Coupled Evolution of Landscape Geomorphology and Species Traits across Environmental Gradients

Abstract:

Biogeomorphology focuses on vegetation-landform interactions. The morphology of the landscape develops as it is driven by abiotic processes, while simultaneously being influenced by organisms to various degrees. Biological activities modify the trajectory of landscape development and transform natural selection acting on a host of species traits, thereby influencing subsequent evolution of organisms involved. Over the past decade, research in biogeomorphology has been focused on the effect of biological processes and/or species traits on landscape morphology. Feedback between evolution and geomorphological development has been rarely investigated. Using a two-locus population genetic model coupled with a landscape evolution model, I outline theoretical predictions for evolutionary and topographic consequences of geo-evolutionary feedbacks along two gradients: (a) the gradient of selection pressure by landscape morphological changes on organisms, and (b) the gradient of biological influences on morphological change. I found that when the strength of the feedback is strong—that is, selection pressure is strong and geomorphic effect by plants is strong, landscape morphology has multiple stable states and shifts between alternative states, driven by the change in plant population genetics. Stronger geo-evolutionary feedback results in a rougher landscape surface, although the effect size is influenced by plant dispersal mode. I also found evidence for environmentally mediated genotypic association when the geo-evolutionary feedback is strong. This association varies in time. In the phase of rapid landscape change, there is strong positive association between the value of the geomorphic trait and the ecological trait (the trait that determines the sensitivity of a plant to landscape change). In the later stage of landscape development as steady state is neared, the association between becomes negative, i.e., negative niche construction. Over the course of landscape development, the mean value of the ecological trait monotonically increases, while the mean value of the geomorphic trait changes in a zigzag manner, alternating between increase and decrease, although in general, its value decreases over time. This may imply the transient nature of fixation of niche construction genes.