Simulating biogeomorphological coevolutionary feedback among pocket gophers, grassland vegetation, and the associated bioengineered landforms

Landscape evolution is often driven by the bioengineering activities of multiple species interacting with one another, which modify the Earth's surface topography and processes. In this study, we used a spatially explicit, individual-based simulation model to investigate potential biogeomorphological coevolutionary feedback relationships. Specifically, we examined how pocket gophers, grassland vegetation, and associated bioengineered soil landscapes may co-define and co-adjust with each other. The model used in this study was parameterized to represent a hypothetical grassland ecosystem typical of those found in California, USA. We found that, as pocket gopher preference for annual plants increased, (i) the number of mounds constructed by these animals increased, (ii) the length of the burrow systems increased, (iii) the complexity of the burrow systems increased, and (iv) the area supporting perennial plants decreased. Collectively, these results would lead to greater food availability (i. e., annual plants) and a more favorable habitat for foraging, breeding, raising offspring, and evading predators. Therefore, the emerging habitat conditions engineered by pocket gophers are expected to eventually enhance their fitness when they increasingly burrow under areas dominated by annual vegetation. As traits associated with preference for annual plants are favored and passed on to future generations, a reinforcing feedback loop between preference for annuals and gopher fitness is anticipated to develop and persist over evolutionary timescales. Our model provides a comprehensive overview by integrating three types of selection pressures: environmental conditions, species interactions, and habitat conditions modified by multiple coevolving engineer species. We anticipate that this study will motivate geoecologists, evolutionary biologists, and geomorphologists to expand their focus beyond their traditional domains within the biological and physical sciences, encouraging exploration of the integrative discipline of biogeomorphology.