific abundance-occupancy relationships require species trait differences. Together, we provide a clear, spatially-explicit framework to explore the potential drivers of abundance-occupancy relationships, with potential extensions to many other macroecological relationships.

Species with broader niches may have the opportunity to occupy larger geographic areas, assuming no limitations on dispersal and a relatively homogeneous environmental space. While there is general support for positive \textit{geographic range size – climatic niche area} relationships, a great deal of variation exists across taxonomic and spatial gradients. Here, we use data on a large set of mammal ($n$ = 1225), bird ($n$ = 1829), and tree ($n$ = 341) species distributed across the Americas to examine the \textbf{1}) relationship between geographic range size and climatic niche area, \textbf{2}) influence of species traits on species departures from the best fit geographic range size – climatic niche area relationship, and \textbf{3}) how detection of these relationships is sensitive to how species range size and climatic niche area are estimated. We find positive \textit{geographic range size – climatic niche area} relationships for all taxa. Residual variation in this relationship contained a strong latitudinal signal. Subsampling the occurrence data to create a null expectation, we found that residual variation did not strongly deviate from the null expectation. Together, we provide support for the generality of \textit{geographic range size – climatic niche area} relationships, which may be constrained by latitude but are agnostic to species identity, suggesting that species traits are far less responsible than geographic barriers and the distribution of land area and available environmental space.