Isolating the Conditions of Drainage Reorganization and its Impacts on Species Evolution using Numerical Models
Abstract
Drainage network reorganization occurs in landscapes with varied conditions and process dynamics. We conducted hundreds of model runs using the Landlab modeling toolkit to evaluate the relative control that earth surface process parameters have on drainage network reorganization in multiple scenarios of heterogeneous uplift and base level change. Large-scale drainage reorganization events occurred in only the model runs within a limited combination of parameters and conditions. Uplift rate, rock erodibility, and hillslope length had the greatest control on the proportion of channels and divides that migrated during simulations. Large stream captures occurred more often when topographic relief was low and perturbation magnitude was high, and stream topology set by initial conditions strongly affected capture occurrence.
Drainage reorganization has been implicated in the formation of high freshwater fish diversity in many regions and taxa. Built into the same model runs described above, we evaluated species richness using a new Landlab component named SpeciesEvolver that simulates macroevolution processes. Fish can disperse across a greater geographic range when the network reorganizes. Conversely, a shrinking range increases the likelihood of species extinction. Stream captures fragment species, leading to new species. Across the model runs, speciation events increased with the parameters and conditions that led to large-scale drainage reorganization. The widely reported power law relationship observed in natural systems between the number of species and the area that these species occupy was approached in the model scenarios where topography was perturbed multiple times. These results elucidate the key role that drainage network dynamics have on influencing ecosystem diversity.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMEP11B..04L
- Keywords:
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- 1815 Erosion;
- HYDROLOGYDE: 1825 Geomorphology: fluvial;
- HYDROLOGYDE: 1826 Geomorphology: hillslope;
- HYDROLOGYDE: 1861 Sedimentation;
- HYDROLOGY