Linking life and landscapes with new modeling tools

Tools to build numerical models have accelerated our understanding of Earth surface dynamics. Yet to be developed and widely shared are tools to build models of coupled surface and biologic processes at geologic, macroevolutionary timescales. These tools can help us explore how evolutionary diversification of species unfolds in complex linkages with surface processes. Here, we demonstrate the utility of a new model component called SpeciesEvolver built into the Landlab modeling toolkit. This component simulates macroevolutionary processes of continentally distributed organisms at the landscape scale. It can be coupled with the Earth surface process components of Landlab, meaning that software users can readily build models that explore landscape-life linkages. The fundamental objects of SpeciesEvolver are species and the landscape zones they inhabit, both of which can be tailored to individual models. Species objects can represent species groups, individual species, or populations (e.g., conifers, domestic yaks (B. grunniens), fish populations in first-order versus higher-order streams). The zone objects describe the spatial aspect of species for the customizable macroevolution rules. The spatial extent of zones can be defined by elevation, landform (e.g. streams), and other attributes set by the software user. We illustrate SpeciesEvolver functionality with models that (1) produce the widely reported power law relationship observed in natural systems between the number of species and the areal extent these species occupy, and (2) illustrate how a landscape with few species can evolve into a biodiversity hotspot following topographic change. Future studies can use SpeciesEvolver to pursue questions regarding the mechanisms by which organismal lineages respond to landscape evolution, taxon-specific and region-specific interactions between biotas and their environments, and biotic impacts on landscapes.